Recyclable EGaIn/TPU sheath–core fibres for superelastic electronics and sensing applications

Abstract

Stretchable conductive fibres show great potential in the field of wearable and flexible electronics, with multifunctional conductive fibres being of particular interest. In this study, a conductive thermoplastic polyurethane (TPU) wire@eutectic-gallium–indium (EGaIn)/TPU (TET) fibre comprising a TPU wire core and EGaIn-based polymer sheath is developed, wherein the fibre obtained via a simple dip coating method realised high conductivity (> 3 × 10⁴ S m⁻¹) after mechanical sintering and particle size optimisation of EGaIn. As a resistance-type strain sensor, the TET fibre responds to various strain states and monitors the behaviour of various parts of the body continuously. The TET fibre can be easily deformed into a stretchable helical electrode at a suitable thermoplastic temperature, and maintains its electrical signal stability at ultra-large strain by adjusting the helical index to realise an ultra-high quality factor (Q) value (6691 at a strain of 2000% with a helical index of 7). Moreover, the TET fibre can be easily integrated with fabrics to generate an emergency underwater SOS signal. Remarkably, the valuable EGaIn in the TET fibres can be recycled at a yield of 94.8% and reused. Overall, the TET fibre exhibits great potential for application in flexible and recyclable human motion detectors, stretchable wires, and electronic textiles.