Pixel-free capacitive touch sensor using a single-layer ion gel†
Capacitive sensors have been studied for various purposes, including detecting touch, pressure, and physical motions. However, a complicated process involving numerous electrode pattern arrays is necessary to detect touch positions. Here, a simply configured capacitive sensor with a single-layer ion gel (SIG) layer and copper electrodes without electrode arrays is reported. The touch sensor with a SIG is capable of precise touch sensing and touch positioning. The SIG touch sensor can detect the touch position by variation of the electric field in the ion gel layer and the change of the capacitance created by the touching object. Such a capacitive touch system has fast and accurate touch sensing capabilities and is independent of touch pressure. In addition, the touch sensor enables dynamic moving touch detection even when attached to the back of the human hand. Furthermore, an epidermal touch keypad is demonstrated by fabricating an array of three SIG touch sensors. The proposed capacitive touch sensor based on a SIG can enable the development of future electronic devices such as wearable electronics, soft robotics, electronic skin, and human–machine interaction systems.