Flexible sensors have been developed for use in consumer electronics, robotics, healthcare, and space flight. Future possible applications could include the creation of electronic skin and prosthetic limbs that allow wearers to feel changes in their environments. One problem with current flexible sensors, however, is that they can be easily scratched and otherwise damaged, potentially destroying their functionality. Researchers at the Technion – Israel Institute of Technology (Technion), Haifa, have developed materials that can be integrated into flexible devices to “heal” incidental scratches or damaging cuts that might compromise device functionality. The advancement, which uses a new kind of synthetic polymer, has self-healing properties that mimic human skin, allowing e-skin “wounds” to heal themselves in less than a day. A paper outlining the characteristics and applications of the self-healing sensor has been published in the current issue of Advanced Materials.
The sensor is made of a self-healing substrate, high-conductivity electrodes, and molecularly modified gold nanoparticles. “The gold particles on top of the substrate and between the self-healing electrodes are able to heal cracks that could completely disconnect electrical connectivity,” said Hossam Haick, PhD, a full professor in the Department of Chemical Engineering and the Russell Berrie Nanotechnology Institute at Technion, and a codeveloper of the sensor.
The healing polymer works quickest, said the researchers, when the temperature is between 0 and 10 degrees C, when moisture condenses and is then absorbed by the substrate. Condensation makes the substrate swell, allowing the polymer chains to begin to flow freely and, in effect, begin healing. Once healed, the nonbiological, chemiresistor still has high sensitivity to touch, pressure, and strain, which the researchers tested in stretching and bending tests. Another feature is that the electrode resistance increases after healing and can survive 20 times or more cutting/healing cycles than prior to healing. Essentially, healing makes the self-healing sensor even stronger, said the researchers.
Editor’s note: This story was adapted from materials provided by the American Technion Society.