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Procedía Engineering
ELSEVIER
Procedía Engineering25 (2011) 203 - 206
www.elsevier.com/locate/procedia
Proc. Eurosacsors XXV, Saptambar 4-7, ngll, Athacs, Graaca
All polymar piazoalactric film for tha ppplicptioc to low rasocpcca fraquaccy acarey hprvastar
S. Tpkpmptsup*, T. Kobpypshib, T. ImpiP, T. Ypmpshitpppcd T. Itohp,b
aBEANS laboratory, 1-2-1 Namiki Tsukuba, Japan bNational Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki Tsukuba, Japan
Abstract
Wa davalopad pll polymar piazoalactric film which cocsists of PET substrpta, cocductiva polymar alactroda, polyvicilidaca fluorida iPVDF) piazoalactric film ic ordar to pchiava tha low rasocpcca fraquaccy of acarey hprvastice davica. Existice piazoalactric films hpva baac dapositad oc rieid silicoc or icorepcic mptaripls which lapd to hieh rasocpcca fraquaccy pcd low afficiaccy of acarey eacarptice ucdar low fraquaccy of humpc motioc or othar motiocs. Tharafora, wa davalopad pll polymaric piazoalactric films oc vary soft PET films. To daposit PVDF film oc PET, low tamparptura coptice procass usice low boilice tamparptura solvact iMathyl athyl katoca) pcd pccaplice mathod iucdar 15) °C) wps davalopad. Davalopad film pchiavad low fraquaccy of 54 Hz.
© ngll Publishad by Elsaviar Ltd.
Key words: PVDF; Mathyl athyl katoca; PEDOT:PSS; acarey hprvastice
1. Introduction
Recently, energy harvesting devices for micro sensors and their networked systems have been much attention because of their advantage of powering them without batteries[1]. Replacing batteries for a large number of networked sensors requires large volume of labours and has disturbed widespread use of them. Since some of sensors networked systems are applied for monitoring human or other machine's conditions, vibrations of them have been thought to be their energy sources[2]. In these applications, conventional silicon or other inorganic based piezoelectric devices are not suitable because their resonance frequency is several kHz[3] although the frequencies of human motions are several tens of Hz. Thus, flexible and soft polymer-based piezoelectric films such as polyvinylidence difufluoride (PVDF) are optimal candidate for these applications. To form these materials on flexible polymer substrate for * Corresponding author. Tel.:+81-29-868-3883; fax:+81-29-868-3884. E-mail address: stakamatsu@beanspj .org.
1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.12.050
S. Takamatsu et al. / Procedia Engineermg25 (2011)203 - 206
(a) Concept
All polymer piezo electric film
vPVDF/TrFE \ (Piezoelectric Polymer) PEDOTrPSS (electrode) PET film (substrate)
Energy harvesting devices.
(b) Structure of PVDF on PET
Induced Strain on PVDF
Large thickness PET substrate is required
Fig. 1. (a) concept of all polymer piezoelectric film for low frequency energy harvesting devices; (b) structure of PVDF film on PET film. PVDF film generates large charge thickness of PET film.
low frequency applications, low temperature process was required because conventional polymer substrate like polyethylene terephthalate (PET) film changes its shape over 150 °C. Therefore, we have developed low temperature process of polymer piezoelectric film on PET film and formed low frequency energy harvesting device (fig. 1 (a)). The device consists of polymer electrode of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), PVDF and PET substrate. Bending the film induces piezoelectric effect between polymer electrode through the generation of strain on PVDF film (fig. 1 (b)). After the developed process was described, the processed film was characterized in this paper.
