A publication of the Micro and Nanoelectrotechnologies Department of

National Research and Development Institute for Electrical Engineering-Advanced Research

Bulletin of Micro and Nanoelectrotechnologies

June 2011, vol. II, no. 2

Editorial Board ____________________________________________________________ Scientific Staff

Alexandru Aldea - INCDFM, Bucharest, Romania Robert Allen, University of Southampton Leonardo G. Andrade e Silva - Institute for Nuclear Energy Research, Av. Prof. Lineu

Prestes, São Paulo, Brazil Ioan Ardelean - Academy Romanian Institute of Biology, Bucharest, Romania Marius Bâzu - IMT Bucharest, Romania Gheorghe Brezeanu - The Faculty of Electronics, Telecommunications and

Information Technology, Politehnica University, Bucharest Maria Cazacu –Petru Poni Institute of Macromolecular Chemistry, Romanian

Academy, Iasi, Romania Mircea Chipara - The University of Texas Pan American, Physics and Geology

Department, USA Sorin Coţofană - The Deft University, The Netherland Olgun Güven - Hacettepe University, Department of Chemistry, Polymer Chemistry

Division, Ankara, Turkey Elena Hamciuc –Institute of Macromolecular Chemistry Petru Poni, Romanian

Academy Iasi, Romania Gabriela Hristea – INCDIE ICPE – CA, Bucharest, Romania Wilhelm Kappel - INCDIE ICPE - CA, Bucharest, Romania Jenica Neamtu - INCDIE ICPE – CA, Bucharest, Romania Yoshihito Osada, Hokkaido University, Riken Advanced Science Institute, Japan Yoshiro Tajitsu, Kansai University, Japan Cristian Teodorescu - INCDFM, Bucharest, Romania Elena Trif – Romanian Academy Institute of Biochemistry, Bucharest, Romania Traian Zaharescu – INCDIE ICPE - CA, Bucharest, Romania Slawomir Wiak - Technical University of Lodz, Poland

Executive Staff

Alexandru-Laurentiu Catanescu, INCDIE ICPE - CA, Bucharest, Romania

Clara Hender, INCDIE ICPE – CA, Bucharest, Romania

George Zarnescu, INCDIE ICPE – CA, Bucharest, Romania

Editor in chief

Dr. Eng. Mircea Ignat - INCDIE ICPE - CA, Dep. MNE, mignat@icpe ca.ro ISSN 2069-1505

Manuscript submission The Guest Editors will send the manuscripts by post or to the e-mail: mignat@icpe-ca.ro Contact e-mail: ghristea@icpe-ca.ro Address: Splaiul Unirii No. 313, sect. 3, Bucharest-030138 - Romania

Our staff will contact the Guest Editors in order to arrange future actions concerning manuscripts.

In 2011 the Romanian electrical engineering community celebrates 90 year from the commencement of the Electrical Engineering (Electrotechnic) Faculty of Bucharest Polytechnic University and 10 years from the debut of the National Institute for Research and Development in Electrical Engineering – Advanced Research (INCDIE ICPE–CA), Bucharest.

Many remarkable teachers and scientific personalities through whom we remember Constantin Budeanu, Vasilescu Karpen, Constantin Buşilă, I. S. Gheorghiu, Alexandru Popescu, Remus Răduleţ, Constantin Mocanu as emeritus professors at Electrical Engineering Faculty and recently Gheorghe Hortopan, Constantin Bălă, Alexandru Timotin, Andrei Ţugulea, Alexandru Fransua, Augustin Moraru, Cezar Flueraşu who represent a part of the prestigious teaching staff of this faculty, must not be forget.

INCDIE ICPE-CA represents a young and developing research institution which promotes new outlook by young scientific paradigm strategy. The new generation of Romanian specialists must to continue the fruitful tradition of our electrical engineering school.

This issue of Bulletin of Micro and Nanoelectrotehnology is dedicated to the above special events, which could be regarded as milestones for the progress on electrical engineering.

Editor in chief Mircea Ignat

Bulletin of Micro and Nanoelectrotechnologies includes research topics regarding:

Microelectromechanical and nanoelectromechanical components. Typical micro and nanostructure of actuators, micromotors and sensors. Harvesting microsystems. Conventional and non- conventional technologies on MEMS and NEMS. Theoretical and experimental studies on electric, magnetic or electromagnetic field with

applications on micro and nano actuation and sensing effects. Design algorithms or procedures of MEMS and NEMS components. Applications of MEMS and NEMS in biology and in biomedical field. New materials in MEMS and NEMS. Standardization and reliability approaches Economic and financial analysis and evolutions of MEMS and NEMS specific markets.

Contents

The European Scientific Network for Artificial Muscles and the EuroEAP conference Federico Carpi ……………………………………………………………………………………….5

Giant Magnetoresistance and Planar Hall Effect Sensors for High Sensitivity Measurements

Jenica Neamtu, Marius Volmer ………………………………………………………………..……10 Microbiology and Nanotechnologies

Ioan I. Ardelean ……………………………………………………………………………………...15 Electromechanical microactuator based on aromatic polyetherimide and pyrite ash powder

Mircea Ignat, George Zarnescu, Elena Hamciuc, Cornel Hamciuc ………………………………....21 Experimental and Theoretical Aspects on a Piezoelectric Linear Micromotor

Ovezea Dragoş .....................................................................................................................................30 Design aspects for magnetostrictive microactuators

Alexandru-Laurentiu Catanescu ……………………………………………………………………..34

5

Abstract - Electromechanically Active Polymers (EAPs) are ‘smart materials’ inherently capable of changing dimensions and/or shape in response to suitable electrical stimuli, so as to transduce electrical energy into mechanical work. They can also operate in reverse mode, transducing mechanical energy into the electrical form. Therefore, they can be used as actuators, mechano-electrical sensors, as well as energy harvesters to generate electricity. The rapid expansion of the EAP technologies has stimulated in Europe the creation of the ‘European Scientific Network for Artificial Muscles - ESNAM’. The network gathers the most active European research institutes, industrial developers and end users in the EAP field. In an effort to disseminate current advances in this emerging field of science and technology, gathering experts from all over the world, the ESNAM network organizes the annual EuroEAP event – ‘International conference on Electromechanically Active Polymer transducers & artificial muscles’. A chronicle of the inaugural edition that was held in Pisa, Italy, in June 2011 is presented here.

Index Terms - Actuator, artificial muscle, EAP, electroactive polymer, electromechanically active polymer, smart material.

I. INTRODUCTION Electromechanically Active Polymers (EAPs)

represent a fast growing and promising scientific field of research and development. EAPs are studied for devices and systems implemented with ‘smart materials’ inherently capable of changing dimensions and/or shape in response to suitable electrical stimuli, so as to transduce electrical energy into mechanical work. They can also operate in reverse mode, transducing mechanical energy into the electrical form. Therefore, they can be used as actuators, mechano-electrical sensors, as well as energy

harvesters to generate electricity [1-6]. For such tasks, EAPs show unique properties, such as sizable electrically-driven active strains or stresses, high mechanical flexibility, low density, structural simplicity, ease of processing and scalability, no acoustic noise and, in most cases, low costs. Owing to their functional and structural properties, electromechanical transducers based on these materials are usually refereed to as EAP ‘artificial muscles’ [1-6].

EAPs are classified in two major families: ionic EAPs (activated by an electrically-induced transport of ions and/or molecules) and electronic EAPs (activated by electrostatic forces), as summarized in Tab. I.

TABLE I. EAP classification. EAP class Materials Ref.

Polymer gels [7] Ionic polymer-metal composites

[8]

Conjugated polymers [9]

Ionic EAPs

Carbon nanotubes [10] Piezoelectric polymers

[11]

Electrostrictive polymers

[12]

Dielectric elastomers [13] Liquid crystal elastomers

[14]

Electronic EAPs

Carbon nanotube aerogels

[15]

Each EAP category shows specific

electromechanical transduction properties, typically suitable to address needs and applications that can be very different. As such, EAPs are studied for applications that so far have been unachievable with conventional transduction technologies, with usage spanning from the micro- to the macro- scale, in several fields, including haptics, optics, acoustics, microfluidics,

The European Scientific Network for Artificial Muscles and the EuroEAP conference

Federico Carpi1,2 1University of Pisa, Interdepartmental Research Centre 'E. Piaggio', School of Engineering,

56100 Pisa, Italy 2Technology & Life Institute, 56100 Pisa, Italy

e-mail: f.carpi@centropiaggio.unipi.it

6

automation, robotics, orthotics, artificial organs, and energy harvesting [1-6].

II. THE EUROPEAN SCIENTIFIC NETWORK FOR ARTIFICIAL MUSCLES

The rapid expansion of the EAP technologies has stimulated in Europe the creation of the ‘European Scientific Network for Artificial Muscles - ESNAM’, established as a COST Action (MP1003) since 8 December 2010 [16]. The COST Action is steered by a Chair, Dr. Federico Carpi (University of Pisa, Italy), and two Vice-Chairs, Dr. Gabor Kovacs (EMPA, Switzerland) and Dr. Peter Sommer-Larsen (Technical University of Denmark, Denmark). The Action has also a honorary coordinator, Prof. Danilo De Rossi (University of Pisa, Italy).

The network gathers the most active European research institutes, industrial developers and end users in the EAP field. Today, ESNAM consists of 50 member organizations from 26 European Countries. The current list is reported in Tab. II.

TABLE II. ESNAM member organizations. Organization Country

RESEARCH INSTITUTES: Åbo Akademi University Finland Ben-Gurion University Israel Centre National de la Recherche Scientifique

France

CIDETEC (Centre for Electrochemical Technologies)

Spain

Czech Technical University in Prague

Czech Republic

Darmstad University of Technology

Germany

Ecole Polytechnique Fédérale de Lausanne

Switzerland

EMPA Switzerland

Fraunhofer IPA Germany Fraunhofer LBF Germany German Institute for Polymers Germany Institute of Polymers Bulgaria Jozef Stefan Institute, Ljubljana Slovenia Linköping University Sweden National Technical University of Athens

Greece

Petru Poni Institute of Macromolecular Chemistry

Romania

Polymer Institute Slovak Republic

Semmelweis University Hungary Technical University of Denmark Denmark

Technical University of Dresden Germany Technology & Life Institute Italy Trinity College Dublin Ireland University of Applied Sciences, Hochschule Ostwestfalen-Lippe

Germany

University of Belgrade Serbia University of Cartagena Spain University of Cergy-Pontoise France University of Linz Austria University of Minho Portugal University of Paris 7 France University of Pisa Italy University of Potsdam Germany University of Reading United

Kingdom University of Southampton United

Kingdom University of Southern Denmark Denmark University of Tartu Estonia University of Trento Italy University of Villeneuve d'Ascq France Vestfold University College Norway VTT Technical Research Centre of Finland

Finland

Warsaw University of Technology

Poland

INDUSTRIES: ABB AG Germany Arquimea Ingeniería Spain BAE Systems United

Kingdom Bayer MaterialScience Germany Danfoss PolyPower Denmark Festo Germany FIAT Research Centre Italy Optotune Switzerlan

d Ossur Iceland Philips Research Netherland

s

The network is primarily aimed at fostering scientific and technological advancement of transducers and artificial muscles based on EAPs as smart materials for electromechanical transduction (actuation, sensing and energy harvesting). Fur further information, interested readers are invited to refer to the network website [16].

III. THE EuroEAP CONFERENCE In an effort to disseminate current advances in

this emerging field of science and technology, gathering experts from all over the world, the ESNAM network has organized and supported EuroEAP 2011 - the ‘First international

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conference on Electromechanically Active Polymer transducers & artificial muscles’, that was held in Pisa on 8-9 June 2011. The event was chaired by Federico Carpi and Danilo De Rossi, from the University of Pisa, and was intended as the inaugural event of many future annual editions, primarily driven by scientific quality and industrial impact [17].

The conference was attended by about 130 delegates. The response to the call for contributions was high, much more than the most optimistic estimate, in consideration of the extremely short time available for organization and dissemination. Actually, the embryonal decision to organize the conference was taken on 8 December 2010 (during the ESNAM kick-off meeting) exactly six months before the beginning of the event. At that time, the conference was just an idea and a lot of efforts have been spent by the Organizing committee (Tab. III) to provide it with shape and content.

TABLE III. Organizing committee of the

EuroEAP conference. Name Function Organization Country Federico Carpi President University of Pisa Finland Edwin Jager Vice-President Linköping University Sweden Guggi Kofod Member University of Potsdam Germany Marc Matysek Member Philips Research Netherlands Mika Paajanen Member VTT Technical

Research Centre of Finland

Finland

Herbert Shea Member Ecole Polytechnique Fédérale de Lausanne

Switzerland

Frédéric Vidal Member University of Cergy-Pontoise

France

The technical programme offered, on one

hand, 11 invited talks from top-level scientists and EAP leaders who have made the history of the EAP field, and, on the other hand, 66 unsolicited contributions from both highly renowned international scientists, as wells new comers in the field who contribute to the rapid growth of the EAP community.

