WEARABFOR H

M.K. Kim1, M.S. K1School of Mechanic

ABSTRACT

In this study, a wearable thermo(TEG) in the flexible fabric is proposhuman body heat energy to electrical eneTEG is composed of a flexible thermoelectric columns (Bi2Te3) and elebased on conductive fabric component. Tshowed the flexibility and the wearabilapplied to the human body. The TEGdispenser printing, and the fabricated applied contact heat into electrical eneWhen the TEG applied to the human booutput power was 178 nW in ambient tem KEYWORDS

Wearable thermoelectric generatorharvesting, human body, dispenser printi INTRODUCTION

The increasing use of portable electmedical implants, the issues such as auwireless power is more important in alternative approach is to extract varioufrom outside [1]. Of these, body heat eneharvest electrical energy at anytime and abody heat energy is converted into electrithermoelectric generator (TEG). The advantages such as compact, silent and horder to harvest body heat, the energy ghave flexibility and wearability for guactivity.

There have been various researchTEGs that are realized on a polymecommon approach is fabricated by evapon flexible substrate [3-4]. J. weber et coiled-up polymer foil TEG for wearabWulf glatz et al. used a combination of coa thick flexible polymer mold formed by[6]. Another approach is dispenserthermoelectric devices [7]. While most flno consideration of wearable form and limited by the thickness of the substechniques require a complex fabrication

In this research, a wearable TEG in fis proposed for applying to human bowearable TEG offers flexibility through ttextile and a polymer structure. The uthread and fabric structure allows the wearability. To simplify the fabrication pdispenser printing method. By a large-scale production is possible. The Edevice using wearable TEG is expected tvariety of applications. These include mo

BLE THERMOELECTRIC GENERATORHUMAN CLOTHING APPLICATIONS

Kim1, S.E. Jo1, H.L. Kim1, S.M. Lee1 and Y.J.cal Engineering, Yonsei University, Republic

electric generator ed for converting

ergy. The wearable fabric material,

ectrical connection The proposed TEG lity suitable to be G was fabricated device converted

ergy (0.98 μV/K). ody, the measured mperature of 5 °C.

r, flexible, energy ing

tronic devices and uxiliary power and

recent years. An us energy sources ergy generator can anywhere [2]. The ical energy using a

TEG has many high reliability. In generator needs to aranteeing human

hes about flexible er substrate. The porating thin films al. used coin-size

ble electronics [5]. opper and nickel in y photolithography r printed planar

flexible TEGs have their flexibility is

strate. And these n of the device. fabric components dy. The proposed the integration of a use of conductive TEG to have the

process, we use the simple process,

Energy conversion to be available in a obile phone battery

charging, real-time checking ofthe positioning signal in emerg

We fabricate a prototype tand tried to test the performanhuman body. In the followinwearable TEG of the design, fas well as discussions on the subody are presented. DESIGN

Figure1. The concept views TEG device. (a) the front viewthe side view.

Thermoelectric generators

Seebeck effect, the temperatujunctions is converted to electrvoltage being converted is coefficient , number of thtemperature difference Δ .

The maximum output ele

impedance matching given by

where internal resistance of

Fig.1. shows the concepprinciple of the proposed wpolymer film is attached to the structure has windows for incolumns of p- and n-type mateand cold junction are arranged bottom side, each thermocoupby conductive fabric fiber, wbottom side contacts to the hum

R

Kim1* c of Korea

f the status of the body and ency situation. through the simple process, nce when applied to a real ng sections, the proposed fabrication steps and results uitability of applying human

of the proposed wearable

w, (b) the back view and (c)

s (TEGs), i.e. the using the ure difference between two ric energy. The open circuit

proportional to Seebeck hermocouples n and the

Δ (1)

ectric power with optimal

(2)

f thermopile. pt views and the working earable TEG device. The fabric structure. The fabric

nserting the thermoelectric erials (Bi2Te3). Hot junction each to the top side and the le is electrically connected

which silver contained. The man body (25~35 °C). The

T3P.117

978-1-4673-5983-2/13/$31.00 ©2013 IEEE 1376 Transducers 2013, Barcelona, SPAIN, 16-20 June 2013

top side is exposed to the outside (-20~4heat exchange with ambient air. The trelatively low temperature and maintaindifference with the bottom. When the ouis lower, the TEG can get a higher powe

Fig.2 shows the simulation result odifference between top and bottom side wTEG is attached on the human body. Inwas assumed that the temperature of theambient air is 32 °C and 15 °C, respecdifference between the body temperaturtemperature is 17 °C, temperature differand cold junction is about 1 °C. The simsmall device shows that the tempebetween each side of the TEG is enelectrical energy on the human body. Allwere made using the ANSYS package awith theoretical calculations. FABRICATION AND EXPERI

The wearable TEG is fabricated by dThe conventional methods of sputtering expensive for future mass market Dispensing printing does not require extechniques. Therefore, there is an advaand batch fabrication process.

