Skin-like sensors bring a human touch to wearable tech

"Since it's hydrogel, it's inexpensive and biocompatible -- you can put it on the skin without any toxic effects. It's also very adhesive, and it doesn't fall off, so there are so many avenues for this material," Professor Xinyu Liu, whose lab is focused on the emerging areas of ionic skin and soft robotics. The adhesive AISkin is made of two oppositely charged sheets of stretchable substances known as hydrogels. By overlaying negative and positive ions, the researchers create what they call a "sensing junction" on the gel's surface. When the AISkin is subjected to strain, humidity or changes in temperature, it generates controlled ion movements across the sensing junction, which can be measured as electrical signals such as voltage or current.