IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 57, NO. 8, AUGUST 2008 1621

An Amperometric Glucose Biosensor With EnhancedMeasurement Stability and Sensitivity Using an

Artificially Porous Conducting PolymerE. M. I. Mala Ekanayake, D. M. G. Preethichandra, Senior Member, IEEE, and Keiichi Kaneto

Abstract—A conducting polymer [polypyrrole (PPy)]-based am-perometric biosensor fabricated on a platinum-coated nanoporousalumina electrode has been described. This fabricating processintroduced artificial porosity into the PPy film, and the tem-plate pore sizes were carefully chosen to match the size of theglucose oxidase (GOx) molecule. The PF−

6 -doped PPy film wassynthesized with 0.05 M pyrrole and 0.1 M NaPF6 at a currentdensity of 0.3 mA/cm2 for 90 s. Immobilization was done byphysically adsorbing 5 µL of GOx on the nanoporous PPy film.Glutaraldehyde (0.1 wt.%, 5 µL) was used for cross-linking.The synthesized films were characterized by using an electro-chemical technique and scanning electron microscopy (SEM).Amperometric responses were measured as a function of differentconcentrations of glucose at 0.4 V. Nanoporous electrodes leadto high enzyme loading, whereas the use of a cross-linking agentincreased stability, sensitivity, reproducibility, repeatability, andshelf life.

Index Terms—Alumina, artificial porosity, cross-linking,nanoporous, polypyrrole (PPy).

I. INTRODUCTION

S INCE the introduction of the Clark electrode for oxidaseenzyme immobilization [1], various types of electrodes

have been developed to produce precise, fast, reproducible,and highly sensitive measurements on glucose concentrations.Among them, amperometric biosensors are prevalent becauseof their high selectivity and simple fabrication methods. Here,the flow of electrons produced in a reduction–oxidation re-action, which resulted by applying a potential between twoelectrodes immersed in a glucose solution, is measured toquantitatively analyze the reaction.

Within this environment, glucose biosensors help in iden-tifying diabetes at early stages and play a vital role in postidentification and patient management in the healthcare indus-try with the increasing number of diabetic patients around the

Manuscript received July 3, 2007; revised March 7, 2008. This work wassupported by a Grant-in-aid for Science Research in a Priority Area “SuperHierarchical Structures” from the Ministry of Education, Culture, Sports,Science, and Technology, Japan, by a foreign postdoctoral research fellowshipfrom the Japan Society for the Promotion of Science, and by a postdoctoralfellowship from the Kitakyushu Foundation for the Advancement of Industry,Science, and Technology (FAIS).

The authors are with the Graduate School of Life Science and SystemsEngineering, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan(e-mail: mala@edu.life.kyutech.ac.jp).

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

Digital Object Identifier 10.1109/TIM.2008.922068

globe. Furthermore, they are being widely used in the food andbeverage industries.

Immobilization of biological agents is the most challengingand important criterion in biosensor fabrication [2], [3]. Re-searchers try to improve the sensitivity, stability, linear range,and reproducibility of glucose biosensors by different tech-niques of immobilization of an enzyme (glucose oxidase (GOx)or glucose hydrogenase) on suitable electrodes with supportivematerials [4]. Until now, several physical adsorption methodswith and without cross-linking, covalent, and electrochemicalimmobilization methods have been tried to fulfill this require-ment [5]. Covalent linking of biomolecules on a transduceris regarded as an efficient method of immobilization, but itstill suffers from low reproducibility [6]. Electrochemicallypolymerized conducting polymers have a surprising switchingcapability between the oxidized and reduced states. Recently,polyconjugated conducting polymers have entered the fieldwith their easy and controllable deposition qualities. Amongthese, polypyrrole (PPy) has extensively been used, with itshigh chemical stability at room temperature, easy oxidation,and electrical conducting characteristics [7]–[9]. Physical ad-sorption methods offer simplicity and ease of preparation,whereas the porosity of the film remains as a challenging factorin determining the enzyme loading.

