Fabrication Of MXene-based Flexible Sensing Fabrics And Their Wearable Applications

Compared with the single-wearing function of traditional textiles,intelligent wearable textiles with multiple functions（communication,sensing,energy harvesting,etc.）have broad application prospects.The choice of fabric structure and sensing materials is essential to achieve a balance between the functionality and comfort of intelligent wearable textiles.However,the accuracy of sensing performance is greatly affected by the deformation of traditional textiles,and the relationship between deformation and sensing is complex.The main challenge for fabricating wearable textiles is to maintain the natural flexibility of textile materials while improving the accuracy and flexibility of sensing performance.In order to improve the application potential of textiles in the wearable field,this thesis used silver nanoparticles（Ag NPs）and silver nanowires（Ag NWs）to carry out functional modification and structural design of Ti₃C₂T_x MXene,fabricating MXene-based flexible sensing fabrics with high sensitivity to pressure,temperature and strain response,realizing wearable applications with dual functions of real-time monitoring of human movement and personal thermal management（electrothermal and photothermal effects）.It meets the requirements of the human body for the flexibility and conformality of wearable electrothermal devices,and can provide scientific guidance for the fabrication of flexible intelligent sensing textiles,which has important theoretical significance and practical value,and the main research contents and results are as follows:（1）Construction and sensing mechanism of MXene-based pressure sensing spacer fabric with highly compressive strain.MXene/Polyacrylonitrile（PAN）/spacer fabric with high compression resilience sensitivity was fabricated by dip-coating and electrospinning technologies.The change value of resistance signal under different pressures was systematically studied,and the wearable pressure range（1-5 k Pa）was optimized.The resistance cycle stability test under constant pressures showed that it had high compression elasticity and sensitivity(508.79 k Pa^-1).On this basis,through the experimental and theoretical analysis of the compression deformation and sensing performance of spacer fabric,the relationship among fabric thickness,pressure and resistance based on spacer deformation was established,and the highly sensitive pressure sensing mechanism of spacer fabric was clarified.The results showed that the monolithic or array smart sensing insole made of spacer fabric can be used to sense the walking posture and the change of pressure resistance during running,and can recognize the walking postures such as"pigeon-toed"and"duck-footed".In the process of running recognition,the pressure sensing insole can also monitor the running frequency and other movements in real time through the relative signal change value of resistance.In addition,the maximum temperature of MXene pressure sensing fabric can reach 87℃under 9 V direct current（DC）voltage,and the electrothermal effect is remarkable.（2）Preparation and electrothermal theoretical model of MXene/Ag NPs-based temperature sensing fabric compounded by electric heating and near-infrared（NIR）light heating.MXene/Ag NPs-based temperature sensing fabric with electric heating and NIR light heating composite was prepared by self-reduction method on the soft and thin Tencel fabric with excellent thermal conductivity.Based on MXene as the intrinsic sensing material,MXene was used as the reducing agent to in-situ reduce Ag NO₃ for Ag NPs that was used to enhance the temperature sensing sensitivity of light and thin Tencel fabric.The electrothermal and photothermal tests showed that the fabric temperature was positively correlated with the resistance change value,showing good electrothermal effect and NIR photothermal conversion effect.On this basis,electrothermal effect and NIR photothermal conversion effect were systematically studied,the intrinsic influence of temperature on the fabric resistance and the temperature sensing mechanism were clarified,and the fabric layered electrothermal model was established,which realized the electrothermal application and NIR photothermal actuation of fabrics.The results showed that the temperature of MXene/Ag NPs temperature sensing fabric reached 91.2℃under 9V DC voltage,and the resistance temperature coefficient was 2.65×10^-3°C^-1.In terms of NIR photothermal application,the asymmetric design in the thickness direction of Ecoflex silicone rubber packaging layer made the maximum bending angle of MXene/Ag NPs fabric reached149°after NIR light irradiation for 31 s,and the resistance temperature coefficient was2.94×10^-3°C^-1。Therefore,the MXene/Ag NPs fabric has a wide range of wearable applications such as temperature sensing,personal thermal management and photothermal actuating,providing a new strategy for the fabrication of temperature sensing and personal thermal management textiles.（3）Fabrication and characterization of MXene/Ag NPs/Ag NWs-based strain sensing fabric with helical wrapping structure and high tensile strain sensitivity.Based on the helical wrapped yarn with high elasticity and multi-level structure,zero dimensional（0D）Ag NPs,one-dimensional（1D）Ag NWs and two-dimensional（2D）MXene were used to modify and weave a highly tensile strain sensitive MXene/Ag NPs/Ag NWs strain sensing fabric.The prepared strain sensing fabric took the spiral wrapped yarn as a strain sensing unit.The helical wrapped structure（two 200denier polyester filaments as sheath yarn）was not only hinder the tensile strain of the yarn,but also protect the polyurethane core yarn（1100 denier）in the middle layer,ensuring the elastic stability in the tensile process under force,and slowing down the electrical and mechanical fatigue under high frequency cyclic tensile strain.The results showed that the sensitivity of the yarn reached 309.10 in the 0-60%strain range,474.38in the 60-150%strain range,and 872.79 in the 150-200%strain range.On this basis,the strain sensing mechanism and resistance change behavior of the helical wrapped structure in the mechanical stretching process were emphatically studied.The relationship among fabric structure,strain range,sensitivity was explored.The yarn and fabric strain sensing model based on helical wrapped yarn was established,and the real-time monitoring of human motion signals（facial expression recognition,pronunciation recognition,gesture recognition,walking/running）was realized.In electrothermal applications,MXene/Ag NPs/Ag NWs strain sensing fabrics reached 80℃after being heated for 50 s under 3V DC voltage,which has great application potential in personal protection and medical care fields such as cold insulation,thermal physiotherapy,and further broadens the application field of heating textiles in wearability.