Additively Manufactured Micro-Pyramid Structured Electronic Skin with [BMIM]BF₄ 3D Morphology Detection at Low Temperature

Electronic skin (e-skin) holds significant potential for applications in health monitoring, human–machine interface, and motion recognition. However, conventional e-skins often exhibit decreased sensitivity and delayed response in low-temperature environments due to the freezing of conductive materials. To solve this, a flexible e-skin suitable for low-temperature environments was fabricated by selecting the ionic liquid [BMIM]BF4 as the conductive medium. Unlike liquid metals and hydrogels, ionic liquids can serve as conductive media with ultralow melting points and high conductivity by selecting appropriate cation–anion combinations. The [BMIM]BF4 we selected maintains high conductivity even with an ultralow melting point of −71 °C, which enables the fabricated flexible sensors to exhibit outstanding pressure-sensing performance under low-temperature environments. The e-skin can accurately respond to pressure loads (100–10,000 Pa), with linear resistance response. In addition, the e-skin maintains stable sensing performance in various curved environments and retains its normal sensing capability for external loads at temperatures as low as −50 °C. Furthermore, it possesses excellent dynamic sliding trajectory recognition capabilities, enabling the simultaneous identification of trajectories from multipoint sliding. To further enhance the three-dimensional microscale sensing capabilities of the e-skin, micropyramids were introduced onto its surface. The micropyramid-decorated e-skin can accurately achieve real-time dynamic detection of height at −10 °C, with a detection error of less than 2%. Therefore, the e-skin can accurately recognize microscale three-dimensional surface morphologies at −10 °C. Moreover, this e-skin can be applied in the field of Braille detection. It exhibits good recognition and reading capabilities for standard Braille currently in use and can identify various complex Braille letters.