Preparation And Performance Of Cellulose-based Self-powered Sensors Via Friction Force

Continuous pollution of the natural environment and gradual depletion of petroleum and fossil resources have become an urgent problem in today's society.Therefore,the collection and development of biodegradable natural biomass materials and clean new energy sources have attracted more and more attention.Lightweight wearable energy and sensor electronic devices have become a major research focus.Cellulose is one of the richest resources in nature,the triboelectric nanogenerator(TENG)prepared with cellulose as a raw material has the characteristics of good biocompatibility,low price,simple structure and environmental protection.Therefore,in this study,cellulose nanocrystals(CNC)were prepared using poplar wood as raw materials,and lignocellulose is chemically modified to prepare cyanoethyl cellulose(CEC).CNC/Zein and CEC/PVDF nanocomposite fibrous membranes were prepared by electrospinning process.The influence of spinning solution concentration on the morphology and properties of nanocomposite fibers was discussed.The cellulose-based TENG was prepared by assembling the two nanocomposite membranes,and the influence of the morphology of the CEC/PVDF nanocomposite fiber on the electrical properties and filtration performance of the TENG was investigated.On this basis,by using different concentrations of CEC/PVDF spinning solution for a multi-fluid mixing electrospinning precess,a multi-level structure cellulose-based frictional self-powered sensor was prepared.The detection and sensing of pressure and wind force of the frictional self-powered sensor were investigated.The major results are as follows:(1)Preparation and characterization of sensor anode-CNC/Zein nanocomposite fibers:The effect of different spinning solution concentration on the morphology and performances of CNC/Zein nanocomposite fibrous membranes was studied.The results showed that with the increase of the concentration of the spinning solution,the viscosity of the spinning solution increased and the conductivity decreased.When the spinning concentration increased to 28wt%,the spinning solution gelled and could not be electrospinned.When the cellulose concentration was 22 wt%,the morphology of the CNC/Zein nanocomposite fibers was optimal,which was fibrous with an average fiber diameter of 370 nm.In the CNC/Zein nanocomposite fiber,there was no chemical reaction between CNC and zein,and there were some hydrogen bonds.The thermal stability of the CNC/Zein nanocomposite fibrous membrane increased slightly with the increase of the concentration,and the overall change was little.(2)Preparation and characterization of sensor cathode-CEC/PVDF nanocomposite fiber:The cyanoethyl cellulose was prepared by chemical modification of cellulose,and the CEC/PVDF nanocomposite fibrous membrane was prepared by the electrospinning process.The influence of the CEC addition and the concentration of the spinning solution on the morphology and performances of nanocomposite fibers was discussed.The results showed that the addition of CEC increased the viscosity and conductivity of the spinning solution,as well as the surface roughness and hydrophobicity of the CEC/PVDF nanocomposite fibers.The viscosity and conductivity of the spinning solution increased with the increase of the spinning solution concentration.The 12wt%CEC/PVDF nanocomposite fibers had the best morphology,and the average fiber diameter was 1.89 ?m.In the nanocomposites,CEC and PVDF were physically bonded,and no chemical reaction occurred.The thermal stability of the CEC/PVDF nanocomposite fibers changed a little with the increased concentration.In addition,the water contact angle of CEC/PVDF nanocomposite fibers decreased with increasing concentration,and the 6wt%CEC/PVDF nanocomposite fibers had the largest contact angle value at 143.8°.(3)Preparation and characterization of triboelectric cellulose-based self-powered sensor:The cellulose-based frictional nanogenerator was prepared by assembling CNC/Zein nanocomposite membrane and CEC/PVDF nanocomposite membrane.On this basis,9wt%and 12wt%of CEC/PVDF spinning solution were electrospun via a multi-fluid mixing electrospinning process.A self-powered sensor with a multi-level structure was prepared by spinning.The influence of the concentration of the spinning solution on the electrical performances,particle filtration performances and formaldehyde filtration performances of the TENG was discussed.The effect of multi-level structure on pressure and wind sensing of cellulose-based triboelectric self-powered sensors was also studied.The results showed that the decrease of nanocomposite fiber diameter and the increase of fiber roughness improved the electrical output performances of the TENG.In addition,the collision frequency could also improve the electrical performances of the frictional nanogenerator.The 6wt%CEC/PVDF TENG had the best electrical performance,with short-circuit current and open-circuit voltage of 3.30 ?A and 10.01 V,respectively.The 12wt%CEC/PVDF TENG showed the best filtration effect,with filtration efficiency and pressure drop of 98.84%and 50 Pa,respectively.The best formaldehyde filtration efficiency was 92%under the condition of low concentration of 0.25 mg/m3.The self-powered sensor prepared by multi-fluid mixing spinning had a three-level structure of fiber-wave-arch shape,which could effectively detect pressure and wind force.