关键词: 针织, 间隔织物, 摩擦纳米发电机, 压缩性能, 智能纺织品

Abstract: Triboelectric nanogenerators (TENGs) represent an emerging energy conversion technology that effectively transforms low-frequency mechanical energy, abundantly available in the environment, into electrical energy through the synergistic effects of contact electrification and electrostatic induction. This is achieved via sliding or contact-separation movements between materials, facilitating charge transfer. Compared to traditional chemical batteries, which face issues such as structural rigidity, limited lifespan, and environmental pollution, TENGs offer advantages including diverse material selection, low manufacturing costs, environmental friendliness, and the ability to meet the lightweight and comfort requirements of smart wearable devices. As a result, TENGs demonstrate significant potential in powering smart wearable technology, with broad application prospects in areas such as wearable power sources, self-powered sensors, and human health monitoring systems. Moreover, when integrated onto fabric surfaces, TENGs can harvest mechanical energy from daily human activities and seamlessly combine with textiles through carrying, wrapping, or embedding methods without adding extra bulk. This makes textile materials a versatile and ideal carrier platform for TENGs. Current fabric TENGs face challenges of low output performance and difficulty in balancing electrical output with mechanical properties. To address this issue, this study proposes a multi-layer spacer fabric structure. Using computerized flat knitting technology, we designed and fabricated a series of spacer fabrics with key structural parameters including the number of fabric layers, the number of separating needles for spacer yarns (3, 5, 7, or 9 needles), and whether the middle area includes empty needles. We systematically tested their compression performance and electrical output performance. The multi-layer structure (negative friction layer–spacer yarn–positive friction layer–spacer yarn–negative friction layer) significantly improved impact resistance and exhibited a layered energy absorption mechanism. The peak compression load of the five-needle separation multi-layer structure (223 N) increased by 78% compared to the single-layer structure (125 N). The multi-layer design also increased the effective contact area between friction layers, thereby enhancing electrical output performance. The number of separating needles for spacer yarns has a critical impact on performance. The five-needle separation design exhibited an optimal balance: it delivered a peak compression load of 223 N, and under 6 kPa pressure, generated a short-circuit current (Isc) of 55 nA, an open-circuit voltage (Voc) of 35.5 V, and a transferred charge (Qsc) of 11 nC. This is attributed to the moderate inclination angle of the spacer yarns, which prevents buckling while maintaining sufficient interlayer contact. In comparison, the seven-needle and nine-needle separation designs exhibit inferior performance. The nine-needle separation structure shows severe buckling (resulting in reduced load) and insufficient contact area (leading to decreased electrical output). Meanwhile, the structure with empty needles in the middle weakens both aspects of performance. The removal of the central spacer yarns compromises structural support, causing a reduction in peak load by over 50%, and also hinders effective contact-separation during operation, resulting in a significant drop in electrical output (e.g., Isc decreases from 55 nA to 12.5 nA). The five-needle separation multi-layer fabric demonstrates exceptional stability, maintaining an open-circuit voltage of approximately 27 V after 3,000 compression cycles under 4 kPa pressure. The shared electrode in the multi-layer structure enables series superposition of voltage, and its effective contact area is twice that of single-layer TENGs. This study demonstrates that the five-needle separation multi-layer spacer fabric structure successfully balances high-impact protection with efficient energy harvesting. It offers a scalable and integrated solution for self-powered wearable devices and pressure-sensitive smart textiles.

Key words: knitting, spacer fabric, triboelectric nanogenerator (TENG), compression performance, smart textiles