Liquid metal circuits developed for stretchable electronics

Researchers from the National University of Singapore (NUS) have developed a flexible, self-healing and highly conductive material suitable for stretchable electronic circuitry. This development could improve the performance of wearable technologies, soft robotics and smart devices. The newly engineered material, called the bilayer liquid-solid conductor (BiLiSC), can stretch up to 22 times its original length without sustaining a significant drop in its electrical conductivity. This electrical-mechano property enhances the comfort and effectiveness of the human-device interface and opens up an array of opportunities for its use in healthcare wearables and other applications.

Professor Lim Chwee Teck, Director of the NUS Institute for Health Innovation & Technology and leader of the research team, said this technology was developed in response to the need for circuitry with robust performance and functionality for next-generation wearable, robotic and smart devices. “The liquid-metal circuitry using BiLiSC allows these devices to withstand large deformation and even self-heal to ensure electronic and functional integrity,” Lim said.

BiLiSC is an innovative technology that is suitable for use in wearable devices, which would need to account for the shape, and varied movements, of the body. It consists of two layers — the first layer is a self-assembled pure liquid metal, which can provide high conductivity even under high strain, reducing the energy loss during power transmission and signal loss during signal transmission. The second layer is a composite material containing liquid metal microparticles and it is able to repair itself after breakage. When a crack or tear occurs, the liquid metal flowing out from the microparticle can flow into the gap, allowing the material to heal itself almost instantaneously to retain its high conductivity.

The researchers demonstrated that BiLiSC can be made into various electrical components of wearable electronics, such as pressure sensors, interconnections, wearable heaters and wearable antennas for wireless communication. In laboratory experiments, a robotic arm using interconnections was quicker in detecting and responding to minute changes in pressure. In addition, the bending and twisting motion of the robotic arm did not impede the transmission of signals from the sensor to the signal processing unit, compared to another interconnection made with a non-BiLiSC material.

Following the successful demonstration of BiLiSC, the researchers are working on material innovation and process fabrication. They are looking to engineer an improved version of BiLiSC that could be printed without needing a template — this could improve the precision in fabricating the BiLiSC.

The research findings were reported in the journal Advanced Materials.

Image caption: The new conductive and stretchable ‘super-material’ developed by NUS researchers can heal cracks or cuts almost instantaneously to maintain its electrical conductivity. Image credit: National University of Singapore.