Liquid Metal Fiber-Based High-Sensitivity Strain and Pressure Sensors Enhanced by Porous Structure

Fiber-based sensors have garnered increasing attention due to their remarkable comfort and adaptability to complex surfaces. Nonetheless, enhancing the sensitivity of fiber-based sensors remains a formidable challenge. In this study, a liquid metal porous fiber-based strain and pressure sensor was designed for monitoring human joint movement, pressure magnitude, and distribution as well as object proximity detection. A hollow double-layer fiber was fabricated via coaxial wet spinning, employing a spinning solution comprising a mixture of sodium chloride particles and thermoplastic polyurethane (TPU) solution, along with TPU solution and deionized water, from the outermost to the innermost layer. Subsequently, liquid metal was injected into the hollow fibers to obtain liquid metal porous fiber-based strain and pressure sensors. Remarkably, the pressure-sensing sensitivity was improved by 6.00 ± 1.70 and 3.42 ± 0.31 times in the pressure ranges of 0–0.06 and 0.06–8 MPa. The incorporation of a porous structure significantly enhanced the sensitivity of the pressure sensor. Furthermore, the developed sensor exhibited exceptional adaptability to pressure and strain stimuli across different magnitudes and application speeds while demonstrating remarkable stability and fatigue resistance, withstanding over 1000 cycles. The methodology established in this study offers an effective strategy for the design and fabrication of high-performance fiber sensors.