Paper-Based Resistive Networks for Scalable Skin-Like Sensing

This work presents a unique approach to the design, fabrication, and characterization of paper-based, skin-like sensors that use patterned resistive networks for passive, scalable sensing with a reduced number of interconnects. When touched or wetted with water, the sensors in the resistive networks detect significant changes in electrical impedance. Fabricating these resistive networks and sensors in a single sheet of metallized paper reduces the number of distinct inputs/outputs to the arrayed sensors. For human–electrode interactions, circuit-based models guide the design/material processing of the resistive networks and selection of operating frequencies—typically ranging between 80 kHz and 1 MHz. As an example, a paper-based touchpad with only two connecting wires (i.e., excitation and ground) functions as a 31-button keypad. These resistive networks are also capable of spatially mapping contact with dispensed droplets of water in a dry environment and operating when bent. The reported results mark a technological advance in capacitive sensing with resistive networks to reduce the number of required interconnects while providing scientific understanding and modeling of human–electrode interactions for flexible electronic devices. Future skin-like sensors with patterned resistive networks have the potential to contribute to scalable forms of human–machine interfaces, wearable devices, and liquid-leak detectors.