All of the invited scientific talks were given by scientists coming from outside of Europe. This was a deliberate choice, driven by the specific intention of this European network to foster scientific cooperation with overseas colleagues and experts. In fact, broad cooperation is considered by ESNAM members as highly beneficial to advance science and technology of this field. This awareness reflects the essential spirit that animates in general the European Science Foundation’s programme COST (Cooperation in Science and Technology) [18], which supports the ESNAM network and the EuroEAP conference.

The invited scientific talks were given by the scientists who are listed in Tab. 4 in order of presentation.

TABLE III. List of invited speakers at the

EuroEAP 2011 conference. Name Organization Country Picture Prof. Yoshihito Osada* RIKEN Advanced

Science Institute Japan Fig. 1a

Dr. Ron Pelrine* SRI International USA Fig. 1b Prof. Keiichi Kaneto Kyushu Institute of

Technology Japan Fig. 1c

Prof. Qibing Pei University of California, Los Angeles

USA Fig. 1d Prof. Geoff Spinks University of

Wollongong Australia Fig. 1e

Dr. Werner Jenninger Bayer MaterialScience Germany Fig. 1f Prof. John Madden* University of British

Columbia Canada Fig. 1g

Dr. Roy Kornbluh SRI International USA Fig. 1h Prof. Zhigang Suo Harvard University USA Fig. 1i Prof. Paul Calvert University of

Massachusetts, Dartmouth

USA Fig. 1l

Dr. Shihai Zhang Strategic Polymer Sciences Inc.

USA Fig. 1m * Plenary speakers

Fig. 1 Invited speakers at the EuroEAP 2011 conference.

Among those invited speakers, two are

representatives of industry. This is a clear sign of the importance that the EAP technologies are gaining for applications. Actually, this year marks a key achievement for industrialization of EAPs,

8

as a mass-produced EAP product with a high expected commercial impact has just been released [19].

During the conference, the following three highly renowned scientists and pioneers in the EAP field were awarded by the ESNAM network, with an informal ceremony in a friendly atmosphere (Fig. 2): Prof. Yoshihito Osada, from RIKEN Advanced Science Institute, Japan (“for a long-standing carrier and important scientific contributions in the field of Polymer Gel Artificial Muscles”), Prof. Keiichi Kaneto, from Kyushu Institute of Technology, Japan (“for a long-standing carrier and important scientific contributions in the field of Conjugated Polymer Artificial Muscles”), and Dr. Ron Pelrine, from SRI International, USA (“for the invention and development of the Dielectric Elastomer Artificial Muscle technology that this year has entered the market with the first mass-produced device”).

Fig. 2. During EuroEAP 2011, three highly renowned scientists and pioneers in the EAP field were awarded by the ESNAM network: (a) Prof. Yoshihito Osada, from RIKEN Advanced Science Institute, Japan, is awarded by Prof. Danilo De Rossi; (b) Prof. Keiichi Kaneto, from Kyushu Institute of Technology, Japan, is awarded by Dr. Peter Sommer-Larsen; (c) Dr. Ron Pelrine, from SRI International, USA, is awarded by Dr. Gabor Kovacs.

The next annual editions of the EuroEAP conference will be moving across Europe. EuroEAP 2012 will take place in Potsdam, Germany, and will be chaired by a highly esteemed scientist, Prof. Reimund Gerhard from the University of Potsdam.

IV. ACKNOWLEDGMENT The author gratefully acknowledges financial support for

networking activities from COST (European Cooperation in Science and Technology), in the framework of “ESNAM: European Scientific Network for Artificial Muscles” (COST Action MP1003).

V. References [1] P. Brochu, Q. Pei, Advances in dielectric elastomers

for actuators and artificial muscles, Macromol Rapid Comm 31(1), 10-36, 2010.

[2] T. Mirfakhrai et al., Polymer artificial muscles, Mater Today 10(4), 30-38, 2007.

[3] J. Madden et al., Artificial muscle technology: physical principles and naval prospects, IEEE J. Oceanic Eng 29(3),706-728, 2004.

[4] Y. Bar-Cohen (Ed.), Electroactive polymer (EAP) actuators as artificial muscles, SPIE, Bellingham, volume PM136, 2004, 1-765.

[5] F. Carpi and E. Smela (Ed.), Biomedical applications of electroactive polymer actuators, Wiley, 2009.

[6] F. Carpi, Electromechanically active polymers (special issue editorial, Polymer International, 59 (3), 277-278, (2010).

[7] T. Tanaka et al. Collapse of gels in an electric field, Sci. 218, 467-469, 1982.

[8] K. Asaka et al., Bending of polyelectrolyte membrane-platinum composites by electric stimuli Polym. J. 27(4), 436-440, 1995.

[9] R. H. Baughman, Conducting polymer artificial muscles, Synth. Met. 78, 339-353, 1996.

[10] R. H. Baughman et al., Carbon nanotube actuators, Sci. 284, 1340, 1999.

[11] H. S. Nalwa, Ferroelectric Polymers, Marcel Dekker, 1995.

[12] Q. M. Zhang et al., Giant electrostriction and relaxor ferroelectric behaviour in electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer, Sci. 280, 2101-2103, 1998.

[13] R. Pelrine et al., High-speed electrically actuated elastomers with strain greater than 100%, Sci. 287, 836-839, 2000.

[14] W. Lehmann et al., Giant lateral electrostriction in ferroelectric liquid-crystalline elastomers, Nat. 410, 447-450, 2001.

[15] Aliev A. et al. Sci. Giant-Stroke, Superelastic Carbon Nanotube Aerogel Muscles, 323:1575-1578 (2009).

[16] European Scientific Network for Artificial Muscles (ESNAM) website: www.esnam.eu.

[17] EuroEAP website: www.euroeap.eu.

9

[18] COST website: www.cost.esf.org. [19] Cheng A., 2011, “ViviTouch™ Offers a New Sensory

Dimension to Mobile Gaming,” WWW-EAP Newsletter, 13, pp. 2.

VI. BIOGRAPHY Federico Carpi was born in Pisa, Italy, on February 10,

1975. He received the Laurea degree in Electronic Engineering, the Ph.D. degree in Bioengineering and a second Laurea degree in Biomedical Engineering from the University of Pisa, Italy, in 2001, 2005 and 2008, respectively. Since 2000, he has been with the Interdepartmental Research Centre “E. Piaggio”, School of Engineering, University of Pisa, where he is currently a Post-Doctoral Researcher. His research interests include the development of electroactive polymer based materials and devices for biomedical engineering and robotics. He serves as Chair of the electroactive polymer based “European Scientific Network for Artificial Muscles (ESNAM)”, member of the Editorial Board of three international scientific journals, and member of the Scientific Committee of several international conferences. His scientific publications include more than 50 peer-reviewed papers in international journals, two edited books and several contributions to books and conferences.

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Abstract In this study we present an overview of the giant magnetoresistance (GMR) and planar Hall effect (PHE) sensing structures made from nanostructured systems of magnetic layers. A giant magnetoresistance device consists at least two ferromagnetic layers, separated by a cooper (Cu) spacer. When the Cu layer is replaced by a thin insulator layer (Al2O3) then, we have a magnetic tunnel junction or, for some deposition conditions, a nanogranular system. Electrical and magnetic characterization of the magnetic thin film layers plays an important role in the design of these sensors and some results are presented in this paper. For a better understanding of the magnetization processes that take place in these nanostructured systems, micromagnetic simulations were performed. Index Terms: anisotropic magnetoresistance, giant magnetoresistance, multilayer, planar Hall effect, thin films.

II. 1. INTRODUCTION Magnetoresistance effects (MR) which arises

in permalloy based thin films is an attractive solution for the fabrication of magnetic sensors. The resistance behavior of such thin films (3d ferromagnetic alloys) is anisotropic with respect to the applied field direction, the MR being positive when the magnetic field is parallel to the current (longitudinal) and negative when the magnetic field is perpendicular to the current direction (transversal). This is the anisotropic magnetoresistance effect (AMR). The AMR effect arises from anisotropic scattering due to spin orbit-orbit interaction. It is worth to mention that the MR effect in ferromagnetic thin films is determined by the sample magnetization rather than the external magnetic field, H.

The working principle of the GMR effect in general and the spin-valve configuration in particular is different of AMR effect. The GMR effect arise from the electronic transport in a multilayer consisting of two ferromagnetic layers (P), which are separated by a non-magnetic spacer layer (NM).

Layer thicknesses are smaller than, or of the order of mean free path for the conduction electrons and the magnetic interactions in the multilayer must be such that the relative

orientation of the magnetizations in neighboring layers is field-dependent.

II. THEORETICAL ASPECTS

The resistance produced by scattering in thin

films is maximum when the magnetization direction is parallel (i.e. 0º or 180º) to the current direction and minimum when the magnetization is perpendicular to the current. In general, the resistance is given as a function of the angle, between the magnetization and current:

R=R0+ RAMR cos2 (1) Here, RAMR=Rl-Rt is the amplitude of the AMR effect calculated in the saturated state when the applied magnetic field is parallel and perpendicular to the current respectively. Usually, R0 is the resistance in the saturated state when H is applied perpendicular to the current direction but in the film plane.

The magnetoresistance ratio RAM /R0 is relatively large for ternary Fe-Co-Ni alloys containing 70 to 90 atomic percent of Ni, amounting to at most 2.5 to 3 % in 30 nm Permalloy (Ni81Fe19) films [1]. This is because when the film thickness becomes comparable or smaller than the mean free path of the carriers we should take in account the scattering processes at the surfaces and interfaces which lower the amplitude of the MR effects.

For many applications in read heads and other sensors, Permalloy (Py) is the preferred choice due to its favorable soft magnetic properties. In the ternary Fe-Co-Ni diagram the Permalloy composition lies close to both to zero magnetostriction and the zero crystalline anisotropy line. Therefore, the magnetic behavior of the prepared Permalloy films is dominated by the uniaxial inplane anisotropy induced by a field applied during deposition. Thus, for a field along the hard axis, i.e. perpendicular to the anisotropy direction, the change of the magnetisation will

Giant Magnetoresistance and Planar Hall Effect Sensors for High Sensitivity Measurements

*Jenica Neamtu, **Marius Volmer *Research and Development National Institute of Electrical Engineering (INCDIE ICPE-CA), Splaiul Unirii 313,

Bucharest, 030138, Romania, jenica.neamtu@gmail.com ** Physics Department, Transilvania University, 29 Eroilor, Brasov 500036, Romania

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result from a coherent magnetization rotation process.

The plot of eq. 1 shows that the maximum sensitivity and linearity is achieved when the magnetization is at 45º with respect to the current. The 45º alignment is commonly achieved by patterning diagonal stripes of highly conductive metal (gold) onto the more resistive AMR material as shown in Fig. 1a. The current will then run perpendicular to these “barber pole” stripes while the magnetization vector remains preferentially along the long direction of the MR device. The application of an external magnetic field will rotate the magnetization with a resulting change in resistance as shown in Fig 1b. The MR ratio for AMR materials is typically a few percent.

Fig.1. (a) Barber-pole structure of conductive shunts that constrain the current to run at 45º to the rest position for the

magnetization. (b) Resistance versus field for a properly biased AMR device.

To develop practical applications, such as

magnetic field sensors, it must to minimize the thermal drift and to optimize the MR response. For this purpose it is convenient to operate the device with the two or four active arms of a Wheatstone bridge. Each arm corresponds to one MR element. We have to mention here that many other materials can be used for this application.

Because of the AMR effect will appear an electric field perpendicular to the applied current, in a Hall effect geometry, even when the magnetic field is in the film plane but it makes an angle =45° with the current direction [3, 4]. This is the so-called planar Hall effect (PHE).

In Fig. 2 we present the field dependence of the PHE effect measured in a nanogranular Py( 2nm)/Al2O3(1 nm)Py(2 nm) thin film [5].

Fig. 2. Field dependence of the PHE for Py/AlO/Py thin film near the percolation limit.

In inset is presented the experimental setup. In

this way we get direct access to the anisotropic part of the resistance with the advantage of a reduced thermal drift of the output signal.

The sensitivity is about 0.04 mV/Oe for a magnetic field variation less 200 Oe and can be increased by a careful choice of the layers thickness, increasing the precision of the measuring setup, using high current pulses, etc. This plot suggests the main utility of the PHE, for building high sensitivity magnetic field sensors. In a single domain approximation, the PHE voltage is determined by the relation [4, 6]: U=CM2 j sin 2=A sin 2 (2) where C is a constant determined by the material properties, j is the current density, M is the saturation magnetization and is the angle between the current and the magnetization vector that, in turn, is determined by the value and direction of the external magnetic field. From eq.2, we see how the PHE effect can provide information about the magnetic properties of the material and allow building of low-cost rotation sensors.

The working principle of the GMR effect is different of anisotropic magnetoresistance. We consider electronic transport in a multilayer consisting of two ferromagnetic layers (F), which are separated by a non-magnetic spacer layer (NM) (Fig.3).

