Intrinsically Conductive Liquid Metal-Elastomer Composites for Stretchable and Flexible Electronics

Liquid metal-embedded elastomers (LMEEs) are a class of deformable composites made of particles of liquid metal dispersed in an elastomeric matrix. Although these composites possess high thermal conductivity, they are not intrinsically electrically conductive unless a stimulus is applied to join the liquid metal inclusions into a conductive pathway. LMEEs with intrinsic conductivity, especially with a conductive surface, have great potential uses in flexible and stretchable electronics as soft, nondamaging contacts for device characterization, stretchable interconnects for deformable circuits, and as a soft solder to electrically connect devices to flexible and stretchable substrates. Here, a simple process is introduced to fabricate intrinsically conductive LMEEs (iLMEEs) with conductive surfaces through the sedimentation of microparticles of eutectic gallium-indium alloy (EGaIn) in the elastomer poly(dimethylsiloxane). During this sedimentation process, an EGaIn-rich 3D percolation network forms at the bottom surface. The resulting iLMEE possesses a conductive surface comprising a mosaic of EGaIn particles embedded in PDMS, with a low sheet resistance of 0.63 +/- 0.04 omega sq(-1). iLMEE is soft, stretchable, and exhibits stable conductivity to 100% strain. We demonstrate the use of iLMEE as nondamaging, reusable soft electrical contact probes and as mechanically robust electrical connections between light-emitting devices and flexible plastic substrates.

Automated summary

Liquid metal-embedded elastomers (LMEEs) are deformable composites made of liquid metal particles dispersed in an elastomeric matrix. A simple process is introduced to fabricate intrinsically conductive LMEEs with conductive surfaces by sedimenting microparticles of eutectic gallium-indium alloy in the elastomer. These materials are soft, stretchable, and exhibit stable conductivity.