Researchers at the University of Toronto have developed a highly stretchable “skin”-like sensor that can be applied directly to our native skin. The material can measure changes in temperature, strain, and humidity, and can monitor the movement of underlying tissues. The sensor has potential as a wearable health monitor. For instance, the material could be used in a patch to monitor movements in patients undergoing rehabilitation or as a smart bandage to enhance wound healing.
Teams around the world have been exploring the potential of flexible materials in healthcare and recent research has resulted in a wide array of stretchy materials with potential as wearables and in soft robotics. This move away from rigid materials is somewhat of a paradigm shift, as flexible materials attempt to mimic and accommodate soft tissues in the body.
This newest material is in keeping with this “soft” revolution, as it is highly stretchable. “Since it’s a hydrogel, it’s inexpensive and biocompatible — you can put it on the skin without any toxic effects,” explains Xinyu Liu, a researcher involved in the study. “It’s also very adhesive, and it doesn’t fall off, so there are so many avenues for this material.”
The hydrogel “skin” consists of two sheets that have opposing charges, resulting in negative and positive ions overlying each other. Appropriate stimuli, such as changes in temperature or strain, cause ion movements across the material, which the researchers can measure as electrical signals. “If you look at human skin, how we sense heat or pressure, our neural cells transmit information through ions – it’s really not so different from our artificial skin,” said Liu.
The material is incredibly robust, and resists damage even when substantially stretched. “Our human skin can stretch about 50 per cent, but our AISkin can stretch up to 400 per cent of its length without breaking,” said Binbin Ying, another researcher involved in the study.
There are numerous potential applications for the material, including in monitoring the progress of rehab patients. “If you were to put this material on a glove of a patient rehabilitating their hand for example, the health care workers would be able to monitor their finger-bending movements,” said Liu.
Another possibility is use as a smart bandage. “If we further advance this research, this could be something we put on like a ‘smart bandage,’” added Liu. “Wound healing requires breathability, moisture balance – ionic skin feels like the natural next step.”
Study in Materials Horizons: An ambient-stable and stretchable ionic skin with multimodal sensation