A new methodology creates stretchable polymer composites with enhanced electrical and thermal properties. The method uniformly incorporates eutectic gallium indium (EGaIn), a metal alloy that is liquid at ambient temperatures, into an elastomer. This creates a new material — a highly stretchable, soft, multi-functional composite that has a high level of thermal stability and electrical conductivity.
Atom transfer radical polymerization (ATRP), a robust method of controlled polymerization, allows scientists to string together monomers in a piece-by-piece fashion, resulting in highly tailored polymers with specific properties. ATRP creates new materials that have consistent, reliable structures and unique properties.
ATRP was used to attach monomer brushes to the surface of EGaIn nanodroplets. The brushes were able to link together, forming strong bonds to the droplets. As a result, the liquid metal uniformly dispersed throughout the elastomer, resulting in a material with high elasticity and high thermal conductivity. After polymer grafting, the crystallization temperature of eGaIn was suppressed from 15 °C to -80 °C, extending the droplet’s liquid phase — and thus its liquid properties — down to very low temperatures.
Liquid metal can be suspended in virtually any polymer or copolymer in order to tailor material properties and enhance performance. This process could be used to combine different polymers with liquid metal and by controlling the concentration of liquid metal, researchers can control the properties of the materials they are creating. The number of possible combinations is vast but with the help of artificial intelligence, the approach could be used to design “made-to-order” elastomer composites that have tailored properties. The result will be a new class of materials that can be used in a variety of applications, including soft robotics, artificial skin, and bio-compatible medical devices.