Multi‐Functional Eutectic Hydrogel for 3D Printable Flexible Omnidirectional Strain Sensors

Abstract Flexible electronic devices are attracting much attention on account of their great potential in artificial intelligence, electronic skin, and biomedicine. However, the poor stretchability, conductivity, and machinability of flexible materials limit the application of flexible electronic devices in practical environments. Herein, hydrogels with excellent mechanical, electrical, and processable properties are synthesized by introducing deep eutectic solvent (DES) and MXene into a polyvinyl alcohol (PVA) matrix, which shows more than 2700% tensile strain, and 1.21 S m⁻¹ conductivity. Interestingly, hydrogels also exhibited 3D printable properties, enabling the fabrication of sensors with complex structures in a short period of time. Besides, the serpentine lines strain sensor is successfully prepared by digital light processing (DLP) 3D printing and assembled into a bidirectional strain rosette sensor and omnidirectional strain rosette sensor, which could recognize the direction and magnitude of stress. More importantly, the omnidirectional strain sensor can accurately distinguish the signal responses of different directions and sizes generated by ping‐pong players swinging the racket, showing excellent strain recognition ability. In brief, the hydrogels designed are expected to realize the manufacture of large‐scale and low‐cost flexible sensors through a simple preparation process, which provides a new idea for the manufacture of flexible electronic devices.