Durable artificial muscles based on hydrophobic and liquid-impermeable reduced graphene oxide paper electrodes

Abstract

Ionic polymer actuators driven by electrical stimuli have been widely investigated for use in practical applications such as bio-inspired robots, sensors, and biomedical devices. However, conventional ionic polymer-metal composite actuators have a serious drawback of poor durability under long-term actuation in open air, mainly because of the leakage of the inner electrolyte and hydrated cations through cracks in the metallic electrodes. By employing crack-free, cost-effective, hydrophobic laser-scribed reduced graphene oxide paper electrodes, we developed a dry-type ionic polymer artificial musclewith outstanding durability and without leakage of the liquid electrolyte or mobile cations. The one-sided laser-scribed reduced graphene oxide paper has good flexibility, suitable for bendable artificial muscles, and a high electrical conductivity of 315 Socm-1, similar to the electrical conductivity of metallic electrodes such as platinum and gold. The water contact angles of the pure and laser-scribed reduced graphene oxide paper surface are as high as 88-89°, resulting in a unique artificial muscle that floats on water. The vapor/liquid impermeability of the laser-scribed reduced graphene oxide paper contributes to the durable performance of ionic polymer-graphene composite actuator because it prevents leakage of the vaporized or liquid electrolyte and mobile cations during actuation. The ionic polymer actuators which incorporate highly hydrophobic, flexible, cost-effective and conductive laser-scribed reduced graphene oxide paper electrodes, exhibit the durable actuation performance that is a prerequisite for their practical application in activebiomedical devices, biomimetic robots, and artificial muscles.