Pressure-tuneable electrical conductivity in copper Nanowire–Polyurethane thin films: Experimental and simulation studies

This work investigates the electrical behaviour under pressure of thin-film nanocomposites combined of synthesised copper nanowires (CuNWs) and thermoplastic polyurethane (PU) using experimental and numerical approaches. CuNWs (∼15 μm length, 70 nm diameter) were chemically synthesised. The scanning electron microscopy (SEM) analysis confirms their uniform and elongated structure of CuNWs, while energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) indicate high copper purity. CuNWs were integrated into the PU matrix using a solution mixing approach, and the resulting mixture was spin-coated to form a thin film exhibiting uniform CuNW dispersion, as confirmed by optical microscopy. Nanocomposite films are prepared with CuNWs concentrations ranging from 3 wt% to 18.5 wt%, exhibiting thermal stability up to 290°C. The electrical conductivity of the thin films under controlled pressure was measured, revealing that the electrical conductivity increased with CuNW concentration, reaching a maximum value of 0.61 S/m for 18.5 wt% CuNW in the nanocomposite under a pressure of 20 kPa. The percolation threshold shifts significantly with pressure (from 15 wt% at 1 kPa to 3 wt% at 20 kPa), governed by pressure-induced percolation transition (PIPT). Finite element method (FEM) simulations capture the combined influence of nano-additive content, nanowire orientation, and pressure-induced densification on macroscopic conductivity.