Artificial Mucsles and Electroactive Polymers

Dariush Semnani Fatemeh Fereydonian Matin MashayekhiIsfahan University of Technology

Electro-active polymers: current capabilities and challenges[52,55]

Artificial Muscles using Electroactive Polymers (EAP):Capabilities, Challenges and Potential[55]

Electronic EAPEAP type Advantages Disadvantages

Electronic EAP -Can operate in room condition for a long time

-rapid response(msec levels)

-can hold strain under dc activation

-induce relatively large actuation forces

-Exhibits high mechanicalenergy density.

-require high voltages(150MV/m).

-require compromise between strain and stress,where≥300% was demonstrated to have a relatively low actuation forces.

-Glass transition tempreture is inadequate for low-tempereture actuation tasks and in the case of ferroelectric EAP,high tempreture application ara limited by curie tempreture

-mostly,producting a monopolar actuation independed of the voltage polarity due to associated electrostriction effect.

Electronic EAP1-Ferroelectric polymers

principle advantage disadvantage Reported type

Polymers th at exhibit nonccntrosymmetric sustained shape in response to electric field.some of these polymers have spontaneous elecrtic polarization making them ferroelectric.recent intruduction of electron radiation in p(vdf-trfe)copo;ymer with defects in their crystalline structure dramatically increased the induced strain.

-induce relatively large strain(5%)

-offer high mechanical energy density resulting from the relatively high elastic modulus

-permit ac switching with little generated heat

-rapid response (msec levels)

-require high voltage(150MV/m).recent development allows of magnitude less voltage.

-difficalt to mass product

-making thin multilayers is still a challenge and sensitive to defect.

-high tempreture applications are limited by the curie tempreture

-electron – radiated p(VDF-TrFE)

-P(VDF-TrFE-CTFE)-CTFE disrupt the order in place of the irradiation.

-P(VDF-TrFE)Terpolymers

Enhancement of Electrical Properties of Ferroelectric Polymers by Polyaniline Nanofibers with Controllable

Conductivities[34]

We present here nanocomposites of polyaniline nanofibers embedded in a vinylidene fluoride and trifluoroethylene [P(VDF-TrFE)] copolymer matrix. P(VDF-TrFE)s are the most thoroughly studied polymeric ferroelectrics and were the first example of a polymer with a well-defined ferroelectric transition behavior.

All-Polymer Electromechanical Systems Consisting ofElectrostrictive Poly(vinylidene fluoride-

trifluoroethylene) and Conductive Polyaniline [31]

ABSTRACT: The low elastic modulus and the ability to withstand high strain without failure make the conducting polymer attractive for a wide range of acoustic applications based on high-strain electroactive polymers. In this article, we examine the electric and electromechanical performance of all-polymer electromechanical systems, fabricated by painting conductive polyaniline (PANI) doped with camphor sulfonic acid (HCSA) on both sides of electrostrictive Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer films, and compare them with those from the same copolymers with gold electrodes.

[31]

Sample PreparationThe P(VDF-TrFE) copolymer with different vinylidene

content was from Solvay and Cie of Bruxelles, Belgium. In the present work, the content of vinylidene are 50 and 65% (mol percent), denoted as P(VDF-TrFE) 50/50 and P(VDF-TrFE) 65/35, respectively. The films were prepared by melt-pressing powder at 225°C and then slowly cooling it to room temperature. The final film thickness was about 30 mm. Two types of films were prepared for the investigation of irradiated films: unstretched and stretched films.

[31]

• To prepare conductive polymer electrodes, the solution of PANI/HCSA was coated on both sides of the P(VDF-TrFE) film by either printing or stamping with a mask.

• Gold electroded P(VDF-TrFE) films were also prepared by sputting Au on opposing faces of the films. The thickness of the gold layer is about 500 Å.

