Compliant mechanosensory composite (CMC): a compliant mechanism with an embedded sensing ability based on electric contact resistance

Abstract

Sensing ability enables a robot to be aware at its motion, or to modulate the locomotory behavior. While many sensing components have been developed for macroscale robots, such off-the-shelf sensors are hardly integrated with millimeter-to-centimeter scaled robots due to the size limitation. In this work, we propose a compliant mechanosensory composite (CMC) to fabricate a small compliant mechanism with an embedded sensing ability. For this purpose, a conductive polymer PEDOT:PSS was directly printed onto the two layers of flexural joints in a compliant mechanism. Owing to the variation of electric contact resistance upon bending, the CMC could measure the bending angle of the flexural joint. Three different sensor pattern topologies (e.g. planar, interdigitated, and serpentine) were tested, and the serpentine pattern was chosen. Also, its performance was further verified by analyzing the cyclic bending and transient response. Overall, a sparsely printed serpentine pattern with thicker line exhibited consistent response without a noticeable hysteresis. To demonstrate the applicability of the CMC, a small inchworm robot actuated by a micro servo motor was built, and its motion was successfully measured using the embedded sensor. In addition, multi degrees-of-freedoms mechanisms such as a four-bar spherical joint was fabricated to measure a three-dimensional motion. We expect the proposed CMC will enable a small robot to become sensible at its self motion, external load, and physical contacts in future.