On-demand Transient Silicone Elastomer Composites for Soft Robotics

One of the important goals in soft robotics is to build a system that can carry out the whole function of living organisms, spanning their birth, growth, and death. Among these, the death of soft robots is nowadays in great interest due to the growing concern towards the disposal of soft robots. An on-demand disintegration of soft robots can figure this out, but materials up-to-date are unsuitable for such functions. Conventional elastomeric materials used in soft robot frames (e.g. silicone elastomers) are extremely difficult to decompose, and on-demand transient materials so far (e.g. cyclic poly(phthalaldehyde)) possess insufficient mechanical properties to be used in soft robots. Here we introduce an on-demand transient silicone elastomer composite as an answer to allow this on-demand death of soft robots. A composite of silicone elastomer matrix and photo-fluoride generator additives degrades into a liquid state via a two-step trigger of ultraviolet radiation and heating at ~100 °C. The composite shows comparable mechanical properties to commercial silicone elastomers, retaining a modulus of 40 kPa and a fracture strain up to ~500%. On-demand transient soft robots and electronics which can degrade under the same stimuli are demonstrated using this material. A robot that self-diagnoses its destruction using embedded ultraviolet and temperature sensors was fabricated. The robot avoids the risk of destruction and carries out the desired function in peacetime, but rapidly degrades upon request by taking sufficient ultraviolet light and heat. Transformable robots that change their functions and actuation aspects upon selective on-demand transience are presented too, showing that on-demand transience can empower novel functions to soft robots. The concept reported in this research presents the domain of on-demand transient soft robotics, which is expected to bring innovation in environmental, medical, and security-related issues.