Materials Science and Engineering B 165 (2009) 50–52
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Polymer temperature sensor for textronic applications Sylwia Bielska a,∗ , Maciej Sibinski a , Andrzej Lukasik b,1 a b
Department of Semiconductor and Optoelectronics Devices, Technical University of Lodz, 211/215 Wolczanska Str., 90-924 Lodz, Poland Institute of Electron Technology, Krakow Division, Poland
a r t i c l e
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Article history: Received 20 June 2008 Received in revised form 24 March 2009 Accepted 23 July 2009 Keywords: Polymer Thin ﬁlms Temperature sensors Textronics
a b s t r a c t The aim of this paper is to present research work of designing prototype textile sensors dedicated to human body temperature measurements. The sensor construction was especially elaborated to be integrated into protective clothing as a practical realization of intelligent e-textile concept. These types of sensors should be easily incorporable in clothing structures without disturbance of fabric ﬂexibility (Carpi and De Rossi ). The construction of the new type functional sensor testing is presented and illustrated by its parameters and thermal characteristics. © 2009 Elsevier B.V. All rights reserved.
2. Thermo-sensitive polymers
Extensive potential of the new, miniaturized electronic equipment gives a hint to develop a new quality of applications. Close cooperation between new electronic materials development, devices research, sensors technology and modern textile solutions resulted in evolving of the textronic ﬁeld. Applications of this interdisciplinary technology seem numerous. One of the interesting potential implementation is a human protective suit, equipped with the complete set of biomedical status monitoring sensors, for example internal temperature monitoring, using textile sensors, external chemical detection, including toxic gases and vapours, continuous monitoring of life signals (biopotentials, breathing movement, cardiac sounds) and others . Major conditions must be performed for proper functioning of textronic body temperature sensor:
Polymers, thermo-sensitive materials, were developed for the project needs. Expected thermo-sensitive polymer paste should be characterized by a high temperature coefﬁcient (TC), resistance to weather and abrasion. It could be positive TC (PTC) or negative TC (NTC) one. During experiments PTC polymer material was obtained, which means that the structure resistance increases with temperature rise. The paste suitable for the screen-printing process was made of carbon–polymer composites. Since adequate selection of polymer binder is a very important part of the paste formation process, as a binder material rubber and polyethylene modiﬁed polystyrene were used . After screen-printing process the thermistor paste was heated at the temperature of 120 ◦ C during 20 min. Decisive inﬂuence for thermistor parameters played cooling time. It should be chosen experimentally, in order to obtain the best TC. Mesh size was stated at the level of 200, thus as a result of screen-printing process the thickness of obtained active layers varied between 6 and 8 m.
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high measurement accuracy in active range (35–42 ◦ C); high ﬂexibility; small dimensions; humidity and environmental endangers resistance; low weight; harmless to human body.
∗ Corresponding author. Tel.: +48 42 636 79 99; fax: +48 42 636 80 24. E-mail addresses: [email protected]
(S. Bielska), [email protected]
(M. Sibinski), [email protected]
(A. Lukasik). 1 Tel.: +48 12 656 34 72. 0921-5107/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2009.07.014
3. Thermistor structure The basic scheme of the manufactured temperature sensor is presented in Fig. 1. As a substrate material the polyamide foil “KAPTON® ” was chosen. This selection guarantees high ﬂexibility, ensuring good adaptation to textile applications and high temperature and moisture resistance. As it was mentioned thermistor paste is a non-commercial polymeric one, deposited by the ﬁne-mesh screen-printing technique on the elastic substrate. At the beginning of the investigation elastic contacts were made of polymeric
S. Bielska et al. / Materials Science and Engineering B 165 (2009) 50–52
In order to temperature sensor realization a few types of contact shape and dimensions were designed. In Fig. 3 contacts made of photolithography method are shown. With the purpose of obtaining diversiﬁed values of initial resistance the different masks were proposed. Such metal contacts are characterized by a good adhesion to the substrate and high durability according to environment inﬂuence, such as oxidation. Obtained thermistors are shown in Fig. 4.
Fig. 1. Temperature sensor—cross-section.
4. Parameters of temperature sensors
Fig. 2. Contact cross-section.
conductive paste. Due to possible mechanical stress the contacts are at risk of serious structure damage, since polymeric paste is not resistant to abrasion. This fact suggested the new approach of contact structure. New ﬂexible thermistor contacts are based on gilding copper. The contact cross-section is presented in Fig. 2.
Thermistors were tested by the help of measurement setup, presented in Fig. 5. The full laboratory setup consists of thermometer, calorimeter covered by thermal insulation, digital multimeter coupled with registration computer, PC equipped with own-designed software tool and examined thermistors (Th 1, Th 2,. . ., Th n). During the resistance measurement thermistors were placed on external wall of internal calorimeter vessel. Resistance is measured from 30 to 42 ◦ C, at 1◦ intervals. Results of measurements of series 1, 2 and 3 are shown in Figs. 6–8, respectively. In these ﬁgures the diversity of thermistor properties is clearly detectable.
Fig. 3. Different thermistor contacts deposited on KAPTON® foil.
Fig. 4. Manufactured ﬂexible temperature sensors.
Fig. 5. Measurement setup.
S. Bielska et al. / Materials Science and Engineering B 165 (2009) 50–52
Fig. 6. Results of series 1.
Fig. 7. Results of series 2.
Fig. 8. Results of series 3.
First series is characterized by the highest initial resistance, which was decreased during the improvement of technological process. Diversiﬁcation of presented results was obtained thanks to different thermistors dimensions and also thanks to modiﬁcation of initial temperature proﬁle. Cooling time, which appeared the key to desired TC value and linearity, was deliberately selected to obtain the best thermistor parameters.
tic, accompanied by high thermal resistance change, ensures wide application ﬁeld. The implementation in new textronic products is under discussion. Acknowledgements The research was conducted within the frame of WKP 1/1.4.4/1/2005/4/4/238/2006/U/I project of Polish Sciences and High Education Ministry.
5. Conclusions References New generation of textronic temperature sensor, based on polymer paste material was elaborated. A few conceptions of the ﬂexible thermistor were manufactured and veriﬁed in respect of temperature measurements. Temperature sensor properties are satisfactory, however, further developments are under consideration. High ﬂexibility of examined sensors assures their compatibility with textronic applications. Good linear characteris-
 A. Lukasik, S. Nowak, Relaxation of stress in polymer–carbon microcomposite resistive layers, in: XXX Conf. IMAPS-Poland, Krakow, 24–27 September, 2006.  K. Gniotek, I. Krucinska, The basic problems of textronics, Fibres & Textiles in Eastern Europe 12 (January/March (1)) (2004) 45.  F. Carpi, D. De Rossi, Electroactive polymer-based devices for e-textiles in biomedicine, IEEE Transactions on Information Technology in Biomedicine 9 (September (3)) (2005) 298.