Preparation And Performance Of Reduced Graphene Oxide/Iron Nanowire Flexible Pressure Sensor

Pressure sensing is one of the key research topics in the field of mechanical engineering.With the increasing attention paid to sports health,wearable pressure-sensing devices have shown great application value in sports health detection.Among them,flexible pressure sensors have good application prospects in detecting human health and motion status due to overcoming the shortcomings of traditional rigid pressure sensors.At present,flexible pressure sensors used in wearable detection devices have key issues such as low sensitivity,large device volume,poor flexibility,and long reaction time.Based on the finite element simulation optimization,the preparation and performance test of high-performance pressure sensitive materials,a reduced graphite oxide/iron nanowire flexible pressure sensor with small size,high flexibility,good mechanical properties,and excellent sensing performance was prepared by using the composite of sensitive layers,the optimization of sensor structure and the modification of microstructure.The main research contents are as follows:（1）The mechanical sensing properties of the sensing layer of reduced graphite oxide/iron nanowire composite polyester fabric were simulated and analyzed,and the mechanical sensing mechanism of the composite pressure-sensitive material was expounded.First of all,the force analysis of the sensor is studied.The sensitive material of ordinary polyester fabric will cause the mold piercing phenomenon and damage the pressure sensor under greater external pressure.The reduced graphite oxide/iron nanowire composite polyester fabric pressure-sensitive material can effectively avoid the mold piercing phenomenon even under greater pressure.Secondly,the influence of fabric-like sensitive layers on the local simulation model performance of flexible pressure sensors was studied.Thanks to the air composition filled in the gaps of the fabric like sensitive layers,the air in the gaps of the sensitive layers is squeezed out under pressure,improving the sensitivity of the flexible pressure sensor.Finally,the sensitization mechanism of microstructure on the sensitive layer was studied,and the feasibility of optimizing flexible sensing materials and structural design in improving the miniaturization,flexibility,and mechanical properties of flexible pressure sensors was verified through simulation.（2）Reduced graphite oxide and iron nanowires were prepared by the Hummers method and magnetic field in-situ reduction technology,respectively.Graphite oxide was prepared based on the oxidation part of the Hummers method,and lamellar graphite oxide with high flexibility and light thickness was prepared by thermal stripping by adjusting the preparation parameters such as reaction time and temperature.In the reduction part of the Hummers method,hydrazine hydrate can remove a large number of oxygen-containing functional groups in the structure of graphite oxide,and obtain reduced graphite oxide with excellent morphology.The magnetic field in-situ reduction technology was used to prepare iron nanowires.However,the iron nanowires were formed by the combination of multiple iron cores,and a large number of impurities were mixed in them,which seriously affected the sensitivity of the flexible pressure sensor.The Differential centrifugation method was used to effectively purify the iron nanowires,and the method was determined to successfully improve the sensing performance of the pressure-sensing materials by characterizing the morphology.（3）The structural design,component construction,and sensing mechanism of reduced graphite oxide/iron nanowire flexible pressure sensor were studied.Optimize the design of flexible pressure sensors through overall structural design,transmission electrode configuration,and composite pressure-sensitive material composition.The influence of fabric type,sensitive material ratio,and deposition frequency on sensor performance was studied,and the composite sensitive layer with the best sensing performance was obtained.Compared with the ordinary planar flexible pressure sensor,the reduced graphite oxide/iron nanowire flexible pressure sensor with modified microstructure effectively improves the deformation of the composite sensitive layer to the pressure,thus improving the sensitivity of the flexible pressure sensor.At the same time,it promotes the miniaturization of the flexible pressure sensor and obtains a pressure sensor with good flexibility,mechanical properties,and sensing properties.（4）We have built a performance testing platform for flexible pressure sensors and tested their sensing performance.Based on the experimental platform,the response performance of the flexible pressure sensor was tested and calibrated.Its sensitivity includes three stages:the first stage（0-10 k Pa）sensitivity S₁=3.240 k Pa^-1,the second stage（10-25 k Pa）sensitivity S₂=6.440 k Pa^-1,and the third stage（25-30 k Pa）sensitivity S₃=1.280 k Pa^-1.It has small hysteresis（6.140%）,high linearity（9.910%）,short response/recovery time（18/20 ms）,and high resolution（0.833%）Excellent performance such as good repeatability.In addition,a preliminary exploration was conducted on the practical application of flexible pressure sensors in the wearable field,and it was found that flexible pressure sensors exhibit good response performance in both low and high pressures.Among them,small-pressure sensing can be based on pulse signals and swallowing detection to achieve non-invasive detection and remote online monitoring of the stiffness of the human arterial system;High-pressure sensing can achieve sports and health management based on human activity detection such as hand and foot movements.