2. Fabrication Process and Experimental
The structure of all polymer piezoelectric film is composed of PVDF, PEDOT:PSS electrode and PET substrate (fig. 1). Figure 2 shows the fabrication process consisting of PEDOT:PSS coating on PET film, PVDF coating, PEDOT:PSS. Firstly, PET film was prepared (fig.3 (a)). The lower electrode was formed with PEDOT:PSS through PEDOT:PSS water-dispersion coating and drying (fig.3 (b)). PVDF was coated with the PVDF solution in which PVDF powder was diluted with low boiling temperature solution of Metylethyle ketone (MEK) (fig.3 (c)). Then, upper electrode was formed with PEDOT:PSS and the resultant film was annealed and poled (fig. 3 (d), (e)).
Figure 3(a) shows the low temperature coating of PVDF. PVDF which solved in solvent should be dried in the temperature under 150 °C because PET film was melt over the temperature. Conventional PVDF solvent is DMF or NMP whose boiling temperature are over 150 °C. To solve this problem, we utilized MEK whose boiling temperature is 79.5 °C.
After coating PVDF film, we optimized the annealing temperature. The temperature of 150 °C achieved (a) PET film_ (d) PEDOT:PSS coating
(e) Anealing and poling
(c) PVDF coating
Fig. 2. Fabrication process of all polymer PVDF film.
S. TSamatsuet al. /Procedia Engineermg25 (2011) 203- 206
Low temperature PVDF eoating
Solvent DMF NMP MEK
Boiling point [°C] 153 202 79.5
Solubility [wt%] 10 10 20
Low temperature annealing PVDF film before annealing PVDF film after annealing
2 6 [de6]
Fig. 3. (a) Low temperature solvent of PVDF. Methylethyl ketone (MEK) is low boiling temperature and high solubability; (b) Aneeling temperatures and their crystallinity
(a) (b)
500 -400
o 300 -rx
200 ' 100 0
100 110 120 130 140 150
Temperature [degree]
Fig. 4. Poling voltage and the residua polarization under different temperatures.
highest crystallinity in fig. 4. In the poling process of PVDF film, the applied voltage of 100 V/^m is required for high residual polarization (fig. 4(a)). The residual polarization was also characterized under different temperatures and poling voltage of 100 V/^m. The film annealed at the temperature of 150 °C exhibited largest residual polarization (fig. 4(b)). Therefore, 150 °C is the optimal temperature for annealing of PVDF film.
The processed PVDF film on PET substrate was shown in fig. 5 (b). When the film was bent, the film generates electric potential of 2 V in figure 5 (b). The frequency of the device was characterized. Fig. 5(c) shows the resonant frequency of 54 Hz which is very low in comparison with several kHz of existing PZT films.
206 S. Takamatsit et al. / Procedia Engineering25 (2011)203 - 206
Time [s]
Frequency [Hz]
Fig. 5. (a) Processed all polymer PVDF film.; (b) Generating voltage of the PVDF film; (c) resonant frequency of the PVDF film.
3. Conclusions
We developed all polymer piezoelectric film which consists of PET substrate, PEDOT:PSS electrodes, PVDF film. To deposit PVDF film on PET, low temperature coating process using low boiling temperature solvent of MEK and annealing method (under 150 °C) was developed. Developed film achieved low frequency of 54 Hz.
Acknowledgements
This study has been being conducted as one of the research items of New Energy and Industrial Technology Development Organization (NEDO) project "Development of Manufacturing Technologies for Hetero Functional Integrated Devices "(BEANS project).
References
[1] J. A. Paradiso, T. Starner, "Energy scavenging for mobile and wireless electronics," Pervasive computing, pp. 18-27, 2005.
[2] M. Renaud, P. Fiorini, R. Schaijk, C. Hoof, "Harvesting energy from the motinon of human limbs: the design and analysis of an impact based piezoelectric generator," Smart Materials and Structures, vol. 18, 235001, 2009.
[3] H. Fang, J. Liu, Z. Xu, L. Dong, L. Wang, D. Chen, B. Cai, Y. Liu, "Fabrication and performance of MEMS-based piezoelectric power generator for vibration energy harvesting," Microelectronics Journal, vol. 37, pp. 1280-1284, 2006.
