An electro-chemo-mechanical theory for hydrogel ionotronics: Application to modeling a capacitive strain sensor and a dynamic large strain actuator

Hydrogel ionotronic devices show substantial potential for use in soft robotics as well as in wearable and implantable actuators and sensors, especially when low weight, high flexibility and optical transparency are important. In this paper we formulate a finite-deformation theory for modeling the coupled electro-chemo-mechanical response of ionic hydrogels, and describe our numerical implementation of the theory in a finite element program. We show that our numerical simulation capability is able to successfully model the response of two ionotronic devices: (i) a capacitance change based large strain sensor, and (ii) a dynamic large strain actuator which have been previously studied experimentally by Sun et al. (2014) and Keplinger et al. (2013).