Measurements and Performance Evaluation of Novel Interdigital Sensors for Different Chemicals Related to Food Poisoning

IEEE SENSORS JOURNAL, VOL. 11, NO. 11, NOVEMBER 2011 2957

Measurements and Performance Evaluation ofNovel Interdigital Sensors for Different

Chemicals Related to Food PoisoningA. R. Mohd Syaifudin, Student Member, IEEE, Subhas Chandra Mukhopadhyay, Fellow, IEEE, Pak-Lam Yu,

Michael J. Haji-Sheikh, Member, IEEE, Cheng-Hsin Chuang, Member, IEEE, John D. Vanderford, andYao-Wei Huang

(Invited Paper)

Abstract—New types of planar interdigital sensors, were fabri-cated using three different methods. These sensors were used to as-sess different chemicals related to food poisoning. The sensors weredesigned to have different configurations and were constructed ondifferent substrates. The substrate variation was used to investi-gate the effect of substrate properties on sensing performance. Thefirst design was fabricated on a Printed Circuit Board (PCB) ma-terial made from a FR4 fiberglass; the second sensor design wasfabricated using thick film on alumina. The third sensor was de-signed using thin-film [microelectromechanical systems (MEMS)]technology and was fabricated on a glass substrate. The perfor-mances of the sensors were evaluated for different configurationsof the electrode structures as well as dielectric materials. Initialexperiments have been conducted to analyze the sensor’s perfor-mance with two peptide derivatives, namely, Sarcosine and Proline.These peptides are closely related to the target molecule of domoicacid, a natural toxin in seafood. Experiments with endotoxin havebeen presented and the possibility of extending the sensors for de-tection of chemicals responsible for food poisoning has been dis-cussed. Initial investigation on the sensors’ performance based onImpedance Spectroscopy method is reported in this paper.

Index Terms—Dielectric, interdigital, microelectromechanicalsystems (MEMS), sensing performance, sensitivity measurement.

I. INTRODUCTION

I NTERDIGITATED capacitive sensors are used for theevaluation of near-surface properties such as conductivity,

permeability, and dielectric properties. The applications of

Manuscript received March 29, 2011; accepted May 04, 2011. Date of pub-lication May 12, 2011; date of current version October 26, 2011. The associateeditor coordinating the review of this paper and approving it for publication wasProf. Boris Stoeber.

A. R. Mohd Syaifudin is with the Mechanization and Automation ResearchCentre, Malaysian Agriculture Research and Development Institute, 50774Kuala Lumpur, Malaysia.

S. C. Mukhopadhyay and P. L. Yu are with the School of Engineering and Ad-vanced Technology, Massey University, Manawatu Campus, Palmerston North5301, New Zealand (e-mail: [email protected]).

M. J. Haji-Sheikh and J. D. Vanderford are with the Department of ElectricalEngineering, Northern Illinois University, DeKalb, IL 60115 USA.

C.-H. Chuang and Y.-W. Huang are with the Institute of Nanotechnology,Southern Taiwan University, Tainan 710, Taiwan.

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/JSEN.2011.2154327

these sensors will depend on both the characteristic of the par-ticular sensor chosen and also on the characteristic of materialunder test. The interdigitated configurations have been used insurface acoustic wave (SAW) sensors [1], [2], dielectrometrymeasurements of moisture diffusion and temperature dynamicfor electric power cables [3], [4], humidity and gas sensors[5] estimation of properties of dielectric material for milk, andsaxophone reeds [6], [7], characterization of different mate-rials of complex permittivity [8] bacterial detection [9], [10],detection of contaminated seafood with dangerous toxin [11]and biosensor applications [12], [13]. Studies have also beenconducted to interface these interdigitated sensors to have highaccuracy and excellent stability during measurements [14],[15]. Three types of interdigital sensors have been designed andfabricated. All developed sensors were of planar type and havea very simple structure. A model using COMSOL multiphysicshave been conducted before the sensors were fabricated. Theresults from the modeling are important in the design of thesensors [16]. A collaborative venture has been establishedwith Northern Illinois University, USA, and Southern TaiwanUniversity, Taiwan, for sensors fabrication. The sensors weredesigned first at Massey University and then were sent to thoseuniversities for fabrication using different techniques. A dataacquisition system using LabVIEW has been developed forauto measurement of the electrical parameters of all sensors.The sensors were sorted to select the best performing devicesand then were tested with different chemicals to observe theirsensitivity. The analyses were conducted to choose the bestsensor for toxins detection. Two different toxins were chosenwhich are related to different target molecules. Amnesic shell-fish poisoning (ASP) (marine biotoxin) which is related todomoic acid from seafood and the other toxin is endotoxinwhich is caused by contaminated food with Gram-negativebacteria.

