The article "Ionic Skin" by Sun et al. (2014) introduces a novel type of sensory sheet called "ionic skin," which is highly stretchable, transparent, and biocompatible. Unlike traditional electronic skin that uses electrons for signal transmission, ionic skin employs ionic conductors to report signals using ions. This approach allows the ionic skin to monitor large deformations, detect stimuli with a wide dynamic range (strains from 1% to 500%), and measure pressures as low as 1 kPa with minimal drift over many cycles. The ionic skin can also report the location and pressure of touch, making it suitable for applications in wearable and implantable electronics. The authors use hydrogels and ionogels, which are highly stretchable and transparent, as ionic conductors. These materials are biocompatible and can be made softer than tissues, achieving "mechanical invisibility" required for biometric sensors. The ionic skin is designed to transmit electrical signals without electrochemical reactions, ensuring long-term stability and drift-free sensing. The design includes a hybrid ionic-electronic circuit where the ionic skin is connected to external electronic conductors using thin lines of ionic conductors, mimicking the function of axons. The article demonstrates the performance of the ionic skin as a strain sensor and a pressure sensor. Strain sensors were fabricated using polyacrylamide hydrogels containing NaCl as the ionic conductor and an acrylic elastomer as the dielectric. The sensors showed a linear relationship between capacitance and stretch, with stable performance over 1000 cycles. Pressure sensors were also fabricated, capable of detecting pressures as low as 1 kPa with high resolution and stability over 1000 cycles. Finally, the authors demonstrate the capability of an array of distributed sensors to detect the location and pressure of touch. The ionic skin was attached to the back of a hand, and the sensors detected the location and pressure of a gentle touch, showing the potential for advanced applications in wearable technology.The article "Ionic Skin" by Sun et al. (2014) introduces a novel type of sensory sheet called "ionic skin," which is highly stretchable, transparent, and biocompatible. Unlike traditional electronic skin that uses electrons for signal transmission, ionic skin employs ionic conductors to report signals using ions. This approach allows the ionic skin to monitor large deformations, detect stimuli with a wide dynamic range (strains from 1% to 500%), and measure pressures as low as 1 kPa with minimal drift over many cycles. The ionic skin can also report the location and pressure of touch, making it suitable for applications in wearable and implantable electronics. The authors use hydrogels and ionogels, which are highly stretchable and transparent, as ionic conductors. These materials are biocompatible and can be made softer than tissues, achieving "mechanical invisibility" required for biometric sensors. The ionic skin is designed to transmit electrical signals without electrochemical reactions, ensuring long-term stability and drift-free sensing. The design includes a hybrid ionic-electronic circuit where the ionic skin is connected to external electronic conductors using thin lines of ionic conductors, mimicking the function of axons. The article demonstrates the performance of the ionic skin as a strain sensor and a pressure sensor. Strain sensors were fabricated using polyacrylamide hydrogels containing NaCl as the ionic conductor and an acrylic elastomer as the dielectric. The sensors showed a linear relationship between capacitance and stretch, with stable performance over 1000 cycles. Pressure sensors were also fabricated, capable of detecting pressures as low as 1 kPa with high resolution and stability over 1000 cycles. Finally, the authors demonstrate the capability of an array of distributed sensors to detect the location and pressure of touch. The ionic skin was attached to the back of a hand, and the sensors detected the location and pressure of a gentle touch, showing the potential for advanced applications in wearable technology.