关键词: 羟丙基纤维素, 聚乙烯醇水凝胶, 交联, 柔性传感器

Abstract: In recent years, the demand for flexible sensors has been increasing. Among them, conductive hydrogel flexible sensors have attracted wide attention due to their excellent flexibility, biocompatibility and conductivity. Conductive hydrogels can be prepared by physical crosslinking, chemical crosslinking and radiation crosslinking. The crosslinking degree of conductive hydrogels directly affects their electrical conductivity and mechanical strength. However, the control of crosslnking degree of conductive hydrogels prepared by physical cross-linking is usually difficult. In order to control it, we chose to add hydroxypropyl cellulose (HPC) to reduce the crosslinking degree of polyvinyl alcohol (PVA) hydrogels. In addition, the traditional conductive hydrogel is hard to meet the high conductivity and high mechanical strength at the same time. Therefore, in order to address the issue of poor mechanical properties of traditional conductive hydrogels, we coated conductive hydrogels directly onto fabrics to produce conductive hydrogel fabrics. With good elasticity, high mechanical strength, good air permeability, and comfortable softness, knitted fabrics, particularly, can fit the human body well and are excellent substrates for preparing conductive hydrogel fabrics. Meanwhile, the introduced HPC can be used as a nano-filler to toughen and improve the mechanical strength of the conductive hydrogel. In this paper, HPC was introduced into the PVA hydrogel, and a hydrogel with controllable crosslinking degree was prepared by cyclic freezing-thawing method, and it was coated on polyester/spandex fabric (90% polyester & 10% spandex). Sodium chloride (NaCl) was used as a conductive material to endow the hydrogel with electrical conductivity. Water (H2O) and ethylene glycol (EG) were used as solvents to make the prepared hydrogel have frost resistance. The introduction of polyester ammonia fabrics and HPC together enhanced the strength of the hydrogel. Analysis of scanning electron microscope images, Fourier transform infrared spectroscopy, mechanical properties, frost resistance and sensing properties was conducted on the conductive hydrogel fabrics we prepared.. It was found that when the PVA content was 10% and the HPC content was 2%, the HPC-PVA conductive hydrogel fabric we prepared had the best performance. The mechanical strength was as high as 16.77 MPa, which was about 25 times that of pure hydrogels. At the same time, it had good conductivity, and the conductivity reached 1.48 S/m. It could recognize a variety of human movements including facial expressions. In addition, due to the introduction of EG, the conductive hydrogel fabric prepared by us had good frost resistance and could still work normally at -18℃. It also proved that the flexible sensor we prepared has a broader application range.

Key words: hydroxypropyl cellulose, polyvinyl alcohol hydrogel, crosslinked, flexible sensor