FOCERS: An Ultrasensitive and Robust Soft Optical 3D Tactile Sensor

Soft optical sensors, characterized by excellent stability, strong anti-interference ability, and rapid response, are particularly suitable for exploring unknown environments. However, the low sensitivity and large size of optical tactile sensors have limited their widespread application. This study presents an ultrasensitive, highly linear, and highly robust three-dimensional (3D) tactile sensor based on a Foldable Optical Circuit Embedded in Rigid-Soft-coupled (FOCERS) structure. This sensor exhibits a high sensitivity of 1228.7 kPa-1 under normal pressure of 5 kPa, a super high sensitivity of 7399.5 kPa-1 under a sheer pressure of 1.5 kPa, and a fast response time of 5 ms. Under normal pressure conditions, the sensors exhibited high linearity performance across the entire sensing range, with linearity reaching up to 95.3%. The rigid-soft-coupled structure enhances the robustness and overload resistance of the sensor (withstanding 50 times the sensing range). Demonstrations show that the FOCERS structure can detect minute pressure variations (induced by sesame seeds) and withstand extreme pressures (such as being run over by a car). Furthermore, we designed a joystick based on FOCERS for force detection in human-machine interactions. This study provides a new structure for optical sensors to increase both sensitivity and robustness, and also provides a convenient way to fabricate 3D tactile sensors.