Temperature Tolerant,preserve Moisture,Conductive Hydrogel Preparation And Its Flexible Sensors

With the development of science and technology,"rigid" electronic devices constructed from traditional inorganic materials cannot fully fulfill people’s needs.Therefore,flexible electronic devices have attracted extensive attention from researchers and have broad application prospects in wearable devices,soft robots,and health monitoring fields.As the core component of flexible sensors,flexible electronic materials are currently the frontiers and hot topics of research in the field of functional materials.Conductive hydrogel is a functional polymer material with conductivity and flexibility,which can be applied to the preparation of high-performance flexible sensors.However,due to the volatility of water and the crystallization of water below zero degrees Celsius,the conductive hydrogel might easily lose its flexibility.This problem limits the development of conductive hydrogels in flexible sensors.To solve this problem,this thesis regulates and controls the hydrogel network structure and solvent to preparation temperature tolerant,moisturizing and conductive hydrogel,including highly stretchable ionogel and intrinsically adhesive ion conductive organohydrogel.In addithon,this thesis explores the application of these gels in high-performance flexible sensors.The main research contents are as follows.(1)Using the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide([EMIm][DCA])replaced water in the poly acrylic acid(PAA)hydrogel to prepare PAA ionogel.The PAA ionogels are highly stretchable(>850%),conductive(1.9 S·m-1),and temperature-tolerant(-28 0C～100℃).The PAA ionogels is applied to construct high sensitivity,low response time(200 ms),wide strain-sensing range(0～750%),excellent durability(>1400 cycles)and good temperature tolerant(-18℃～80℃)flexible strain sensor.The capacitive pressure sensor constructed with PAA ionogel has low response time(256 ms)and excellent sensitivity(GF=0.73 kPa-1).Sensors based on PAA ionogels can be utilized to monitor human motions and physiological activities such as muscle movement,joint bending,breathing and swallowing.(2)Glycerin/water mixed solvent is used as the medium to improve the organohydrogel’s temperature resistance and moisturizing properties,while further improving the intrinsic reversible adhesion of the organohydrogel.Potassium chloride(KCl)as the conductive component,using the "one-pot method" to construct polyvinyl alcohol(PVA)-glutaraldehyde(GA)/poly(acrylic acid-co-Acrylamide)(P(AA-co-Am))double network organohydrogel.The organohydrogel uses glutaraldehyde(GA)cross-linked polyvinyl alcohol(PVA)as the first network,and physically cross-linked poly(acrylic acid-co-acrylamide)as the second network.PVA-GA/P(AA-co-Am)double network organohydrogel has excellent stretchability(>2000%),self-healing(healing efficiency of 96.5%),adhesion and temperature resistance(-20℃～100℃).The flexible strain sensor assembled by the organohydrogel has a wide sensing range(0～1000%),low response time(180 ms),good temperature tolerant and sensing stability(>1000 times).The capacitive pressure sensor assembled with this organohydrogel has high sensing sensitivity(2.14 kPa-1)and low response time(249 ms).The flexible sensor based on organohydrogel can be applied to monitor human movement and physiological movement such as finger touch,blowing,heartbeat,breathing,etc.,and the flexible strain sensor can be integrated with a wireless Bluetooth transmission device to realize real-time wireless monitoring of human movement.(3)This thesis drawing inspiration from glutinous rice,amylopectin was introduced into the P(AA-co-Am)gel network to prepare amylopectin/P(AA-co-Am)organohydrogel with reversible adhesion properties.The organohydrogel has excellent tensile properties(1089%),strength(197 kPa),temperature tolerant(-20℃～80℃),electrical conductivity and reversible adhesion properties.The flexible strain sensor assembled by the organohydrogel has a wide strain detection range(0～1000%),low response time(100 ms),good cyclic stretchability(>1000 cycles)and temperature resistance(-20 ℃～100 ℃).The capacitive pressure sensor based on the organic-hydrogel assembly has excellent sensitivity(GF=8.77 kPa-1)and a wide pressure detection range(0～196 Pa).The flexible sensor constructed based on the organohydrogel can be used for the detection of human motion,and the flexible strain sensor is integrated with a wireless Bluetooth transmission device to realize real-time wireless monitoring of human motion.