Assessment of Biodegradable Materials for Next Generation of Artificial Muscles

New biodegradable materials for artificial muscles and soft actuators are required for biomedical and soft robotic applications. Here we present an investigation into the biodegradability and electroactive actuation characteristic of a series of off-the-shelf biodegradable materials. Eight materials were examined: cellulose, collagen, two forms of natural rubber latex, biodegradable chewing gum, paper, starch based bio-plastic and polycaprolactone. Samples of each material were buried in an outdoor compost heap at more than 30cm depth for up to ten months. The temperature in the compost ranged from 1.5 - 20 degrees Celsius and degradation loss was assessed visually every two weeks. Laboratory evaluation of the materials as electroactive soft actuators as well as ion exchange membranes within microbial fuel cells highlighted the natural rubber latex glove (NRL-G), prophylactic (NRL-P), and collagen derivatives as the three materials with the greatest potential for biodegradable biomedical and soft robotic applications. For these three materials, greater than 90 % natural biodegradation occurred in the compost heap after 285, 241, 18 days respectively. The electoactive actuation response of these materials to an electrical stimulus was also measured. Voltages up to 2kV were applied to NRL materials (acting as high voltage dielectric elastomer actuators) and voltages up to 10V were applied to the collagen derivatives such as gelatine (acting as low voltage ionic actuators). This study, providing an assessment of the electroactive actuation and biodegradation characteristics of natural polymers, provides a unique perspective on these important multi-functional materials.