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Fig. 3 The principle of GMR effect, the Mott model.

Layer thicknesses are smaller than, or of the order of mean free path for the conduction electrons. The magnetic interactions in the multilayer must be such that the relative orientation of the magnetizations in neighboring layers is field-dependent.

We furthermore assume the scattering of electrons in a ferromagnetic layer and/or at the interfaces, to depend on the spin of the electrons (“up” or “down”) and the spacer layer to have a high transparency (i.e. low scattering probability) for conduction electrons.

In Fig. 3, the scattering is strong if the electron spin is parallel to the local magnetization (down) and much weaker if it is a parallel (up). When the magnetizations are antiparallel, spin-down electrons are scattered strongly in both layers. Spin-up electrons are much less frequently scattered. On the other hand, if the layers are antiparallel, an electron will scatter intensely in one layer and less intensely in the other layer. This applies to both spin channels. The total conductance is, for both cases, found by simply adding the conductance due to spin up and spin-down electrons. The total resistavity ρ for the combination of spin-up and spin-down electrons can be considered as the sum of two parallel resistivities:

2

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(3)

The relation (3) is applied for low temperatures (-4K).

Now, it can easily be seen that for the situation of parallel magnetizations, the very low resistance of the spin-up channel results in a very low total resistance (shunting by the low resistance channel). The resistance for the other situation is higher, because there, such a spin channel with very low resistance is absent. The resistance of the system thus depends on the relative

orientation of the magnetizations in neighboring layers, with the antiparallel state.

For obtaining the nanostructures with GMR effect, the spacer layers must be thin compared to the mean free path of electrons so that electrons spin polarized in one layer can pass into the other layers before their polarization is disturbed by scattering.

Basically there are two methods to obtain the antiparallel orientation of the magnetizations in the adjacent layers and hence the GMR effect:

(i) the nonmagnetic layer has such at thickness (about 1 nm) for which the coupling between the adjacent ferromagnetic layers is an antiferromagnetic one and

(ii) the magnetization of a ferromagnetic layer is pinned through exchange biasing effect using an antiferromagnetic layer as FeMn. So only the magnetization from the second layer known also as sensing layer is free to rotate, this is spin valve structure.

A typical magnetization curve and field dependence of an exchange-biased spin valve is presented in Fig.4. For practical applications there are used only magnetic fields smaller than the exchange biased field Hexch for which only the magnetization from the free layer will be reversed, Fig. 4a. This field is well described by the Néel model for positive magnetostatic interlayer coupling (orange peel coupling) [7]. The MR ratio RGMR/R0 for these exchange-biased spin valves is typically 4.5 – 6 % at room temperature.

Fig. 4. Representation of (a) the magnetization curve and (b) the field dependence of the resistance of an exchange biased spin valve. Magnetization reversal of the sensitive

and the exchange-biased layer takes place at the offset field Ho and the exchange-biased field Hexch, respectively.

GMR devices are typically operated with the

sense current in the plane of the films (CIP, current-in-plane) using electrical contacts at the ends of long lines.

Although the magnetoresistance is reduced because of current shunting through

13

the layers the alternative current-perpendicular-to-pane (CPP) configuration will typically have a resistance that is too low for practical circuit applications. Tunneling Magnetoresistance (TMR) structures are similar to CPP spin valves except that they utilize an ultra-thin insulating layer to separate two magnetic layers rather than a conductor. Electrons pass from one layer to the other through the insulator by quantum mechanical tunneling.

III. RESULTS AND DISCUSSION

A. Micromagnetic characterization by PHE of a rotation sensor based on the giant

magnetoresistance effect. We used three samples to study the angular

dependence of the AMR effect: (i) a Ni80Fe20(10 nm) film, (ii) a Ni80Fe20(10 nm)/Cu(4 nm)/Ni80Fe20(10 nm) multilayer structure and (iii) Ni80Fe20(2 nm)/Al2O3(1nm)/Ni80Fe20(2 nm) nanogranular film. The multilayer structure presents, in addition to the AMR effect, the GMR effect. Details regarding the samples preparation were given in a previous work [8]. The four-lead setup used to investigate the angular dependence of the PHE is presented in Fig. 5(a). The equivalent resistor arrangement model [3] is presented in Fig. 5(b) and helps us to understand the angular behavior of the PHE voltage. Also it is shown the orientation of the magnetic field vector which is applied in the film plane. The DC current sources I1 and I2 drive the same current, I, through the sample, S, and are computer controlled. When the source I1 is ON, the source I2 is OFF and the measured PHE voltage is U1. When the source I2 is ON, the source I1 is OFF and the measured PHE voltage is U2. In this way, for a given angle, , between the magnetic field, H, and the direction of the current driven by I1, we made two measurements for the PHE.

Fig. 5. (a) Schematic setup used for PHE measurements and (b) the four-resistor arrangement model to account for the

electric behaviour of the sample. H is applied in the sample plane.

The PHE voltage was detected by a 2 channel Keithley digital voltmeter 2182A with a precision better than 100 nV. The angular dependence was achieved by using a stepper-motor allowing rotation with a precision of 0.1° and the results of the measurements made on these samples, voltage U1, are presented in Fig.6.

Fig. 6 Angular dependencies of the PHE effect, for different values of the applied field, measured for (b) Ni80Fe20(10 nm)/Cu(4 nm)/Ni80Fe20(10 nm) ML and (c) Ni80Fe20(2

nm)/Al2O3(1nm)/Ni80Fe20(2 nm) nano-layered film.

Because of the contacts misalignments the angular behavior of the PHE, voltage U1, is distorted. For magnetic fields lower than 200 Oe the PHE voltage depends also on the amplitude of the applied field because the magnetization is less than the saturated value. On the other hand, we see that for the ML sample, Fig. 6(b), the angular dependencies of the PHE voltage for low magnetic fields (H=100 and 200 Oe respectively) present some irregularities that are far from the shape predicted by the eq. 2. This is because the magnetization cannot follow accurately the direction of the magnetic field due to the coupling effects between the magnetic layers through the Cu layer.

B. Micromagnetic Simulation To simulate the response of this structure, we

considered a biasing setup like in figure 5(a). We used a disk shape structure of magnetic thin film, divided in a mesh with magnetic single domains [9, 10].

14

Fig. 7 The structure (disc of Permalloy) used for micromagnetic simulations placed above the conductive

stripe (a) the magnetic moments orientations for Happl=0 and (b) for Happl=100 Oe.

Figure 7 illustrates this setup and presents the magnetic moments orientations for a biasing field of 50 Oe (Ib=5.25 Ma) without an applied field, figure 7(a), and for an applied field of 100 Oe, figure 7(b). We see that the structure polarized at 50 Oe is not behaving like a single domain and explains the behavior observed in figure 6.

IV. CONCLUSIONS In this paper we presented, using a

phenomenological approach, an overview of the magnetoresistive effects (AMR, GMR and PHE) that are used to design magnetic sensors made from multilayer nanostructured systems. The anisotropic magnetoresistance, giant magnetoresistance and planar Hall effects were presented. We presented a method to increase the response quality of a rotation sensor based on the giant magnetoresistance and planar Hall effects. Electrical characterization of rotation sensor shows that for magnetic fields lower than 200 Oe the PHE voltage depends also on the amplitude of the applied field because the magnetization is less than the saturated value. For a better understanding of the magnetization processes that take place in these nanolayered structures, micromagnetic simulations were performed.

V.References [1] J. C. S. Kools, R. Coehoorn, W. Folkerts, Philips J. Research 51, (1998) pp. 125-130. [2] L. Balcells, E. Calvao, J. Fontcuberta, J. Magn. Magn. Mater. 242-245, (2002) pp. 1166-1169. [3] C. Prados, D. Garcia, F. Lesmes, J. J. Freijo, A. Hernando, Appl. Phys. Lett. 67, (1995) pp. 718-722. [4] F. Montaigne, A. Schuhl, F. Nguyen Van Dau, Sensors and Actuators 81, (2000) pp. 324-328. [5] J. Neamtu, M. Volmer, Journal of Materials Research, vol.746, (2003), pp. 551-558 [6] E. M. Epshtein, A. I. Krikunov, Yu. F. Ogrin, J. Magn. Magn. Mater, 80 (2003) pp. 258-259.

[7] J. C. S. Kools, Th. G. S. M. Rijks, A. E. M. De Veirman, IEEE Trans. Magn. 31, (1995) 3918-3821. [8] M. Volmer, J. Neamtu, J. Magn. Magn. Mater, 316, (2007), pp. 265-268 [9] M Volmer and J Neamtu, Physica B: Condensed Matter 403 (2008) pp. 350-353 [10] Oti John , SimulMag Version 2.0j, Micromagnetic Simulation Software, User’s Manual, Electromagnetic Technology Division, National Institute of Standards and Technology Boulder, Colorado 80303.

VI. BIOGRAPHIES Jenica Neamtu was graduated on 1968 at the Faculty of

Physics, University of Bucharest. Ph.D in Solid State Physics from Institute of Atomic Physics Bucharest, with the subject "Magnetic and structural properties of magnetic oxide thin films and ferrite thin films". Research area: giant magnetoresistance effect, spin valve structures and magnetic tunnel junctions for sensing applications. Nano-particles, core-shell nano-composites with application in Bio&Nanomedicine. Thin films, multilayer structures, nanostructures with electric, magnetic and sensorial properties.

Marius Volmer was graduated on 1984 at the Faculty of Physics, University of Bucharest. PhD in Physics obtained at Bucharest University, Faculty of Physics with subject: Magnetic and electric properties of magnetic thin films, 2001. Associate Professor at Transilvania University of Brasov, Physics Department. Research area: spin valve structures and magnetic tunnel junctions for sensing applications, biomolecules detection, lab on a chip devices and micromagnetic simulations.

15

Abstract - This contribution shows the interplay between Microbiology and Nanotechnologies with special emphasis on few main topics of intense research. There are shortly presented different ultrastructural components of microbial cells which are true biological nanostructures important for Nanobiotehnologie, the use of intact microbial cells for nanoparticule biosynthesis as well as the study of biocompatibility/ cytotoxicity of different nanoparticule. The relationship between Microbiology and Nanotechnologies is discussed with respect to the (emerging) field of nanomicrobiology.

Index Terms - biological nanomotors, microorganisms, microbial nanostructures, nanotechnology, nanomicro-biology

I. INTRODUCTION

Whereas Microbiology has a rather long history [1]-[4] nanotechnology was used for the first time by Norio Taniguchi in 1974 who stated that "'Nano-technology mainly consists of the processing of, separation, consolidation, and deformation of materials by one atom or one molecule" [5], following the seminal words of Richard Faymann: “The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big” [6]. We, the humans we are indeed very big as compared with the atoms and molecules, but microorganisms are significantly smaller than us, and very important for nanotechnologies. One of the strategic objectives of nanotechnology is the development of new materials having nanometer sizes and microorganisms are producing nanomaterials since their apparition around three billions years ago. The emergence and the development of Microbiology was dependent on progress in Physics and Chemistry, starting with simple optical microscope till the tremendous progresses in analytical instruments enabling the

scientists to interact with a single molecule or atom. Theses progresses put Microbiology in the position to study individual cell, the emerging topic Single Cell Microbiology being one of the most exciting of nowadays Microbiology, and a strong evidence of the interplay between Nanotechnology and Microbiology. The export of concepts and methods from Nanotechnology to Microbiology is evolving toward a mutual interplay, where Microbiology not only benefits from using instruments invented and produced by physicists but is playing n active and creative role in this cooperation. These interactions are so intimate and fruitful that there are some strong voices putting forward that a new field is emerging, namely Nanomicrobiology [7].

II. MICROBIOLOGY- A DECENT PARTNER FOR NANOTECHNOLOGIES

It has to stress here that Microbiology (Biology in general) interacts with Nanotechnology based on its theoretical and natural richness.

Theoretical richness of Microbiology is simply argued by its development during several centuries [2],[3],[8],[9] and here one can only focus on the significant participation of Microbiology to three of the main important Scientific Revolutions during XXth century: the emergence and development of molecular biology, of modern biotechnologies and of molecular phylogeny [2],[3],[8],-[10]. These major advances not only changed our view about the living world but enable the scientists and engineers to control in vivo or in vitro some of the processes occurring in cells, thus understanding in deeper details what life is, with the possibility to produce new substances following a new protocol or a new biotechnological process with benefits for billions of people (the dark sides are not discussed here).When it comes to the natural richness of Microbiology it is argued by the structural and functional diversity of already known species (and their nanostructures), and those to be discovered in the future. At this point

MICROBIOLOGY AND NANOTECHNOLOGIES

Ioan I. Ardelean Institute of Biology Bucharest, Romanian Academy, Department of Microbiology, Splaiul

Independenţei 296, Bucharest 060031, Ovidius University Constantza, Department of Biology and Ecology, Romania, ioan.ardelean@ibiol.ro

16

one has to focus on the fact that microorganisms (as well as cells belonging to multicellular organisms) are composed by ultrastructural components which are true nanomaterials, many of them having dimensions up to 100nm. It is not here the place for an exhaustive description of all these ultrastructural components, information which can be found in classical books of microbiology and cell biology [10]-[16] but some of the most interesting components are shortly presented: flagellum, thylakoid membrane, ATP synthase. Flagellum is a tail-like projection that protrudes from the cell body of certain microorganisms and whose main function is locomotion, being itself a true nanomotor. In figure 1 it is presented the molecular structure of the flagellum belonging to a Gram- negative bacterium.

