Preparation And Application Of Multi-Network Hydrogel-Based Flexible Sensor

The concept of active health had been deeply rooted in hearts of people.People paid more and more attention to disease prevention.As a kind of health monitoring device,sensors gradually came into people’s vision.Hydrogel was a kind of soft material which was composed of flexible macromolecule and water and had similar structure and performance as human soft tissue.It had shown broad application in the fields of wearable devices,flexible sensors and biomedical devices.At present,how to construct a stable conductive hydrogel-based flexible sensor is still one of the key problems faced by researchers.To solve this problem,a series of multi-network conductive hydrogels were designed,and mechanical and electrical properties were systematically analyzed.On this basis,flexible sensors were further constructed.The fatigue resistance,sensing ability and sensitivity of its were discussed,feasibility of its application in the field of human motion detection and disease diagnosis was verified successfully.It included the following three aspects:(1)A high adhesion hydrogel-based flexible sensor for sound detection was designed and prepared.rGO@PVA-PAA hydrogel was prepared by using PDA to reduce and modify GO.The effects of PDA:GO ratio and rGO concentration on properties of hydrogel were discussed.The results showed that when PDA:GO=3:1 and rGO concentration was 0.3%,conductivity of hydrogel could reach 8.26 S/m and elongation at break was 672%.The modification of PDA could make GO more evenly distributed in the hydrogel.In addition,PDA functionalized rGO had good synergistic adhesion with hydrogel matrix PAA,showing good adhesion on a variety of materials,adhesion strength on skin tissue materials was 0.81 k Pa,and could show good adhesion after 5 cycles.It showed good sensitivity and fatigue resistance in different preset strain stretching cycles and 100 load-to-unload cycles,respectively.For sound detection,rGO@PVA-PAA hydrogel-based flexible sensor could monitor five sound chambers and recognized coughs or a variety of speech signals;In terms of human joint movement,hydrogel-based flexible sensor could accurately monitor human movement many times.(2)An anti-high pressure hydrogel-based flexible sensor for gait detection was designed and prepared.The effects of uniaxial orientation structure and ANI concentration on performance of hydrogel were analyzed.The results showed that PANI@PVA-PAA ternary network hydrogel prepared by freeze-thaw method and ANI in-situ polymerization method had obvious layered structure and directional pore structure.When ANI concentration was 0.30mol/L,PANI@PVA-PAA hydrogel had compressive strength of 423.44 k Pa and conductivity of 2.02 S/m.It showed excellent fatigue resistance in 500 loading and unloading cycles,and response time and recovery time were only 200 ms.The construction of uniaxial directional structure and ternary network was conducive to the formation of new conductive path for the hydrogel-based flexible sensor in motion monitoring,improving the longitudinal relative resistance change rate.It could effectively and real-time identify the motion state of shoulder,knee and plantar for gait detection,especially suitable for high pressure and low frequency plantar motion monitoring.(3)A hydrogel-based flexible sensor was designed and prepared for the monitoring of early symptoms of Huntington’s disease.The influence of SF and rCNT on performance of ternary network hydrogel was explored.The results showed that hydrogen bond interaction between SF and PVA and PAA improved mechanical properties of ternary network hydrogel.rCNT was evenly dispersed in hydrogel,which improved electrical properties of hydrogel.When concentration of SF was 15%and concentration of CNT was 0.35%,tensile strength of rCNT@SF-PVA-PAA hydrogel was 64.92 k Pa,compressive strength was 391 k Pa,toughness was 171.99 k J/m~3,and conductivity was 0.079 S/m.It showed excellent fatigue resistance in1000 loading and unloading cycles,response time was only 100 ms and recovery time was 300ms.In addition,rCNT,as a one-dimensional linear conductive substance,was uniformly distributed in hydrogel,which could construct new conductive pathway during health monitoring.It could improve detection efficiency of hydrogel-based flexible sensor and effectively identify gait,human joint movement and facial muscle movement,which was suitable for the monitoring of early symptoms of Huntington’s disease.