Human skin may be the ultimate multitasker: It can sense pressure, feel temperature and detect humidity and motion –all at the same time. It’s no wonder, then, that it’s been tricky and expensive for scientists to create a direct analog for the stuff.
Hussain, who just published the results in the inaugural edition of the journal Advanced Materials Technologies, is an associate professor of electrical engineering at the King Abdullah University of Science and Technology in Thuwal, Saudi Arabia. He heads the university's Integrated Nanotechnology Laboratory, a place where engineers use everything from Lego to saliva to stickers to solve the world’s problems.
Over the past several years, other engineers have made progress on “smart skins” – which could be used to make prosthetics smarter, make wearable technology even more wearable and give robots a more sophisticated sense of touch, among other things – using pricey two-dimensional components such as carbon nanotubes.
“It’s great to explore those things,” Hussain says, “but the electronics should be as fundamentally affordable as possible.” When it comes down to it, he notes, human skin takes up a lot of surface area. Frustrated by what he saw as the romanticization of new materials, Hussain went rooting around in the kitchen for existing products that could work instead.
The result is part DIY experiment, part engineering coup. Hussain’s “skin” uses sponges to detect pressure, aluminum foil to sense motion, and sticky note paper to detect humidity. Thanks to conductive silver ink and graphite pencils, it can also sense temperature and acidity. After stacking three layers of sensors, the team used various electronic devices to test its ability to sense.
“Paper Skin,” as the team calls it, can detect everything from pressure to pH to proximity and differentiate between those sensations, too. It’s recyclable and affordable, with a 6.5-centimeter square costing $1.67 in materials.
While these sensors aren't ready for showtime just yet, Hussain hopes that eventually they could be used to create a true artificial skin – one meant to replace the real thing. As a child in Bangladesh, he recalls seeing victims of acid attacks whose skin was distorted and damaged. “They lived lives of humiliation,” he recalls. As a grad student in the United States, wounded, homeless veterans caught his attention. "With plastic surgery we can probably help get them back to normal life and restore their confidence," he says, "but if we can make an artificial skin and eventually connect it to their neurological embodiment, that would be fantastic."
Hussain says it’s not enough to develop new materials or tinker with electronics in a lab. “We can add new dimensions with electronics to enhance quality of life,” he says. “The first people who need our support are the people who have lost something.” Those people have little to gain from niche, expensive and far-off smart skins, he says, making the effort to create something that’s affordable and accessible that much more important.
The team members thinks that they can scale Paper Skin for mass production within the next two years. But they face hurdles along the way. Hussain admits that he had trouble getting his results published. “The establishment was not happy that we used such ridiculously available material,” he laughs.
Hussain’s “skin” may look modest — and almost laughably simple — for now, but his team’s tests show that it performs just as well, if not better, than more high-tech materials. In the future, says Hussain, burn victims, hospital patients and robots could very well wear smart skin that’s a direct descendant of his pile of Post-its and tape. “I’m not against carbon nanotubes or any other materials,” he says. “But tomorrow should be today.”