A novel flexible large strain sensor was developed to be use with an air muscle. A piece of butyl rubber was coated with the conducting polymer, polypyrrole through bulk solution and chemical vapour deposition method. The strain sensor was able to response to sudden movements represented by the multiple step functions of the applied strain. Consistency of the sensor's output was studied and the average error in the change of resistance was calculated to be 0.32% and 0.72% for elongation and contraction respectively for the sample made using chemical vapour deposition. However, a hysteresis was observed for this sample for a single cycle of elongation and contraction with the highest error calculated to be 3.2% at a 0% applied strain. SEM images showed the propagation of surface micro-cracks as the cause of the variation in surface resistance with applied strain. In addition, slower relaxation rate of the rubber prevented the surface micro-cracks to open and close at the same rate. The idea of utilizing conducting polymer coating can be applied to the inner rubber tube of the air muscle. As such, a complete integration between actuator and sensor can be realized.

Date Published: 9 April 2010
PDF: 8 pages
Proc. SPIE 7642, Electroactive Polymer Actuators and Devices (EAPAD) 2010, 764228 (9 April 2010); doi: 10.1117/12.847440

Published in SPIE Proceedings Vol. 7642:
Electroactive Polymer Actuators and Devices (EAPAD) 2010
Yoseph Bar-Cohen, Editor(s)