II. SENSOR DESIGN, FABRICATION AND ANALYSIS

Interdigitated capacitive sensor operates in the same principleas parallel plate capacitor. The capacitance between a positiveand negative electrode is given by

(1)

1530-437X/$26.00 © 2011 IEEE

2958 IEEE SENSORS JOURNAL, VOL. 11, NO. 11, NOVEMBER 2011

Fig. 1. The relationship between capacitance and number of negativeelectrodes.

where is the capacitance, is the permittivity of free space( F/m), is the relative permittivity, is theeffective area and , is effective spacing between positive andnegative electrodes. In order to get a strong signal, the electrodepattern are repeated many times [17]. Electric field distributionbetween positive and negative electrodes can have multiple ex-citation patterns at different levels of proximity for differentelectrode arrangements with suitable pitch length (distance be-tween two adjacent electrodes). The penetration depth of the de-signed sensor can be calculated from two adjacent electrodes ofsimilar polarity [18]. Based on these information novel inter-digital sensors have been developed to have optimum numbersof negative electrodes, higher penetration depth, and uniformelectric field distribution throughout the sensor geometry. Theoptimum number of negative electrodes between two positiveelectrodes of interdigitated configuration contributes to highestsensitivity measurement. The analysis was carried out usingCOMSOL Multiphysics and was used to model the designedsensors to evaluate their performances. The software applica-tions are based on partial differential equations (PDEs). TheAC/DC module of COMSOL was used for analysis of novel in-terdigital sensors. The application was in 3D mode and quasi-statics mode for dielectric material was selected. The sensorswere modeled using the actual size of the fabricated sensors. Allelectrodes were modeled to have the same pitch of 250 m, elec-trode width of 125 m, and length of 4750 m. The calculatedcapacitance as a function of the number of negative electrodesbetween two positive electrodes obtained, as shown in Fig. 1. Itwas observed that the highest capacitance value can be achievedfor sensors with numbers of negative electrodes between 5 and13. All sensors have different dielectric constant of mate-rial, where the initial sensor using FR4 with and thenew sensor was fabricated on alumina and glass withand , respectively. The value for electric energy density

can be obtained from the simulation. Then, the capacitancefrom simulation can be calculated by

(2)

TABLE INOVEL INTERDIGITAL SENSOR PARAMETERS FOR DIFFERENT CONFIGURATIONS

where is the stored electric energy density and is the ap-plied voltage to the positive electrode. The negative electrode iskept at 0 V. The calculation in (1) shows the value of capacitancegenerated by each sensor depends on as other parameters re-mained constant.

Three sensors with different electrode configurations havebeen designed. The configurations were based on differentnumber of negative electrodes introduced in the sensors de-sign. All sensors have the same effective area of 4750 mby 5000 m and having pitches of 250 m. The positive andnegative electrodes have the same length and width of 4750and 125 m, respectively. Table I shows the parameters usedto design the sensors with different configurations. The sensorswere fabricated on three different materials with differentfabrication process. Different substrates were used for dif-ferent fabrication process will have different influence on thesensitivity of the fabricated sensors [19]. The first design ofsensors was fabricated using photographic printed circuit board(PCB) technology and was fabricated on the fiberglass, FR4.The sensor design was printed on Overhead Projector (OHP)transparency/film and placed onto the precoated photoresistFR4 board. The board was then exposed to the Ultraviolet(UV). The UV light transmits through the clear portion of thefilm and cures the photoresist. After that, the board was sub-merged into a developer bath which will develop and removethe sensitized photoresist. The neat traces of the interdigitalelectrode structures are being constructed on the FR4 board.The representations of novel interdigital sensors are shownin Fig. 2. The second group of sensors was fabricated usingalumina as a substrate. The sensors were constructed usingstandard thick film printing methodologies. The pattern wasdrawn in AutoCad and then printed on a Fire 9500 photoplotter.The patterns were then transferred to three 325 mesh screens.The printer used in the fabrication was a Presco 435, whichis capable of printing up to a 100 mm 100 mm substrate.The top trace layer was printed using a PdAg 850 C firingalloy, while the ground plane was made using a 850 C silvermaterial. The solder dam was made using a 600 C low thermalconductivity dielectric. The wet paste was dried and fired aftereach individual layer was printed. The paste was dried at 150 Cthen inspected. The dried substrate was then placed on the beltof a BTU firing furnace profiled to deliver 850 C C for10 min. The entire firing cycle is approximately 30 min. Thesubstrates were then patterned for the next layer and the cyclewas repeated. The final layer is a low thermal conductivitydielectric to limit the solder flow during the mounting of a chip

