Newly developed materials such as a metal-polymer conductors (MPC) made by researchers in China are the key to stretchable circuitry. The material is made from elastic polymer and liquid metal and can be bent and stretched at will.
The metal component gives the material the ability to conduct electricity. Instead of relying on familiar solids such as copper, silver and gold, however, it makes use of thick, syrupy liquids like gallium and indium. By embedding globs of it within a network of silicone-based polymer, the researchers were able to create mechanically resilient materials with enough conductivity to support functioning circuits.
"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," said Xingyu Jiang, a professor at the National Center for Nanoscience and Technology who served as senior author for a just-published study on the new material. "We believe that they will have broad applications for both wearable electronics and implantable devices."
Indeed, the researchers successfully tried out different MPC formulations for a variety of applications, including wearable keyboard glove sensors and electrodes designed to stimulate the passage of DNA through the membranes of live cells.
"The applications of the MPC depend on the polymers," explained study first author Lixue Tang, a graduate student in Jiang's research group. "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."
The researchers’ manufacturing method, which involves screen printing and microfluidic patterning, can accommodate any two-dimensional geometry. Varying thicknesses and electrical properties can also be controlled by the concentration of the liquid metal ink sprayed.