Application of flexible sensors based on ion-conductive hydrogels

Composite conductive hydrogels have become a hot research topic in the field of flexible sensors due to their good adhesion and mechanical flexibility. In order to improve the electrical conductivity of conductive hydrogels, conductive ions Li⁺ and Cl⁻ were added to the polyacrylamide hydrogels. The conductivity of the hydrogels was characterized using scanning electron microscopy for internal characterization of the materials. The effect of the content of conductive ions on the conductivity of hydrogels was investigated, and the amount of crosslinker addition was optimized to achieve the best adhesion and mechanical flexibility. Furthermore, the hydrogel sensor was designed to monitor the movements of human finger joints and back of the wrist. The results show that the conductivity of the hydrogel improves with the increase of ionic content. The maximum conductivity is 5.34 S·m⁻¹ when the LiCl addition is 15 mmol, and the amount of cross-linking agent in the hydrogel is controlled at 3-6 mg, and obtain good adhesion and mechanical flexibility. After sensing and monitoring the human mechanical action and Morse code, the sensor is capable of capturing mechanical signals stably, accurately and quickly, converting them into corresponding electrical signals, and has repeatability of the output electrical signals for the same behavior. Results illustrate the good application development prospect of this sensor in monitoring, transmission and conversion of human body signals.