Preparation And Properties Of Polyvinyl Alcohol/Polypyrrole Composite Hydrogels

As a new type of "soft and wet" material,hydrogel has a cross-linked three-dimensional network structure and high water content,and has shown great promise in the fields of human-machine interface,flexible electronic devices,soft robotics and other applications.However,due to the inhomogeneous microscopic network and the lack of an efficient energy dissipation mechanism,conventional hydrogels are often soft and fragile,and cannot meet the mechanical performance requirements of practical applications.Ideally,the basic requirements for hydrogels as new wearable sensors are that they can deform with human movement,but also need to have certain mechanical properties such as toughness,tensile properties,puncture and friction resistance,higher information perception capability and human comfort,which places higher demands on the structural design and preparation process of hydrogels.In this paper,with the research goal of improving various mechanical properties and human suitability of the material,strong Polyvinyl Alcohol conductive hydrogel films were prepared by film-casting and Glycerol-Water secondary hydration,and the system was initially explored in the field of strain sensors.Firstly,a new conductive hydrogel film based on crystal structure was constructed in this research to address the problem of incomplete mechanical properties of strong,friction and puncture resistance of hydrogel materials.By introducing Polypyrrole,a conducting polymer dispersed by Cellulose derivatives,an interpenetrating network formed by a conductive network and a flexible mechanical dissipative network was constructed.By establishing synergistic interactions such as hydrogen bonding and π-π stacking between the networks,a variety of excellent mechanical properties of the hydrogel films could be achieved simultaneously,including elongation at break of up to 747%,toughness of up to28.5 MPa and good friction and puncture resistance.Besides,the hydrogel films prepared from the biocompatible materials selected in this paper also demonstrated excellent biocompatibility,the dense network structure gave the hydrogel films anti-swelling properties and the addition of polypyrrole resulted in a significant increase in the UV shielding effect of the material.In addition,unlike previous infusion moulding methods,the hydrogel films prepared by the film-casting and secondary hydration method were only 0.11-0.20 mm thick,and the ultra-thin strain sensors assembled with electrochemical workstations were more sensitive and comfortable to use.In addition,the ultra-thin structure not only reduced the possibility of motion artefacts during signal transmission,but also allowed rapid sensing and transmission of weak signals during small deformations.The hydrogel-based sensor could not only accurately identify the surface texture and roughness of external objects such as glass,brushes,wood and sandpaper with different mesh numbers(mesh number of80,50 and 24),but also record human physiological signals and movement signals(e.g.breathing,finger flexion,wrist movement up and down).This provided a new way to develop emerging soft material smart devices,such as hydrogel-based electronic skins and soft body robots.