SYAIFUDIN et al.: MEASUREMENTS AND PERFORMANCE EVALUATION OF NOVEL INTERDIGITAL SENSORS 2959

Fig. 2. Representation of novel interdigital sensors with different configura-tions of 1-11-1, 1-5-1-5-1 and 1-3-1-3-1-3-1.

Fig. 3. The interdigital sensors fabricated on Alumina.

resistor. Fig. 3 shows the design of fabricated sensors whichwere fabricated at Northern Illinois University, USA.

The third design of sensors was fabricated on a 25 75 mmmicroscope slide by conventional micromachining techniques.The glass slide was cleaned in the acetone solution for 5 minand followed by a 5 min ultrasonic bath in a methanol solution.The cleaned glass then was dried using with an N gun anddehydrated by a hotplate for an additional 30 min at 225 C.After the cleaning, 300 of chromium (Cr) and 700 ofgold (Au) were deposited in sequence on the surface of glassslide by E-beam evaporator, as shown in Fig. 4(a). Next, theinterdigital electrodes (IDT) were patterned by photolithog-raphy process using a positive photoresist (Shipley 1813),as shown in Fig. 4(b)–(c). The developed photoresist was

Fig. 4. The IDT electrode fabrication process.

Fig. 5. The interdigital sensors fabricated on glass.

utilized to be an etching mask for the wet etching of metallayer as in Fig. 4(d). Finally, the sensor was obtained afterremoval of the photoresist, as shown in Fig. 4(e). An exampleof MEMS interdigital sensor (Sensor 1-11) is illustrated inFig. 5. Fig. 6 shows the samples the fabricated interdigitalsensors. All sensors were coated with thin Incralac and curedovernight at room temperature. Incralac has been widely usedas a coating material to protect metallic substrates and studieshave been conducted using EIS (electrochemical impedancespectroscopy) to analyze its performance [20].

The equivalent circuit diagram of interdigital sensor is shownin Fig. 7.

The sensor impedance can be calculated by

(3)

The sensing voltage across the series resistance is ob-served, to measure the current (I) flowing to the sensor. Theselection of the should be such that it does not influencethe impedance of the sensor and at the same time a sufficientsignal is available across it for the purpose of measurement. Thechosen (120 k ) produced a good sensing voltage as well as


Fig. 6. The fabricated interdigital sensors of different substrates.

Fig. 7. The equivalent circuit diagram of interdigital sensor.

provides phase angle which is close to 90 . Both the magnitudeand the phase angle of the sensor impedance are measured. Theabsolute value of the real part of the sensor (R) and the imagi-nary part (capacitive reactance, ) is given by

(4)

(5)

The phase angle measured was closed to 90 , so the real partof the sensor impedance, is very small compared to the imag-inary part. Also, the change of resistance with the dielectric ma-terial is negligible. The real part has not been considered forestimation of the system properties. Therefore, at low operatingfrequency, the capacitive reactance becomes the only parameterbeing measured in the system. The effective capacitance can becalculated by

(6)

and the effective permittivity can be calculated by

(7)

III. EXPERIMENTAL RESULTS AND DISCUSSION

The Instek LCR-821 was linked to a LabVIEW auto mea-surement program to capture the electrical parameters of eachsensor. The experimental setup is shown in Fig. 8. The operatingfrequencies were set between 12 Hz to 100 kHz with constant

Fig. 8. Experimental setup for Impedance Spectroscopy (IS) measurement.

