Semi-Crystalline Rubber as a Light-Responsive, Programmable, Resilient Robotic Material

Abstract

Polymers with large and reversible light-induced deformation offer a plethora of opportunities for the wireless control of small-scale soft robots. However, their widespread adoption in real-world applications is hindered, mainly due to their intrinsic softening upon illumination. Such limitation has detrimental effects on the achievable stress, durability, and precise positional control of the soft actuators after multiple cycles of use. Here, a synthetic rubber from a polybutadiene-polyethylene copolymer is reported as a durable material for light-controlled soft robots. The rubber can be programmed to exhibit various deformation modes controlled by visible-to-infrared light through a photothermal effect. Semi-crystallinity of polyethylene within the rubbery network provides this material with a remarkable modulus at high temperatures (2.5 MPa at 100–140 °C), deformation repeatability (>90%) and shape-recovery (>98%) after 100 actuation cycles subject to loads ranging from 10 to 10 000 times of its body weight (1.4 kPa–1.4 MPa). Soft robotic applications are demonstrated, such as thermally-driven jumping and photo-driven cargo transport carrying up to 1200 times its own weight. The results expand the portfolio of materials in designing remotely-controlled, robust, and resilient soft robots working at small scales.