Multi-Axis Soft Sensors Based on Dielectric Elastomer

This article proposes a methodology to design, analyze, and fabricate a multi-axis soft sensor, made of a dielectric elastomer (DE) that is capable of detecting compressive and shear loads. The multi-axis soft sensors are applicable to soft robots because of low stiffness and large strain properties. The sensor consists of four modules aligned in a 2x2 array, each module can be modeled as a capacitor-a DE membrane with an embedded air chamber sandwiched by compliant electrodes. To investigate the effect of structure on sensitivity, detection range, linearity, and hysteresis, rectangular and circular prototypes are analyzed, fabricated, and tested. When the multi-axis soft sensor is subject to compressive or shear load, the induced deformation of thickness or overlapping area results in capacitance change. We build an analytical model to describe the mechanical-electrical property of the soft sensor induced to shear load. Because of the complexity of compressive load, the mechanical-electrical property in this case is obtained numerically through the finite element method. Specially, a strategy to decouple shear and compressive loads is proposed in this article. By detecting a capacitance signal of four modules, both direction and magnitude of external stimuli are obtained. From experimental and analytical results, the rectangular prototype is superior to the circular one in sensitivity, linearity, and stability.