Fig. 9. The impedance characteristic of all fabricated sensors with respect toAir.

voltage of 1 Vrms. The LCR meter is set to have slow mea-surement for better accuracy with average of ten measurementsfor each frequency and all data were saved into csv format.The initial test is to calibrate the sensors with respect to air(without any chemicals). Since the sensors will respond differ-ently with different chemicals, it is important to establish thesensor characteristic with respect to air. The impedance charac-teristic of all sensors varies with frequency, as shown in Fig. 9.With the increase in operating frequency of exciting voltage, theimpedance decreases. The interdigital sensor connected in ACcircuit is frequency dependent. The sensors fabricated on FR4materials create very high impedance as compared to the sen-sors fabricated on Alumina and Glass. Analyses of character-istic impedance of fabricated sensors with air have shown thatAlumina sensors will have better sensing performance. There-fore, for analyses of sensors characteristic with Air only data ofAlumina sensors were presented. Fig. 10 shows the relationshipof the real part and imaginary part of the Alumina sensors fordifferent configurations at different frequencies. The change of


Fig. 10. The real part and imaginary part of Alumina sensors for three differentconfigurations with respect to Air.

Fig. 11. The phase measurement of Alumina sensors with respect to Air.

the resistive part of all sensors is small compared to the imagi-nary part of the sensors. From the figure, it can be said that theinterdigital sensors will have better sensing performance as itproduces a large change of the imaginary part. Fig. 11 showsthe change of phase measurement at different frequencies. It isshown that all sensors have the phase angle closed to 90 at aparticular low frequency and as the frequency increase the phaseangle decreases. As for the interdigital sensor, at low frequen-cies, the sensor will behave better as a capacitive sensor. As forFR4 and Glass sensors analyses of phase angle characteristichave shown the same behavior with respect to air.

Experiments were conducted to analyse the sensor perfor-mance with pure chemicals which are related to food poisoning.The experiments were conducted in a desiccator to control thetemperature and humidity. The experiments were conducted atroom temperature between 23 C–26 C with humidity between40%–50%. Two peptide derivatives, namely, sarcosine and pro-line were used for the initial studies, which are structurally andclosely related to the target molecule. N-methyl glycine or sar-cosine represents the simplest structure and the proline molecule

Fig. 12. The target molecules of two different peptides.

Fig. 13. Nyquist plot of two different peptides and MilliQ (control) for Alu-mina, 1 11 configuration.

is arguably the most important amino acid in peptide confor-mation, containing the basic structural similarity to the domoicacid. Fig. 12 shows the chemical structure of the target mol-ecule. These peptides were readily available at the laboratoryand since the domoic acid is too expensive for reproducibilityof the experiments, therefore, these two chemicals were chosen.Each chemical was diluted in Milli-Q water (with minimal saltmedium) and the solutions were prepared for 1 mg/ml each.Small amount of 50 l of each solution was taken for sensormeasurement. The exposure time of 12 min was establishedafter a few experiments with the same chemicals of same con-centrations. These measurements were observed frequently forany changes in measurement signals. The sensitivity measure-ment can be calculated by

% (8)

where is the impedance value of peptides on the sensor.is the impedance of control solution (Milli-Q water) on

the sensor.It was observed from the experimental results that only

Alumina and Glass sensors give a good response to the targetmolecules. Alumina sensors were then chosen for furtheranalyses and discussion in this paper since we have limitednumber of Glass sensors and because of limited amount of sam-ples for replication of the experiments. Figs. 13 and 14 showthe Nyquist plots of each Alumina sensor for different peptides.Only the sensor with configurations 1 5 and 1 3 response verywell to the peptides and it is possible to discriminate the dif-ferent peptides from the output of the sensor. The Nyquist plotof 1 5 sensor has shown better result. Sensor 1 11 has shown


Fig. 14. Nyqusit plot of two different peptides and MilliQ (control) for Alu-mina, 1 5 and 1 3 configurations.

Fig. 15. Impedance behavior of Alumina 1 3 for Sarcosine, Proline andMilli-Q (control).

Fig. 16. Impedance behavior of Alumina 1 5 for Sarcosine, Proline andMilli-Q (control).

less response to the peptides since it has higher impedancevalue which limits the mobility of electron flow through thesystem. The impedance behaviors of both configurations (1 5and 1 3) are shown in Figs. 15 and 16. It is clearly observed

Fig. 17. Phase Angle of different peptides and control for sensor 1 5 and 1 3.

