From Proximity to Contact Perception of Piezoelectric Extended-Gate Amorphous Oxide Thin Film Transistors

In consumer electronics and industrial electronics today, transistors are common devices. With the rapid development of electronic skin and wearable electronics, there has been an escalating demand to extend thin film transistors as sensors to perceive multiple physiological signals and varieties of external stimuli. However, conventional single-function sensors are limited to detecting only one physical parameter, which is inadequate to meet the growing requirement for multifunctional integration in increasingly complex application scenarios. Consequently, recent efforts have been put forward to develop multimodal sensors for simultaneous detection of multiple physical quantities. To achieve full process perception of varieties of targets from proximity to contact, here in-plane interdigital piezoelectric polymer capacitors were introduced to amorphous oxide thin film transistors as extended gates to construct flexible multimodal sensors, in which the piezoelectric effect endowed the sensors with contact perception capability, and electrostatic induction realized sensitive proximity perception of a charged object, while the fringe capacitance effect further guaranteed noncontact perception of a zero potential and conductive target. The synergistic effect of both the piezoelectric effect and field effect further endowed the devices with effective perception of both static and dynamic mechanical excitation beyond the capability of a piezoelectric capacitor alone. Such devices realized proximity perception of a variety of common objects and tactile perception of pulse, breath, and bending of human joints. This piezoelectric extended gate transistor configuration was further developed as an electronic skin to control the grasping action of a mechanical hand as well as the measurement of the applied force. This work provides a feasible solution to design multimodal sensing systems for applications in electronic skin, wearable devices, and robotic perception.