Attempts have been made to improve GOx entrapment byinvestigating the ion exchange capabilities, optimum tempera-tures, GOx concentration, pH, etc., and, particularly, increasingadsorption ability by increasing the effective surface area ofthe polymer film. Fabricating microporous films by ion ex-change or by other means of chemical interference to increasethe enzyme entrapment has been tried [10], [11]. Our novelapproach is to use a nanoporous electrode to fabricate a PPyfilm by introducing artificial nanoporosity into the film from theelectrode. This is a unique fabrication procedure for nanoporousPPy films and has led to a very simple thin-film fabricationmethod with all other requirements of a quality biosensor witha very high loading capacity of GOx. With this novel technique,the proposed biosensor will remain as a unique device amongexisting biosensors.

When the GOx electrode consists of a highly porous PPyfilm, more enzymes are immobilized, and H2O2, which isproduced as a result of the reaction catalyzed by the enzyme,can reach the electrode at a high rate for sensing. Thus

Glucose + O2GOx−→ Gluconic acid + H2O2. (1)

0018-9456/$25.00 © 2008 IEEE

1622 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 57, NO. 8, AUGUST 2008

Electrooxidation of this H2O2 by-product can easily be cat-alyzed on a Pt/PPy electrode [12]. Thus

H2O2 −→ O2 + 2H+ + 2e−. (2)

The consequent electron flow can be detected as an ampero-metric response, and it can be used to indicate the measure ofadded glucose. The high effective surface area provided by theartificial nanoporous conducting polymer PPy accelerates thedetection of this current.

In this experiment, we used PF−6 as the doping agent for

electropolymerization. PF−6 itself acts as a good dopant to

produce microporous PPy films, but to entrap GOx, it needsa nanoporous structure due to the physical dimensions ofthe GOx molecule. To fulfill this requirement, a nanoporousalumina (Al2O3) template coated with a thin layer of Pt wasselected as our electrode to electropolymerize a thin layer ofPPy with PF−

6 as the dopant. As a result, a nanoporous PPy filmis patterned, and the amperometric response of this electrodeis improved. The response current has remarkably improvedwith the introduction of glutaraldehyde as a cross-linking agentduring enzyme adsorption. It helped the sensor maintain itsstability, reproducibility, and repeatability well within the ex-pectations with a high sensitivity. Here, a novel sensor withenhanced GOx adsorption and improved characteristics hasbeen reported.

II. EXPERIMENTAL

A. Materials, Methods, and Apparatus

GOx (EC 1.1.3.4., 210 U/mg, from Aspergillus niger),pyrrole monomer, and sodium tetrafluorophosphate werepurchased from Wako (Japan). D-Glucose and 50 wt.% glu-taraldehyde were obtained from Aldrich. Pyrrole monomerwas distilled before use. Phosphate-buffered solutions (PBS,0.05 M; pH 6.50) were freshly prepared with Na2HPO4

and KH2PO4. Glucose, NaPF6, and glutaraldehyde solutionswere also freshly prepared before use. The glucose solutionwas allowed to reach equilibrium in an aqueous condition.Nanoporous alumina disks (Anodisc) with maximum pore di-ameters of 100 and 200 nm were purchased from Whatman.All other chemicals used were of analytical grade. Experimentswere conducted at 25 ± 2 ◦C, unless otherwise stated.

All electrical studies were performed on an automatic polar-ization system (Hokuto Denko, model HSV-100) with a three-electrode cell consisting of a working electrode, a Pt counterelectrode, and a Ag/AgCl reference electrode. A stirring beadand a magnetic stirrer were used to homogenize the solution af-ter addition of glucose during response current measurements.Scanning electron microscope (SEM) images were obtainedusing Shimadzu Superscan (model SS-550). Anodisc electrodeswere Pt coated by plasma sputtering using a JEOL quick coater(JFC 1500).

B. Fabrication of Nanoporous PPy Electrodes

The fabrication procedure is given in [13] and is briefly men-tioned here. Anodisc electrodes were appropriately masked,

and a Pt film of 50-nm thickness was coated by plasma sputter-ing. Then, a PPy/PF6 film was electrochemically synthesized onthe prepared alumina/Pt nanoporous electrode using a solutioncontaining 0.05 M pyrrole and 0.1 M NaPF6 at a constantcurrent density of 0.3 mA/cm2 for 90 s in a galvanostatic mode.Soon after the film was deposited, the electrode was washedtwice with PBS and cold air dried.