Fig. 1. Schematic diagram of a flagellum in a Gram-negative bacterium.

The bacterial flagellum is driven by a rotary engine (the Mot complex) made up of different type of proteins located at the flagellum's anchor point on the inner cell membrane (plasma membrane). The rotary engine is powered by an energy source, the concentration gradient of protons across cell membrane called proton motive force which is set up during cell metabolism (respiration or photosynthesis, as the main bioenergetics processes in microorganisms). The rotor transports protons across the membrane, and is turned in this process. The rotor alone can operate at 6,000 to 17,000 rotations per minute (rpm), but with the flagella filament attached usually only reaches 200 to 1000 rpm. Flagellum do not rotate at a

constant speed but instead can increase or decrease their rotational speed in relation to the strength of the proton motive force. Flagellum rotation can move bacteria through liquid media at speeds of up to 60 cell lengths/second which is extremely fast, even when it is compared with cheetah’ speed, the fastest land animal, which can sprint at approximately 25 body lengths/sec. The difference is further put in evidence by the fact that the cheetah can run with this maximal speed for only very short time, up to one minute, as compared with bacteria who swim continuously. Flagellum is deeply studyied as a molecular biological nanomotor and as a model of self assembled (motor) nanostructures [17]. Thylakoid is a membrane-bound compartment inside cyanobacteria (or other photosynthetic organisms), which perform oxygenic photosynthesis. Thylakoids consist of a thylakoid membrane (containing three types of macromolecular assemblies –photosystem II, cytochrome b6/f complex and photosystem I) surrounding a thylakoid lumen (Fig.2). The three types of macromolecular assemblies are involved in biochemical and biophysical reaction dependent on light, where the light energy is converted in chemical energy, including the proton motive force.

Fig. 2. Schematic diagram of a thylakoid membrane; in cyanobacteria thylakoid membrane/ vesicle separates the thylakoid lumen from cytoplasm ; in higher plants which have chloroplasts, thylakoid membrane/ vesicle separates

the thylakoid lumen from chloroplast stroma.

This force can be used in many different ways by the cell, to drive the flagellum (as shown above) or to be further converted in another form of chemical energy, namely the chemical energy of adenosine a triphosphate (ATP) which is the usual energy „currency” of all cells

17

This process occurs at the level of another molecular circular motor called ATP synthetase; the passage of protons from the higher concentration (inside the thylakoid lumen-fig 2 and at the external surface of cell membrane in bacteria carrying out either aerobe or anaerobe respiration- fig.3 ) to lower concentration (cytoplasm in all prokaryotes performing photosynthesis or aerobe or anaerobe respiration) is party conserved as chemical energy during the ATP synthesis from ADP and inorganic phosphate.

Fig. 3. Schematic diagram of ATP synthase activity in aerobic or anaerobic respiring

bacteria.

The complexes conversions of chemical and mechanical energy during ATP synthase function are models for biology and nanotechnology how to control very small and discrete amount of energy at nanometric level. The ability of living cell to built true nanostructures which are components of microbial cell could serve as a model for humans to mimic these processes and to construct such components (almost) identical with their pure biological models, as is the case for other biological nanostructure such as S-layers, sex pillum, cell membrane and some related proteins (porins, ionic pumps etc) [18]-[22].

III. MICROBIAL CELLS CAN PRODUCE NANOPARTICLES

Microbial cells are also able to synthesize nanoparticule (NP) by ordered chemical oxido-reduction of salt of some metals (gold, platinum, silver, iron etc. ) being chemically reduced to zero valent metal atoms which are regularly deposited one against other, thus forming a crystal. In some of these reactions, the formation of crystals is really controlled by microbial cells. This controlled biomineralization is well documented in magnetotactic bacteria which are able to produce inside the cell magnetic nanocristals composed of either pure magnetite, pure greigyte or even a mixture of magnetite and greigyte. Magnetosomes synthesized by magnetotactic bacteria, were originally defined as intracellular, magnetic single domain (SD) crystals of a magnetic iron mineral that are enveloped by a trilaminate structure, the magnetosome membrane (MM). In other words, a magnetosome consists of magnetic iron mineral particles (the inorganic phase) enclosed within a membrane (the organic phase). The organic phase (the magnetosome membrane or the magnetosome vesicle), consists in Magnetospirillum strains (M. magnetotacticum or M. gryphiswaldense) of a bilayer of about 3-4 nm containing phospholipids and proteins. In the last few years the study of the proteins found in magnetosome membranes has raised a special interest because it was expected that these proteins would enable the processes of mineral formation of nanocrystals to be regulated by biochemical pathways. The magnetosome particle is characterized by a nearly perfect crystalinity and the size and morphology of magnetic crystals are species specific and uniform within a single cell, for example, in M. gryphiswaldense the dimension of magnetosomes is around 45 nm. This uniformity is an advantage of biogenic magnetic nanocrystals of MTB used for different bio(nano)technological application, as compared with biogenic magnetic nanocrystals produced by other types of bacteria(e.g. Shewanella sp.) or by artificial/abiogenic magnetic nanocrystals obtained by man using different physical/chemical protocols. Biogenic magnetic nanocrystal can be produced by metabolic activities of dissimilatory iron-reducing bacteria and sulphate-reducing bacteria. This process is known as biologically induced mineralization. However, unlike the mineral particles in the

18

magneto-tactic bacteria, biologically induced mineralization is not controlled by the organism and is characterized by no uniformity in size distributions and non-unique crystal habits. Magnetosomes, as natural nanomaterials, have many application biotechnology and medicine, further arguing for the importance of some microorganisms in producing useful nanomaterials.[23]-[30].

Magnetotactic bacteria are also important for nanotechnology because the synthesis of magnetosomes is a model for in vitro synthesize magnetic nanoparticule by different protocols, including the use of (genetically modified) proteins involved in vivo in magnetosome synthesis Furthermore, the development of future autonomous bacterial microrobots is another trend in which magnetotactic bacteria can be involved. Acting like a compass, this chain of magnetosomes enables the bacteria to orient themselves and swim along the lines of a magnetic field. Hence, the basic control method consists of modifying the swimming paths of the magnetotactic bacteria with the generation of local directional magnetic fields using small programmed electrical currents passing through special embedded conductor networks. This new method referred to as controlled bacterial micro-actuation is a serious candidate for its integration in future untethered microrobots operating in an aqueous medium, as originally proposed [31]. The implementation of such bio-carriers with (non magnetic) micro-objects being propelled by a single magnetotactic bacteria was also demonstrated. The effect of various diameters magnetotactic bacteria -pushed beads on the velocity of this bio-carrier and the retarding effect caused by the proximity of the walls of the microchannels were also investigated. These type of research using both the ability of some organisms to be motile ,and to orient themselves following different physical or chemical factors (the line of magnetic field, temperature gradient, light gradient etc) open the opportunity to use living organisms as precise carriers for nanoobjects.[32],[33] Microorganisms are also used as living model systems to study the interaction between nanomaterials and living mater; many of these studies are of medical significance, either using microbial cells as preliminary models for human cells either as target for potential new antibiotics

to control pathogenic microorganisms. There is an increase interest in studying the possible effects of nanomaterials on natural ecosystems, with special emphasis on photosynthetic microorganisms (anoxygenic phototropic bacteria, oxygen phototrophic bacteria- cyanobacteria and related prokaryotes, unicellular eukaryotic algae) as the main organism in aquatic systems involved in molecular oxygen production and dioxide de carbon fixation as organic matter [34],[35].

V. FURHTER PROSPECTS

There are also other topics were the interaction between microorganisms and nanotechnology is very deep, and important for mankind One of these domains concerns the use of molecules such as DNA (in solutions) or proteins(either in solution or at the level of membranes) for developing new computers inspired from biological systems, as for example, Membrane computing. Membrane computing belongs to computer science aiming to abstract computing ideas, paradigms and models from the structure and functioning of the living cells (either microorganisms or macroorganisms), the greatest promise of biological computers being that they can operate in biochemical environments.[36]. The interplay between Biology, Microbiology in particular, and nanotechnology will have very strong and fruitful impact on other topics such as nanoelectronics and DNA-based bionano-technology , biomimetics, biotemplating, and de novo-designed structures, bionanoarrays, tissue engineering and regenerative medicine.[19],[37]-[41].

VI. REFERENCES

1. Gould S.J., “Planet of the bacteria”, Washington Post Horizon, vol. 119, 1996, pp. 344

2. Schaechter M., “Integrative microbiology — the third Golden Age”, J. Biosci 28, 2003, pp. 149-154

3. Zarnea G., “Microorganismele un exerciţiu de admiratie. Prezentare orala Şcoala de vara - Realizări şi perspective în Biologie”, Piteşti, 2001, 3-8 septembrie.

4. Woese C.R., “A New Biology for a New Century”, Microbiol. Mol. Biol. Rev. 2, 2004, pp. 173–186

5. Nussinov R., Aleman S., “Nanobiology: from physics and engineering to biology”, Phys. Biol. 3, 2006

6. Feynman R., “There’s Plenty of room at the bottom: An invitation to enter a new field of physics”, Engineering and Science, Feb. 1960

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7. Alsteens D., Etienne D., et al ”Nanomicrobiology”

Nanoscale Res. Lett. 2, 2007, pp. 365–372 8. Botnariuc N., “Concepţia şi metoda sistemică în

biologia generală” Ed. Acad. RSR, 1976 9. Woese C.R., Kandler O., Wheelis L., “Towards a

natural system of organisms: proposal for the domains Archaea, Bacteria and Eucarya” Proc. Nat. Acad. Sci. USA 87, 1990, pp. 4576-4579

10. Zarnea G., “Tratat de Microbiologie Generala” vol. I., Ed. Acad. Rom. 1983

11. Bîlbîie V., Pozsgi N., “Bacteriologie Medicală“, vol I., 1984

12. Bîlbîie, V., Pozsgi, N., “Bacteriologie Medicală“, vol. II., 1985

13. Buiuc D., Neguţ M., “Tratat de microbiologie clinică“, Ed. II, Editura Medicală, Bucureşti, 2008

14. Zarnea G., “Tratat de Microbiologie Generala“, vol. II., Ed. Acad. Rom, 1984

15. Zarnea G., “Tratat de Microbiologie Generala“, vol. III., Ed. Acad. Rom, 1986

16. Zarnea G., “Tratat de Microbiologie Generala“, vol. V., Ed. Acad. Rom, 1994

17. Zhang L., Abbott J.J., Dong L., Kratochvil B.E., Bell

D., Nelson B.J., “Artificial bacterial flagella: Fabrication and magnetic control” Appl. Phys. Lett. 94, 064107 2009,

18. Drexler K.E., “Engines of Creation”, 1986 19. Rocco M.C., “Nanotechnology: convergence with

modern biology and medicine” Current Opinion in Biotechnology 14, 2003, pp. 337-34Sara M., Pum D., Schuster B., Sleytr U.B., “S-layers as patterning elements for application in nanobiotechnology”, J Nanosci Nanotechnol 5, 2005, pp. 1939-1953

21. Delcea M., Krastev R., Gutberlet T., Pum D., Sleytr U.B., Toca-Herrera J.L., “Thermal stability, mechanical properties and water content of bacterial protein layers recrystallized on polyelectrolyte multilayers” Soft Matter 4, 2008, pp. 1414-1421

22. Delcea M., Madaboosi N., Yashchenok A. M., Subedi P., Volodkin D.V., De Geest B.G., Möhwald H., Skirtach A.G., “Anisotropic multicompartment micro - and nano – capsules produced via embedding into biocompatible PLL/HA films”, Chem Commun 47 (7) 2011, pp. 2098-100

23. Ardelean I., Moisescu C., Ignat M., Constantin M., Virgolici M., “Magnetospirillum gryphiswaldense: fundamentals and applications”, Biotechnol. & Biotechnol. Eq., 23 (2), 2009, pp. 751-754

24. Ardelean I., Ignat M., Moisescu C., “Magnetotactic Bacteria and Their Significance for P Systems and Nanoactuators”, In Proceedings of the Fifth Brainstorming Week on Membrane Computing, Sevilla, Spain, ISBN 978-84-611-6766-0 2007, pp. 21-32

25. Logofatu P.C., Ardelean I., Apostol D., Iordache I., Bojan M., Moisescu C., Ionita B., “Determination of the magnetic moment and geometrical dimensions of the magnetotactic bacteria using an optical scatteringmethods”, J. Appl. Phys. 103, 2008, pp. 094911 – 094916

26. Moisescu C., Bonneville S., Tobler D., Ardelean I., and Benning L.G., “Controlled biomineralization of magnetite (Fe3O4) by Magnetospirillum gryphiswaldense”, Mineralogical Magazine, 72, 1, 2008, pp. 333–336

27. Igant, M., Zarnescu G., Soldan S., Ardelean I., Moisescu C., “Magneto-mechanic model of the magnetotactic bacteria. Applications in the microacuator field”, Journal of Optoelectronics and advanced materials 9, 4, 2007, pp. 1169-1171

28. Ignat M., Ardelean. I., “Distinct nano-biological structure: magnetotactic bacteria. Models and applications in the electromechanical nano-actuation”, Romanian Journal of Physics, vol. 49, nr.10-11, 2004, pp. 835-848

29. Staniland S, Moisescu C, Benning LG. 2010. Cell division in magnetotactic bacteria splits magnetosome chain in half. J. Basic Microbiol. 50: 1-5

30. Moisescu, C., Bonneville S.,, Staniland, , Ardelean, I. ,Benning, L.G., “Iron uptake kinetics and magnetosome formation by Magnetospirillum gryphiswaldense as a function of pH, temperature and dissolved iron availability”, Geomicrobiology Journal, 2011, in press

31. Martel S., Tremblay C., Ngakeng S., Langlois G., „Controlled manipulation and actuation of micro-objects with magnetotactic bacteria”, Appl Phys Lett 89, 2006, pp. 233804–233806

32. Kim D.H., Kei U. et al., „Artificial magnetotactic motion control of Tetrahymena pyriformis using ferromagnetic nanoparticles: A tool for fabrication of microbiorobots”, Appl. Phys. Lett. 97, 2010, pp. 173702

33. Cheng M.M, Cuda G., Bunimovich Y.L., „Nanotechnologies for biomolecular detection and medical diagnostics”, Curr Opin Chem Biol 10, 2006, pp. 11–19.