Fig. 18. Sensitivity measurement for different peptides with respect to Milli-Q.

that at a particular frequency range (0.3–2 kHz) there is nochange of real part, whereas there is a significant change ofthe imaginary part of the system. The change of imaginarypart is higher for 1 5 configuration as compared to 1 3, whichindicates that 1 5 configuration has better sensing performance.The change of phase angle for different peptides and control isshown in Fig. 17. The change of the phase angle is particularlysmall for different peptides. Fig. 18 shows the percentage ofsensitivity measurement for different peptides with respect tocontrol (Milli-Q). It was observed that the percentage differenceof target molecules is higher for Alumina 1 5 sensor comparedto 1 3 sensor. As for 1 11 sensor, since the measurement is onlyvalid after 120 Hz and above (because of very high impedanceto be captured by the LCR meter between 12–120 Hz), that iswhy in the figure it shows no change until the frequency reach120 Hz and it is noticed that there is a very small change of thispercentage for 1 11 sensor. The 1 5 sensor has been chosen forfurther analysis for endotoxin detection.

Experiments were conducted to evaluate the Lipopolysac-charides (LPS) structure where the endotoxic activity happens.The commercial product of LPS O111:B4 was purchased fromSigma-Aldrich, USA. This pure LPS product was extractedusing phenol extraction, which contains less than 3% of protein[21]. 100 mg of each sample of O111:B4 and LPS rough


Fig. 19. The Nyquist plot of LPS O111:B4 and Milli-Q for Alu mina 1 5sensor.

Fig. 20. The impedance behavior of LPS O111:B4 and Milli-Q for Alumina1 5 sensor.

were diluted into 100 ml of Milli-Q water (with minimalsalt medium). The pH of each solution was measured usingpH meter model 420 A from Orion Research Inc with thenew pHoenix Tuff Tip® Combination pH electrode model5733534-003B. It was observer that the pH reading of Milli-Qwater was 6.50 and pH of LPS O111:B4 solution is 6.59. Itcan be said that the signal measurements from the experimentsconducted using these pure LPS will not be affected by proteinor pH of each samples. A small amount (50 l) of each solutionwas pipetted using 10 l pipettor onto the sensor. The changeimpedance and the phase angle were recorded. Fig. 19 showsthe Nyquist plot of the LPS O111:B4 and Milli-Q water. Thesensor shows a significant result to discriminate between thetarget LPS with the control. The impedance behavior of theLPS O111:B4 is shown in Fig. 20. It is noticed that any changein absolute value of the real part of the signal is negligible atcertain a frequency between 1–5 kHz. So, the effect of conduc-tivity does not have any influence on the signal. Moreover, toeliminate the effect of water on the results, the amount of waterused in the experiments has been kept constant. Therefore, thechange of measured signal is due to the change of the effectivepermittivity of the solutions. Results from the experiments haveshown that the Alumina sensor with configuration 1 5 has abetter sensing performance. This sensor can be used to sensethe contaminated food with dangerous toxins.

IV. CONCLUSION

New types of interdigital sensors have been fabricated toinvestigate their sensing performance. New sensors have beenfabricated using different method of manufacturing. Each man-ufacturing technique used different substrates. Due to differentvalues of permittivity of different substrate, the capacitancevalues and corresponding impedance values are influencedby these substrates. Analyses of characteristic impedancehave been conducted using LCR meter and auto measurementprogram from LabVIEW. Experiments were conducted toinvestigate how sensors behave with pure chemicals whichare related to dangerous toxins. Results have shown thatAlumina sensor with 1 5 configuration has better sensitivitymeasurement. More experiments are currently being conductedto evaluate new sensors for verifications especially the Glasssensors. Further experiments are planned to be conducted toinvestigate the significance of any molecular selectivity orresolution as well as the effect of residual adsorption. Theexperiments with different coating materials are currentlyconducted. Carboxyl-functional polymer, 3-Aminopropyltri-ethoxysilane (APTES) and Gold nanoparticle have been usedas a coating layer on the sensor electrodes as these materialshave effective binding properties to certain molecules. Thenovel sensors need to be selective with higher sensitivity mea-surement in order to detect the toxins effectively. Experimentsare also being conducted to establish thin films and porousmaterials on top of the sensors, which can be replaced easilywithout contaminating the sensor electrodes.

ACKNOWLEDGMENT

The authors would like to acknowledge Massey University,New Zealand, Northern Illinois University, USA, SouthernTaiwan University, Taiwan, and the Malaysian AgriculturalResearch and Development Institute (MARDI), researchersreferenced throughout this paper, and also to whom that hadfruitful discussions and collaboration with the authors.