C. Entrapment of GOx

Initially, 5 µL of GOx (from a 5-mg/ml solution) was care-fully dropped on the polymer and allowed to dry at 4 ◦C. Inthe case of cross-linking, 5 µL of glutaraldehyde (0.1 wt.%)was placed on the electrode, followed by enzyme adsorption.Hereafter, the two types of sensors (i.e., without and withglutaraldehyde) will be referred to as S1 and S2, respectively. Inour previous studies, it has been shown that the 200-nm nano-porous PPy sensors give a lower sensitivity than the 100-nmsensors [14]. Therefore, to study the influence of a cross-linker,the 200-nm electrodes were used. Both electrodes were rinsedwith PBS after drying to remove any unbound or loosely boundenzyme from the polymer surface and were again dried withcold air and stored at 4 ◦C for response measurements.

D. Characterization of Electrodes by ResponseCurrent Measurements

During the characterization of electrodes, the same procedurewas followed, regardless of whether the electrodes were cross-linked or not. The alumina/Pt/PPy/GOx electrode was placedas the working electrode in the three-electrode cell containing10 mL of PBS. A step potential of 0.4 V versus Ag/AgClwas applied to the sensor electrode and allowed to reach theequilibrium state. A known amount of glucose was added toPBS while stirring, and the current responses were obtained.

E. SEM Analysis

For a clear view of the Pt/PPy nanoporous sensor, theAnodisc was dissolved by using a NaOH alkali solution andwashed with distilled water. The top surface morphology ofnanopores in the PPy film and the longitudinal cross sectionobtained by dissolving alumina in NaOH are shown in Fig. 1(a)and (b), respectively.

III. RESULTS AND DISCUSSION

A. Surface Morphology of the Pt/PPy Electrode

It is clearly visible from Fig. 1(a) that the Pt/PPy electrode isof well-structured nanoporous morphology for efficient adsorp-tion of GOx. This nanoporosity is merely from artificial poros-ity introduced by the nanoporous alumina template. The crosssection shown in Fig. 1(b), which was obtained by dissolvingAl2O3 in NaOH, reveals the internal structure of the PPy filmgrown inside the nanoporous alumina template. The irregularityshown in the figure is due to the washing of the dissolvedalumina and the limited freestanding capability of the thin-walled PPy tubes. When a thin film of PPy is deposited on the

EKANAYAKE et al.: AMPEROMETRIC BIOSENSOR WITH ENHANCED MEASUREMENT STABILITY AND SENSITIVITY 1623

Fig. 1. SEM images of (a) nanoporous PPy film surface and (b) cross sectionof the sensor electrode after dissolving the alumina disk.

surface of the electrode, it penetrates the nanopores followingthe morphology of the previously coated Pt. The PPy depositedinside the walls of the nanotubes results in a honeycomb-like structure. These PPy nanotubes support the high enzymeloading of electrodes. It is apparent that after Pt sputtering andeven after polymerizing, nanoporosity still exists. It has beenfound that 90 s is the optimum time for polymerization, anda shorter or longer time to polymerize tends to decrease theperformance of the sensor.

IV. CURRENT RESPONSE MEASUREMENTS

At a potential of 0.4 V, the response current variation ofS1 for an increment of 0.5 mM of glucose concentration isshown in Fig. 2, whereas Fig. 3 gives the sensor responsesfor consecutive addition of 5 mM for a similar sensor. Ascan be observed, with addition of glucose to PBS at steadystate, the current sharply increases and reaches a new steadyvalue. Here, at each addition of glucose, H2O2 is produced,and oxidation is started, initiating a current. When the rates ofproduction of H2O2 and oxidation of H2O2 reach equilibrium,

Fig. 2. Response current measurements of S1 for successive addition ofglucose in steps of 0.5 mM at a time.

