Consider the main difference between living systems and electronics: the former is generally tender and spongy, while the latter is tough and stiff. Now, in work that could have implications for human-machine interfaces, biocompatible devices, tender robotics and more, MIT engineers and collaborators have developed a tender, adaptable gel that dramatically changes its conductivity when exposed to airy.
Enter the emerging field of ionotronics, which involves transmitting data through ions, or charged particles. Electronics does the same thing, with electrons. But while the latter method is now well established, ionotronics is still being developed, with one huge exception: living systems. Cells in our body communicate with a variety of ions, from potassium to sodium.
Ionotronics, in turn, can provide a bridge between electronics and biological tissues. Potential applications range from tender wearable technologies to human-machine interfaces
“We have discovered a mechanism for the dynamic control of the local population of ions in a soft material,” says Thomas J. Wallin, the John F. Elliott Career Development Professor in MIT’s Department of Materials Science and Engineering and principal investigator of the work. “This could allow for the creation of a system that will self-adapt to environmental stimuli, in this case light.” In other words, the system could automatically change in response to changes in lighting, which could enable complicated signal processing in tender materials.
An open-access article about this work has been published online recently in .
Growing field
Although others have developed high-conductivity ionotronic materials that enable rapid movement of ions, this conductivity cannot be controlled. “What we’re doing is using light to change a soft material from being insulating to one that’s 400 times more conductive,” says Xu Liu, first author of the paper and a former postdoctoral fellow at MIT in materials science and engineering and now an assistant professor at King’s College London.
Key to the work is a class of materials called photoion generators (PIGs). When exposed to airy, they can become about 1,000 times more conductive. The MIT team optimized how to incorporate PIG into polyurethane rubber by first dissolving the PIG powder in a solvent and then using a swelling method to incorporate it into the rubber.
Massive potential
In the material presented in the current work, the change in conductivity is irreversible. However, Liu is confident that future versions will be able to switch between insulating and conducting states.
He notes that the current material was developed using only one type of PIG, polymer (polyurethane rubber) and solvent, but there are many other types of all three. There is therefore enormous potential to create tender materials that respond even better to airy.
Liu also notes the potential to develop tender materials that respond to other environmental stimuli, such as heat or magnetism. “It inspires us to continue working in this area by changing the driving force from light to other forms of environmental stimuli,” he says.
“Our work may lead to the creation of a subfield we call soft photoiontronics,” Liu continues. “We are also very excited about the opportunities our work offers to create new soft machines impacting soft wearable technology, human-machine interfaces, robotics, biomedicine and other fields.”
Additional authors on the paper include Steven M. Adelmund, Shahriar Safaee and Wenyang Pan of Reality Labs at Meta.