Design of Multi-channel Electrical Stimulator Integrated with Online Impedance Measurement

Purpose: An intuitive perception about the hand is essentially important for a prosthesis user. However, it is not well addressed in current bidirectional human–machine interface (HMI) design due to various electrode–skin conditions. Herein, we intend to propose a multi-channel transcutaneous nerve electrical stimulator (TNES) with online skin-impedance measurement. Methods: Using non-woven electrode and flexible printed circuit (FPC) electrode, the time-varying behavior of the skin impedance is explored and the linear relationship between sensory threshold and skin impedance is verified. An online approach on adjusting the stimulus parameters is also proposed on basis of the real-time impedance measurement. Results: Experiments show that this method can adaptively adjust the stimulation intensity in line with the changing impedance, which improves the safety and applicability of the electrical stimulation feedback system. Conclusion: As the stimulator measures the impedance between the skin and the electrode in real time, it can achieve a progressive electrotactile sensory feedback at different body locations.