Soft\nand Stretchable Liquid Metal Composites with\nShape Memory and Healable Conductivity

Abstract

Shape\nmemory composites are fascinating materials with the ability\nto preserve deformed shapes that recover when triggered by certain\nexternal stimuli. Although elastomers are not inherently shape memory\nmaterials, the inclusion of phase-change materials within the elastomer\ncan impart shape memory properties. When this filler changes the phase\nfrom liquid to solid, the effective modulus of the polymer increases\nsignificantly, enabling stiffness tuning. Using gallium, a metal with\na low melting point (29.8 °C), it is possible to create elastomeric\nmaterials with metallic conductivity and shape memory properties.\nThis concept has been used previously in core–shell (gallium-elastomer)\nfibers and foams, but here, we show that it can also be implemented\nin elastomeric films containing microchannels. Such microchannels\nare appealing because it is possible to control the geometry of the\nfiller and create metallically conductive circuits. Stretching the\nsolidified metal fractures the fillers; however, they can heal by\nbody heat to restore conductivity. Such conductive, shape memory sheets\nwith healable conductivity may find applications in stretchable electronics\nand soft robotics.