'Liquid metal' coating could transform wearable electronics

A global team of scientists has developed a simple metallic coating treatment for clothing or wearable textiles which can repair itself, repel dangerous bacteria from the wearer and monitor a person’s electrocardiogram (ECG) heart signals. Researchers from North Carolina State University, Flinders University and South Korea say the conductive circuits created by liquid metal (LM) particles can transform wearable electronics and open doors for further development of human–machine interfaces, including soft robotics and health monitoring systems.

The ‘breathable’ electronic textile material has special connectivity powers to ‘autonomously heal’ itself even when cut, according to the US team led by Professor Michael Dickey. When the coated textiles are pressed with significant force, the particles merge into a conductive path, which enables the creation of circuits that can maintain conductivity when stretched.

Flinders University biotechnology researcher Dr Khanh Truong said the conductive patterns autonomously heal when cut by forming new conductive paths along the edge of the cut, providing a self-healing feature which makes these textiles useful as circuit interconnects, Joule heaters and flexible electrodes to measure ECG signals.

The technique involves dip-coating fabric into a suspension of LM particles at room temperature. “Evenly coated textiles remain electrically insulating due to the native oxide that forms on the LM particles. However, the insulating effect can be removed by compressing the textile to rupture the oxide and thereby allow the particles to percolate. This enables the creation of conductive circuits by compressing the textile with a patterned mold. The electrical conductivity of the circuits increases by coating more particles on the textile,” Truong said.

The LM-coated textiles also offer antimicrobial protection against Pseudomonas aeruginosa and Staphylococcus aureus. This germ-repellent ability gives the treated fabric protective qualities and prevents the porous material from becoming contaminated if worn for an extended time, or put in contact with other people. The particles of gallium-based liquid metals have a low melting point, metallic electrical conductivity, high thermal conductivity, effectively zero vapour pressure, low toxicity and antimicrobial properties.

LMs have fluidic and metallic properties and show promise in applications such as microfluidics, soft composites, sensors, thermal switches and microelectronics. One of the advantages of LM is that it can be deposited and patterned at room temperature onto surfaces in unconventional ways that are not possible with solid metals. The research findings were published in Advanced Materials Technologies.

Image credit: Flinders University