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The present study newly attempts the numerical simulation of the mechanical sensors using conducting polymers which generate electricity in the transient response to mechanical stimulation. The generated electric potential in the mechanical sensors is very much smaller than the supplied electric potential of the actuators with respect to the same deformation and structure. The present simulation procedure modifies and integrates the existing theories, and then the features of the transient behaviors, e.g. the non-invertible relation between electrical potential and deformation, relaxation and hysteresis, are numerically simulated. The governing equations of the physical phenomena in the sensation are coupled by embedding driving forces with physical parameters such as solid stress, fluid pressure, ion concentration and electric potential. The governing equations and fields of the physical parameters are spatially simplified as one-dimensional in the thickness direction of the sensors, because their variations over thickness dominantly determine the behavior of the sensor. In addition, the numerical procedure is efficiently simplified as possible as the transient behaviors are expressed. Next, the undrained Poisson's ratio is modified with a correction factor, and its significant effect on the transient behavior is investigated. Lastly, the procedure of the computational system for the sensors is introduced and fully coupled simulation is conducted. As a result, the present study reports the simulation results of the important physical quantities over the microscale thickness.

IntroductionIPMCs (ionic polymer-metal composites) have been known as intelligent materials having actuating and sensing functions, e.g. from electricity to deformation and from electricity to deformation. Owing to versatile characteristics such as low voltage, lightweight, easy access and flexibility, IPMCs have attracted attention as prospective applicants for artificial muscles, robotics, MEMS and so on (Jung et al., 2010). Such applications are based on actuating and sensing functions with mechanical and electrical measures. In order to investigate the actuating and sensing functions, some papers Zamani, 2006 andJung et al., 2010) have attempted to simulate the actuating behaviors of IPMCs with more complicated models. However, the simulation of mechanical sensors using IPMCs has not been reported except for black box models. Numerical simulation is needed to understand and verify the complicated behaviors of the mechanical sensors, and its quantitative results are necessary for the design and control. Hence, the present study investigates a white box model with continuum mechanics, following macroscopic measurements.The typical structure of IPMCs is illustrated in Fig. 1. It consists of an ionic conducting polymer and metal deposits. The ionic polymer is a membrane that play roles electrolyte in the transport of ions and solvent, and the metal deposits function as electrodes.In the membrane, ionomers are composed of hydrophobic backbone polymers and the covalently attached anions which are 1 Numerical simulation of mechanical sensors using hydrated IPMCsSeongwon YOO* and Yutaka TOI* * Institute of Industrial Science, University of Tokyo E-mail: yoosw@iis.u-tokyo.ac.jp Received 1 August 2014 AbstractThe present study introduces the numerical simulation of mechanical sensors using IPMCs (ionic polymer-metal composites). IPMCs can be applied into both of actuators (from electricity to deformation) and mechanical sensors (from deformation to electricity), but the existing models of the actuators cannot be inversely applied to the mechanical sensors.

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