Crosslinking‐Modulated Hydrogel Piezoionic Sensor for Pattern Security Authentication in Human‐Machine Interfaces

Abstract Ionic hydrogels are uniquely suited as force‐sensing layers because of their good biocompatibility and controlled electromechanical properties. The emerging piezoionic effect allows them to sense the position of pressure, but the low response rate limits their applications. Herein, this work focuses on modulating the response time of piezoionic outputs through crosslinking. The underlying mechanism is investigated through the perspective of deformation recovery rate and ion migration behavior in the ionic hydrogels. As a result, the developed piezoionic sensors are capable of distinguishing static forces in the range of 0.1–5 s while monitoring dynamic force, breaking the limitations of conventional self‐powered pressure sensors that have trouble tracking static forces. Furthermore, by utilizing the piezoionic effect to convert the touch indentation into transverse gradient ionic potential, the constructed piezoionic sensors achieve accurate monitoring of finger pressing position and sliding trajectory. As a proof‐of‐concept, pattern unlocking in security authentication is successfully validated based on the developed piezoionic sensors. This design strategy of modulating ionic tactile sensor by crosslinking is expected to provide a fresh path for the large‐scale flexible human‐machine interfaces.