Preparation And Performance Of Polyvinyl Alcohol-Based Conductive Hydrogels For Bioelectrodes

The rapid development of wearable electronics provides timely,remote,wearable and comfortable and convenient functions for medical devices,and the development of sensors and bioelectrodes as an important part of wearable electronics has an important significance.How to reduce the contact resistance between the device and skin and obtain better electrical signals to recognize weak bioelectricity and large scale limb movements,while ensuring the comfort of conformality with the limb,are the current problems faced by sensors and bioelectrodes.In this thesis,polyvinyl alcohol/glycerol-based hydrogels were synthesized by compounding various inorganic materials（Carbon materials,Inorganic salt materials,MXene）.The effects of inorganic components on the mechanical and electrical properties of the gels were investigated,and their applications as flexible sensors and bioelectrodes were explored.The main studies in this paper are as follows:1.Polyvinyl alcohol/glycerol/MXene hydrogels were synthesized by twice freeze-thawing method by doping MXene in polyvinyl alcohol/glycerol hydrogels.MXene formed a cross-linked network structure in the hydrogels,which enhanced the mechanical properties and gave the hydrogels electronic conductivity with a fracture strength of 338 k Pa,a compressive strength of 3635.24 k Pa,and an electrical conductivity of The strain sensor designed with polyvinyl alcohol/glycerol/MXene hydrogel can detect 1%-100%of deformation.The strain sensor has a sensitivity of0.64 and can be stabilized for 3200 cycles.The strain sensor can be used to detect finger joint flexion and pressing movements.2.Ag@CNTs were doped in polyvinyl alcohol/glycerol/Na Cl to obtain a hydrogel with electronic and ionic dual conductive network by freeze-thawing method.The hydrogel has good flexibility and conductivity.Resin molds were designed and 3D printed,and the hydrogels were placed in the molds for freeze-thawing to obtain claw electrodes.Its performance as a bioelectrode was investigated,and the electro-ocular（EOG）signal was tested and compared with that of commercial electrodes.It was proved that due to the high conductive network structure and the good skin conformability of the gel material,the hydrogel can obtain clear EOG signals and is comfortable to wear,solving the problems of poor comfort and short usage time of traditional Ag/Ag Cl electrodes.3.Polyvinyl alcohol/glycerol/graphene/Fe Cl₃ hydrogel was prepared.By constructing a more stable structure of macroporous hydrogel through graphene sheet layer,Fe Cl₃ exists in the pores in a semi-free state,thus obtaining a more conductive electronic and ionic dual-conducting network.Part of Fe Cl₃ is free in the form of aqueous solution between the pores,which significantly improves the ionic conductivity,resulting in a hydrogel conductivity of 0.219 S/m and skin-gel interface impedance as low as 1.8×10⁴（Ω·cm²）.The hydrogel has excellent weathering properties and maintains low impedance after 14 days in air.It was used as an electrode for the acquisition of EOG and electromyography（EMG）signals.Compared with commercial electrodes,the acquired signals are clear,comfortable,weather resistant,and reusable,and have a wide range of applications in the field of bioelectrodes.