Fig. 3. Response current measurements of S1 for successive addition ofglucose in steps of 5 mM.

the resultant current becomes constant. At this stage, a newconcentration of substrate addition will cause repetition of thesame phenomenon. At the initial stages of substrate (glucose)addition, the response current linearly increases, and at latterstages, it tends to reach saturation. These figures give evidenceof the Michaelis–Menten behavior of the enzyme sensor. Theresponse time or the time taken to reach from 5% to 95% ofits steady state was 4 s, and the linear range was 0.5–10 mMwith a correlation coefficient of 0.9962 (where n = 26). Thesensitivity of the sensor was 7.4 mA · M−1 · cm−2. All thesecharacteristic values were well within the range of a qualitybiosensor [15]. The response of this sensor was measured after14 days, and it was found that the sensitivity dropped by 50% ofthe original value. Therefore, the shelf life is not appealing for acommercial sensor, and further improvements made to increasethis are described in the next section.

V. CALCULATIONS

Fig. 4 depicts the calibration curve of sensor S1 with meancurrent values for four separate identical sensors. At 5 mM ofglucose, the mean response current was 41.2 µA · cm−2 with5.09% relative standard deviation. The apparent Michaelis–Menten constant Kapp

m and the maximum current Im of the

1624 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 57, NO. 8, AUGUST 2008

Fig. 4. Calibration curve for sensor S1.

sensor were calculated using the Lineweaver–Burk method,which showed a Kapp

m value of 7.01 mM and an Im value of120 µA. As this Kapp

m value is much less than the reported valueof the Kapp

m of a free enzyme [16], it assures the nondenaturiz-ing behavior of the enzyme due to toxic substances [17].

VI. IMPROVEMENTS

Although sensor S1 has good characteristics, its stability wasnot up to the required level. Because an enzyme is a foldedpolypeptide, a specific folded pattern is needed to maintain itsactivity. Several factors, namely temperature, pH, solvents, andtime, cause unfolding and denaturation of enzymes. Therefore,we added glutaraldehyde as a cross-linking agent, and thesensor made under this scheme is named S2. The intendedfunction of glutaraldehyde is to keep the enzyme withoutbeing denatured by unfolding. When glutaraldehyde is usedas the cross linker in enzymatic biosensors, the bifunctionalaldehyde groups found at opposite ends of a five-carbon chainin glutaraldehyde reacts with lysines in the protein. The cross-linked protein is thereby resistant to unfolding, giving severaladvantages. It mainly increases the thermal and pH stabilityof the enzyme and increases operational lifetime by preventingthe unfolding process. The solubility of the enzyme decreasesdue to coupled molecules by cross-linking, and the enzymeshows resistance to solvents. Most of these advantages couldbe gained in our effort to cross-link GOx with glutaraldehydeon the nanoporous PPy electrode. Despite the fact that cross-linking increases lifetime, it affects the catalytic activity ofthe enzyme [18]. Therefore, the same enzyme and substratemay show different Kapp

m values, depending on the degree ofcross-linking.

Fig. 5 shows the time responses of sensor S2 after additionof various glucose concentrations. In this case, the same sensorwas washed with PBS, and a new PBS was added to the three-electrode cell every time before proceeding to the next stepof measurement. Fig. 6 shows the responses for successiveaddition of 0.5 mM of glucose to PBS with the same sensor.In both cases, the sensor shows similar current responses forthe same amount of glucose, regardless of the procedure thatwas followed to obtain repetitive measurements, and it gives

Fig. 5. Steady-state stability current density measurements of S2 for differentconcentrations of glucose. From bottom to top: 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 1, 2,5, 10, 12, 15, 20, and 50 mM, respectively.

Fig. 6. Current responses for successive addition of 0.5 mM of glucose to S2

at 0.4 V versus Ag/AgCl.

evidence of the good repetitive proposition of the sensor forthe same measurand. Furthermore, the sensitivity of sensor S2

was calculated to be 62.5 mA · M−1 · cm−2, and even after14 consecutive measurements, the sensor retained 80% of itssensitivity.

Fig. 7 gives the calibration curve of S2 (for three identicalsensors). The Kapp

m and Imax values for S2 were 3.3 mM and333 µA, respectively, from the Lineweaver–Burk method. Withtwo different values of Kapp

m for S1 and S2, we can clarify howthe affinity of the sensor is increased by introducing a cross-linking agent to the system. From these results, it is evidenthow the two sensors act as two different systems, although thesame enzyme and substrate have been used. Because of the highsensitivity caused by cross-linking in S2, saturation is morequickly reached than in the previous case.

