A soft sandwich structure enables voltage-induced actuation of liquid metal embedded elastomers

Dispersing liquid metal droplets in a soft elastomer matrix yields a composite, called liquid metal embedded elastomer (LMEE), with less modified stiffness but noticeably increased relative permittivity. Stretching and applying voltage through the thickness of the elastomer composite directly, it is vulnerable to the loss of being an insulator due to the conductive pathway formed during prestretching. Here, we describe a very simple sandwich structure that enables electromechanical actuation of LMEE. It consists of two very high bonding tapes as skins and a layer of LMEE as the core, making the sandwich all polymeric and thus stretchable. The electromechanical performance of a LMEE made of Ecoflex and Galinstan at various mass ratios was systematically measured. For a typical circular actuation made of the sandwich structure, a 90% areal actuation strain was achieved. Our efforts pave the way for various applications of LMEE.