January 2022

PROCESS TURNS ORDINARY CLOTHING INTO BIOSENSORS

In this graphic, a compression sleeve is turned into a biosensor that measures electrical impulses generated from muscle movement. Shown is the measurement of electrical activity picked up by the sleeve when a fist is made. Image courtesy of the University of Utah.

The University of Utah chemical engineering assistant professor Huanan Zhang, PhD, and his team have developed a process that turns ordinary textile made of a cotton/polyester blend into sensors that measure electrical impulses generated from muscle movement. This could become a much better solution for measuring muscle activity for physical rehabilitation or for other medical applications, as compared to bioelectrical sensor technology in which sensors with wires are taped to the skin.

“This new method can enable clinicians to collect a muscle’s long-term electrical signals with more precision,” said Zhang. “And we can get a better understanding of a patient’s progress and therefore their therapeutic outcomes over time.”

When human muscle contracts, it emits electrical signals in the form of ions (as opposed to electrons from an electrically powered device). Zhang’s process involves depositing a microscopic layer of silver over a piece of fabric to make the material conductive and therefore receive the electrical signal from the muscle. But since having just a layer of silver can be problematic as the metal can be somewhat toxic when in prolonged contact with the skin, the researchers also deposit a second, microscopic layer of gold, which is non-toxic to the touch. The gold not only protects the skin from the silver, but it also enhances the electrical signal, Zhang said.

The silver layer is applied to the fabric in a process similar to screen printing a graphic onto a T-shirt, and it’s applied to just the areas of the clothing that touch the muscle being measured. Then the gold layer is deposited by an electrochemical method. The patches of sensors are then attached to wires and a portable electromyography device that measures muscle contractions. Just as important, the process is also resistant to repeated cycles in a washing machine, Zhang said.

Currently, Zhang and his team have tested the method on a compression sleeve for the forearm. While this technology would mostly be used on compression sleeves or socks since it requires the clothing constantly touch the skin, Zhang imagines it could also be used for other skin-tight clothing such as bicycle pants or athletic tights.

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