One of the greatest design challenges for wearables is making them as indistinguishable from skin as possible.
Scientists are getting closer and closer to this goal. In a recent paper published by Nature Nanotechnology, researchers at the University of Tokyo show the process behind creating electronics that can be worn on the skin for more than a week without suffering any inflammation or adverse effects. It’s a significant step toward creating electronic wearables that affix to the skin and can monitor health for long periods of time.
Scientist Takao Someya tells Co.Design in an email that human skin is incredibly sensitive, making it difficult to create on-skin wearables that won’t irritate it. Anything affixed to the skin for long periods of time must be made entirely from nontoxic, breathable materials that are stretchable, lightweight, and ultra-thin. Just think about how shriveled your skin gets after several days of wearing a bandage.
Others have developed similar types of wearables: MIT’s temporary tattoo interface DuoSkin and the stamp-sized circuits developed at the University of Illinois. But these can’t be worn for long periods of time. That limits their use, particularly as health monitors for both medical purposes and for athletes. But Someya says that his team has engineered an on-skin wearable that checks all of these boxes–nontoxic, flexible, light, thin, and breathable–for the first time.
The breakthrough is a skin-safe electrode made of nanomesh that includes a water-soluble polymer, a substance called polyvinyl alcohol (PVA), and gold, which are all safe for the body. It can be applied simply by spraying water onto the material, which dissolves the PVA and helps it stick and conform to the skin’s pores. Under a microscope, the material looks like a tangle of overlapping fibers.
Someya and his team applied the nanomesh material along the top of a finger and found it was durable enough to stretch and return to its shape when the finger was bent. It’s also more permeable to gases than ultrathin plastic foil or thin rubber sheets, vital for the skin to access oxygen. The researchers were also able to use the nanomesh material to measure temperature, pressure, and muscle health with little discomfort for the wearer. As a test, 20 participants wore the material for a week, at the end of which an expert dermatologist found no inflammation on their skin.
The research represents a step toward wearables that are so thin, breathable, and durable that they almost dissolve into the body. Whether this enables more comfortable monitoring of patients’ vital signs in a hospital setting or sensors for athletes to wear that don’t impact their physical state at all, the nanomesh is an indication that technology living on the skin is closer than ever.