Preparation Of Superhydrophobic Microcrack Based Flexible Strain Sensor And Research On Its Response Performance

With the rapid development of wearable smart devices,flexible strain sensors have attracted widespread attention in the fields of artificial intelligence,human-computer interaction,electronic skins,and human health monitoring.In order to better monitor subtle deformations(such as voice recognition,pulse,swallowing,and heartbeat),highly sensitive flexible strain sensors have been extensively studied.In addition,wearable strain sensors are also facing another outstanding practical problem-water resistance.To this end,this dissertation intends to take the flexible conductive polymer composite material with excellent force-sensitive response characteristics as the research object,achieving high sensitivity of strain sensor by constructing a highly sensitive micro-crack structure,and excellent waterproof,anti-corrosion,and self-cleaning properties by constructing a super-hydrophobic surface.The main research contents are as follows:(1)Super-hydrophobic flexible paper-based bending strain sensorSuperhydrophobic flexible conductive paper was successfully prepared by dip-coating the printing paper into the carbon black(CB)/carbon nanotube(CNT)/methylcellulose(MC)dispersion and hydrophobic fumed silica(Hf-SiO2)dispersion.Uniform conductive coating was obtained due to the synergistic effect between different dimensional conductive fillers and the dispersion effect of MC.A large number of microcracks was built in the conductive layer due to the difference in thermal expansion coefficient between the conductive layer and the paper-based.The conductive paper can be used as a flexible strain sensor based on the opening and closing of the microcracks.The strain sensor exhibited a sensitivity(GF)of 7.5,an ultralow detection limit of 0.1%,and the response performance was also well-maintained even after 1000 tension cycles,showing excellent stability and durability.In addition,the paper-based sensor exhibits excellent superhydrophobicity(water contact angle of 154°),self-cleaning and corrosion resistance,based on the micro-nano composite structure and low surface energy of the Hf-SiO2 layer.The super-hydrophobic surface ensures that the sensor can stably detect strain signals in wet or rainy environments.Finally,the paper-based sensor can accurately detect physiological signals such as human pulse,joints,and throat,and shows great application prospects in human health monitoring.(2)Super-hydrophobic flexible fabric-based tensile strain sensorSuperhydrophobic flexible conductive fabric was successfully prepared by dip-coating the thermoplastic polyurethane non-woven fabric(TPU NWF)into the graphene(G)/cellulose nanocrystal(CNC)dispersion and hydrophobic fumed silica(Hf-SiO2)dispersion,and designed microcracks were successfully constructed through the pre-strain treatment due to difference of modulus of the conductive layer and TPU matrix.As a result,flexible strain sensor with a wide response range and high sensitivity was prepared,and the prepared strain sensor(G content is 25 wt%)exhibited high sensitivity(GF up to 22500),broad and tunable sensing range(0?98%),ultralow detection limit as low as 0.1%,short response time(33 ms)and excellent sensing stability(over 1000 cycles).In addition,the fabric-based sensor exhibits excellent superhydrophobicity(water contact angle of 155°),self-cleaning and corrosion resistance based on the micro-nano composite structure and low surface energy of the Hf-SiO2 layer.The super-hydrophobic surface ensures that the sensor can stably detect strain signals in wet or rainy environments.Finally,the sensor can accurately detect the full-scale and multi-range motion conditions of the human body based on its excellent comprehensive response performance,including small strains including pulse and voice recognition,and strenuous motions of fingers,joints and wrists,showing excellent performance Reliability and stability.