Researchers at MIT have developed an e-skin technology that contains artificial sweat ducts. The ducts prevent sweat accumulation underneath the e-skin, helping to prevent interference with built-in sensors. Incorporating a kirigami-style design, the material conforms to human skin but maintains a high porosity and reduced sweat accumulation. The design should help the e-skin to stay in place over extended periods, allowing incorporated sensors to monitor health over this time.
Wearable patches or ‘e-skin’ are a hot research area at present, with the ultimate of goal of unobtrusive health monitoring that does not require bulky and inconvenient monitoring devices. The technology is constantly evolving, and this latest device tackles a problem that all e-skin technology faces: sweat. Our skin is constantly producing moisture, and if it can’t escape through an e-skin patch, it will accumulate, potentially leading to sensor malfunction or detachment.
“Sweat can accumulate between the e-skin and your skin, which could cause skin damage and sensor malfunctioning,” said Jeehwan Kim, one of the developers of the new e-skin, in an MIT announcement. “So we tried to address these two problems at the same time, by allowing sweat to permeate through electronic skin.”
Previous e-skin technologies have attempted to make such devices breathable, by using woven fibers for example, but sweat has posed a stubborn challenge. Initially, these researchers designed simple films with regular holes that would allow sweat to escape through. However, while this design lets sweat escape, the resulting e-skin was not sufficiently flexible and broke easily. To side-step this problem, the researchers used a kirigami-style design, which incorporates small slits between the e-skin pores, providing flexibility and strength along with sweat diffusion.
“If you wrap a piece of paper over a ball, it’s not conformable,” said Kim. “But if you cut a kirigami pattern in the paper, it could conform. So we thought, why not connect the holes with a cut, to have kirigami-like conformability on the skin? At the same time we can permeate sweat.”
The e-skin is made using ultrathin semiconductor films, and the researchers have already tested it in a volunteer, who wore it for over a week. During this time the patch measured hydration levels, temperature, pulse, and UV exposure. The researchers put the volunteer through his paces, asking him to run on a treadmill for 30 minutes and eat a spicy meal, to produce plenty of sweating. The e-skin held up under this punishment.
“With this conformable, breathable skin patch, there won’t be any sweat accumulation, wrong information, or detachment from the skin,” said Kim. “We can provide wearable sensors that can do constant long-term monitoring.”
Study in Science Advances: Long-term reliable physical health monitoring by sweat pore–inspired perforated electronic skins