Long-term shelf-life time measurements were conducted toobserve the decay of the sensor performance with time. Thesensor sensitivity showed a mean value of 41.31 mA · M−1 ·cm−2 (σ = 3.4, N = 4) after three months, giving only areduction of 33% of its initial value. This assures the possibilityof using this type of nanostructured PPy biosensor in a wide

EKANAYAKE et al.: AMPEROMETRIC BIOSENSOR WITH ENHANCED MEASUREMENT STABILITY AND SENSITIVITY 1625

Fig. 7. Calibration curve for the cross-linked sensor S2.

Fig. 8. Schematic of the proposed potentiostat measuring system.

range of applications with its long-term stability, shelf-life time,fast response, and very high sensitivity.

VII. MEASUREMENT AND SIGNAL

PROCESSING CIRCUITRY

In the current experimental setup, we have used an auto-matic polarization system (Hokuto Denko, model HSV-100)in a potentiostat mode. However, for this sensor to becomea marketable product, the measuring circuit also has to bedesigned at low cost while maintaining high precision. Fig. 8shows the schematic of the proposed measuring circuitry, wherethe working electrode (WE) is the newly devised nanoporousPPy electrode, the reference electrode (RE) is a Ag/AgCl thinwire, and the counter electrode (CE) is a thin platinum wire,all three integrated into a single sensor package. The requiredpotential can be set as VR, and the current flow is measured bythe instrumentation amplifier connected across the resistor R.This is only a schematic, and the noise elimination andimpedance matching has to be accordingly designed. A mi-crocontroller with high-resolution analog-to-digital and digital-to-analog converters is the most appealing way to cut downthe cost.

VIII. CONCLUSION

The artificially introduced nanoporous surface of the PPythin film has enhanced enzyme adsorption and led to a sig-nificant improvement in sensor characteristics. The use of glu-taraldehyde as a cross-linking agent has remarkably increasedthe sensitivity, reproducibility, stability, and shelf life of thisnanoporous glucose biosensor.

REFERENCES

[1] S. F. Peteu, D. Emerson, and R. M. Worden, “A Clark-type oxidaseenzyme-based amperometric microbiosensor for sensing glucose, galac-tose, or choline,” Biosens. Bioelectron., vol. 11, no. 10, pp. 1059–1071,1996.

[2] J.-H. Cho, M.-C. Shin, and H.-S. Kim, “Electrochemical adsorption ofglucose oxidase onto polypyrrole film for the construction of a glu-cose biosensor,” Sens. Actuators B, Chem., vol. 30, no. 2, pp. 137–141,Jan. 1996.

[3] S. Cosnier, A. Senillou, M. Gratzel, P. Comte, N. Vlachopoulos,N. J. Renault, and C. Martelet, “A glucose biosensor based on enzymeentrapment within polypyrrole films electrodeposited on mesoporous ti-tanium dioxide,” J. Electroanal. Chem., vol. 469, no. 2, pp. 176–181,Jul. 1999.

[4] S. Kaimori, T. Kitamura, M. Ichino, T. Hosoya, F. Kurusu, T. Ishikawa,H. Nakamura, M. Gotoh, and I. Karube, “Structural developments ofa minimally invasive sensor chip for blood glucose monitoring,” Anal.Chim. Acta, vol. 573/574, pp. 104–109, Jul. 2006.

[5] V. K. Gade, D. J. Shirale, P. D. Gaikwad, P. A. Savale, K. P. Kakde,H. J. Kharat, and M. D. Shrisat, “Immobilization of GOD on electro-chemically synthesized Ppy–PVS composite film by cross-linking via glu-taraldehyde for determination of glucose,” React. Funct. Polym., vol. 66,no. 12, pp. 1420–1426, Dec. 2006.

[6] T. Ahuja, I. Mir, D. Kumar, and Rajesh, “Biomolecular immobilizationon conducting polymers for biosensing applications,” Biomater., vol. 28,no. 5, pp. 791–805, Feb. 2007.

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[8] Rajesh, W. Takashima, and K. Kaneto, “Amperometric tyrosinase basedbiosensor using an electropolymerized PTS-doped polypyrrole film as anentrapment support,” React. Funct. Polym., vol. 59, no. 2, pp. 163–169,May 2004.

