Research On Preparation And Performance Of Flexible Pressure Sensor Based On 3D Printing Pressure Sensitive Materials

Flexible sensors have good flexibility and can be integrated in various wearable products for signal collection,thus playing an important role in biomedical engineering and health monitoring.The traditional soft lithography method manufacturing technology has problems such as expensive process equipment,complex process flow,and high production cost.3D printing technology is expected to solve the problem of flexible sensor manufacturing.This paper focuses on the manufacture of flexible pressure sensors from 3D printing pressure-sensitive materials,and conducts the following research:1.Using multi-walled carbon nanotube(MWCNTs),graphite(EG),mesophase carbon microspheres(MCMB)as conductive fillers and polyurethane(TPU)as the matrix,the MWCNTs/EG/MCMB/TPU flexible 3D printing pressure-sensitive material was prepared by melt blending method.The melt flow rate analysis,mechanical performance analysis,and electrical performance analysis were carried out.It was found that as the proportion of carbon conductive fillers increased,the melt flow rate of the material decreased,the mechanical properties decreased,and the electrical conductivity increased.Orthogonal experimental results show that EG and MCMB have similar effects on the material properties,indicating that the morphology of the conductive filler has little effect on the material properties.The reason is that the carbon filler is wrapped by TPU in the molten state.In contrast,uniformly distributed MWCNTs show a strong size effect,which has a greater impact on the melt flow rate,mechanical properties and electrical conductivity of the composite material.2.The piezoresistive test was carried out on the prepared MWCNTs/EG/MCMB/TPU flexible 3D printing pressure-sensitive material,distinguish the effect of volume compression responses and interface compression responses in experimental tests,and analyzed the influence of carbon fillers on the piezoresistive performance.The piezoresistive performance test of repeated loading cycles has been carried out.The results show that the piezoresistive properties of the prepared flexible 3D printing pressure-sensitive material have good repeatability.With the increase in the proportion of carbon conductive fillers,the volume piezoresistive sensitivity and interface piezoresistive sensitivity of the material gradually decrease,and the interface piezoresistive sensitivity of the material is greater than the volume piezoresistive sensitivity,which is more suitable for designing sensors with higher sensitivity.Considering the pressure-sensitive characteristics and the requirements of the 3D printing process,the best mass fraction of the conductive filler is 5% for MWCNTs,10% for EG,and 10% for MCMB.3.Considering the random distribution of conductive particles in a limited space,using Monte Carlo method to simulate conductive composite materials,establish a three-dimensional model of conductive composite materials.The results show that the minimum distance between conductive particles obeys a normal distribution.Under the same volume addition,the addition of MWCNTs can rapidly reduce the spacing of conductive particles,and has the greatest impact on the resistivity of the composite material,showing the size effect of MWCNTs.The larger graphite and carbon balls have little effect on the spacing of conductive particles,and also have no obvious effect on the resistivity of the composite material.4.Designed and manufactured a flexible pressure sensor with the help of3 D printing,and then manufactured a sensor array composed of multiple sensor units,and analyzed its sensing performance.The experimental results show that the flexible pressure sensor has a response sensitivity of 0.07 ?/k Pa,a loading response time of 0.2 s,and an unloading response time of 0.2 s;It can still maintain good sensing characteristics under long-term cyclic pressure loading.The array-type flexible pressure distribution sensor can not only detect the pressure distribution ability,but also display information such as the position,shape,and duration of the loaded object.