[31]

Nucleation of electroactive β-phase poly(vinilidene fluoride)with CoFe2O4 and NiFe2O4 nanofillers: a new methodfor the preparation of multiferroic nanocomposites[44]

Abstract: Multiferroic and magnetoelectric materials show enormous potential for technological developments. Multiferroic composites are more attractive for applications due to their enhanced properties with respect to single-phase multiferroic materials. In this paper we report on the nucleation of the electroactive β-phase of poly(vinylidene fluoride), PVDF, by the addition of CoFe2O4 and NiFe2O4 nanoparticles in order toprepare poly(vinylidene fluoride)/ferrite nanocomposite for multiferroic and magnetoelectric applications,. The dispersed ferrite nanofiller particles strongly enhance the nucleation of the β-phase of the polymer matrix.

Review of some lesser-known applicationsof piezoelectric and pyroelectric polymers[45]

The piezoelectric effect was first observed in polyvinylidene fluoride polymer (PVDF) in 1969, and the pyroelectric effect was found several years later. A number of additional ferroelectric polymers have been discovered since that time including the copolymer PVDF with trifluoroethylene (P(VDF-TrFE)), and the odd-numbered nylons.

Electronic EAP(2- Dielectric EAP or (Electroststically stricted polymer

principle advantage disadvantage Reported type

Coulomb forces between the electrodes squeeze the material,causing it to expand in the plane of the electrodes.when the stiffness is low a thin film can be shown to stretch 200-380%.

-large displacements reaching levels of 200-380%strain area

-rapid response(msec levels)

-inexpensive to produce

-require high voltage(150MV/m)

-obtaining large displacements compromises the actuation forces

-require prestrain

-silicone

-polyurtane

-polyacrylate

[2]

[2]

•[2]

Fundamental research on polymer material as artificial muscle [42]

Until now, the conducting polymer actuator (CPA), the ionic conductive polymer actuator (ICPA), and the dielectric elastomer actuator (DEA) have been proposed as EAP actuators according to their electric physicality.

The CPA can be driven by a low voltage (under 2 V), and a high output force and a high strain ratio can be realized. The ICPA consist of a thin polymer membrane with metal electrodes plated on both surfaces which can be driven by a low voltage (under 3 V). Both CPA and ICPA have a slow reaction time, and the electrochemical reaction needs a solvent that prevents the movement of the actuator in three-dimensional space.

[42]a DEA such as silicon rubber, urethane rubber, and acrylic

form fi lm can work as an actuator using the phenomenon of electrostriction, which causes the strain in a dielectric substance by impressing the electric field.

A DEA can produce a high-strain response, a high response time, and a high output force, and can perform without the solvent which is needed by the CPA and ICPA.

A high voltage of about 4000 V is impressed on the fi lm

Stability analysis of dielectric elastomer film actuator[47]

Dielectric elastomers, featuring super large deformation (380%), high elastic energy density (3.4 J/g), high efficiency, high responsive speed, good reliability and durability, are the most promising electroactive polymer material for actuators.

This paper discusses the stability analysis methods of dielectric elastomer by applying the elastic strain energy function with two material constants. The results show that for dielectric material with larger dimensionless constant k, its stability performance is higher.

The Transverse Strain Response of ElectroactivePolymer Actuators[51]

In this work, a transverse strain measurement system based on a ZYGO laser Doppler interferometer has been developed. This system can measure transverse strain responses of polymer actuators of different sizes over a wide displacement and frequency range. By using this system, we have investigated the electric-field-induced strains of electroactive polymer actuators fabricated from silicone films.

[51]

Electromechanical Response of

Nanostructured Polymer Systems

with no Mechanical Pre-Strain[53]

Here, we describe a route to dielectric elastomers with no (0%) pre-strain by using electroactive nanostructured polymers (ENPs) with tunable properties.

PERFORMANCE OF MULTI-LAYER ELECTROACTIVE POLYMER ACTUATORS USED FOR ACTIVE

VIBRATION CONTROL [54]

Our experimental investigation of the transverse strain response of dielectric elastomers has now been extended to study the transverse strain responses of multi-layer elastomer actuators fabricated from polyurethane films.

Electronic EAP3- Liquid crystal elastomers

principle advantage disadvantage Reported type-Exhibit spontaneous ferroelectricity

-contracts when heated offering no-electroactive excitation

-when heated it induces large stress and strain(200kpa and 45%respectvely)

-require much lower field than ferroelectricsand dielectric EAP (1.5MV/m,4%strain).

