Liquid metal that transforms itself into a humanoid is so far a thing of fiction. However, the liquid metal idea is being applied to futuristic sensors for use in robots and other flexible objects.
New materials for sensors are being tested all the time. Now, Swiss-based EPFL engineers have come up with a combination of indium and gallium that stays in a liquid state at room temperature and holds potential for use in electronic fibers for sports and health wearables, as well as robots.
A team from EPFL’s Laboratory of Photonic Materials and Fiber Devices published findings in Nature Electronics that describe how the lab used a thermal drawing technique to make fibers that have high conductivity and stretchability. Thermal drawing is a technique typically used in making fiber optics.
They were able to create an intelligent knee brace that can track a user’s movements and joints during exercise. In a demonstration, the brace was used by a subject while walking, running, squatting and jumping and it consistently tracked the angle of the knee and precisely reconstructed the subject’s gate while running.
To make the material, they subjected a preform to heating and elongation like melted plastic that created fibers of a few hundred microns to a few millimeters. They were also able to regulate when sections of a single fiber are conductive or insulating. Liquid metal is mixed with a soft elastomer matrix to form small droplets and the heating and stretching process breaks the droplets and activates the liquid metal.
The fibers they developed remained electrically sensitive even when stretched to more than 10 times their initial length.
“Conventional electronic devices can be too fragile or too rigid to be integrated into textiles but our fiber could be integrated into meters, or even kilometers, of fabric with sufficient scale-up, which is what we are working on next,” Fabien Sorin, head of FIMAP, noted in a report from AZO Materials. “Such fabric could then be used to produce wearables, soft prostheses or sensors for robotic limbs.”