Deformable liquid metal polymer composites with tunable electronic and mechanical properties

Room-temperature liquid metals, such as eutectic gallium–indium–tin (galinstan), dispersed in a polymer matrix present unique potential as conductors that may have minimal influence on the host polymer mechanical performance while providing enhanced electrical performance. Work described herein systematically evaluates the influence of uncured polydimethylsiloxane (PDMS) viscosity and galinstan loading on final dispersion viscosity and cured modulus. Dispersions of up to 80 vol% galinstan were obtained with relative permittivity values up to 170 that otherwise exhibited similar uncured rheological changes to a solid filler. Cured galinstan-in-PDMS dispersions, however, exhibited a reduced stiffness increase with respect to the host polymer relative to a solid filler. At a critical PDMS viscosity and metal, loading phase inversion to a conductive PDMS-in-metal dispersion was observed. It is anticipated that this work will enable the development of liquid metal polymer composites with independently controlled mechanical and electrical properties for a wide variety of stretchable electronic applications.