Preparation And Properties Of Multifunctional Ionic Hydrogels And Their Application In Strain Sensors

In recent years,flexible electronic sensors have played a crucial role in smart wearable electronic devices.By converting mechanical deformation into electrical signals,they have broad application prospects in fields such as human motion monitoring,health detection and soft robotics.With the continuous improvement upon social demand,higher standards and requirements are put forward for the application of sensors in different applications.In addition to basic requirements including flexibility,durability,low power consumption,and biological compatibility,flexible sensors must also meet various functional requirements such as self-healability,self-adhesiveness,transparency,UV-filterability,anti-freezing feature,moisture retention and thermoplasticity.Hence,it is crucial to prepare multifunctional,high-performance and stable strain sensors that can be applied in wearable electronic devices,artificial intelligence and soft robotics.Therefore,two kinds of multifunctional ionic hydrogel strain sensors were fabricated to accomplish the multiple performance combination.The main research contents and conclusions were as follows:（1）Preparation and properties of CS/TA/PAA-Al³⁺ionic hydrogels and their application in strain sensorWe designed a multifunctional composite self-adhesive conductive hydrogel（CTPA）by using chitosan（CS）,tannic acid（TA）,polyacrylic acid（PAA）and physical cross-linker Al³⁺.The synergistic multiple and reversible coordination bonds and hydrogen bonds in the matrix lead to a combination of high stretchability,rapid self-recovery,great anti-fatigue and rapid self-healing properties of the composite hydrogel.Additionally,the CTPA gels displayed durable and repeatable adhesiveness ascribed to the presence of catechol groups from TA.Furthermore,the CTPA hydrogel sensors could adhere directly on human skin,which exhibited a broad strain window（0-1400%）and demonstrated brilliant stretching sensitivity（gauge factor as high as12.2）.And it displayed stable sensing performance for repeated real-time monitoring of both large and subtle deformation（e.g.knee joint motions,breathing modes,and even the slight pulse changes in different motion states）.This work provides a feasible method to construct self-adhesive and self-healing hydrogel sensors with high sensitivity and a large-range detection capacity.（2）Preparation and properties of multifunctional PVA/Gel/EG/TA@CNC-Al³⁺hydrogels and their application in strain sensorsTannic acid-coated cellulose nanocrystals（TA@CNC）were incorporated into polyvinyl alcohol/gelatin/glycol/Al³⁺organohydrogel to prepare a multifunctional ionic organohydrogel（PGETA）by a one-step freeze-thaw method.The dispersibility problem of Al³⁺in binary solvents was solved by introducing TA@CNC.The prepared PGETA hydrogel showed high tensile strength（1.95 MPa）,stretchability（519.7%）,high transparency（>80%）,great UV-filtering property,excellent anti-freezing feature（below-90℃）and great moisturizing performance.Moreover,the completely reversible dynamic hydrogen bonding and ionic coordination interaction provided the PGETA hydrogel with good self-healing capability and thermoplasticity.The PGETA hydrogel strain sensor could be employed as wearable device to monitor large deformations as well as subtle physiological signals in different body parts at room or low temperature.The novel PGETA hydrogel holds great promise for applications in electronic skin and wearable devices.