Fig.3 shows the fabrication polyester-based fabric, commonly usedflexible and lightweight material. The made of silver-plated, was used to fix to telectrically connecting. The polymer filmthe fabric layer for substrate of thermoand electrical isolation between the thermskin. The prepared printable ink of Bi2Tethe windows of the fabric layer and cure

The weaving process is needed forfixing to the substrate fabric. First, Fix toconductive thread in a line, and then eacThermoelectric elements have to be cdown electrically in each section.

Figure2. FEM simulation results of theelement on the human body (Tambient_air=1Thuman_body=32 °C).

40 °C), there occur top surface has a ns the temperature utside temperature r.

of the temperature when the wearable

n the simulation, it e human body and ctively. When the re and the outside rence between hot

mulation result of a erature difference nough to generate l simulation results and it is consistent

IMENT dispensing printing. or evaporation are

products [8-9]. xpensive thin film antage to low cost

processes. A d for clothing, is conductive fiber,

the fabric layer for m was attached to oelectric elements mocouples and the e3 was inserted into d. r conductive fiber

o the substrate with ch section cutting. connected up and

Complex thermoelectric Bi2Se3, or Sb2Te3 have a hitemperature [10]. In this researBi2Te3 powder (100 meshes) ofto consist of a thermocoupstoichiometric ratio can get the have used the each type of the pA mixture of the ceramic bindinject to using a dispenser in eacthe TEG, it needs curing at rooand sintering at 100 °C for relatively low temperature canand there is no damage to theexcellent electrical performanceclothing.

Relevant dimensions of thein table 1. The TEG included t80 mm × 45 mm area. Each thethickness is 0.5 mm. The totaTEG is about 300 ohms. Fiwearable TEG and photos of human body. As shown in figuhighly flexible and durable.

Table1. Table of measured matparameters.

e thermoelectric 15 °C,

Figure3. Fabrication process fothermoelectric device.

materials such as Bi2Te3, igh thermopower at room rch, thermoelectric material f the n- and p-type was using ple. By adjusting precise

n-and p-type character. We products sold in the market. der and the Bi2Te3 powder, ch hole. For high strength of

om temperature for 24 hours 2 hours. The process of

n make simple manufacture fabric. The used binder is e and durable to suitable for

e fabricated TEG are shown twenty thermocouples in an ermopile radius is 5 mm and al internal resistance of the ig.4 shows the fabricated

f the device applied to the ure, the fabricated TEG was

terial properties and design

for a dispenser-printed

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Figure4. (a) Images of printed 20-coupledevice. (b) Demonstration of bending wethermoelectric generator by hand. (c) Clthe dispenser printed thermocouples andworn on the human body.

In order to test the thermoelectric prowe set up the thermal experimental temperature difference can be adjusted viPeltier cooler. The wearable TEG put itand then temperature and voltage changby the temperature sensor and the optimal output, load resistance was matcresistance (300 ohms). The open circfunction of temperature difference Δthen temperature difference is from 3 °C

The following experiment wasperformance in real-world envithermoelectric devices attached to theoutput power was estimated at the ind(about 25 °C). Another experiment wascold outside environment (about 5 °C).

RESULTS AND DISCUSSION

Fig.5-(a) and (b) shows the measurand power as a function of the tempbetween each junction, respectivelygenerates, at 30 °C temperature differencabout 25 mV with optimal impedance man electrical output power is up to 2.shows the linear dependence between thtemperature difference of the wearthermopower can be calculated from the to a value of about 0.98 mV/K.

