The bionic signal encoding of the Ruffini-ending-inspired flexible sensor. (a) Illustration of prosthesis sliding perception. The Ruffini-ending-inspired sensor with processing circuits is applied to a prosthetic hand of a woman with a lower-arm amputation. (b) Schematic diagram showing a circuit that converts analog signals recorded from the sensor into low-frequency pulse signals (nerve-like signals). (c) The pulse shape through the processing circuit. The pulse frequency changed with the applied sliding friction forces. (d) The pulse frequency responses in the 0 to 4 N range of the sliding friction force.