Performance comparison of capacitive silicone-based curvature sensors with planar and interdigitated electrodes

This paper presents a class of fully elastomeric capacitive sensors that can be employed to measure the bending angle of flexible structures. Two possible sensing architectures are proposed here, which are obtained by similar manufacturing processes. The first solution is based on a parallel plate deformable capacitor featuring two compliant electrodes separated by a dielectric silicone membrane. The second design is based on interdigitated electrodes placed on the same side of a silicone membrane. Both types of sensors are intended to be coupled with a bending structure that, during its deformation, induces a capacitance change correlated with the value of the bending angle. The operating principle is presented and a possible simplified modeling approach is identified for both the architectures. Additionally, a simple and repeatable manufacturing process is implemented. This made it possible to realize multiple specimens of the two sensor topologies that have been tested through an experimental campaign conducted on a dedicated testbench for bending angle measurement. The results of these tests are reported and elaborated, and the two sensing strategies are compared and discussed.