Ultra-high Filling Ratio of Non-Percolative Rapeseed-Shaped Liquid Metal Fiber Mats for Pressure Sensors Via Electrospinning Aided Inhomogeneous Dispersion

Abstract

Liquid metal (LM) dielectric elastomers with high flexibility and excellent dielectric properties are ideal for flexible capacitive pressure sensors. However, the development of LM dielectric elastomers is hindered by the challenge of unavoidable percolation at high LM fill ratios. Inhomogeneous distribution is an effective strategy to manipulate the percolation threshold. Herein, thermoplastic polyurethane (TPU) fiber mats featuring a unique rapeseed-shaped structure were designed for high LM content filling (up to 90 vol%) and prepared with the aid of an electrospinning technique, in which LM was locally concentrated in the TPU fibers of the composite mats to form isolated clusters, leading to an incredible improvement in the percolation threshold surpassing our calculated theoretical prediction (>90 vol% vs. 83 vol%). The LM/TPU-Fiber mats are proven to be recyclable, temperature-insensitive, and waterproof, making them suitable for multiple usage environments. A flexible capacitive sensor prepared with LM/TPU-Fiber mats, capable of exceptional relative capacitance change (Max. ΔC/C₀ = 6.32), an impressive pressure range of 0–550 kPa with a sensitivity of 55 MPa⁻¹, and high cyclic stability (>6000 cycles). With these outstanding attributes, the sensor holds great promise for applications in intelligent sorting, pressure distribution monitoring, and human–machine interaction.

Graphical abstract