34. Damian V., Ardelean I., Armăşelu A., Apostol D., „Fourier transform spectra of quantum dots. Proceedings of the SPIE, Volume 7469, 2010 Nanophotonics and Quantum Optics pp. 74690E-74690E-6,

35. Văcăroiu C., Enache M., Gartner M., Popescu G., Anastasescu M., Brezeanu A., Todorova N., Giannakopoulou T., Trapalis C., Dumitru L., “The effect of thermal treatment on antibacterial properties of nanostructured TiO2(N) films illuminated with visible light”, World J. Microbiol. Biotechnol. 25 (1), 2009, pp. 27-31

36. Gh. Paun, Membrane Computing. An Introduction, Springer-Verlag, Berlin, 2002 (420 + xii pages

37. Dorobantu L.S., Bhattacharjee S., Foght J.M., Gray M.R., “Atomic force microscopy measurement of heterogeneity in bacterial surface hydrophobicity”, Langmuir 24, 2008, pp. 4944- 4951

38. Dufrene Y.F., “Using nanotechniques to explore microbial surfaces”, Nat Rev Microbiol. 2, 2004, pp. 451–460

39. Fortina P., Kricka L.J., Surrey S., Grodzinski P., “Nanobiotechnology: the promise and reality of new approaches to molecular recognition”, Trends. Biotechnol. 23, 2005, pp. 168–173

40. Kricka L.J, Park J.Y., Li S.F., Fortina P., “Miniaturized detection technology in molecular diagnostics”, Expert. Rev. Mol. Diagn. 5, 2005, pp. 549–559

41. Ignat M., Ardelean I., Zărnescu G., Soltan S., “Actionări electromecanice neconvenţionale”. Ed. Electra 200, 2006,

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VII. BIOGRAPHIES Ioan I. Ardelean born in Arad on March 10, 1957. He

graduated in 1981 and he received Ph.D. degree in General Microbiology and Immunology from Institute of Biology Bucharest, Romanian Academy in 1997.

He is Senior researcher 1 at the Institute of Biology Bucharest, Romanian Academy and Professor at the University Ovidius Constanta.

The research preoccupation include: cyanobacteria and magnetotactic bacteria, marine microbiology, biotechnology and nanobiotechnologies. He is member of Romanian Society of Biochemical and Molecular Biology.

In 2000 he received “Emil Racovitză” Prize of the Romanina Academy and in 2011 Albert Einstein Award of Excellence ( American Biographical Institute)

21

Abstract - A polymer composite material containing pyrite ash powder dispersed into a polyetherimide matrix was used for an planar electrostrictive actuator. The paper presents the synthesis of this polymer, the structure of the microelectro-mechanical actuator, the specific experiments and the theoretical aspects.

Index Terms - magnetostriction, magnetostrictive rod, magnetizing coil, magnetic circuit, magnetostrictive microactuator

I. INTRODUCTION The development of new technologies has

generated an increasing demand for the preparation of new materials with special properties. Polymer composites based on metal oxides are known as alternative materials for a wide area of applications due to the good combination of the properties induced by the metal presence with those of polymers, especially their easy processability. There is currently much research directed towards the synthesis of new materials to be used in the fabrication of microsensors, microactuators and microelectro-mechanical components [1]. More attention has been paid to the preparation of different kinds of magnetic polymeric composites because of their potential application in various fields [2-4].

Aromatic polyimides are a class of high-temperature polymers that are widely used in microelectronics and microelectromechanical systems (MEMS) due to their excellent thermal, mechanical and electrical properties, high breakdown voltage, good planarization, low thermal expansion, good adhesion, chemical and radiation resistance [5, 6].

In this paper, an electromechanical microactuator based on a composite polymer membrane was obtained. Nanometric displacements were measured under applying an electric field. The composite material was prepared from pyrite ash powder dispersed into a polyetherimide matrix. The polymer was synthesized by solution polycondensation reaction of 4-[bis(4-aminophenyl)amino]benzonitrile with a bis(ether anhydride), namely 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride.

Nanometric displacements were measured under applying an electric field.

II. BASIC MATERIAL CHARACTERISTICS II. 1. SYNTHESIS OF THE MONOMERS

4-[Bis(4-aminophenyl)amino]benzonitrile 1 was obtained by the hydrogenation using hydrazine hydrate and a catalytic amount of Pd/C of the corresponding dinitro-compound resulting from the reaction of 4-aminobenzonitrile and 1-fluoro-4-nitrobenzene [8]. Mp: 228-230°C. IR (KBr, cm-1): 3407, 3329 (NH2), 2222 (CN). 1H NMR (DMSO-d6, ppm): 7.3 (2H, d), 6,65 (2H, d), 6,5 (4H, m), 5.1 (NH2).

2,2-Bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride 2 was provided from Aldrich and used as received.

II. 2. SYNTHESIS OF THE MONOMERS An aromatic polyimide 3 was prepared by

solution polycondensation reaction of equimolar amounts of aromatic diamine 1 and bis(ether anhydride) 2, in N-methyl-2-pyrrolidone (NMP) as solvent (Scheme of Fig.1), [12].

N

C N

NH2 N H2

N

C N

NH

NH

O C O

H O O C

n

O CN

O C

O

C ON

C OO

N

C N

n

C OO

C O O HC H 3

C H 3

O

C OO

C OOO CO

O C C H3

C H3

C H 3

C H 3

+

N M P

3 '

3

2

1

Fig. 1. Preparation of polyimide 3

II. 3. Preparation of polymer films Polyimide films were prepared by casting a

solution of 5% concentration of polymer in chloroform onto glass plates, followed by drying at room temperature for 24 h under a Petri dish and for another 2 h at 130°C [13]. The resulting flexible transparent films were stripped off the plates by immersion in hot water for 2 h.

Electromechanical microactuator based on aromatic polyetherimide and pyrite ash powder

*Mircea Ignat, *George Zarnescu, **Elena Hamciuc, **Cornel Hamciuc Research and Development National Institute of Electrical Engineering (INCDIE ICPE-CA), Splaiul

Unirii, No. 313, District 3, 030138, Bucharest, Romania, *mignat@icpe-ca.ro **Petru Poni Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda, 41 A, Iasi,

700487, Romania

22

Using the same procedure a composite polymer film was prepared by casting a 5% dispersion of polymer 3 and pyrite ash powder in chloroform. The quantity of pyrite ash was calculated to be 20% in the composite material. Pyrite ash was obtained like wastes from burning of pyrite ores to produce sulfuric acid. The granulometric distribution of pyrite ash particles, performed with vibrating sieves, was in the range of 140 m.

Melting points of the monomers and intermediates were measured on a Melt-Temp II (Laboratory Devices). The inherent viscosity (inh) of the polymer was determined with an Ubbelohde viscometer, by using polymer solution in NMP, at 20°C, at a concentration of 0.5 g/dL. Infrared spectra were recorded with a Specord M80 spectrometer by using KBr pellets. 1H-NMR spectra were recorded on a Bruker Avance DRXx400, at room temperature, by using solutions in deuterated chloroform (CDCl3) or dimethyl sulfoxide (DMSO-d6). Measurements of molecular weights were performed by gel permeation chromatography with a PL-EMD 950 evaporative mass detector instrument. Heat flow vs. temperature scans from the second heating run were plotted and used for reporting the glass transition temperature. The mid-point of the inflexion curve resulting from the typical second heating was assigned as the glass transition temperature of the respective polymers.

Thermogravimetric analysis (TGA) was performed on a MOM derivatograph (Hungary) in air, at a heating rate of 10°C/min. The initial decomposition temperature (IDT) is characterized as the temperature at which the sample achieves a 5% weight loss. The temperature of 10% weight loss (T10) was also recorded.

III. THE STRUCTURE OF THE MICROACTUATOR

Fig. 2 shows the structure of the planar composite polymer electrostrictive microactuator and fig. 3 ilustrate a photo of this microactuator.

On the glass support 1 is fixed a ramificated conductive structure (by nickel) 2 and on this structure is mounted the active composite polymer disks 3. The connection 4 assures the electric voltage supply.

Fig. 2. a) represents the lower support, fig. 2. b) a lateral view and fig. 2. c) the superior support 5.

The active composite polymer discs are mounted in parallel electric circuit. In fig. 3 is

presented the mounted microactuator configuration.

Fig. 2. The structure of the planar composite polymer microactuator.

Fig. 3. The mounted microactuator configuration

In fig. 4 is showed a photo of the

microactuator.

23

Fig. 4. The electrostrictive planar polymer microactuator

The diameter of the polymer discs are 4 mm

and the thickness of the membrane disc 0,12 mm. The thickness of the support (lower and superior) is 0,5 mm and the dimensions are 10x10 mm. The thickness of the conductive structure is 0,1mm.

The pyrite ash particles can influence the membrane microroughness as resulted from the surface roughness measurement of the composite polymer film taken by optical profilometry. The films surface (an aromatic polyimide 3) was analyzed with an optical interferometric microscope (VEECO NT 1100 Profilometer), which is an optical interferometric microscope based on Mirau interferometry [11].

An image of the pyrite ash powder is presented in fig. 5 and the roughness diagram of the membrane surface is presented in fig. 6.

Fig. 5. An image of the polyimide polymer with pyrite ash powder.

The performance of NT 1100 interferometric profiler: Vertical Resolution: < 1Angstrom.

Vertical Measurement Range: 0,1nm to 1mm.

RMS Repeatability: 0,01nm.

Vertical Scan Speed: up 7,2 .sec/m

The main specific parameters of the surface roughness analysis are [11]: Rt - the height difference between the highest point and the lowest point in the region. Rp - the highest point in the region relative to the zero level. Rv - the lowest point in the region relative to the zero level. Ra - average roughness as calculated over the entire region. Rq - mean root squared roughness calculated over the entire region.

Fig. 6. The roughness of a polyimide membrane with the VEECO NT 1100 microscope

In Tab.1 are presented the main specific

parameters of a polyimide polymer membrane. Tab. 1. The main roughness parameters.

Rt m

Rp m

Rv m

Ra m

Rq m Profil

5,48 3,38 -2,11 1,39 1,45 X 5,81 2,99 -2,82 1,12 1,42 Y

In fig. 5 are showed the two pyrite end

nanoparticles on the surface of polyimide film and this discontinuities achieve an important effect of the electric and mechanic microcontacts and have the

24

major contribution to the parameters of the surface roughness.

IV. THE CALCULATION PARAMETERS OF ACTUATORS

The linear micro and nanodisplacement of polymeric membranes was determined using an experimental setup for linear measurements, based on a Michelson type interferometer using AGILENT 5529A system [9, 10].

The polymer films were analysed in order to obtain nanometric displacements, when an electric voltage is applied on their surface. The nanoactuation of polymer films was determined using an interferometric AGILENT 5529A system, an instrument dedicated to investigate and measuring the linear micro and nanodisplacement with a resolution of 1 nm (see fig. 7).

Fig. 7. Experimental method for membrane nanodisplacement determination with an

AGILENT interferometer (5529/55292A system).

