Noncontact Perception\nof Thin-Film Transistors by\nthe Synergy of Both Capacitive and Electrostatic Induction Mechanisms

In recent years, the rapid expansion of research and\napplication\nof the Internet of Things and wearable electronics has prompted the\ndevelopment of a variety of sensors to perceive physical or chemical\ninformation from both the human body and the environment, among which\nthe proximity sensor is a kind of noncontact sensor used to detect\nthe approach of a target and thus exhibits promising applications\nin human–machine interactions. Thin-film transistors are one\ntype of key components in modern electronics and have been further\ndeveloped as electrostatic-induction-type proximity sensors to perceive\nthe approach of electrically charged objects. However, they are immune\nto the approach of a zero-potential object. Capacitive-induction-type\nproximity sensors are capable of detecting the approach of conductive\ntargets while being less sensitive to insulated ones. Integration\nof both electrostatic and capacitive induction mechanisms into one\nproximity sensor is highly expected to broaden its perception to a\nvariety of targets. Here, an interdigital electrode was introduced\nas an extended gate into an amorphous metal oxide thin-film transistor\nto construct proximity sensors that combine both electrostatic and\ncapacitive induction mechanisms and therefore can sensitively perceive\nthe approach of a variety of objects that were electrically charged,\ngrounded, or floated. Besides proximity sensing, remote velocity measurement\nand positioning of an invasive object were also realized, which further\nextended its functions as a kind of interdigital-electrode gate transistor.