-fast response(≤133 HZ

-low electro-strictive response

-slow response

-Hysteresis

-polyacrylate

-polysiloxane

Electronic EAP4- Electrostrictive graft elastomers

principle advantage disadvantage Reported type

Electric field causes molecular alignment of the pendant group made of graft crystalline elastomers that are attached to the backbone

-strain levels of5%

-relatively large force

-cheaper to produce -rapid response(msec levels)

-require high voltage(150MV/m)

Copolymer poly(vinylidene-fluoride-trifluoroethylene

Ionic EAPEAP type Advantages DisadvantagesIonic EAP -Produce large bending

displacment

-require low voltage

-natural bi-directional actuation that dependens on the voltage polarity

- Some ionic EAP likeconducting polymers havea unique capability of bistability

-except cps and CNT,ionic EAP don’t hold strain under dc voltage

-slow response(fraction of a second)

-bending EAPs induce a relatively low actuation forces

-except CPs,it is difficalt to produce a consistent material(particulary IPMC)

-in aqueous system the material sustain electrolysisat≥1.23v

-need an for electrolyte and encapsulation

-low electromacanial coupling efficiency

Ionic EAP1-Ionic polymer Metal polymers(IPMC)

principle advantage disadvantage Reported type

THE base polymer provides channels for mobility of positive ions in a fixed network of negative ions on interconnected clusters.electrostatic forces and mobile cations are responsible for the bending.

-Require low voltage(1-5v)

-provide significant bending

-low frequency response(in the range of 1HZ)

-Extremely sensitive to dehydration

-dc causes permanent deformation

-subject to hydrolysis above 1.23v.

-displacement drift under dc voltage

Base polymer----made by DNafion(perfluorosulfonate upont)Flemion(perfluorocaboxylate)Cations:Tetra-n-butylammoniumMetal:pt and gold

“Equivalent” Electromechanical Coefficient for IPMC Actuator Design Based on Equivalent Bimorph Beam

Theory[48]

Ionic Polymer Metal Composites (IPMCs) along with ionic gels and conductive polymers belong to the class of ionic electroactive polymer (EAP) systems that can be used for actuation and sensing

There are several ionic polymer membranes used in IPMCs: Nafion® (E. I. Du Pont de Nemours and Company, Inc. 0.18 mm thick, 1,100 g mol−1 of equivalent weight) most widely used one with backbone ionomer perfluoro-sulfonate, Flemion® (Asahi Glass, 0.14 mm thick, 690 g mol−1 of equivalent weight) with the perfluoro-carboxylate group, and rarely Aciplex® (Asahi Chemical)

[48]

[48]

Design and test of IPMC artificial muscle microgripper[49]

Ionic EAP2-Conductive polymers

principle advantage disadvantage Reported type

Material that swell in response to an applied voltage as a result of oxidation or reduction,depending on the polarity ausing insretion or deinsertion of (possibly solvated)ionc.

-require relatively low voltage -induce relatively large force

-extensive body of knowledge

-biologically compatible

-exhibit slow deterioration under cyclic actuation

-suffer fatigue after repeated activation.

-slow response(≤40 Hz)

Polypyrrole

PolyethylenedioxythiOphene

Polyaniline

polythiophenes

Speed and strain of polypyrrole actuators: dependenceon cation hydration number [46]

The aim was to clarify the role of cations in the electrolyte on the speed of response and on the strain of the film.

[46]

A flexible strain sensor from polypyrrole-coated fabrics[5]

Experimental1-A typical procedure for preparation of PPy-coated fabrics by CVD is as follows:

plain knitted fabric of 83% Tactel blended with 17% (40 denier) Lycra2- A typical procedure for preparation of PPy-coated fabrics by solution

polymerization is as follows:

A flexible strain sensor from polypyrrole-coated fabrics[5]

Electrospinning of Nanomaterials and Applications inElectronic Components and Devices[23]

2.5. ActuatorsActuators can take electrical and other energy and convert it into a mechanical

motion. However, large strain and quick response times still remain the most important challenges in actuator design. Large strain can be obtained by enhancing mechanical properties, and flexible electrospun fiber templates can be used to improve strain. This is because a large amount of electrolyte can be localized in the porous structure of electrospun fiber mats.

