| Flexible multi-parameter sensors have great potential application value in the field of smart wearable.Such as,for amputees,people with damaged skin and robots,artificial devices are needed to simulate skin function and restore similar perception ability.Thermoelectric material and elastic support can be compounded by making a simple single device,reading out pressure and temperature signals without crosstalk.Poly（3,4-ethylenedioxythiophene）:Poly（styrene sulfonate）（PEDOT:PSS）is an excellent organic thermoelectric material,with high conductivity,Seebeck coefficient and good adhesion.At the same time,wood fiber elastic material（WF）has stable mechanical properties,low density,high porosity,high specific surface area,non-toxicity and biodegradability,which has attracted extensive attention of researchers.In this paper,WF was prepared by removing lignin and hemicellulose from balsa wood in two steps,and flexible thermoelectric wood fiber composite material（WPG-0.25,WPG-0.5 and WPG-0.75）with different solid ratios were prepared by combining WF with mixed solution of PEDOT:PSS and glycidoxypropyl trimethoxysilane（GOPS）by impregnation-freeze drying method.Scanning Electron Microscope（SEM）,Fourier Transform Infrared Spectroscopy（FT-IR）,Nitrogen Adsorption Method（BET）,Mercury Intrusion Porosimetry（MIP）,Energy Dispersive Spectrometer（EDS）,chemical composition analysis,four-probe tester and flexible sensor performance detection system were used to test and analyze the microstructure,pore characteristics,composition,electrical and mechanical properties of the materials.Furthermore,a flexible temperature and pressure integrated sensor is prepared with thermoelectric wood fiber composite material as sensing material,and the sensing performance of the sensor,such as pressure working range,sensitivity,detection limit,response time,repeatability,thermal level,pressure-temperature decoupling,etc.,is analyzed by using flexible sensor performance detection system and digital source meter.Then the flexible pressure-temperature sensor is tested in practical application.Through the characterization and analysis of WF and temperature and pressure integrated sensor,it is found that WF is basically composed of cellulose,with high porosity,high specific surface area and special layered structure.The mixed conductive solution has a good impregnation effect on the wood sponge,the original layered porous structure of the WF is preserved,and the temperature and pressure integrated sensor shows good conductivity and compression resilience.The flexible temperature and pressure integrated sensor based on WPG has a wide working range of 0.01-20 k Pa,and the sensor based on WPG-0.75 has an ultra-high micro-pressure sensitivity of108.34 k Pa-1,a low detection limit of 10 Pa,a fast response time of 108 ms,good linearity and excellent stability.Then,finite element simulation is established to analyze the effect of 3D layered porous structure on the sensing performance of the sensor.Dimethyl sulfoxide（DMSO）treatment is used to remove the temperature dependence of the resistance and realize the temperature sensing of the sensor.The sensor has the working range of temperature difference of 0.1-25℃,the temperature sensitivity of15.3μV/℃,the low detection limit of 0.1℃and the response time of 1.05 s,and can realize the pressure-temperature decoupling reading.The slope of the current-voltage（I-V）curve represents the pressure and the intercept with the V axis.The actual application test shows that the sensor can stably detect human pulse and vocal cord vibration,and monitor the change of pressure-temperature electrical signal in real time.The ultra-high micro-pressure sensitivity of the flexible sensor can be used to detect weak physiological signals of human body.Wide working range,low detection limit,quick response,high repeatability and decoupling reading of pressure and temperature make it widely used in cold chain transportation,robot,environmental temperature change,human motion monitoring,medical care and so on. |
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