Preparation And Application Of Adhesive Conductive Hydrogel Based On Zwitterionic Polymer

Hydrogels are a kind of three-dimensional network polymer material with high water content.They are widely used in tissue engineering,wearable/implantable devices,energy collection devices and electronic skin due to their similar microstructure to human tissue and biocompatibility.In recent years,conductive hydrogels have important application prospects in sensing fields such as biosensors,flexible electronic devices,and electronic skins due to their excellent conductivity,adjustable network structure,and excellent mechanical properties.However,currently most conductive hydrogels do not possess adhesive properties and need to be adhered to the substrate through tape or other means to achieve the purpose of collecting signals,which greatly limits the application of conductive hydrogels in the biomedical field.Therefore,the development of conductive hydrogels with excellent adhesion properties,self-healing properties,and stretchability is a key issue that needs to be solved at present.Mussels can adhere to the surface of a variety of materials under wet conditions by secreting adhesion proteins.Polydopamine(PDA)has a molecular structure similar to that of mussel adhesive protein,and can react with functional groups on the surface of a variety of materials similar to the o-phenol hydroxyl reaction of dopamine molecules in adhesive protein.Zwitterions contain both cationic quaternary amine groups and anionic sulfonic acid groups in the same repeating unit.The zwitterions are electrically neutral,have a high dipole moment,and can promote ion conduction.Zwitterionic groups can form dipole-dipole interactions with polar groups on the surface of other materials,which makes the hydrogels prepared based on zwitterionic materials closely combine with the surfaces of other materials.Therefore,based on the adhesion mechanism of dopamine and zwitterion,conductive hydrogels with selfadhesion,self-repair and stretchability were prepared and their applications were explored.The main contents of this study are as follows:The co-adhesion mechanism of polydopamine and zwitterion was proposed,and a zwitterionic hydrogel compounded with dopamine intercalated clay nanosheets was prepared,which was expected to be used as an implantable device for human health monitoring.At the hydrogel-tissue interface,the synergistic effects of dipole-dipole interaction,hydrogen bonding,Michael addition,and Schiff base reaction give the hydrogel a stable and repeatable adhesion properties on the surface of tissue.Its adhesion strength on the surface of heart tissue is as high as 19.4k Pa.In addition,the weak interaction between the movable ion and the zwitterionic polymer can enhance the movement of the ions,which can assist the ion conduction.The ionic conductivity of the hydrogel is 0.0215 S/m.The tribological nanogenerator,as an energy collecting device,has attracted wide attention due to its high safety,clean environment and sustainability.It is difficult to make a long-term firm contact between the conventional conductor layer and the electrification layer,which affects the power generation performance.In response to this problem,as a conductive layer to prepare a contact generator.The ion-dipole or dipole-dipole interaction formed by zwitterions and other charged groups or polar groups is used to achieve a close bond between the conductor layer and the electrified layer.The produced contact generator has good power generation performance and can output an open circuit voltage of 8 to-33 V.In addition,the physical cross-linking of the nanoclay gives the hydrogel excellent stretchability,By changing the content of nanoclay,the effect of clay content on mechanical properties,adhesion,transparency and other properties of hydrogel and contact generator was studied.PDA-clay-PSBMA hydrogel is a good material for wearable devices due to its excellent adhesion properties,conductivity and stretchability.The sensitivity(GF)of the strain sensor is 4.3 at 0 ～ 670% strain.This electrical sensing performance and adhesiveness help to achieve a close bonding of the polydopamine zwitterionic nanocomposite hydrogel to the tissue surface for real-time monitoring of human motion.Meanwhile,by attaching the strain sensor to the lung tissue,the respiratory signals of the lung tissue can be wirelessly transmitted,demonstrating its potential application in the manufacture of implantable human health monitoring devices.