Scientists have figured out how the piezoionic effect works in hydrogels

Service Engineering

Scientists have figured out how the piezoionic effect works in hydrogels, paving the way for ionic skins to be used in prosthetic limbs and robot hands.

Ionic skins are comprised of flexible, biocompatible hydrogels that use ions to convey an electrical charge to simulate the sensory characteristics of normal skin. Unlike smart skins comprised of plastics and metals, hydrogels are more comfortable to wear and have the softness of real skin.

“Scientists have figured out how the piezoionic effect works in hydrogels.“

When these hydrogels are contacted, they generate voltages - the piezoionic effect - but scientists didn't know how until a team from the University of British Columbia (UBC) devised a one-of-a-kind experiment, which was reported in Science.

Yuta Dobashi, the study's primary author, developed hydrogel sensors containing salts with varied sizes of positive and negative ions under the direction of UBC researcher Dr. John Madden. Magnetic fields were used by him and researchers from UBC's physics and chemistry departments to track how the ions moved when pressure was applied to the sensor.

According to the researchers, this new information demonstrates that hydrogels perceive pressure in the same manner that humans do, which is by shifting ions in reaction to pressure, thus opening up new uses for ionic skins.

Another application, according to UBC, is a soft hydrogel sensor placed on the skin that can monitor a patient's vital signs while being unobtrusive and self-powered.

Yael Petel, a UBC chemistry PhD graduate, and Carl Michal, a UBC professor of physics, contributed to the research, which employed the interplay between strong magnetic fields and the nuclear spins of ions to track ion motions within the hydrogels. Giao Nguyen, Cédric Plesse and Frédéric Vidal of France's CY Cergy Paris University contributed to the creation of a new hypothesis on how charge and voltage are formed in hydrogels.

Dobashi stated: “When pressure is applied to the gel, that pressure spreads out the ions in the liquid at different speeds, creating an electrical signal. Positive ions, which tend to be smaller, move faster than larger, negative ions. This results in an uneven ion distribution which creates an electric field, which is what makes a piezoionic sensor work. We can imagine a future where jelly-like ‘iontronics’ are used for body implants. Artificial joints can be implanted, without fear of rejection inside the human body. Ionic devices can be used as part of artificial knee cartilage, adding a smart sensing element. A piezoionic gel implant might release drugs based on how much pressure it senses, for example.”

An electrical and computer engineering professor in UBC’s faculty of applied science, Dr Madden, stated: “The obvious application is creating sensors that interact directly with cells and the nervous system since the voltages, currents and response times are like those across cell membranes. When we connect our sensor to a nerve, it produces a signal in the nerve. The nerve, in turn, activates muscle contraction. You can imagine a prosthetic arm covered in an ionic skin. The skin senses an object through touch or pressure, conveys that information through the nerves to the brain, and the brain then activates the motors required to lift or hold the object. With further development of the sensor skin and interfaces with nerves, this bionic interface is conceivable. Smart skins can be integrated into clothing or placed directly on the skin, and ionic skins are one of the technologies that can further that growth.”

See all the latest jobs in Service Engineering
Return to news