2.5.1. Electrospun Fibers Coated with Conductive Polymers Among the many materials suitable for actuators, conducting polymers have received

considerable attention as promising candidates for actuator design, owing to their moderately high actuation strain at low operational voltages below 1 V . Despite being good candidates for designing actuators, the brittleness and poor elongation at break of conducting polymers limit their active applicability in devices.

An electrospun polyvinyl alcohol (PVA) nanofiber mat containing a flexible conducting polymer actuator, prepared by in situ polymerization of aniline has been reported.

[23]

[23]2.5.2. Porous Electrospun Fiber Mats Enhance Ion Mobility Nanofiber mats have been prepared by electrospinning a sulfonated

tetrafluoroethylenebased fluoropolymer–copolymer (NafionTM.103 When these mats are saturated with ionic liquids they show approximately three-fold improvement in ionic conductivity compared to conventional film-type membranes. Also these fabricated fiber mat-based transducers showed higher strain speed of 1.34% per second, which is 52% faster than the film-based actuators (Fig. 9).

[43] Correlation of capacitance and actuationin ionomeric polymer transducers

In thi s paper we discuss a series of experiments that characterize the electromechanical actuation response of three families of ionomers: Nafion (a product of DuPont), BPSH (sulfonated npoly(arylene ether sulfone)) and PATS (poly(arylene thioether sulfone)).

The strain response of the materials varies from 50 μstrain/V to 750 μstrain/V at 1Hz.

Compared to other types of electromechanical transducers, such as piezoelectric materials, ionomeric transducers have the advantage of high-strain output (>1%is possible), low-voltage operation (typically less than 5 V), and high sensitivity in charge-sensing mode.

[43]

Optimization of Electrically Conductive Films:Poly (3-methylthiophene) or Polypyrrole in Kapton[6]

Examples of the highest conductive hybrid films produced within the previously referenced studies are summarized in Table I

Optimization of Electrically Conductive Films:Poly (3-methylthiophene) or Polypyrrole in Kapton[6]

Polypyrrole nanofiber surface acoustic wave gas sensors[30]

Polypyrrole nanofibers were synthesized through a template-free chemical route by introducing bipyrrole as an initiator to speed up the polymerization of pyrrole in the presence of iron (III) chloride (FeCl3) as the oxidizing agent.

Electrospun Poly(Lactic acid) based Conducting Nanofibrous Networks[35]

Electrically conductive polymers are of special interest for tissue engineering because new technologies will require biomaterials that not only physically support tissue growth but also are electrically conductive, and thus able to stimulate specific cell functions or trigger cell responses. Common classes of organic conductive polymers include polyacetylene, polypyrrole, polythiophene, polyaniline (PANi), and poly (para-phenylene vinylene). The present research has focused on PANi as the conducting polymer and poly(L-lactic acid) (PLLA) as the biopolymer.

Polypyrrole-coated conductive fabrics as a candidate for strain sensors [39]

In this paper, the fabrication of PPy-coated conductive fabric by the method of vapor phase polymerization, and the investigation on its strain sensing properties are reported.

The conductive fabrics were prepared by covering a non-conductive substrate with a layer of Ppyconductive film which was formed by vapor phase polymerization. The typical preparation method for the PPy-coated fabrics is as follows: 30 g FeCl3·6H2Owas mixed with 190 mL white spirit, 40 mL water and 5 g emulsifier A.C. to prepare a print paste. It was then printed on the surface of the textile substrate composed of 83% Tactel and 17% Lycra

[39]

[39]

Electrochemically controlled drug delivery based on intrinsically conducting polymers[40]

CONDUCTING POLYMERS[38]

CONDUCTING POLYMERS[38]

Conducting polymers in biomedical engineering [41]

[41]

[41]

Ionic EAP3- Electro-rheological fluids(ERF)

principle advantage disadvantage Reported type

ERFs experience dramatic viscosity change when subjected to electric field causing induced dipole moment in the suspended particles to form chains along the fueld lines

-viscosity control for virtual valves

-enable haptic mechanisms with high spatial resolation

-require high voltage Polymer particles in fluorosilicone base oil

Ionic EAP4- Ionic Gels(IGL)

principle advantage disadvantage Reported type

Application of voltage causes movement of hydrogen ions in or out of the gel.the effect is a simulation of the chemical analogue of reaction with acid and alkaline.

