| Cellulose is a high-molecular polysaccharide composed of glucose units.It is the main component of plant cell walls and the largest natural renewable polymer material in nature.The use of cellulosic materials as starting materials to prepare sensor materials and matrix materials is of great significance for protecting the ecological environment and promoting the sustainable development of human society.In this paper,sodium periodate is used to oxidize softwood cellulose fibers and freeze-dried to form a porous and loose cellulose fiber network.Then,after low-temperature pre-carbonization at 300°C and high-temperature carbonization at 800°C,and the reinforcement of polydopamine,a compressible and flexible carbon fiber network was prepared.It was used to assemble a piezoresistive pressure sensor,and the mechanical and electrical properties of the prepared piezoresistive pressure sensor were studied.Use birch pulp board to prepare anionic cellulose nanofibers by TEMPO(2,2,6,6-tetramethylpiperidine oxide)oxidation method,and prepare cationic cellulose nanofibers by periodic acid oxidation and Schiff base reaction.The cellulose nano paper was prepared by mixing and suction filtration of cationic cellulose nanofibers and anionic cellulose nanofibers.Carbon nanotubes are added to cationic cellulose nanofibers and anionic cellulose nanofibers.Using the principle of interface recombination,the ultrafine nanofiber conductive yarn was pulled out,and the mechanical properties of nanopaper and the mechanical and electrical properties of the ultrafine fiber conductive yarn were explored.Sodium chloride was used as a porogen to prepare polydimethylsiloxane(PDMS)aerogels,and multi-walled carbon nanotubes(MWCNT)were loaded onto PDMS aerogels to prepare MWCNT-PDMS aerogels.The aerogel is used as the sensing material to assemble the sensor.The mechanical and electrical properties of the prepared sensor and its application in human body monitoring and temperature measurement are explored.The experimental results show that the cellulose fibers of softwood oxidized by periodic acid can directly gelate.After freeze-drying at-80?,the porous cellulose network material obtained after carbonization still retains the cellulose intact.The network skeleton,and has a certain compression resilience performance.The obtained carbonized fiber network is combined with polydopamine to obtain a polydopamine-reinforced carbonized fiber network,and the network is assembled into a piezoresistive pressure sensor.The sensor has a high sensitivity of 8.4k Pa-1 and 40.0k Pa-1 in the pressure range of 0-10k Pa and 10-50k Pa,respectively,and a low detection limit of0.47Pa.When the pressure of 50Pa is loaded and unloaded,its loading response time is50ms,and the unloading recovery time is 20ms.In 1000 cycles of loading and unloading 20k Pa pressure test,it has excellent repeatability.These excellent performances enable the sensor to accurately and quickly identify various human activities,monitor human biomedical signals,and be used as an LED light in a varistor control circuit.It can also distinguish spatial pressure and pressure distribution.When the cationic cellulose nanofibers and anionic cellulose nanofibers prepared by birch pulp board are mixed to make cellulose nano-paper,the forming time can be greatly reduced.At a ratio of 1:1,the water drainage time of the nano-paper is less than60 minutes.In addition,the nano-paper and the nano-paper made from a single cellulose nanofiber have similar light transmittance,higher tensile strength and stability.The ultra-fine fiber conductive yarn prepared by the interface compound principle has a diameter of less than 30?m,a tensile strength of 130 MPa,and a conductivity of4169s/m.After the conductive wire is wrapped with PDMS,the tensile strength is increased to 148MPa,which can be used as a wire to light up LED lights.The four conductive filaments are wrapped in PDMS in parallel to form a film,which is used as a sensing material to assemble a sensor,which can be used to detect human pulse.The PDMS aerogel prepared with sodium chloride as a porogen,and the MWCNT-PDMS aerogel prepared after further loading multi-walled carbon nanotubes has good compressibility,tensile properties and elasticity.It also has excellent electrical conductivity and resistance stability.It is a flexible piezoresistive pressure sensor assembled as a sensing material with a high pressure detection limit of 300k Pa,and has extremely high stability and repeatability after up to 10,000 compression and rebound experiments.It also has a short response time and temperature detection performance.These excellent performance make the flexible pressure sensor can be used to detect the health of the human body,can detect the environmental temperature more accurately,and can also detect the spatial pressure distribution,which has broad application prospects. |
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