Research And Preparation Of Flexible Temperature Sensors

With the ongoing development of the internet of things and information technology,flexible electronic devices have attracted more and more attention,and flexible temperature sensors are favored.Temperature is the most fundamental physical parameter reflecting the state of the measured object and the surrounding environment,which involves almost all chemical reaction processes.Traditional temperature sensors mostly use rigid materials as substrates,which limits temperature sensor development and application in industry,manufacturing,and biomedical fields.Therefore,it is critical to combine temperature-sensitive materials with flexible substrates to develop high sensitivity,strong anti-interference,and low-cost flexible temperature electronic devices.In this paper,the polydimethylsiloxane/multi-wall carbon nanotubes(PDMS/MWCNTs)flexible temperature sensor,the PDMS/Ti₃C₂T_xflexible temperature sensor,and the temperature-sensitive fabric based on Ti₃C₂T_xwere prepared by simple processes and low-cost experimental schemes.The characterization and temperature sensing mechanisms of them were studied,and the prepared flexible temperature sensor was tested.The following is the specific work:(1)PDMS/MWCNTs composites with negative resistance temperature coefficients were prepared.The cross-sectional morphology of PDMS/MWCNTs was observed by scanning electron lens(SEM).Polyimide(PI)was selected as the substrate to prepare PDMS/MWCNTs flexible temperature sensors by MEMS micromachining processes such as lithography and magnetron sputtering.The stability,sensitivity,repeatability,and curved surface application of PDMS/MWCNTs flexible temperature sensors are tested.When the mass fraction of MWCNTs is 10%of PDMS,the resistance temperature coefficient(TCR)of the sensor is-0.183%/°C.In addition,PDMS/MWCNTs have good reproducibility and stability(resistance fluctuates only 0.15%).When in the tensile state,the sensor still maintains the original temperature sensitivity(-0.247%/°C).PDMS/MWCNTs_10%has the advantages of high linearity(99.94%)and strong corrosion resistance.It is expected to be used in precision electronic equipment in the form of temperature-sensitive film.(2)The two-dimensional transition metal carbide Ti₃C₂T_xwas prepared,and the stability of Ti₃C₂T_xwas studied.The PDMS/Ti₃C₂T_xcomposite with a positive temperature coefficient(PTC)was prepared by the ultrasonic solution blending method.The structure and surface morphology of Ti₃C₂T_xand composites were observed and verified by SEM and Raman spectroscopy.The PDMS/Ti₃C₂T_xflexible temperature sensor was encapsulated in the Parylene-C film.It has good anti-interference and is hardly affected by oxygen(resistance fluctuation is only 0.192%),and the resistance fluctuation of PDMS/Ti₃C₂T_xis only 1.128%in the range of 30%–60%relative humidity.Using numerical analysis software,the thermal expansion deformation of the composite was simulated in the range of20°C–41°C,and the maximum displacement of PDMS changed by 3.5 times.The internal conductive network of Ti₃C₂T_xwas elongated under thermal stimulation,and the sensor resistance increased by10%at 26°C–75°C.Among them,the sensor shows good TCR and linear variation in the range of30°C–42°C,the average TCR is 0.417%°C^-1,and the linear correlation coefficient(R~2)is 0.9959.Compared with the reported Ti₃C₂T_xbased temperature sensor,it has better cycle stability and can withstand continuous thermal stimulation.The PDMS/Ti₃C₂T_xflexible temperature sensor can not only be used to monitor the temperature changes of objects and daily activities but also has great potential in wearable skin electronic products.(3)The Ti₃C₂T_xink without additives was prepared.The Ti₃C₂T_xtemperature-sensitive fabric was prepared by using natural polymers(cotton,wool)and synthetic fibers(polyester,nylon)with the dip-coating method combined with Ti₃C₂T_xink.Among them,the TCR_maxof Ti₃C₂T_x/nylon is as high as-2.6%/°C.Through the combination of conductive ink and textile substrates,the temperature sensor can be embedded in the fabric-based network,which is expected to provide good temperature sensing function and comfort for wearers in the future.