Shielded soft force sensors

Force and strain sensors made of soft materials enable robots to interact intelligently with their surroundings. Capacitive sensing is widely adopted thanks to its low power consumption, fast response, and facile fabrication, but is susceptible to electromagnetic interference and proximity effects and thus requires electrical shielding. Shielding has not been previously implemented in soft capacitive sensors due to parasitic capacitance between the shield and sensing electrodes that changes with deformation. We address this by patterning the central sensing elastomer layer to control its compressibility. One design uses an ultrasoft silicone foam, and the other includes microchannels filled with liquid metal and air. The force resolution is sub-mN in both normal and shear directions while withstanding large forces (>20 N), demonstrating a wide dynamic range. Performance is unaffected by nearby high DC and AC electric fields and even electric sparks.