Liquid Metal Composites with Anisotropic and Unconventional Piezoconductivity

Anisotropic elastic composites-that is, elastomers containing aligned fillers-often have enhanced properties in the direction of alignment. Depending on the fillers, these composites can have desirable electrical, thermal, or mechanical properties. Here, a silicone composite filled with both solid magnetic metal microparticles and liquid metal microdroplets has been developed. Aligning the solid particles within a magnetic field during curing imparts anisotropy in several properties. Thus, the composite is called an anisotropic liquid metal-filled magnetorheological elastomer (ALMMRE). Compared with isotropic liquid metal-filled composites, the conductivity of the ALMMRE is significantly enhanced in all directions. The ALMMRE also exhibits anisotropic piezoconductivity and a significantly enhanced electrical anisotropy under mechanical deformation; these properties are not observed in conventional anisotropic composites. The ALMMRE also shows anisotropic mechanical, thermal, and magnetic properties and demonstrates its several proof-of-concept applications. The sensitivity of the ALMMRE's properties to strain may help advance future flexible sensors and soft electronics.