REFERENCES

[1] B. H. Fisher and D. C. Malocha, “Study of the acoustoelectric effectfor SAW sensors,” IEEE Transactions on Ultrasonics Ferroelectricsand Frequency Control, vol. 57, pp. 698–706, Mar. 2010.

[2] D. R. Gallagher, M. W. Gallagher, N. Saldanha, J. M. Pavlina, and D. C.Malocha, “Spread spectrum orthogonal frequency coded SAW tags andsensors using harmonic operation,” IEEE Transactions on MicrowaveTheory and Techniques, vol. 58, pp. 674–679, Mar. 2010.

[3] A. V. Mamishev, Y. Du, J. H. Bau, B. C. Lesieutre, and M. Zahn, “Eval-uation of diffusion-driven material property profiles using three-wave-length interdigital sensor,” IEEE Transactions on Dielectrics and Elec-trical Insulation, vol. 8, pp. 785–798, Oct. 2001.

[4] Y. Sheiretov and M. Zahn, “Dielectrometry measurements of moisturedynamics in oil-impregnated pressboard,” IEEE Transactions on Di-electrics and Electrical Insulation, vol. 2, pp. 329–351, June 1995.

[5] C. Laville and C. Pellet, “Interdigitated humidity sensors for a portableclinical microsystem,” IEEE Transactions on Biomedical Engineering,vol. 49, pp. 1162–1167, Oct. 2002.

[6] S. C. Mukhopadhyay, C. Goonerate, G. S. Gupta, and S. Demidenko,“A low cost sensing system for quality of dairy products,” IEEE Trans-actions on Instrumentation and Measurements, vol. 55, pp. 1331–1338,Aug. 2006.

[7] S. C. Mukhopadhyay, J. D. M. Woolley, G. S. Gupta, and S. Deidenko,“Saxophone reed inspection employing planar electromagnetic sen-sors,” IEEE Transactions on Instrumentation and Measurements, vol.56, pp. 2492–2503, Dec. 2007.


[8] E. Fratticcioli, M. Dionigi, and R. Sorrentino, “A simple and low-costmeasurement system for the complex permittivity characterization ofmaterials,” IEEE Transactions on Instrumentation and Measurement,vol. 53, pp. 1071–1077, Aug. 2004.

[9] S. Radke and E. Alocilja, “Design and fabrication of a microimpedancebiosensor for bacterial detection,” IEEE Sensors Journal, vol. 4, pp.434–440, Aug. 2004.

[10] S. A. Radke and E. C. Alocilja, “A high density microelectrode arraybiosensor for detection of E-coli O157: H7,” Biosensors & Bioelec-tronics, vol. 20, pp. 1662–1667, Feb. 15, 2005.

[11] A. R. M. Syaifudin, K. P. Jayasundera, and S. C. Mukhopadhyay,“A low cost novel sensing system for detection of dangerous marinebiotoxins in seafood,” Sensors and Actuators B—Chemical, vol. 137,pp. 67–75, Mar. 28, 2009.

[12] M. Varshney and Y. B. Li, “Interdigitated array microelectrodes basedimpedance biosensors for detection of bacterial cells,” Biosensors &Bioelectronics, vol. 24, pp. 2951–2960, June 15, 2009.

[13] S. Radke and E. Alocilja, “A microfabricated biosensor for detectingfoodborne bioterrorism agents,” IEEE Sensors Journal, vol. 5, pp.744–750, Aug. 2005.

[14] R. Nojdelov and S. Nihtianov, “Capacitive-sensor interface with highaccuracy and stability,” IEEE Transactions on Instrumentation andMeasurement, vol. 58, pp. 1633–1639, May 2009.

[15] J. E. Gaitan-Pitre, M. Gasulla, and R. Pallas-Areny, “Analysis of a di-rect interface circuit for capacitive sensors,” IEEE Transactions on In-strumentation and Measurement, vol. 58, pp. 2931–2937, Sept. 2009.

[16] Y. Sheiretov and M. Zahn, “Modeling of spatially periodic dielectricsensors in the presence of a top ground plane bounding the test dielec-tric,” IEEE Transactions on Dielectrics and Electrical Insulation, vol.12, pp. 993–1004, Oct. 2005.

[17] K. Sundara-Rajan, L. Byrd, and A. V. Mamishev, “Moisture contentestimation in paper pulp using fringing field impedance spectroscopy,”IEEE Sensors Journal, vol. 4, pp. 378–383, June 2004.

