Circuits made with this part elastic polymer, part liquid metal hybrid – known as a metal-polymer conductor (MPC) – can take most 2D shapes and are non-toxic, the researchers say.
"These are the first flexible electronics that are at once highly conductive and stretchable, fully biocompatible, and able to be fabricated conveniently across size scales with micro-feature precision," says senior author, Professor Xingyu Jiang of the National Center for Nanoscience and Technology. "We believe that they will have broad applications for both wearable electronics and implantable devices."
The metals used to create this conductive material are gallium and indium, which exist as thick, syrupy liquids that still permit electricity to flow. The researchers discovered that by embedding globs of this liquid metal mixture within a supporting network of silicone-based polymer yielded mechanically resilient materials with enough conductivity to support functioning circuits.
The researchers successfully tried out different MPC formulations in a variety of applications, including in sensors for wearable keyboard gloves and as electrodes for stimulating the passage of DNA through the membranes of live cells.
"The applications of the MPC depend on the polymers," says first author Lixue Tang. "We cast super-elastic polymers to make MPCs for stretchable circuits. We use biocompatible and biodegradable polymers when we want MPCs for implantable devices. In the future, we could even build soft robots by combining electroactive polymers."
In principle, the authors state that their method for manufacturing MPCs, which involves screen printing and microfluidic patterning, can accommodate any 2D geometry, as well as different thicknesses and electrical properties, depending on the concentrations of the liquid metal inks to be sprayed. This versatility could lead directly to desirable biomedical applications, such as flexible patches for identifying and mitigating heart disease.