For dielectric elastomers, fringe-sensing is not as quirky as it sounds

Capacitive dielectric elastomer sensors (DES) are well-known in robotic sensing applications due to their sensitivity and stability under tensile strain. These sensors rely on changes in geometry to detect deformation. Since DES are thin, they are resistant to out-of-plane compression and this is made more difficult if they are bonded to a rigid surface. Here, we present a new type of DES that detects changes in the fringe field between interdigitated electrodes (IDEs). This is made possible using a compression sensitive silicone/carbon black composite that sits atop the electrodes. The IDEs create a fringing field extending into the composite whose relative permittivity can change by 250% when compressed. As a result, there is no longer any design challenges brought on by the incompressibility of elastomers. Additionally, since compliant electrodes are not required in this configuration, and the electrodes are kept in a single plane on a commercial PCB, the fabrication process is simple. This sensor is convenient to be used as a tactile sensor for either conventional rigid or soft robotic grippers, allowing the safe manipulation of soft and delicate objects.