Air-Working Electrochemical Actuator and Ionic Sensor Based on Manganese Dioxide/Gelatin-Glycerol Composites

Soft materials with large actuation and strain sensing are highly sought after for robotic applications. There are several electrochemical material systems capable of both functions, but as they are developed into air-working systems, the deformation is compromised by the electrolyte packaging so that they actuate less than in liquid environments. This study develops a novel air-working film-actuator by compositing manganese dioxide, which actuates by electrochemical redox reactions, and gelatin-glycerol hydrogel, which serves not only as the electrolyte for the manganese dioxide but also provides strain sensing function. By properly designing the compositions of the materials and structure, the composite film can produce large bending actuation. Depending on the application and structure adopted, the actuator can produce a tip displacement equal to its own length, a bending angle of >360°, or a radius of curvature of 2.5 mm, which is a very large actuation compared to other air-working film actuators. Different bending modes or shapes can be achieved by the independent actuating hinges fabricated on the actuator, and strain sensing function and resilient recovery from external compression are achievable by the hydrogel. With these properties, the material system is used to fabricate a robotic inchworm to demonstrate its capability in robotic applications.