Preparation And Strain Sensing Properties Of Chitosan-based Adhesive And Tough Conductive Hydrogels

Hydrogel has attracted the attention of the scientific community because of its high water content and three-dimensional network structure.Hydrogel has the characteristics of moisture retention and flexibility.Because it is similar to biological tissues,hydrogel has developed significantly in wound dressings,drug delivery,artificial tissues,and flexible electronic devices.The researchers made the hydrogels conductive by adding a conductive material to them.In recent years,flexible and stretchable sensor assembled from conductive hydrogels have received extensive attention in recent years.However,due to the single properties of some hydrogels,the wide application of hydrogels is limited.Therefore,it is of great significance to prepare a hydrogel with excellent adhesion,toughness and various properties.In this work,P(AMPS/ AAM)-CS hydrogel was successfully prepared by introducing chitosan(CS)and 2-acrylamide-2-methylpropylsulfonic acid(AMPS)into the polyacrylamide hydrogel system.The hydrogel exhibited excellent mechanical properties,self-adhesion,transparency and electrical conductivity.The introduction of AMPS not only provides the acidic conditions required for the dissolution of chitosan,but also forms physical cross-links with chitosan through electrostatic interactions,so that the hydrogel exhibits high mechanical properties.The fracture stress and strain of hydrogel can reach111 k Pa and 2840%,respectively.The hydrogel showed fatigue resistance.In addition,the molecular skeleton of chitosan and AMPS contained a large number of reactive functional groups,which made the hydrogel exhibit excellent adhesion on the surface of various solid materials and human skin.The maximum peel strength of hydrogel can reach 800 N/m.As an acidic electrolyte,AMPS endowed the hydrogel with electrical conductivity and good strain sensitivity.The highest electrical conductivity of hydrogel was 0.0848 S/cm.The strain sensitivity of hydrogels was up to 7.08.Based on the excellent electrical conductivity and strain sensitivity of the P(AMPS/AAM)-CS hydrogel,we successfully assembled the hydrogel into a wearable sensor with high transparency.Due to the self-adhesive nature of the hydrogel,the hydrogel sensor fitted tightly to the skin and didn’t come off during testing.Not only can hydrogel sensors accurately convert a wide range of human movements into electrical signals,such as wrist,elbow and knee,but they can also convert small movements into electrical signals,such as throat and fingers.We believe that this hydrogel will provide a new option for the design and preparation of multi-functional self-adhesive hydrogel sensors.