Table 2 shows the measured output vwhen the fabricated TEG was worn onhuman body. The measured human bodyabout 32 °C. When ambient air temperatgenerated output power of the TEG was output power of the TEG increased tambient air temperature decreased to 5 °

As a result of applying to the humabetter than the results of the laboratory reason seems to that the skin temperatquickly according to ambient temperatuused to thin polyester base fabric. But

e thermoelectric earable lose-up view of d (d) TEG being

operty of the TEG, equipment. The

ia a hot-plate and a t on the hot-plate, ge were measured oscilloscope. For

ched to the internal cuit voltage as a is recorded. And

C to 30 °C. s to verify the ironments. The e chest, and then door environment s conducted in the

red output voltage erature difference . The prototype

ce, an open voltage matching. And then .08 μW. Fig.5-(a) he voltage and the rable TEG. The slope, which leads

voltage and power n the chest of the y temperature was ure was 25 °C, the about 15 nW. The to 178 nW when °C. an body, it was not environment. The ture was changed

ure. The prototype if using the good

insulation material for a substrahigher. The prototype in this welectrical contact resistance beand dispenser printed thermoeable to get better performanceelectrical performance binder.

Table2. The energy transductiTEG on the human body.

CONCLUSIONS

In this work, we present type energy harvester using prototype has been applied to the thermoelectric performanshowed the flexibility and wapplied to the human body.

The fabrication process ofsuccessfully performed. The fa20 thermocouples has a thermomV/K and is able to generatetemperature difference of 30 °Ccan generate up to 178 nW in am

Figure5. Output results of generator (a) open circuit outpas a function of top-bottom tem

ate fabric, efficiency will be work has the loss due to the etween the conductive fiber electric elements. It will be e by using a more superior

ion results of the wearable

the possibility of clothing the wearable TEG. The

an actual fabric, and tested nce. The proposed TEG wearability suitable to be

f the dispenser printing was abricated TEG consisting of opower output of about 0.98 e a voltage of 25mV at a C. In actual environment, it mbient temperature of 5 °C.

the 20-couple prototype put voltage and (b) power mperature difference.

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Our future work is focused on improves performance by using excellent thermoelectric materials and a variety of fabrics. And we will develop packaging technique for a more appropriate form of the wearable TEG. ACKNOWLEDGEMENTS

This research was supported by the Pioneer Research Center Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (2011-0001672) and Priority Research Centers Program through the National Research We verify the performance of a thermoelectric device in lab through the following experiment was to verify the performance in real-world environments. Education, Science, and Technology (2009-0093823).

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[3] A. Yadav, K.P. Pipe, M. Shtein, “Fiber-based flexible thermoelectric power generator”, Journal of Power Sources, Vol. 175, pp.909–913, 2008.

[4] Koichi Itoigawa, Hiroshi Ueno, Masayoshi Shiozaki, Toshiyuki Toriyama and Susumu Sugiyama, “Fabrication of flexible thermopile generator”, J. Micromech. Microeng., vol. 15, pp.S233–S238, 2005.

[5] J. Weber, K. Potje-Kamloth, F. Haase, P. Detemple, F. V¨olklein, T. Doll, “Coin-size coiled-up polymer foil thermoelectric power generator for wearable electronics”, Sensor. Actuat. A, vol. 132, pp. 325-330, 2006.

[6] Wulf Glatz, Simon Muntwyler, Christofer Hierold, “Optimization and fabrication of thick flexible polymer based micro thermoelectric generator”, Sensors and Actuators A vol. 132, pp. 337–345, 2006.

[7] A Chen D Madan1, P K Wright and J W Evans, “Dispenser-printed planar thick-film thermoelectric energy generators”, J. Micromech. Microeng. Vol. 21, 2011.

[8]L. Francioso, C. De Pascali, I. Farella, C. Martucci, P. Cretì, P. Siciliano., “Flexible Thermoelectric Generator for Wearable Biometric Sensors”, IEEE Sensor, 2010.

[9] L M Goncalves, J G Rocha, C Couto, P Alpuim, GaoMin, D M Rowe and J H Correia, “Fabrication of flexible thermoelectric microcoolers using planar thin-film technologies”, J. Micromech. Microeng. vol. 17, pp. S168–S173, 2007.

[10] D.M. Rowe (Ed.), “CRC Handbook of Thermoelectrics”, CRC Press, New York, 1995.

[11] A. J. Minnich, M. S. Dresselhaus, Z. F. Ren and G. Chen, “Bulk nanostructured thermoelectric materials: current research and future prospects”, Energy Environ. Sci., vol. 2, pp. 466–479, 2009

CONTACT

*Y.J. Kim, tel: +82-2-2123-2844; yjk@yonsei.ac.kr

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