Study On The Preparation,properties And Application Of Borate-Based Dynamic Bond Self-healing Hydrogel

Biomimetic electric skin is a kind of artificial bionic material,which is capable of strongly adhering to different parts of human bodies and precisely detecting different types of human motions.It has broad application prospects in the field of wound dressing repair,human/machine interaction,wearable devices and software robots.In order to mimic human skin,high sensitivity and excellent mechanical properties are required in addition to good biocompatibility.Self-healing hydrogel is a new kind of material with the ability of self-healing damage,excellent stretchability and mechanical strength.It has potential of making biomimetic electronic skin.The self-healing gel was produced by polymerizing acrylamide.Modified chitosan was introducted to give the hydrogel abilities of self-healing and adhension.Salt ions was introduced to provide sensing capability.In this study,H-bonding,dynamic covalent bonds and chemical cross-linkers were combined together to produce this hydrogel.Chemical cross-linkers were introduced by adding N,N?-methylenebis(acrylamide)(MBAA)for copolymerization.It gives hydrogels high mechanical strength beacuse of its high chemical-bond energy.The mussel-inspired catechol groups in chitosan were capable not only of forming dynamic ester bonds with phenylboronic acid groups of PAAPBA,but also of forming H-bond with polar groups of polyacrylamide and chitosan.The presence of these dynamic interactions offered the resultant ionic gel with excellent self-healing properties and large stretchability.The gel is divided according to whether there is chemical crosslinkers.One is elastic hydrogel with chemical bonds.It shows a high stress at break up to 30 kPa and stretchability of 1150%.One is plastic hydrogel,it shows a yield strain of 1060% and stretchability beyond 20000%.Before the yield point,the hydrogel shows elasticity that the stress rises continuously.After the yield point the hydrogel shows plasticity that the stress reduces continuously until the stress approaches zero,and it can continue to be stretched without breaking.The surface of the modified chitosan contains a large amount of hydroxyl groups,and citosan is a biomass polysaccharide,so both have adhesion and biocompatibility.In the study,elastic hydrogel with salt ions is chosen to be an electronic skin.It has stable electrical conductivity(25 m?/s),fast response(0.2 s),and a specific response based on the motion of different parts of the human body.