High-Performance Flexible Capacitive Proximity and Pressure Sensors with Spiral Electrodes for Continuous Human–Machine Interaction

Flexible perception sensors play important roles in the artificial intelligence era. An integrated proximity and tactile pressure sensor, with the capability to continuously perceive the approach of an object until a pressure variation is sensed through contact and manipulation, is in demand for the improvement of proximity-sensing distance, flexibility, and integration. Herein, capacitive proximity and pressure dual-mode sensors based on a novel complementary Archimedean spiral electrode design and dielectric calcium cross-linked alginate film are reported. The results of theoretical analysis and finite element simulation show that the electrode pattern design with a higher specific fringe length (i.e., fringe length divided by electrode cover area) significantly enhances the fringe field. As the dielectric layer, the flexible and transparent calcium cross-linked alginate film with crater-shaped morphology is prepared by a novel interfacial reaction method with ultrasonic spraying that improves the sensitivity and linearity of the tactile perception response. Sensors with optimized electrodes and dielectric layers exhibit unprecedented performance in terms of high sensitivity, long detection distance (∼55 mm), fast responding time (<10 ms), and highly linear response (R2 = 0.995). Furthermore, the applications of the integrated perception sensors for noncontact tapping and swiping gesture recognition and continuous human–machine interaction for controlling image scaling are demonstrated.