Soft Capacitive Force Sensors with Low Hysteresis Based on Folded and Rolled Structures

Force sensors made of a polymer material with soft characteristics have application potential in the fields of soft robotics, exoskeletons, and human motion measurement. However, the hysteresis of soft force sensors is generally large because their sensing materials are rubbers with large dynamic viscoelasticity. The problem of large hysteresis caused by this dynamic viscoelasticity needs to be solved to improve the dynamic measurement precision of these force sensors. In this article, we have tested and found that the hysteresis of silicone rubber is significantly reduced when it operates in a large strain range. Therefore, we propose a design idea to allow the silicone rubber to work at large strain ranges involving a folded and rolled capacitive sensor structure based on large prestretching. Compared with previously reported silicone rubber force sensors, this sensor has a lower hysteresis error of 4.73% and a lower repeatability error of 3.42%. In addition, the folded and rolled sensor exhibits quick response, long-term stability, and durability under periodic dynamic load.