For membrane nanoactuation determination was used an AGILENT interferometer with the mounting of the fig. 7 which include: 1 - laser head; 2 - interferometer assembly; 3, 10 - retroreflector mounted on a height adjuster with a base and post; 4 - support electrode with disc geometry; 5 - isolated support; 6 - supply cable; 7 - polimeric membrane; 8 - laser beam; 9’ - reflected laser trajectory; 9 - reflected laser trajectory.

The retroreflector is mounting in contact with the superior support of microactuator.

In fig. 8 is presented two nanoactuation with aproximate 30nm and 4sec. respective 5sec. are the temporarily floors.

Fig. 8. The electromechanical actuation of a polyimide membrane actuator to 10Vdc

On the microactuation diagram is distinguished

a depolarization phenomenon which is indicated in fig. 8.

It is a progressive phenomenon which has an effect of negative nanodisplacement. By two switching the value is ~ - 100nm.

The behaviour of the microactuator in switching on - switching out successive state to 10 Vdc is presented in fig. 9.

It is noticed that the amplitude of electromechanical actuation lowers at each switching: in the presented experiment from 300nm to approximate 150 nm., also the time of switching on (tc1) or the time of switching out (td1) lowers. (We consider the switching on state the time necessary to touch the amplitude of microactuation).

It is presented in a comparative manner the switching state:

tc1~12 s > tc2~ 7s; td1~ 30s > td2~ 14 s.

It is interesting that the amplitude diminuation is

linear by the time. The microdisplacement performance of the

polyimide membrane to breakdown is showed in fig. 10.

The breakdown is produced 10Vdc voltage at a uniform electric field and the approximate level of the displacement (membrane contraction) is - 4000 nm. Because of the breakdown effect the final dimension (thickness) of the membrane remains stable (to see the the diagram of microdiplacement, fig. 10).

For aromatic polyimide 3 membrane, the breakdown was favourised by the presence of grains of pyrite ash powder.

The experiments which are presented in fig. 8, 9, 10 was realized to a force of 2,2 N.

25

Fig.9. The electromechanical actuation of a polyimide membrane actuator to 10 Vdc

Fig. 10. The electromechanical breakdown actuation of a polyimide membrane actuator to 10Vdc

V. THEORETICAL ASPECTS An attempt to model the polyimide membrane actuation is presented in fig. 11.

Fig. 11. The model of polymide actuator

The governing equation for microactuation system follows directly from Newton’s second law [13]:

dse FFFdt

udm 2

2

(1)

where: m - mass, u - displacement, sF - the spring force, dF - the damping force, eF - the electrostrictive force [12].

dtdukFs (2)

dtducFd

(3)

with: k - spring ratio, c - damped ratio.

20 0

2

12

re

S UUFd d

(4)

with U - the voltage, 0 - the permittivity of free space, r - the relative permittivity, w - the width of the active polymide membrane, l - the length, d - the thickness of membrane.

Where the energy associated:

22 0 01

2 2r

aS UE CUd

(5)

with C - the capacitance of the membrane, 0S - the section of the membrane.

tc1 td1 tc2

26

Thus, the functional equation of this microactuator type in condition of DC voltage is:

2

200

2

2

21

dUS

kudtduc

dtudm r

(6)

which represents an in- homogenous equation [14,

15] and by division with m , becomes

mKu

mk

dtdu

mc

dtud 12

2

(7) where

2

200

1 21

dUS

K r (8)

The characteristics equation is [14, 15]:

02 mkr

mcr (9)

with the solutions:

)141(21

ck

mcr (10)

)141(22

ck

mcr (11)

Taking into account the condition necessary to

have real solutions

041 ck

(12)

or

41

ck

(13)

The homogenous part of equation (6) has the

solution:

trtr eCeCu 2121 (14)

and the particularly solution (inhomogeneous equation) is

BtmKAu 1

0 (15)

and

mKA

dtdu 10 , 02

02

dt

ud (16)

Ec 16 is introduced in the equation (7):

mKBt

mKA

mk

mcKA 11

21 )( (17)

To determinate the ratio A and B it is

identified:

021

121

Am

kKmK

BmkA

mcK

(18)

with: k

KBA 1,0 .

The solutions become:

particular solution:

kKu 1

0 (19)

and general solution:

kKeCeCu c

kmc

ck

mc

1)141(

22

)141(2

1

(20)

The microactuator membrane can be

assimilated with a heterogeneous mixture [16, 17] dielectric which include polyimide, pyrite ash powder and air cavities.

Fig. 12. A simple model a composite polyimide/magnetic powder membrane

A simple model is presented in fig. 12. The equivalent capacitive model includes pC -

polyimide capacitor, mpC - pyrite ash powder capacitor, aC - air cavities capacitor.

27

amppeq CCCC (21) or

memec

aampmpppaoampomppop

eq

Sg

SSSgg

SgS

gS

C

0

0

(22)

with

aampmpppmemech SSSS (23)

And the equivalent permittivity:

mem

aampmpppech S

SSS

(24)

It is considered:

mem

aa

mem

mpmp

mem

pp S

SkSS

kSS

k ,,

(25)

results:

aampmpppech SSS (26) with [1] relation:

1 ampp kkk (27) where ratios: ampp kkk ,, are proportional with the polyimide, pyrite powder and air volumes (in the our case: 1,0,2,0,7,0 ampp kkk ).

On the model we consider that:

- the capacitors are plans; - o - permittivity of free space

( 128,854 10 /F m ), p - the polyimide permittivity, mp - magnetic powder permittivity, a - permittivity air cavity;

- the conductivity and dielectric losses may be neglected;

- it is a constant thickness (g); - we assumed:

amppmem SSSS (28)

where: memS - the area of the membrane; mpS - the area of the pyrite ash powder; aS - the area of the air insertion.

If is considered the series model, see in fig. 13.

Fig. 13. The series model

In this case the essential relation is:

amppeq CCCC1111

(29)

The electric field in a heterogeneous dielectrics. It is assuming that :

- the conductivity and dielectric losses may

be neglected; - the intensity of the electric field ( E ) to

each point of a membrane does not generally depend on the value of the permittivity.

We consider the parallel model (see fig. 12)

with the relations between the electric field intensities in each domain (p - polyimide, mp - pyrite ash powder, a - air).

EEEE ampp (30)

gUE

(31)

gEgEgEU ampp (32) with the ampp gggg (for parallel model), (U - the voltage whis is applied the surfaces of membranes, g - the thichness).

And relation on the electric inductions:

28

EDEDED aoampomppop ,, (33)

For series model (see fig. 13):

aaompmpopp EEED 0 (34)

p mp a p p mp mp a aU U U U E g E g E g (35)

Result:

amppmppapamp

ampp ggg

UE

(36)

amppmppapamp

apmp ggg

UE

(37)

amppmppapamp

pmpa ggg

UE

(38)

The nano and microactuations appear because

the electrostriction forces [1, 2]:

2ppop EF (39)

2mpmpomp EF (40)

2aaoa EF (41)

VI. CONCLUSION An aromatic polyimide containing nitrile

groups 3 was prepared from the diamine 1 and bis(ether anhydride) 2 by a conventional two stage process, as shown in scheme 1. The first step took place at room temperature in an aprotic polar solvent such as NMP at a concentration of 10-15% solids.

The structure of the polymer was identified by IR and 1H NMR spectroscopy. In the IR spectrum of the polymer the strong bands appearing at 1780, 1720, 1375 and 740 cm-1 were attributed to imide rings.

The flexible and tough polymer films were obtained by casting the polymer solution in chloroform followed by the evaporation of solvent under controlled conditions. Also, a flexible and tough composite polymer film containing 20% pyrite ash was prepared under the same conditions, by casting a 5% dispersion of polymer 3 and pyrite ash in chloroform.

The polymer films were analysed in order to obtain nanometric displacements, when an electric voltage is applied on their surface.

It was realised a microelectrostrictive actuator based on this polymer (see fig. 2, fig. 3 and fig. 4).

The micro and nanoactuation of this microactuator was determined using an interferometric AGILENT 5529A system, an instrument dedicated to investigate and measuring the linear micro and nanodisplacement with a remarkable resolution of 2 nm (see fig. 7).

The pyrite ash particles can influence the membrane micro roughness as resulted from the surface roughness measurement of the composite polymer film taken by optical profilometry. The films surface was analyzed with an optical interferometric microscope (VEECO NT 1100 Profilometer).

The composite polymer film actuation behavior to an electric DC field with a voltage of 10V, with flexible thin electrodes, was investigated.

The nanodisplacement field was of 300 - 400 nm to a force of 2.2 N. This result represents a very distinct parameter for Microelectro-Mechanical Systems (MEMS) or Nanoelectro-Mechanical Systems (NEMS) applications. The initial polymer film 3a, not containing pyrite ash, did not show displacement under the conditions of this experiment.

It was identified in the research study a new actuation type: the electric breakdown actuation.

Was presented same theoretical aspect on the specific microactuator equation and the method to calculate the specific electrostrictive microactuation force of composite membrane.

VII. References [1] Wilson SA, Jourdain RPJ, Zhang Q, Dorey RA, Et al., New materials for micro-scale sensors and actuators. An engineering review. Materials Science and Engineering, R 56, 2007, 1-129. [2] Lagorce LK, Allen MG. Magnetic and mechanical properties of micromachined strontium ferrite/polyimide composites. IEEE J. Microelectromech. Syst. 6, 1997, 307-312. [3] Farshad M, Clemens F, Le Roux M. Magnetoactive polymer composite fibers and fabrics – processing and mechanical characterization. Journal of Thermoplastic Composite Materials, 20, 2007, 65-74. [4] Zhan J, Tian G, Jiang L, Wu Z, Wu D, Yang X, Jin R. Superparamagnetic polyimide/g-Fe2O3 nanocomposite films: preparation and characterization. Thin Solid Films, 516, 2008, 6315-6320. [5] Sroog CE. Polyimides. Prog. Polym. Sci., 16, 1991, 561– 694. [6] Mittal, K.L., Ed., Polyimides and other high temperature polymers: synthesis, characterization and applications. VSP, Boston, 2003. [7] Li L, Kikuchi R, Kakimoto MA, Jikei M, Takahashi A. “Synthesis and characterization of new polyimides

29

containing nitrile groups”. High Perform. Polym., 17, 2005, 135–47. [8] Hamciuc C, Hamciuc E, Ignat M, Zarnescu G.” Aromatic poly-(ether imide)s containing nitrile groups”. High Perform. Polym., 21, 2009,pp. 205-218. [9] AGILENT 5529A/55292A Measurements Reference Guide, Agilent Technologies. [10] Ignat, M., Zarnescu, G., Hamciuc, E. and Cazacu, M. “Interferometric Measurement Method for Nanoactuation of Polymeric Membranes”. The 4th International Workshop on Nanoscience and Nanotechnologies, Thessaloniky 16-18 July, 2007, Abstract Book, p. 188. [11] VEECO NT 1100 Profilometer. Advanced Analysis Package. User Guide. [12] T.R.Hsu,”MEMSandMicrosystems. Design, manufacture and nanoscale engineering”,John Wiley &Sons,inc.New Jersey,2008. [13] J.A.Pelesko,D.H.Bernstein,”Modeling MEMS and NEMS”, Chapman Hall/CRC Press Company, London,New York, 2003. [14] M.Rosculet ,”Analiza matematica”,vol.II,Ed.Didactica si Pedagogica , Bucuresti,1966. [15] N.Piskounov, “Calcul differentiel ei integral”, Ed.MIR, Moscou, 1970 [16] B.Tareev, “ Physics of dielectric materials “, Mir Publishers, Moscow,1975. [17] T.R.Hsu, “MEMS and Microsystems. Design Manufacture and Nanoscale Engineering”,JohnWiley &sons,Inc.,Second Editition, 2008.

VI. BIOGRAPHIES Mircea Ignat was born in Bucharest on March 4th ,

1953. He graduated in 1977 and received Ph.D. degree in electrical engineering from Bucharest Politehnica University in 1999.

His employment experience included the National Research Electrical Engineering Institute, Dep. of Electrical Micromachines in present being the head of Electromechanics Department.

The research preoccupation include: the syncrone generators and the high speed electric machines. Is member of IEEE.

Elena Hamciuc was born in Tutora-Iasi on May 10th ,

1957. She graduated in 1982 and received Ph.D. degree in chemistry from “Gh. Asachi” Polytechnic Institute Iasi in 1996.

Her employment experience included the “Petru Poni” Institute of Macromolecular Chemistry, Department of Polycondensation.

The research preoccupation include: materials based on thermostable heterocyclic polymers and polymer composites.

Corneliu Hamciuc was born in Ruginoasa-Iasi on June 07, 1957. He graduated in 1982 and received Ph.D. degrees in chemistry from “Petru Poni” Institute of Macromolecular Chemistry of Iasi in 1996. His employment experience included the “Petru Poni” Institute of Macromolecular Chemistry, Department of Polycondensation.

The research preoccupation include: flame-retardant polymer materials, thermostable polymers, and polymer composites.

