Researchers have worked to build a smart skin that can mimic the sensing capabilities of natural skin, but this has been elusive. Now, a team of scientists at the University of British Columbia (UBC) have had success with ionic skins made of flexible, biocompatible hydrogels that use ions to carry an electrical charge.
In contrast to smart skins made of plastics and metals, the hydrogels have the softness of natural skin, which offers a more natural feel to the prosthetic arm or robot hand on which they are mounted, so they are more comfortable to wear.
“How hydrogel sensors work is they produce voltages and currents in reaction to stimuli, such as pressure or touch – what we are calling a piezoionic effect. But we didn’t know exactly how these voltages are produced,” said the study’s lead author Yuta Dobashi.
Working under the supervision of UBC researcher Dr. John Madden, Dobashi devised hydrogel sensors containing salts with positive and negative ions of different sizes. He and collaborators in UBC’s physics and chemistry departments applied magnetic fields to track precisely how the ions moved when pressure was applied to the sensor. The researchers say this new knowledge confirms that hydrogels work in a similar way to how humans detect pressure, which is also through moving ions in response to pressureThis inspires potential new applications for ionic skins.
Dr. Madden added that the market for smart skins is estimated at $4.5 billion in 2019 and it continues to grow. “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.”
The research was published in Science and includes contributions from UBC chemistry Ph.D. graduate Yael Petel and Carl Michal, UBC professor of physics, who used the interaction between strong magnetic fields and the nuclear spins of ions to track ion movements within the hydrogels. Cédric Plesse, Giao Nguyen, and Frédéric Vidal at CY Cergy Paris University in France helped develop a new theory on how the charge and voltage are generated in the hydrogels.