High Force Density Textile Electrostatic Clutch

Clutches are key elements for blocking or coupling motion in wearable systems such as soft exoskeletons, haptic clothing, and rehabilitation equipment. Electrostatic clutches (ESclutches) are compact and light, making them particularly well-suited for wearable applications. They are variable capacitors whose electrodes can slide with respect to each other, with a frictional force between electrodes proportional to the square of the applied voltage. A high force-density textile-based ESclutch is reported here, generating frictional shear stresses of 21 N cm(-2) at only 300 V, a stress level 11 times higher than any other ESclutch, and 88 times better than textile-based ESclutches. Actuation and release time are inferior to 5 and 15 ms. Power consumption is below 1.2 mW cm(-2). To reach such high frictional stresses, a dielectric material with high permittivity is chosen (P(VDF-TrFE-CTFE)), a fabrication process that enables highly planar dielectric and conductive films on textile is developed, and an alternating current waveform is optimized to minimize space charge. The ESclutch is thin, highly flexible, and weighs only 30 mg cm(-2). The device demonstrated here is designed for wearable applications such as kinesthetic haptic feedback for virtual reality or for soft exoskeletons.