[18] A. V. Mamishev, K. Sundara-Rajan, F. Yang, Y. Q. Du, and M. Zahn,“Interdigital sensors and transducers,” Proceedings of the IEEE, vol.92, pp. 808–845, May 2004.

[19] J. Hong, D. S. Yoon, S. K. Kim, T. S. Kim, S. Kim, E. Y. Pak, and K.No, “AC frequency characteristics of coplanar impedance sensors asdesign parameters,” Lab on a Chip, vol. 5, pp. 270–279, 2005.

[20] E. Cano, D. Lafuente, and D. M. Bastidas, “Use of EIS for the evalu-ation of the protective properties of coatings for metallic cultural her-itage: A review,” J Solid State Electrochem, vol. 14, pp. 381–391, Aug.2010.

[21] S.-A. Catalogue, Biochemicals, Reagents and Kits for Life Science Re-search, pp. 1437–1440, 2009–2010.

A. R. Mohd Syaifudin (S’09) received the B.S.Eng.degree (Hons) from the University of Leeds, Leeds,U.K., in 1998 and the M.S.Eng. degree (Hons) fromMassey University, Palmerston North, New Zealand,in 2009. Currently, he is working towards the Ph.D.degree at the School of Engineering and AdvancedTechnology (SEAT), Massey University.

He is a Senior Research Officer at the MalaysianAgriculture Research and Development Institute(MARDI). During 1998–2002, he worked al-most four years as an Instrument Engineer with

Rohm-Wako Electronics Company, Malaysia. In 2003, he joined MARDIand worked as a Research Officer with the Mechanization and AutomationResearch Centre. His interest includes electromagnetic sensors and biosensors.He is currently involved with the development of smart sensing system for foodinspection.

Mr. Syaifudin is a graduate member of the Board of Engineers Malaysia(BEM) and the Institution of Engineers Malaysia (IEM).

Subhas Chandra Mukhopadhyay (SM’02–F’11)graduated from the Department of Electrical En-gineering, Jadavpur University, Calcutta, India, in1987, with a Gold medal and received the Master ofElectrical Engineering degree from Indian Instituteof Science, Bangalore, India, in 1989 and the Ph.D.(Eng.) degree from Jadavpur University, India, in1994, and the Doctor of Engineering degree fromKanazawa University, Kanazawa, Japan, in 2000.

Currently, he is working as an Associate Professorwith the School of Engineering and Advanced Tech-

nology, Massey University, Palmerston North, New Zealand. He has over 21years of teaching and research experiences. He has authored/coauthored over240 papers in different international journals, conferences, and book chapters.He has edited nine conference proceedings. He has also edited eight specialissues of international journals as lead guest editor and ten books out of whicheight are with Springer-Verlag. His fields of interest include sensors and sensingtechnology, electromagnetics, control, electrical machines, and numerical fieldcalculation, etc.

Dr. Mukhopadhyay was awarded numerous awards throughout his careerand attracted over NZ $3.5 M on different research projects. He is a Fellowof IEE (U.K.), an Associate Editor of the IEEE SENSORS JOURNAL and theIEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENTS. He is onthe Editorial Board of the e-Journal on Non-Destructive Testing, Sensors andTransducers, the Transactions on Systems, Signals and Devices (TSSD), theJournal on the Patents on Electrical Engineering, and the Journal of Sensors.He is the Coeditor-in-Chief of the International Journal on Smart Sensing andIntelligent Systems (www.s2is.org). He is on the Technical Program Committeeof the IEEE Sensors Conference, the IEEE IMTC Conference, the IEEEDELTA Conference and numerous other conferences. He was the TechnicalProgram Chair of ICARA 2004, ICARA 2006, and ICARA 2009. He was theGeneral Chair/Co-Chair of ICST 2005, ICST 2007, IEEE ROSE 2007, IEEEEPSA 2008, ICST 2008, IEEE Sensors 2008, ICST 2010, and IEEE Sensors2010. He has organized the IEEE Sensors Conference 2009 at Christchurch,New Zealand, during October 25–28, 2009, as General Chair. He is the Chairof the IEEE Instrumentation and Measurement Society, New Zealand Chapter.He is a Distinguished Lecturer of the IEEE Sensors Council.