-potentially capable of matching the energy density of biological muscles

-require low voltage

Operate very slowly it would require very thin layers and new type of electrodes to become practical

Examples include:PAMPS,Poly(vinyl alcohol)gel with dimethyl sulfoxide,and polyacryl-onitrile(PAN)with conductive fibers

Ionic EAP5- Carbon nanotubes

principle advantage disadvantage Reported type

The carbone-carbone bond of nanotubes(NT)suspended in an electrolyte changes length as aresult of charge injection that affects the ionic charge balance between the NT and the electrolyte

-potentially provide superior work/cycle and mechanical stresses

-carbon offers high thermal stability at high tempreture ≤1000 c

-expensive

-difficult to mass product

Single and multi – walled carbon nanotubes

[56]

Properties and Applications of FilledConductive Polymer Composites[33]

Abstract : The electrical properties of polymers filled with different types of conducting particles are reviewed. Following a theoretical description of a general effective media (GEM) equation, the experimental conductivityÈvolume fraction data for thermoplastic filled with vanadium oxide particles as well as thermosetting polymer composites, are Ðtted to the equation. The calculated propertyrelated parameters in the equation are discussed. The electrical conductivity of the composites is combined with an extremely large positive temperature coefficient (PTC) e†ect, depending on the Ðller type (V2O3 or carbon black), as well as 2Oon its distribution and volume fraction. Both m3elting and recrystallization behaviour are responsible for the PTC e†ect.

Morphological and Electromechanical Studies of Fibers Coated with Electrically Conductive Polymer[36]

CONCUSIONSThis study investigates the relationship between the morphology and

electromechanical behavior of the electrically conductive fibers and analyzes the mechanisms governing their electromechanical behavior based on microscale observations by means of SPM, AFM with current measurement, and SEM. The following can be concluded:

(1) The electromechanical behavior of the conductive composites depends strongly on the microstructure of the coating layer and the material of the substrate. On PA6 base, PPy forms a continuous layer with finer, denser, and more uniform grains than those on the PU base. A smooth and uniform coating and matched mechanical properties will lead to a satisfied performance of conductive fiber sensors. The relationship between the fractional increment in resistance, R/R0, and the applied strain is reasonably linear, which is of practical importance in sensing applications.

(2) The variation in resistance for the PPy-coated PA6 fibers results from the change in the dimension of the fibers. By contrast, the variation in resistance with the applied strain for PPy-coated PU fibers is mainly attributed to the damage on the coating layer.

Intrinsically conducting polymers for electromagnetic interference shielding[32]

Electromagnetic interference (EMI) consists of any unwanted, spurious, conducted, and/or radiated signals of electrical origin that can cause unacceptable degradation of system or equipment performance and contains components with frequencies ranging from the lower power frequencies of 50, 60 and 400 Hz, on up to the microwave region, as man-made or natural, be either narrowband or broadband.

Traditional approach for EMI shielding relies on the use of metallic materials, which supply excellent shielding effectiveness (SE).

Carbons are also used in EMI shielding applications, mainly as conductive fillers (fibers, particles, powders, filaments, tubes) in composite materials, due to their electrical conductivity, chemical resistance and low density.

Intrinsically conducting polymers (ICPs) are attractive alternative materials for EMI shielding. Since the discovery of ICPs in the late 1970s,16 EMI shielding, as well as electrostatic discharge, have been well projected and evaluated by many early papers.

