In recent years, flexible electroluminescent devices have attracted much attention in the field of smart textiles, especially in lighting displays, wearable electronics, and interactive information systems. However, most current electroluminescent devices rely on petroleum based polymer matrices, complex high-voltage power sources, and embedded sensors, limiting their applicability in sustainable, lightweight, and visually intuitive wearable electronic products. In addition, mechanical mismatch between functional layers can easily lead to interface cracking or even delamination, further restricting its practical application.

The collaborative team of Associate Professor Yao Yijun, Professor Zhang Pengfei, and Dr. Zhang Zhenfang from Xi'an Engineering University has successfully developed a flexible silk fibroin based electroluminescent fiber (SFELF) with a coaxial structure. The fiber is prepared using conjugate electrospinning, coating, and winding techniques. By precisely regulating the beta folding of silk fibroin to enrich its secondary structure, the fiber exhibits excellent mechanical toughness (5.29 MJ · m ⁻ ³) and high brightness (up to 366 cd · m ⁻ ²), surpassing similar products based on polydimethylsiloxane and cellulose. It is worth noting that the fiber maintains stable luminescence performance after more than 10000 bending cycles, demonstrating excellent mechanical durability. More notably, even with the removal of external electrodes, the fiber can still emit light through finger or metal material touch, and its luminescent behavior can be regulated by external electric or thermal fields without the need for an external power source. In addition, the fiber also integrates frictional electricity and liquid sensing functions, providing new possibilities for real-time visual monitoring and human-computer interaction.

Figure 1 shows the preparation process and luminescence mechanism of SFELF. By using conjugate electrospinning technology, PVDF dielectric layer is uniformly coated on silver plated nylon yarn, followed by coating with ZnS: Cu/BaTiO ∝/SF luminescent layer solution and natural drying, and finally wrapped with stainless steel wire to form coaxial structural fibers. The secondary structure of silk fibroin (α - helix, random curl, β - fold, β - turn) contributes to the stable dispersion of ZnS: Cu luminescent particles. In terms of luminescence mechanism, under the excitation of an alternating electric field, Cu ₂₋ₓ S promotes the injection of electrons from the conduction band into ZnS and holes from the valence band, resulting in luminescence when electrons and holes recombine. The contact point between the external electrode and the luminescent layer forms a local electric field, further promoting electron tunneling and composite luminescence.

Source: Sensor Expert Network