Magnetic and conductive liquid metal gel.

Liquid metals are fast becoming a new class of universal and frictionless additives for the development of multifunctional soft and flexible materials. Here, nano-droplets of eutectic gallium-indium alloy, liquid at room temperature, were used as a platform for the formulation of electrically conductive and magnetically responsive gels with the incorporation of Fe3O4 nanoparticles. The nano-additives were prepared in-situ within a water-based solution of polyvinyl alcohol. A borax cross-linking reaction was then performed to yield multifunctional flexible and self-healing gels. The physico-chemical properties and changes of the nano-additives at each step of the gel preparation method were characterized. Oxidation and complexation reactions between the liquid metal and iron oxide nano-additives were observed. A mix of nano-sized functional magnetic Fe3O4/Fe2O3 and In-Fe oxide complexes was found to enable the magnetic susceptibility of the gels. The mechanical and self-healing properties of the gels were assessed, and finally, this flexible and multifunctional material was used as an electronic switch via remote magnetic actuation. The developed conductive and magnetic gels demonstrate great potential for the design of soft electronic systems.