[9] M. Trojanowicz, O. Geschke, T. Krawczynski vel Krawczyk, andK. Cammann, “Biosensors based on oxidases immobilized in variousconducting polymers,” Sens. Actuators B, Chem., vol. 28, no. 3, pp. 191–199, Oct. 1995.

[10] M. M. Verghese, K. Ramanathan, S. M. Ashraf, and B. D. Malhotra,“Enhanced loading of glucose oxidase on polyaniline films based on anionexchange,” J. Appl. Polym. Sci., vol. 70, no. 8, pp. 1447–1453, Dec. 1998.

[11] M. Ma, L. Qu, and G. Shi, “Glucose oxidase electrodes based on mi-crostructured polypyrrole films,” J. Appl. Polym. Sci., vol. 98, no. 6,pp. 2550–2554, Sep. 2005.

[12] S. Gamburzev, P. Atanasov, A. L. Ghindilis, E. Wilkins, A. Kaisheva, andI. Iliev, “Bifunctional hydrogen peroxide electrode as an amperometrictransducer for biosensors,” Sens. Actuators B, Chem., vol. 43, no. 1–3,pp. 70–77, Sep. 1997.

[13] E. M. I. M. Ekanayake, D. M. G. Preethichandra, and K. Kaneto, “En-hanced adsorption of glucose oxidase by introducing artificial porosityinto polypyrrole based glucose biosensors,” in Proc. IMTC, Warsaw,Poland, May 1–3, 2007, pp. 1–4. #7410.

[14] E. M. I. M. Ekanayake, D. M. G. Preethichandra, and K. Kaneto,“Polypyrrole nanotube array sensor for enhanced adsorption of glucoseoxidase in glucose biosensors,” Biosens. Bioelectron., vol. 23, no. 1,pp. 107–113, Aug. 2007.

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[16] B. E. P. Swoboda and V. Massey, “Purification and properties of theglucose oxidase from Aspergillus niger,” J. Biol. Chem., vol. 240, no. 5,pp. 2209–2215, May 1965.

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[18] H. K. Das, Textbook of Biotechnology, 2nd ed. New York: Wiley, 2005.p. 695.

1626 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 57, NO. 8, AUGUST 2008

E. M. I. Mala Ekanayake received the B.Eng. de-gree from the University of Peradeniya, Peradeniya,Sri Lanka, the M.Eng. degree in multifunctionalsensing from Saga University, Saga, Japan, and thePh.D. degree from Kyushu Institute of Technology,Kitakyushu, Japan.

She was an Engineer with Sri Lanka Telecom. Sheis currently with Kyushu Institute of Technology. Herresearch interests include applications of conductingpolymers in sensors and actuators.

D. M. G. Preethichandra (M’96–SM’03) re-ceived the B.Sc. degree in electrical and electron-ics engineering from the University of Peradeniya,Peradeniya, Sri Lanka, and the M.Eng. degree intelecommunication engineering and the Ph.D. degreein electrical engineering, specializing in multifunc-tional sensors, from Saga University, Saga, Japan.

He was a member of Academic Staff with theOpen University of Sri Lanka, Colombo, Sri Lanka;Saga University; the University of Melbourne,Parkville, Vic., Australia; and the University of

Southern Queensland, Toowoomba, Australia. After winning a postdoctoralfellowship from the Japan Society for the Promotion of Science, he joinedKyushu Institute of Technology, Kitakyushu, Japan, where he is currentlya Research Fellow with the Kitakyushu Foundation for the Advancementof Industry, Science, and Technology (FAIS). His research interests includehuman-imitating robotics, robotic education, sensors, and actuators.

Keiichi Kaneto received the B.E. and M.E. degreesin electrical engineering and the Ph.D. degree inelectrical engineering, specializing in organic elec-tronics, from Osaka University, Osaka, Japan.

He was an Assistant Professor with the Faculty ofEngineering, Osaka University, from 1976 to 1989.He moved to the Faculty of Information Scienceand Systems Engineering, Kyushu Institute of Tech-nology, Kitakyushu, Japan, as a Full Professor. In2000, he became a Full Professor with the GraduateSchool of Life Science and Systems Engineering.

His research interests include organic electronic devices, particularly diodes,solar cells, and memory. He is working as a pioneer on soft actuators based onconducting polymers.