Abstract:

Objective To develop a cross-scale manufacturing technology that simultaneously optimizes the mechanical performance of the substrate and the construction of conductive networks, a custom-designed water-bath electrospinning apparatus was employed to fabricate cross-scale micro/nano structured composite yarns, which are expected to integrate high specific surface area with excellent mechanical properties. Through a synergistic electrostatic spraying process, conductive materials were directionally deposited to construct a conductive network, thereby enabling the preparation of stretchable strain-resistance sensing yarns applicable to motion detection, error correction, and speech recognition.

Method By integrating sheath yarns with electrospinning techniques, nanofiber membranes were deposited onto the surface of a water bath, while the self-rotation of the yarns facilitated the fabrication of nanofiber-coated yarns. During the deposition process, electrostatic spraying was simultaneously applied. Due to electrostatic repulsion, carbon nanotubes (CNTs) were uniformly deposited onto the surface of the nanofibers, forming a conductive network. As the coating process progressed, CNT-adhered nanofiber-coated yarns (NFCY-CNTs) were obtained.

Results This paper introduces the one-step fabrication method for NFCY-CNTs, based on an independently developed water-bath electrospinning system, utilizing a coupled electrospinning-electrospraying technique. Experimental results demonstrated the successful construction of a multilayer structured composite yarn, where the core yarn provided mechanical support, the electrospinning process formed the nanofiber coating layer, and the electrospraying technique achieved directional deposition of a CNTs network so as to establish conductive pathways. Systematic characterization revealed that NFCY-CNTs possessed a dense and uniform nanofiber coating layer, with strong interfacial adhesion between CNTs and the fiber layer. The micro/nano structural integrity remained stable after prolonged tensile stress and washing treatments. Mechanical tests showed a synergistic reinforcement effect between the core yarn and the outer coating, with the breaking strength increasing from (1 092.8 ± 22.9) cN to (1 182.1 ± 28.0) cN, and the elongation at break improving from (577.6 ± 12.25)% to (585.3 ± 8.20)%, confirming the mechanical enhancement offered by the composite structure. The conductive network endowed the yarn with excellent strain-sensing performance, with its gauge factor exhibiting a strain-dependent graded response. Stable electrical signal output was maintained under long-term cyclic loading and the composite yarn demonstrated a consistent strain-resistance response even within small strain ranges. Experimental results verify the yarn's high sensitivity and fast response in joint motion monitoring, posture analysis, and speech vibration sensing, confirming its potential for intelligent medical monitoring, sports biomechanics assessment, and human-machine interfaces. Highlighting its potential for wearable sensing applications.

Conclusion This study proposes a one-step synergistic electrospinning-electrospraying technology for constructing NFCY-CNTs. The technique achieves uniform nanofiber coating and orderly assembly through electrospinning, which enhances the yarn's surface properties and increases the mechanical strength of the yarn. Concurrently, electrospraying facilitates directional CNT deposition to form a stable 3D conductive network, resulting in a linear resistance response over a broad strain range (0%-200%). To address interfacial instability in flexible sensing yarns, a medical elastic bandage-inspired fixation strategy was implemented to suppress yarn slippage and ensure reliable dynamic signal acquisition for more than 5 000 cycles. In summary, this fabrication strategy broadens functional yarn design via nanomaterial synergy and enables future integration of miniaturized signal processors with optimized multiscale compatibility, advancing flexible e-textiles toward wearable health monitoring applications.

Key words: electrospinning, electrospraying, carbon nanotube, micro/nano structured composite yarn, polyurethane fiber, sensing yarn, strain sensing, smart wearable textiles