Electric control of friction on surface of high-strength hydrogels

Recently high-strength and high-functional gels have been developed and are expected to be used in industrial and the medical fields. However, the research of gel application has not made much progress from the reason why an environmental range to use being small and properties of matter evaluation are not performed enough. To control the surface friction of gel mechanical materials by the electric field, here we study the effect of the applied voltage on the frictional properties of double-network gel (DN gel) with high strength. We found that impressed voltage on the gel has an ability to control the frictional force of the hydrogel. The results of the tensile and compression tests showed that the behavior of the DN gel was similar to a rubber, and effective data as mechanical materials were obtained. The results of friction measurement using reciprocating friction tester showed that the coefficients of friction depend on the sliding velocities. In the case of the cathode measurement ball, the coefficients of friction decreased with increase in voltage in the range of 0.0–3.0 V and increased with increase in the applied voltage in the range of 3.0–5.0 V. In the case of the anode measurement ball, the coefficient of friction increased with increase in the voltage. The current value measurement was performed in a measurement ball and a stainless-steel plate, and the electric current flowed at approximately 2.5 V and above. It is considered that the applied voltage controls the thickness of water lubricant layer and change the coefficient of friction of the gel. These findings provide a new insight into our understandings of application of the high-performance gels device as well as the development of high-performance gel materials.