[32]These materials combine high conductivity (as compared with carbons), ease

of processability, low density (e.g. the density of polyaniline (PANI) and polypyrrole (PPY) are 1.1–1.3 g/cm3 35 and ca. 1.2 g/cm3 36 respectively, far less than that of metals, such as 8.9 g/cm3 for copper) and corrosion resistance (as compared with metals) with unique shielding mechanism of absorption (differing from the reflection one for metals and carbons37) which is more preferred in military applications like camouflage and stealth technology.38 The objective of this paper is to review the past works concerning EMI shielding with ICPs, focused mainly on PANI and PPY. It should be emphasized that the paper is only intended to provide a brief summary of the literature and detail, to some extent, the material preparations, the testing protocols and the results obtained. Omissions are inevitable due to the myriad of investigations carried out on this subject. The organization of the rest of the paper is as follows. In the next section the fundamentals of ICPs and the shielding theory are briefly described. In the following two sections the EMI shielding results of PANI and PPY respectively, are discussed in pure material or composites. Then in the subsequent section the EMI shielding studies of some other ICPs are presented. In the last section concluding remarks on EMI shielding with ICPs are given.

[32]

Three-dimensional conductive constructs for Three-dimensional conductive constructs for nerve

regeneration[37]

APPROACHES TO ACHIEVE SMARTER ELECTROACTIVE MATERIALS

AND DEVICES[50]Smart materials are a class of materials that can

significantly change their mechanical (such as shape, stiffness, and viscosity), electric, thermal, optical, magnetic, electromechanical or electromagnetic properties in a predictable or controllable manner in response to their environment.1 These materials include piezoelectric and electrostrictive ceramics, electroactive polymers (EAP), magnetostrictive materials, shape-memory materials, and magneto-rheologic fluids.

Actuators can be classified into two types: conventional actuators and solid state actuators.

[50]

[50]

[50]

References 2-Dielectric Elastomer Artificial Muscle Actuators: Toward Biomimetic Motion5- A flexible strain sensor from polypyrrole-coated fabrics6- Optimization of Electrically Conductive Films: Poly (3-methylthiophene) or

Polypyrrole in Kapton8- Smart fibres, fabrics and clothing23- Electrospinning of Nanomaterials and Applications in Electronic Components

and Devices30- Polypyrrole nanofiber surface acoustic wave gas sensors31- All-Polymer Electromechanical Systems Consisting of Electrostrictive

Poly(vinylidene fluoride-trifluoroethylene) and Conductive Polyaniline32- Intrinsically conducting polymers for electromagnetic interference shielding33- Properties and Applications of Filled Conductive Polymer Composites34- Enhancement of Electrical Properties of Ferroelectric Polymers by Polyaniline

Nanofibers with Controllable Conductivities35- Electrospun Poly(Lactic acid) based Conducting Nanofibrous Networks36- Morphological and Electromechanical Studies of Fibers Coated with Electrically

Conductive Polymer37- Three-dimensional conductive constructs for Three-dimensional conductive

constructs for nerve regeneration38- CONDUCTING POLYMERS

39- Polypyrrole-coated conductive fabrics as a candidate for strain sensors40- Electrochemically controlled drug delivery based on intrinsically conducting

polymers41- Conducting polymers in biomedical engineering42-Fundamental research on polymer material as artificial muscle43- Correlation of capacitance and actuation in ionomeric polymer transducers44- Nucleation of electroactive β-phase poly(vinilidene fluoride) with CoFe2O4 and

NiFe2O4 nanofillers: a new method for the preparation of multiferroic nanocomposites

45- Review of some lesser-known applications of piezoelectric and pyroelectric polymers

46- Speed and strain of polypyrrole actuators: dependence on cation hydration number

47- Stability analysis of dielectric elastomer film actuator48- “Equivalent” Electromechanical Coefficient for IPMC Actuator Design Based on

Equivalent Bimorph Beam Theory49- Design and test of IPMC artificial muscle microgripper 50- APPROACHES TO ACHIEVE SMARTER ELECTROACTIVE MATERIALS AND DEVICES

51- The Transvers e Strain Response of Electroactive Polymer Actuators52- Electro-active polymers: current capabilities and challenges53- Electromechanical Response of Nanostructured Polymer Systems with no

Mechanical Pre-Strain54- PERFORMANCE OF MULTI-LAYER ELECTROACTIVE POLYMER ACTUATORS USED

FOR ACTIVE VIBRATION CONTROL 55- Artificial Muscles using Electroactive Polymers (EAP): Capabilities, Challenges and

Potential56-