Abstract:

Objective Flexible sensor devices based on fabrics have shown wide application prospects in fields such as healthcare and human-computer interaction in recent years due to their excellent bendability, good flexibility, and breathability. However, the roughness of the fabric surface makes it difficult to construct high-precision electrode patterns and structures on its surface. Therefore, using low-pressure ultraviolet light and chemical surface treatment methods, a high-precision and high-sensitivity patterned conductive matrix was constructed on the surface of the fabric.

Method By combining nano silver composite conductive dispersion with fabric substrate and using low-pressure ultraviolet light irradiation and chemical treatment methods, the surface energy differentiation of specific parts of the fabric surface is achieved, resulting in differences in hydrophilicity and hydrophobicity. This leads to the positioning, attachment, and spreading of the conductive dispersion on the fabric surface. The positioning, adhesion, and spreading of conductive dispersion on the substrate surface were regulated through microstructure morphology construction and surface chemical structure, thereby achieving specific conductive circuit patterns on non-planar substrates.

Results To improve the sensitivity and stability of conductive dispersion in sensing applications, silver nanowires were prepared using the polyol method, and carbon nanofibers were introduced to prepare a highly sensitive sensing nano silver composite conductive dispersion. Preparation of high aspect ratio silver nanowires by adjusting silver ion concentration and high-temperature reaction time. Through the synergistic effect between silver nanowires and carbon nanofibers, high aspect ratio silver nanowires were used as the conductive skeleton, and brittle carbon nanofibers are introduced as the "weak link". When the base fabric was stretched, the brittle carbon nanofibers would be shifted first, causing a change in resistance and improving the sensitivity of the conductive network. In order to obtain a sensing fabric substrate with higher fineness and adhesion, the mass ratio of long-chain silane to TiO₂ was used to regulate the substrate roughness. It was found that when the mass ratio of long-chain silane to TiO₂ was 1∶3, the surface roughness of the hydrophobic fabric became higher, which is conducive to the adhesion of the conductive dispersion and reduces the time cost. As the proportion of long-chain silane increases, the depth of the fabric surface increases, resulting in a higher surface roughness of hydrophobic fabrics. Due to the mechanical anchoring effect, increasing surface roughness can enhance the adhesion between the deposited metal pattern and the substrate. Finally, the UV illumination time was set to 30 minutes. UV irradiation was found to be able to break anaerobic bonds, induce substrate oxidation, cause changes in surface structure, and increase surface energy and adhesion. Using a nano silver composite conductive dispersion with a volume ratio of 20% ethylene glycol, it showed good stability and self-assembled circuits with a small fineness of up to 100 μm. After adjusting the solvent composition, the nano silver composite conductive dispersion quickly and accurately adhered to the hydrophilic region of the self-assembled patterned fabrics with good resolution. The conductive matrix prepared by this method achieved stable cyclic performance at strains of 1%, 5%, 10%, and 15%, and sensitively captured signals of small vibrations such as elastic ruler vibration, Adam's apple vibration, blinking, and finger bending. The resistance remained stable after 200 bending, twisting, and friction cycles.

Conclusion This strain sensor has high sensitivity in capturing signals of small vibrations and can monitor and record different degrees of limb movements. As the degree of limb bending increases, it displays varying degrees of changes in electrical resistivity. These results demonstrate the potential of the sensor in monitoring human motion. With the rapid development of artificial intelligence and IoT technology, smart wearable electronic products have attracted more attention. The method used in this research is simple to operate, cost-effective, and can be integrated into various complex patterned conductive lines. In addition to strain sensors, it can also be applied in fields such as fabric thermal management and health textiles, and its application can be expanded to achieve multifunctional development of products.

Key words: silver nanowire, surface energy difference, hydrophilicity/hydrophobicity, self-assembly, patterning, sensor