Pak-Lam Yu graduated from the Department ofMicrobiology, Oregon State University, Corvallis,and the Ph.D. degree from the University of Freiburg,Freiburg, Germany.

After a two-year Postdoctoral Fellowship at theMax-Planck Institute, Cologne, he was appointed asa Lecturer with the Department of Biotechnology,Massey University, Palmerston North, New Zealand.He is currently an Associate Professor with theBiotechnology Group, School of Engineering andAdvanced Technology, Massey University. He has

over 25 years of teaching and research experience and as a Consultant to Med-safe, Ministry of Health, Wellington, New Zealand. He has authored/coauthoredover 60 journal articles and over 80 conference presentations. He had an editedbook and one patent. He is a member of the NZBio and Biocommerce Centre,the NZ Microbiological Society, and the American Society of Microbiology.He has completed numerous funded projects, a recent project (2005–2007)was on antimicrobials from ovine blood funded by Meat and Wool, NewZealand, which looks after the NZ meat industry. His research interest includesantimicrobial peptides, food pathogens, and recombinant protein production.

Michael Haji-Sheikh (M’01) received the interdis-ciplinary Ph.D. degree in engineering from the Uni-versity of Texas at Arlington, Arlington, in 1993.

He joined the faculty of the Department ofElectrical Engineering, Northern Illinois University(NIU), DeKalb, and is a Researcher at NIU’s Micro-electronics Research and Development Laboratory(MRDL) and the Laboratory for Nanoscale Scienceand Engineering Technology (LNSET). He joinedNIU’s faculty after spending nine years at Honey-well’s Sensor Fabrication Facility, Richardson, TX.

With his colleagues at the Richardson Sensor Fab, he has developed more than25 sensor products as he was an active Production Engineer overseeing thewafer-level C4 process, platinum deposition, and the UltraTech 1 x Steppers.


He holds eight patents and has several more pending. Prior to receiving thePh.D. degree, he was with the Composite Materials Test Laboratory at Bell He-licopter for two years, where he was involved with the full-scale developmentprogram for the V-22 Osprey.

Cheng-Hsin Chuang (M’04) received the B.S. andPh.D. degrees from the National Cheng Kung Uni-versity (NCKU), Tainan, Taiwan, in 1995 and 2002,respectively, both in civil engineering.

He then held the Postdoctoral Research Scholar-ship with the Center for Micro/Nano Science andTechnology, NCKU, where he held the lead positionin the core facilities for MEMS Fabrication andNanotechnology. In 2004, he joined the ElectronicsResearch Organization and Service (ERSO) at ITRI,where he conducted development of the MEMS

microphone and SAW based biosensor. In 2005, he was recruited by theDepartment of Mechanical Engineering and the Institute of Nanotechnology,Southern Taiwan University, as an Assistant Professor. Currently, he is anAssociate Professor and leads the Micro and Nano Sensing TechnologyLab (MANST Lab). His research interests focus on flexible tactile sensors,roll-to-roll imprinting technology, and DEP chips for single-cell-based biosen-sors. He has published over 100 papers in different international journals andconferences and has ten patents in biosensor and tactile sensor.

Dr. Chuang won two Special Awards, the HIWIN Thesis Award in 2007 and2008 as well as two Best Conference Paper Awards at the Third IEEE NEMS in2008 and the Taiwan Automation Conference in 2010.

John D. Vanderford graduated from the Departmentof Electrical Engineering, Northern Illinois Uni-versity, DeKalb, Illinois, USA. The B.S. and M.S.degrees include focuses on thick-film engineering,thin-film engineering, semiconductor analysis, andphotovoltaics. His M.S. thesis includes works in thefabrication and characterization of n-type transparentconducting oxides using neutralized ion beam sput-tering and pulsed laser deposition. During graduateschool, he worked as a teacher’s assistant where heinstructed and supervised numerous student projects

orientated toward thick film and thin film engineering.He currently works as a process engineer for a company in Oberlin, OH,

which manufacturers vertical multi-junction solar cells for photovoltaicconcentrators.

Yao-Wei Huang received the B.S. degree from theDepartment of Mechanical Engineering, SouthernTaiwan University, Tainan, in 2009. Currently, he isworking towards the M.S. degree at the Institute ofNanotechnology, Southern Taiwan University.

His research interests include DEP chip andbiosensors.

Documents

Measurements and Performance Evaluation of Novel Interdigital Sensors for Different Chemicals Related to Food Poisoning