Research On Flexible Film Pressure Sensor Based On Silver Nanowires

Ag nanowires(Ag NWs),with great aspect ratio,have received more and more.attention from the researchers due to the fact that Ag NWs have large specific surface,good conductivity and easy dispersion,mixture to prepare flexible conductivity membrane.Therefore,Ag NWs can be used for the conductive filling material of flexible sensors,electrode of flexible solar cell,electrode super-capacitor and other fields.In addition,flexible membrane pressure sensors based on Ag NWs have presented great applied prospect in smart wearable field.In this article,the modified one-step polyol method is employed to prepare high-aspect-ratio Ag NWs with controlled morphology and size uniformity using copper chloride as the nucleating agent.Carbon nanotubes and self-prepared Ag NWs are dispersed into polyurethane(PU)to prepare flexible membrane.Ag NWs morphology which is influenced by the parameters of reaction temperature,nucleating agent,molecular weight of polyvinylpyrrolidone(PVP),mass ratio of silver nitrate toPVP are characterized by FE-SEM,EDS,XRD and UV-Vis spectrophotometer.Then,the sensitivity,repeatability and hysteresis of the flexible membrane pressure sensor are characterized by universal testing machine and digital multimeter.The experimental result shows that Ag NWs is synthesized by a modified one-step polyol method within only 30min successfully.With the reaction temperature increasing,the content of Ag nano wires is decreased gradually,the diameter increased from 130±39nm to 348±87nm,the length decreased from 12.3um±1.6um to 3.6±0.7um.When the temperature is at 160℃,the content of Ag nanowires is the most,and the aspect ratio is largest.As NaCl and FeCl3 are nucleating agent,the aspect ratio of Ag NWs is[75,109]and[11,22]respectively.The reaction speed of the former is slower than the latter.When CuCl2 is nucleating agent,the reaction speed is fast and the aspect ratio of Ag NWs reaches up to[74,113].With the molecular weight(MW)of PVP increasing,the viscosity of solution is increasing too,resulting in increased difficulty in experimental operation.When the MW of PVP is 58000,the morphology of Ag NWs is optimal and the aspect ratio is[74,113].With the increasing of mass ratio of silver nitrate to PVP,the yield of Ag NWs is increasing.When the ratio is 1:2,the aspect ratio of Ag NWs is the largest,and the content of silver particles is the lowest.The mechanical properties of PU conductive membrane are improved by doping Ag NWs.the mechanical properties of flexible conductive membrane with 1wt%Ag NWs is the best.The breaking load and the breaking elongation are 21913.1±296.OMPa and 440.6±18.3%.Compared with 5wt%carbon nanotube membrane,the breaking load and the breaking elongation are improved 81.8%and 39.7%;the resistance of flexible conductive membrane;with the content of Ag NWs are lwt%and 5wt%,is improved obviously with the stretch increasing,the maximum is 1.7363×108Ω and 1.3985×108Ω respectively.When the loading is at 0-50KPa,the sensitivity of sensors are optimal with different content of Ag NWs,the sensitivity is from 0.00111 to 0.6631.For the compression cycle test,the sensor with 10wt%Ag NWs show optimal repeatability in 10 compression cycles.When the content of Ag NWs is 10wt%,the maximum hysteresis error is only 0.0486 which is the smallest of all.The flexible membrane pressure sensor give the great support for smart wearable equipment in the monitoring of human health data,such as pulse,blood pressure,respiration,heart rate and so on.