Capacitive Sensor Combining Proximity and Pressure Sensing for Accurate Grasping of a Prosthetic Hand

Intelligent control of a prosthetic hand is the core to realize accurate grasping. The traditional sensors inside the hand or finger can only give indirect information regarding the events occurring at the interface of the finger tip and objects, which may cause misjudgment in grasping. Herein, we design a capacitive sensor with the capability of both proximity and force detection for the prosthetic hand (HIT-V). The sensor is composed of a pair of ring-circle copper foils as electrodes, in which is the dielectric layer with a pyramid microstructure. As a result, the sensor can detect an object approaching from as far as 100 mm and contact forces up to 12 N, which, respectively, denote the finger operation space and maximum force load of the prosthetic hand. Furthermore, the proposed sensor exhibited excellent stability, mechanical flexibility, and deformability. Finally, capacitive sensors are used for grasping control on the prosthetic hand, which exhibit the abilities of stopping an approaching process and tracking a step force. The abovementioned performance shows the sensor's potential ability to achieve complex control on prosthetic hands.