Fabrication process and enhanced electromechanical properties of the muscle-like gel actuator doped with glycerol

Abstract

At present the Muscle-like Gel Actuator (MLGA), an emerging ionic Electro Active Polymer (EAP), has advantages of small driving voltage, low cost and good biocompatibility, so it is widely used in bionic engineering, marine equipment and medical science etc. But the small output force and slow response speed still seriously restrict further implementation of the MLGA in engineering applications. In this paper, using glycerol as the plasticizer, Calcium Alginate Hydrogel (CAH) was fabricated as electrically actuating membrane to promote its electromechanical properties, and the complete preparation process was proposed. The MLGA was a double-layer capacitor similar to ‘sandwich’ structure, which consisted of the middle actuating membrane and non-metallic electrode membrane on its bilateral surface, where the electrode membrane was made from Sodium Alginate (SA) blended with Multi-walled Carbon Nanotube (MWCNT). Furthermore, the output force performance of the MLGA doped with various glycerol contents was tested by an experimental platform, to obtain the effect law and optimum doping amount. By the tensile test and Cyclic Voltammetry (CV), elastic modulus and specific capacitance of the actuating membrane were acquired, and then from the microcosmic viewpoint, electrically actuating mechanism of the MLGA was deeply analyzed to further clarify the influencing mechanism. Experiments revealed that with the increase of glycerol amount, the elastic modulus decreased gradually but the specific capacitance increased first and then declined after 2 ml. When 1 ml glycerol was added, the output force reached the maximum and its density was 49.560 mN g−1, which was 1.87 times larger than that of the sample without glycerol. Because the ion channel could be improved in a small amount of glycerol, which resulted in easy pass for internal ions. Instead, owing to the viscosity, large amounts of glycerol would block ion migration, which caused small output force density and poor electromechanical performance.