Integrated Soft Ionotronic Skin with Stretchable and Transparent Hydrogel–Elastomer Ionic Sensors for Hand-Motion Monitoring

Skin-like stretchable sensors with the flexible and soft inorganic/organic electronics have many promising potentials in wearable devices, soft robotics, prosthetics, and health monitoring equipment. Hydrogels with ionic conduction, akin to the biological skin, provide an alternative for soft and stretchable sensor design. However, fully integrated and wearable sensing skin with ionically conductive hydrogel for hand-motion monitoring has not been achieved. In this article, we report a wearable soft ionotronic skin (iSkin) system integrating multichannel stretchable and transparent hydrogel–elastomer hybrid ionic sensors and a wireless electronic control module. The ionic sensor is of resistive type and fabricated by curing ionic hydrogel precursor on a benzophenone-treated preshaped elastomer to form a hydrogel–elastomer hybrid structure. The hydrogel–elastomer hybrid iSkin is highly stretchable (∼300% strain), transparent (∼95% transmittance in the visible light range), and lightweight (<22 g). Experiments demonstrate that the fully integrated iSkin system can conformably attach onto the dexterous hands for recognizing the joint proprioception and hand gesture, and understanding the sign language. Our iSkin system would also provide a test bed for customized material selection and construction in a variety of applications.