Construction Of Multifunctional Hydrogel Driven By Al³⁺ And Its Application In Flexible Sensor

Flexible wearable strain sensors convert external stimuli into recordable electrical signals and play a non-negligible role in areas such as artificial intelligence systems,human motion monitoring and health monitoring.To meet the diverse needs of people,there is an urgent need for a flexible material that combines tensile,self-healing and conductive properties to build wearable strain sensors.The inherent rigidity of conventional conductive materials limits their application as flexible wearable devices.Conductive hydrogels have the advantages of stretching,electrical conductivity and self-healing properties,and can be better fitted to different parts of the body,solving the problems of poor stretching performance,low sensitivity and narrow sensing range of traditional wearable sensors.Natural biopolymers have the advantages of being renewable,non-toxic and biodegradable.Conductive hydrogels prepared based on natural biopolymers have excellent flexibility and electrical conductivity and show great potential in the application of flexible wearable strain sensing devices.Therefore,in this thesis,Al³⁺-driven multifunctional ionic conductive hydrogels were prepared using natural biopolymers to construct high-performance flexible sensors that combine various properties such as excellent tensile properties,good adhesion,wide strain sensing range and stable electrical signal transmission,and were investigated as patch sensors for monitoring human motion,providing a new idea for flexible wearable devices.The main research of this paper is as follows:（1）Construction of a multifunctional CS/HA/Al³⁺conductive hydrogel and its application in human motion monitoring.In water,the natural biomolecules chitosan（CS）and hyaluronic acid（HA）have been used in a synergistic manner based on multiple physical cross-linking to construct a multifunctional ionic conductive hydrogel(CS/HA/Al³⁺)with excellent stretchability（2000%）,good toughness(121 kJ·m^-3),high self-healing efficiency（97%）and good fatigue resistance.Because of the abundance of hydroxyl groups in CS and HA,the gel exhibits strong adhesion properties to a wide range of material surfaces.Due to the stable conductivity of CS/HA/Al³⁺hydrogels,the hydrogels exhibit high sensing sensitivity（sensitivity factor（GF）=4.42）,a wide strain range（800%）,and excellent durability（>300 cycles）,allowing them to be constructed as strain sensors for monitoring human joint movements and subtle expression changes.（2）Construction of SD-AA/Al³⁺conductive hydrogels with frost resistance and excellent tensile properties and their application in flexible sensors.A conductive hydrogel with excellent stretching（3700%）,high conductivity(24.5 S·m^-1),self-healing and frost resistance has been constructed by cross-linking poly（acrylic acid-acrylamide）（P（AA-co-Am））networks with polydopamine（PDA）under non-covalent bonding interactions such as metal coordination and hydrogen bonding.The micelle structure formed by the sodium caseinate（SC）molecules based on a balance of hydrophobic interactions and electrostatic interactions provides an energy dissipation center during cyclic stretching and improves the fatigue resistance of the hydrogel.SD-AA/Al³⁺hydrogels exhibit good adhesion to a wide range of substrates with a maximum peel strength of 56 k Pa against tin foil.in addition,the SD-AA/Al³⁺hydrogel strain sensor exhibited high sensitivity（GF=23.7）over a wide strain range（0-2500%）and multiple cycles（>260 cycles）,and the hydrogel showed good strain sensitivity even at temperatures of-20°C.Thus,SD-AA/Al³⁺hydrogels are capable of real-time monitoring of a wide range of human motions.This work provides new ideas for the design and development of freeze-resistant conductive hydrogels and broadens the application of hydrogel sensors in artificial intelligence systems,extreme environmental health monitoring systems and flexible wearable devices.