Study On The Construction And Application Of Lignin-based Resistive Sensors

Flexible,stretchable and wearable functionalized electronic products are gradually entering people's daily life.Due to their characteristics such as comfort,remote operation and real-time monitoring,they have been widely applied prospects in disease diagnosis,personal health,and human motion monitoring,etc.The flexible sensors,as a key component in wearable electronic products,have been attracting more and more research attentions.Lignin,renewable,abundant and cheap byproduct of biorefinery(pulping mill),has benzene ring and high carbon content,which can be used as an ideal carbon precursor.In this study,the carbonized lignin with good electrical conductivity and chemical stability was prepared by high temperature carbonization.The carbonized lignin was used as conductive filler in the sensor,and the performance and mechanism of sensor were investigated.The main results were presented as follows.(1)Preparation of carbonized lignin and its properties.The carbonized lignin with good electrical conductivity was prepared by high temperature carbonization technology.The results indicated that the graphitization degree of carbonated lignin and its conductivity were increased with the increasing temperature.When 900?carbonization temperature was applied,the best conductivity of the carbonized lignin was achieved,which was 102.92 S/m.(2)Preparation of carbonized lignin/sodium alginate(CL/SA)composite film and its humidity sensitivity.The CL/SA composite film was prepared by the oriented liquid self-assembly method,and its humidity sensing performance was explored.The CL/SA-3 composite film had excellent electrical conductivity(conductivity up to 53.82 S/m),ultra-high responsiveness(97%RH,502895.40%),low hysteresis and stability(satisfy 30 days).At the same time,as a humidity sensor,CL/SA composite film attached to human skin,which can accurately monitor human respiratory rate.(3)The preparation of carbonized lignin/cellulose(CL/MCC)conductive hydrogel and study its strain sensitivity.The CL/MCC conductive hydrogel was prepared by the blending method,and its strain sensing performance was studied.The CL/MCC conductive hydrogel sensor had good mechanical properties(80%compression strain and 1.562 MJ/m~3 toughness),high sensitivity(50-70%,GF=23.060)and stability(satisfies 100 cycles).In addition,as a strain sensor,CL/MCC conductive hydrogel can be attached to human skin to monitor human activities such as finger bending,writing,elbow joint bending and voice making.Conclusively,CL with good electrical conductivity was prepared by high temperature carbonization technology.The CL/SA humidity sensor and the CL/MCC hydrogel strain sensor were prepared with carbonized lignin as conductive particles,respectively.The sensing properties and mechanism of the two sensors were explored and elucidated.It indicated that carbonized lignin is an excellent conductive material,which provides a theoretical and applied research basis for the high value utilization of lignin.