30

Abstract - This paper presents the design of a linear piezoelectric inchworm motor and the results of a test concerning the force output. The motor is able to hold the position even when power fails, due to the fact that the shaft is normally locked by two clamping systems. Because of its structure, the motor exhibits ~70N capable force when moving and roughly twice that when stopped. The stroke of the motor is 20mm and the step size is controllable between 0...20µm.

Index Terms - inchworm, linear, motor, piezoelectric.

I. INTRODUCTION Many applications require precise positioning

while maintaining large strokes. Common (mechanical) positioning systems provide large strokes but fail to offer high precision.

One way to solve this problem is the use of special components, such as piezoelectric stacks that have small controllable strokes. In order to expand stroke more complex structures are required such as piezoelectric motors.

The linear motor presented in this paper [1] is of inchworm [2] type, consisting of two clamps (a mobile and a stationary one) and a shaft that is moved through the center of the motor by a specific set of commands applied to three piezoelectric stacks.

II. MOTOR STRUCTURE AND WORKING PRINCIPLE

A. Motor structure The structure of the motor can be seen in figure

1 and is composed of a shaft (1) concentric to the motor shell (2), a stationary clamping system - consisting of a clamp (3), cone (4), disc-spring stack (5), spacer (9), special conical nut (8), spherical washer (7) and piezoelectric stack (6) - , a mobile clamping system housed inside a cup (10) covered by a lid (11). The mobile clamping system can be pushed by another piezoelectric stack (12) against a disc-spring stack (13).

Fig. 1. CAD section through the linear

piezoelectric motor

B. Motor command The movement of the shaft is achieved

controlling the supply voltage of each of the three piezoelectric stacks, as seen in figure 2.

Fig. 2. Supply voltage phase order that results in

one step When the motor is supplied the piezoelectric

stacks extend and open the clamps or push the mobile clamping system and achieve one step of proportional length to the voltage level of the advance piezoelectric stack (12). In order to move the shaft in the opposite orientation, phase order must be reverted.

The step size is in the range of 0...20µm (depending on the maximum level of voltage applied) and when added up, a motor stroke of 20mm can be achieved.

C. Clamping system The most important part of the clamping

system is the clamp and the shaft assembly. An estimation of the factor of safety by Finite Element Method for these components is shown in figure 3 and a representation of the forces in figure 4. Fa is the puling force of the spring stack, Ff1, Ff2, Ff3 - friction forces between clamp, cone

Experimental and Theoretical Aspects on a Piezoelectric Linear Micromotor

Ovezea Dragoş Universitatea Politehnica din Bucureşti, Splaiul Independenţei, No. 313, 060042, Bucharest,

Romania, ovezeadragos@gmail.com

31

and shaft, µ1 - friction coefficient between clamp and cone, µ2 - friction coefficient between clamp and shaft, N1, N2, N3 - normal reaction forces, α - inclination angle of the clamp and cone.

When solving the equilibrium problem of the system of forces, the Ff3 force (pushing or pulling force of the motor) can be calculated as shown in equation (1).

Fig. 3. Estimation of the factor of safety for the

clamping system

Fig. 4. Simplified representation of the clamp-

shaft system and of the local forces

2 13

1 2 2

sin cos1 sin 2 cosaFf F

(1) When the motor is loaded, the load ( loadF ) is

added or subtracted from aF according to its orientation. Equation (1) becomes (2):

2 1

31 2 2

sin cos( )

1 sin 2 cosa loadFf F F

(2)

Defining:

2 1

1 2 2

sin cos1 sin 2 cos

k

(3)

and because 3 loadFf F , the equation becomes for each case:

( )load a loadF F F k (4) ( )load a loadF F F k (5)

and loadF can be calculated using (6) for the case where aF and loadF have the same orientation and with (7) if different.

1load akF F

k

(6)

1load akF F

k (7)

For the constructed prototype, α=45° and the

friction coefficients were estimated as µ1=µ2=0.15 resulting in:

0.110871load a a

kF F Fk

(8)

0.090751load a a

kF F Fk

(9)

The force of the sprig stacks of the prototype

(that are closing the clamps) is 702aF N and the resulting forces are:

77.83loadF N (10) 63.70loadF N (11)

14.13load load loadF F F N (12)

III. THE EXPERIMENTAL SETUP In order to measure the motor's capable force

an experimental setup was devised. As shown in figure 5, the experimental setup consists of a special stand (1) on which sits an aluminum board (2) that supports the motor (3) and a pulley (5), a steel wire (4) connects the motor and the clamp (6) of a force sensor (7). The force sensor is of IMADA type and has a RS232 interface. In order to measure the force output of the motor a special program was written in LabView (figure 6) which allowed to independently set the voltage of the three piezoelectric stacks while

32

continuously reading the force values at the serial port. When the desired voltage values combination was set (and thus a certain phase or piezoelectric stack displacement was achieved), a crank was manually turned and the force sensor (7) pulled the motor's shaft until it started to move. The recorded force expressed the motor's capable force with the shaft held by one or two clamps.

Fig. 5. Experimental setup for the measurement

of the motor's force output

Fig. 6. The program used to record the force

output of the motor

IV. EXPERIMENTAL RESULTS AND THEIR INTERPRETATION

Several tests were performed in order to determine the force of each clamping system, when the resistant force was either aiding or working against the disc-spring stacks and when both clamping systems were closed.

When tested, the system has shown irregular clamping forces due to both stick and slip phenomena and microscopic variations in the shaft's diameter and roughness. This can be observed in figure 7 where stick and slip is visible

near force sample at index 25, followed by irregular variations in force.

Fig. 7. Retention force of the motor when both

clamping systems are closed The roughness of the motor's shaft is shown in

figure 8 as transversal striations, most likely present due to fabrication process.

Fig. 8. Close-up picture of the motor's shaft

showing irregularities on it's surface In figure 9 is presented the force variation for

both clamping systems, and for two pulling directions. Mobile clamping system was designated "IM" and fixed clamping system "IF". The four curves show the similar behavior of the clamping systems. When the voltage supplied to the piezoelectric stacks is increasing, their expansion pushes the nut, washer and spacer assembly and compresses the disc-spring stacks. This lowers the force pulling the clamps inside the cones and thus frees the shaft proportionally to the voltage applied.

In order to build the graphical representation in figure 9, only the smallest values of the force were considered as viable data. This allows for minimal retention force estimation and because the irregularities are intrinsic to the motor and

33

thus repeatable, a viable force characteristic could be extracted.

As seen in figure 9, there is a difference between the cases when the pulling force has the same orientation as aF and when not.

Fig. 9. Clamps retention force for multiple

directions of pull The measured maximum clamping forces for

different orientations of the load are 77N and 69N producing the difference:

77 69 8loadF N N N

The measured forces are very close to the

expected values and the effect of the load is smaller than anticipated, only 8N instead of 14N. This fortunate occurrence is caused by the fact that in reality, although of close value, µ1 is not equal to µ2.

The equations form a very good model of the clamping system and are suitable to be used for the design optimization of the motor.

V. CONCLUSIONS The tests have shown that the motor's capable

force is similar to the force estimated by calculus. Although the force exhibited by the motor does not have a very linear characteristic, the fact that is repeatable and it has an estimable minimum force makes the motor suitable for commercial applications.

In order to improve performance, better manufacturing processes will be needed in order to improve the shaft's shape and roughness.

As seen in equation 1, the motor's capable force depends mainly on three factors: the force of the spring stack, the angle of the clamp and the friction coefficients. While friction coefficients depend mainly on the components manufacturing quality, the other parameters can be easily modified by design in order to achieve larger forces.

VI. ACKNOWLEDGMENT The prototype motor was funded through a

research project called MINIROBNANOTEH.

VII. REFERENCES [1] „Motor piezoelectric liniar, cu forţă activă în stare normală” – Alexandrescu Nicolae, Ovezea Dragoş, Comeagă Constantin Daniel, , Apostolescu Tudor Cătălin, O.S.I.M., patent nr. 122943, 30.04.2010. [2] William G. May, "Piezoelectric electromechanical translation aparatus", United States Patent 3.902.084, Aug. 26, 1975.

VIII. BIOGRAPHY Ovezea Dragoş was born in Bucharest on November 26,

1979. He graduated in 2005 and is currently a Ph.D. student in mechatronics at the Politehnica University of Bucharest.

His employment experience include several research and development projects at Politehnica University of Bucharest's Center for Research and Development for Mechatornics (CCDM).

The research preoccupations include piezoelectric and electric actuations, electric circuit and PCB design, CAD.

Abstract - An essential reason for the increasing interest in magnetostrictive materials is the capability to perform simultaneous sensing and actuation due to inherent sensorial capability of the material. Thus, miniaturized, simpler and cheaper systems are favorite.

The main objective of this paper is to present some design aspects which are of interest in magnetostrictive microactuators such as: structure, magnetic circuit and electromagnetic parameters of coil.

Index Terms - magnetostriction, magnetostrictive rod, magnetizing coil, magnetic circuit, magnetostrictive microactuator.

I. INTRODUCTION There has been a steady trend toward

minaturization, [8]. The effect of scaling is to reduce the power requirements of a device as well as increasing the speed of response and resistance to body forces such as selfweight. A microactuator can be defined as a miniaturized actuator for a miniaturized system. When an actuation mechanism has choosing many aspects must be taken into account such as: piezoelectric, electrostatic, electromagnetic, and magnetostrictive effects, [5].

Magnetostriction is a transduction process in which an electrical energy is converted into a mechanical energy, [6].

The paper presents a magnetostrictive microactuator with applications in mechanical vibrations.

Another potential technology is piezoelectric microactuators. The ratio between magnetic ( mw ) and electric ( ew ) volume density justifies the choice of the magnetostrictive technology. At typical values 1B T and 30 /E kV cm the

ratio is 2

402

0

/ 10m

e

w Bw E

.

Moreover magnetostrictive microactuator has the ability to respond faster.

II. DESIGN ASPECTS OF THE MAGNETOSTRICTIVE

MICROACTUATOR The geometrical configuration of the magnetic

circuit of microactuator is presented in fig. 1. The equivalent scheme of the magnetic circuit is shown in fig. 2; a simplified scheme is obtained considering 0FR .

In fig. 2: rm- magnetostrictive rod, mp-permanent magnet, f-flange. The magnetostrictive rod is Terfenol-D.

Fig. 1. The geometrical configuration of the magnetic circuit.

Fig. 2. Equivalent scheme of magnetic circuit.

In the simplified scheme is considered only the magneto motive force generated by the permanent magnet:

0, 0mmM BU (1)

Design aspects for magnetostrictive microactuators

*Alexandru-Laurentiu Catanescu Research and Development National Institute of Electrical Engineering (INCDIE ICPE-CA),

Splaiul Unirii, No. 313, District 3, 030138, Bucharest, Romania, *catanescu@icpe-ca.ro

35

Kirchhoff”s laws lead to the equation

system:

T= S

T T S S

T T mM

R RR U

(2)

The material equations are:

mmM M M

M M M

T T mM

U H lk B A

R U

(3))

The results are:

[ / ]T OTM

M

RH A ml

(4))

(1 )[ ]TM OT

S

R WbR

(5))

[ ]MM

M

B Tk A

(6))

The geometrical configuration of the winding

is presented in Fig. 3.

Fig. 3. The geometrical configuration of magnetizing coil.

The induction in the centre of winding (in the

magnetostrictive rod core) is calculated with the relation, [1]:

1 1

1

1 1[ ][ ]2 ( 1)T

N IB sh sh Ta

(7))

By using the superposition principle (the

magnetic flux into the branch of the circuit is the algebric sum of the fluxes generated by the each magnetomotive forces), the magnetic flux into the terfenol rod is:

T OT TB B B (8))

III. COMMENTS ON THE STRUCTURE OF MAGNETOSTRICTIVE

MICROACTUATORS Fig.4 shows a typical structure for the

magnetostrictive microactuator; the model for calculating the electric and magnetic equivalent circuits is shown in fig. 4. Magnetostrictive microactuator performance can be expressed by the ratio of the main stream (corresponding reluctance of the terfenol bar) and leakage flux.

Fig. 4. Electric and magnetic equivalent circuits of the drive coil and flux return paths of a magnetostrictive

actuator, [4].

A magnetizing coil can be described by the

parameters, [4], 2

1

aa

, 12

cla

and 1

r

ar

,

where rr is the radius of the rod-shaped magnetostrictive material, 1a and 2a the inner and outer radius of the magnetizing coil, and cl the length of the driver coil. An estimate value of the generated H field inside the coil and the corresponding leakage inductance can then be derived if one assumes that the field penetrates a linear homogeneous soft magnetic material, see eqs. (9) and (10).

36

1

( 1)( , )( 1)coil coil coil

c

H G NIl a

(9)

22 2 2

0

1

( 1) ( 1)(( 1)

1 ( 1)( 3))6

leak coil rL G N r

a

(10)

Uniform penetration of the magnetic field

hypothesis is valid if the corresponding reluctance of return flux ( pathR ) is small compared with the corresponding reluctance of the leakage.

