| With the continuous development of current medical technology,the performance requirements of wearable sensors for life monitoring are also increasing.People urgently need sensors not only with good comfort and skin affinity,but also with good stability,high sensitivity,multi-function and low cost.Compared with traditional metal and semiconductor sensors,flexible sensors have great advantages in flexibility and elasticity,which makes them have a broad application prospect in human life monitoring.For flexible sensors,the core is the perception of deformation,which is transformed into electrical signal changes,so as to realize the monitoring of human breathing,voice,pulse and motion characteristics.However,besides deformation monitoring,temperature sensing and skin friendliness are also important factors to consider the performance of sensors.Therefore,as a wearable flexible sensor,while improving its sensitivity to deformation sensing,it is more necessary to have high sensitivity in temperature sensing and be friendly to human skin.Based on this,in this study,polyimide nanofibers with high flexibility were used as matrix,and silver nanoparticles were coated on them.The following aspects were accomplished:1.The uniform diameter polyimide nanofibers were prepared by electrospinning,and the flexible piezoresistive sensor was prepared by coating silver nanoparticles on the nanofibers by chemical method.The response of the flexible piezoresistive sensor was studied systematically.The results show that the sensor has the best sensitivity when the concentration of silver nitrate solution is 0.06mol/L in the process of silver coating.Its GF value can reach about 10,000.At the same time,the sensor can detect the pressure change in the range of 100 Pa to 100 KPa,and its response time is only200 ms.In addition,the theoretical model is established and the formula of sensor current varying with pressure is obtained.The theoretical value is in good agreement with the experimental value.2.The temperature response of silver-coated reticulated polyimide nanofibers sensor is systematically studied.If the voltage at both ends of the sensor remainsunchanged,its resistance will increase with the increase of temperature.In addition,the interaction between pressure and temperature is studied.The current response to pressure is instantaneous,while the response to temperature is close to 100 s.At the same time,the sensitivity to pressure response varies at different temperatures.By establishing a theoretical model to analyze this phenomenon,the theoretical value is in good agreement with the experimental value.At the same time,the sensor can simultaneously perceive temperature and pressure,which is applied to human motion monitoring.It is found that the sensor can not only detect different temperatures in different parts of the human body,but also detect its deformation characteristics.3.The antimicrobial properties of silver-coated reticulated polyimide nanofibers were studied.They have strong antimicrobial effects on both Escherichia coli and Staphylococcus aureus.This makes it possible to prevent bacterial accumulation during the long-term human skin monitoring process.It proves that the sensor is a wearable sensor friendly to human skin.4.Based on the development of reticulated polyimide nanofibers,we have prepared a silver-coated polyimide nanofibers film sensor with parallel arrays.The sensor can not only sense pressure,but also detect deformation characteristics such as tension,bending and distortion.Its maximum tensile ratio can reach 55%,when the GF value is as high as 4000,which has excellent sensitivity and flexibility.It can also be used to monitor and analyze human motion behavior.Similarly,we also analyze the deformation process by establishing a physical model and get the theoretical formula of the response.The theoretical and experimental values are in good agreement. |
PDF Full Text Request