Research: Electromechanical Response of Polymers
Zhao H. Fang and Peng Jiang
Advisors: Dudley A. Saville and Ilhan A. Aksay
In collaboration with George M, Whiteside, Harvard University
Electric field induced deformation in electroactive polymer is a well-known phenomenon [1,2]. First, a dielectric polymer is sandwiched between the two parallel electrodes. Then, as an electric field is applied, contraction of the polymer will occur to bring the two electrode plates closer to each other. The two well recognized contributions to such effect are the Maxwell’s stress and electrostriction [3,4]. The Maxwell stress stems from the electrostatic attraction between the two electrodes, while electrostriction is related to the change of dielectric constant of the material being strained. Field type electroactive polymers are considered to be effective actuators for their large strain levels (>100%) [5], fast response, low hysteresis, and high elastic energy density (>0.3 J/cm3) [6]. One drawback of using field type electroactive actuators is the requirement for high voltage due to the small dielectric constant in polymeric materials [7]. Encouraged by other workers who succeeded in enhancing the dielectric constant in polymer matrix by addition of high-dielectric fillers [8,9], we now focused on incorporating different high dielectric materials (self-made or externally provided) into elastomers and testing the electric field induced strains.
Figure 1: Schematic of basic electromechanical system in which an electric field causes elastic polymers to deform.
Currently, we are conducting experiments on PDMS (polydimethylsiloxane) (Sylgard 184, Dow Corning) filled with barium titanate particles (HPB 4000, NanoxideTM) with size of about 400 nm. PDMS is an elastomer with a reported dielectric constant of 2.65, while barium titanate particles have dielectric constants between 300 and 3000. So far, we have been able to achieve uniform dispersion at concentration below 10 vol% barium titanate. After the composites are cured, gold is deposited on the surface to serve as the counter electrode.
For more information on this research topic, please contact Zhao Heng Fang. Additional information concerning the CML can be found on our website.
References
1. Y.M. Shkel, D.J. Klingenberg, J. Appl. Phys. 80, 4566 (1996)
2. I. Krakovsky, T. Romijin, A. Posthuma de Boer, J. Appl. Phys. 85, 628 (1999)
3. M. Zhenyi, J.I. Scheinbeim, J.W. Lee, B.A. Newman, J. Polym. Sci., Part B, Polym. Phys. 32, 2721 (1994)
4. Q.M. Zhang, J. Su, C.H. Kim, R. Ting, R. Capps, J. Appl. Phys. 81, 2770 (1997)
5. R. Pelrine, R. Kornbluh, Q. Pei, J. Joseph, Science. 287, 836 (2000)
6. Q.M. Zhang, V. Bharti, X. Zhao, Science. 280, 2101 (1998)
7. Y. Bar-Cohen (ed.), Electroactive Polymer [EAP] Actuators as Artificial Muscles (SPIE, Bellingham, WA, 2001)
8. Q.M. Zhang, H. Li, M. Poh, F. Xia, Z.-Y. Cheng, H. Xu, C. Huang, Nature. 419, 284 (2002)
9. D. Khastgir, K. Adachi, J. Polym. Sci., Part B, Polym. Phys. 37, 3065 (1999)
© 2006 Princeton University, Ceramic Materials Laboratory.All Rights Reserved.