The fraction of the leakage inductance ,rel leakL do not contribute to the magnetostrictive effect (frequency independent) that determines the magnetization current for a given voltage can be written as:

2 2,

1 1(( 1) ( 1)( 3))6rel leak

r

L

(11)

The quantity coilG is called Fabri factor of the

magnetizing coil and is a function of and , as shown in equation (12).

2 2 1/21/2

2 2 1/21 2 ( )( , ) ( ) ln[ ]5 1 1 (1 )

G

(12)

The maximum value coilG , 0,179G , for

3 , 2 . For 1.1 and 5r the corresponding ,rel leakL will be 72.6% . The usual coil geometry factor G is in the range 0.1 0.179 . Evidently there is a trade off between a high specific generated H field and the low leakage inductance.

IV. THE CALCULATION PARAMETERS OF ACTUATORS

IV. 1. MAGNETOSTRICTION COEFFICIENT

In terms of practical applications, magnetostriction coefficient is what determines the choice of a particular type of magnetostrictive material.

The linear magnetostriction, , for magnetization of the material is less than the saturation, and is defined as the relative change in

length of the material under the influence of an external magnetic field.

LL

(13)

where: L - rode extension from

magnetostrictive effect; L - core length of magnetostrictive rod

(Terfenol-D).

The ratio of /L L in Terfenol-D is in the range of more than 1500 ppm, and can be up to 4000 ppm at resonance frequency.

IV. 2. ESTIMATING FORCE FOR ON ACTUATORS

The mechanical force F follows from the stress

T in the rod according to next relation:

| |aF T A (14) where: T - tractive effort of the characteristics of

magnetostrictive material; A - magnetostrictive core section.

V. CONCLUSIONS High power density and simple design of the

magnetostrictive actuator has been evaluated and optimized. A literature survey for magnetostriction - technology presented in article [7] has been extended with analytical calculations.

The precise small motions with high energy density and fast control response could be applied as well in some automotive and aerospace applications.

Therefore, the developed microactuator has to be improved to be useful in nanometric displasment control.

VI. ACKNOWLEDGMENT The paper was possible due to the financial

support of the Romanian project PN 09-35-01.01.

37

VII. References [1] Bushko D.,Goldie J., ”High performance Magnetostrictive Actuators”, IEEE AES Systems Magazine, pp. 251 – 267, November 1991. [2] Claeyssen F.,Lhermet N.,Le Letty R., ”State of the art in the field of magnetostrictive actuators”, JASA, 89(3), pp. 1231 – 1239, 1991. [3] Moffett M.B., “Characterization of Terfenol–D for magnetostrictive transducers”, JASA, 89(3), pp.1448 - 1455, 1991. [4] G. Engdahl Kungliga Tekniska Högskolan, Stockholm, Sweden, Design procedures for optimal use of giant magnetostrictive materials in magnetostrictive actuators applications, ACTUATOR 2002, 8th International Conference on New Actuators, Bremen, Germany, pp. 554 - 557, 10-12 June 2002. [5] M. Tabib-Azar, Microactuators, Kluwer Academic Publishers, Dordrecht, 1997. [6] J.E. Butler, Application Manual for the Design of ETREMA Terfenol-D Magnetostrictive Transducers, Edge Technologies, Inc., 1998. [7] A. G. Olabi, A. Grunwald, Design and optimization of magnetostrictive actuator, Materials & Design, Vol 29, Issue 2, 2008, pp. 469-483. [8] Young-Woo Park, Do-Youn Kim, Development of a magnetostrictive microactuator, Journal of Magnetism and Magnetic Materials 272–276 (2004) e1765–e1766.

VI. BIOGRAPHIES Catanescu Alexandru-Laurentiu was born in

Slatina, Romania, on March 22, 1983. He graduated the Faculty of Electrical Engineering, Polytechnic University in Bucharest in 2007, and received a Masters Degree Diploma from the same Faculty in 2009. Now is a Phd student of Bucharest Politehnica University, faculty of Electrical Engineering.

His employment experience includes the National Institute for Research and Development in Electrical Engineering ICPE-CA, Department of Electro-mechanical Engineering.

His fields of interest include electrical machines, electromagnetic, piezoelectric and magnetostrictive actuators.

38

Abstract - This document is itself an example of the desired layout (inclusive of this abstract) and can be used as a template. The document contains information regarding desktop publishing format, type sizes, and typefaces. Style rules are provided that explain how to handle equations, units, figures, tables, abbreviations, and acronyms. Sections are also devoted to the preparation of acknowledgments, references, and authors' biographies. The abstract is limited to 150 words and cannot contain equations, figures, tables, or references. It should concisely state what was done, how it was done, principal results, and their significance.

Index Terms - The author shall provide up to 10 keywords (in alphabetical order) to help identify the major topics of the paper and to be enough referenced.

I. INTRODUCTION This document provides an example of the

desired layout for a published MNE technical paper and can be used as a Microsoft Word template. It contains information regarding desktop publishing format, type sizes, and typefaces. Style rules are provided that explain how to handle equations, units, figures, tables, abbreviations, and acronyms. Sections are also devoted to the preparation of acknowledgments, references, and authors’ biographies.

II. TECHNICALWORK PREPARATION Please use automatic language check for your

spelling. Additionally, be sure your sentences are complete and that there is continuity within your paragraphs. Check the numbering of your graphics (figures and tables) and make sure that all appropriate references are included.

A. Template This document may be used as a template for preparing your technical paper. When you open the file, select "Page Layout" from the "View" menu (View | Page Layout), which allows you to

see the footnotes. You may then type over sections of the document, cut and paste into it (Edit | Paste Special | Unformatted Text), and/or use markup styles. The pull-down style menu is at the left of the Formatting Toolbar at the top of your Word window (for example, the style at this point in the document is "Text"). Highlight a section that you want to designate with a certain style, then select the appropriate name on the style menu.

B. Format If you choose not to use this document as a template, prepare your technical work in single-spaced, double-column format, on paper A4 (21x29.7 centimeters). Set top, bottom margins and right margins to 15 millimeters and left margins to about 20 millimeters. Do not violate margins (i.e., text, tables, figures, and equations may not extend into the margins).

C. Typefaces and Sizes Please use a Times New Roman font. (See your software’s “Help” section if you do not know how to embed fonts.) Table I is a sample of the appropriate type sizes and styles to use.

TABLE I. Table name will be written in Times New Roman font.

Micromotor Code

b [mm]

a [mm]

h [mm]

Material

MPR33 33 25 20 PZT 5 MPR27 27 18 9 PZT 5 MPR15 16 10 10 PZT 5

D. Section Headings A primary section heading is enumerated by a Roman numeral followed by a period and is centered above the text. A primary heading should be in capital letters and bolded. The standard text format is considered times new roman 12.

The paper title should be in times new roman 20 uppercase and lowercase letters, not all uppercase.

Preparation of a Formatted Technical Paper for the Bulletin of Micro and Nanoelectrotechnologies

*Alexandru-Laurentiu Catanescu, **George Claudiu Zarnescu Research and Development National Institute of Electrical Engineering (INCDIE ICPE-CA),

Splaiul Unirii, No. 313, District 3, 030138, Bucharest, Romania, *catanescu@icpe-ca.ro, **

39

Author name is set to times new roman 12, institution and contact address (E-mail) are set to times new roman 10. Financial support should be acknowledged below the author name and institution. Example: This work was supported in part by the U.K. Department of Defence under Grant TX123.

A secondary section heading is enumerated by a capital letter followed by a period and is flush left above the section. The first letter of each important starting word is capitalized and the heading is bolded and italicized.

Tertiary and quaternary sections are accepted only in special cases, so usually must be avoided in order to keep a clear article structure. If required, a tertiary and quaternary section heading must be italicized and enumerated by adding an arabic numeral after each letter. E. Figures and Tables

Figure axis labels are often a source of confusion. Try to use words rather than symbols. As an example, write the quantity "Torque," or "Torque, M," not just "M." Put units in parentheses. Do not label axes only with units. As in Fig. 1, write "Torque (cNm)" not just "(cNm)". Do not label axes with a ratio of quantities and units. For example, write "Current (A)," not "Current/A." Figure labels should be legible, approximately 10-point type.

Large figures and tables may span both columns, but may not extend into the page margins. Figure captions should be below the figures; table captions should be above the tables. Do not put captions in "text boxes" linked to the figures. Do not put borders around your figures.

All figures and tables must be in place in the text centered and written with times new roman 10. Use the abbreviation "Fig. 1" in sentence and for each figure name. Each table must be defined as „TABLE I”, with capital letters and roman numbers.

Digitize your tables and figures. To insert images in Word, use Insert | Picture | From File.

Fig. 1. Total torque function of angular speed. (Note that "Fig." is abbreviated and there is a

space after the figure number.) F. Numbering

Number reference citations consecutively in square brackets [1]. The sentence punctuation follows the brackets [2]. Multiple references [2], [3] are each numbered with separate brackets [1]-[3]. Refer simply to the reference number, as in [3]. Do not use "Ref. [3]" or "reference [3]" except at the beginning of a sentence: "Reference [3] shows….". Number footnotes separately with superscripts (Insert | Footnote). Place the actual footnote at the bottom of the column in which it is cited. Do not put footnotes in the reference list. Use letters for table footnotes. Check that all figures and tables are numbered correctly. Use Arabic numerals for figures and Roman numerals for tables. Appendix figures and tables should be numbered consecutively with the figures and tables appearing in the rest of the paper. They should not have their own numbering system. G. Units Metric units are preferred in light of their global readership and the inherent convenience of these units in many fields. In particular, the use of the International System of Units (“Système International d'Unités” or SI Units) is advocated. This system includes a subsystem of units based on the meter, kilogram, second, and ampere (MKSA). British units may be used as secondary units (in parentheses). An exception is when British units are used as identifiers in trade, such as 3.5-inch disk drive.

H. Abbreviations and Acronyms

40

Define less common abbreviations and acronyms the first time they are used in the text, even after they have been defined in the abstract. Standard abbreviations such as SI, CGS, AC, DC, and rms do not have to be defined. Do not use abbreviations in the title unless they are unavoidable.

I. Math and Equations Use either the Microsoft Equation Editor or the MathType commercial add-on for MS Word for all math objects in your paper (Insert | Object | Create New | Microsoft Equation or MathType Equation). "Float over text" should not be selected. To make your equations more compact, you may use the solidus ( / ), the exp function, or appropriate exponents. Italicize symbols for quantities and variables. Use a long dash for a minus sign or after the definition of constants and variables. Use parentheses to avoid ambiguities in denominators. The number of each equation must be consecutively added in parentheses and arranged at the right margin, as in (1). Be sure that the symbols in your equation have been defined before the equation appears or immediately following.

Don’t use "Eq. (1)" abbreviation instead of "equation (1)," in a sentence.

2AmLm

(1) With m mechanical mass, A force factor,

mL Electromechanical inductance.

III. ACKNOWLEDGMENT The following is an example of an acknowledgment. The authors gratefully acknowledge the contributions of

Mircea Ignat and Puflea Ioan for their work on the original version of this document.

IV. APPENDIX Appendixes, if needed, appear before the

acknowledgment.

V. References References are important to the reader; therefore, each citation must be complete and correct. There is no editorial check on references, only the format times new roman 10 must be considered.

[1] Satanobu J., Lee D.K, Nakamura K., Ueha S., ”Improvement of the Longitudinal Vibration System for the Hybrid Transducer Ultrasonic Motor”, IEEE Trans. On Ultrasonic ferroelectrics and Frequency Control, vol. 47, no. 1, January 2000, pp. 216-220. [2] Morita T., Yoshida R., Okamoto Y., Kurosawa M., ”A Smooth Impact Rotation Motor Using a Multi-Layered Torsional Piezoelectric Actuator”, IEEE Trans. On Ultrasonic ferroelectrics and Frequency Control, vol. 46, no. 6, November 1999, pp. 1439-1446.

VI. BIOGRAPHIES A technical biography for each author must be

included. It should begin with the author’s name (as it appears in the byline). Please do try to finish the two last columns on the last page at the same height. The following is an example of the text of a technical biography:

Mircea Ignat was born in Bucharest on March 4, 1953.

He graduated at 1977 and he received Ph.D. degrees in electrical engineering from Bucharest Polytehnic University in 1999.

His employment experience included the National Research Electrical Engineering Institute, Dep. of Electrical Micromachines Research and he is the head of Electromechanics Department.

The research preoccupation include: the syncrone generators and the high speed electric machines. Is member of IEEE.

41

"We master an area of research if we meet the following three conditions:

- We know the primitive values, the main derived values and the domain laws - We know how to demonstrate from the laws the important theorems of the domain - We can deduce, using laws and theorems, the future, present or past evolution of

any phenomenon from the field, depending of the real data conditions, that are related to the initial state of the physical system. These phenomena are generated in that state of that physical system, and its border. Initial conditions and borders conditions are sufficient for the determination of uniqueness phenomena " Acad. Remus Radulet “Fundamentals electrodynamics” 1954