Development And Performance Research Of Flexible Foot Pressure Sensitive Element Based On Laser Sintering Process

Plantar pressure distribution can reflect the patient's foot injury,pathology,and physical condition,and is used as a basis for health monitoring and medical diagnosis.However,it is difficult to collect plantar pressure distribution information due to the limitation of the expensive testing equipment and the convenience of testing.The flexible pressure sensor is a kind of flexible electronic device used to sense the force on the surface of an object.It can be attached to the surface of a variety of irregular shapes.Because of its advantages such as softness,stretchability,better adhesion,it can effectively collect plantar pressure distribution.However,there are compatibility problems in the flexibility of the current flexible pressure sensor and the excellent pressure detection performance.The introduction of microstructures can not only improve the sensitivity of the flexible pressure sensor,but also quickly restore the elastic deformation of the sensor,with fast response capabilities.Therefore,building microstructures is an effective way to solve flexible pressure sensors.This paper analyzes the laser scanning energy distribution,studies the interaction mechanism of laser and powder,explores the mechanism of laser sintering and melting of powder particles,and constructs a sensor model suitable for laser sintering flexible pressure sensitive components by analyzing the internal three-dimensional morphology of laser sintering parts.The influence of the size distribution of the microstructure on the force-sensitive effect of the LS sensor reveals the sensing mechanism of the LS sensor.Through analyzing the characteristics of the conductive network of carbon nanotubes and the mechanism of the force-sensitive effect of sensitive components,it is found that the change rule of the equivalent tunnel junction resistivity and the change in the concentration of carbon nanotubes caused by material deformation are the source of the force-sensitive effect.Using MCNTs powder as conductive filler and TPU powder as matrix material,TPU/MCNTs composite powder was prepared by a strong acid oxidation-ball milling method.Using FT-IR,TEM and SEM testing techniques,the MCNTs powder and TPU/MCNTs composite powder before and after oxidation were analyzed,and the microscopic morphology,surface functional groups of MCNTs powder particles before and after oxidation,surface functional groups,TPU/MCNTs composite powder particle morphology,the binding effect between MCNTs and TPU powders were studied.The thermal properties of TPU/MCNTs composites were analyzed using DSC and TG testing techniques,and the influence of carbon nanotube powder content on the crystallization temperature of TPU was studied.The sintering feasibility test of the TPU/MCNTs composite powder was carried out by the selective laser sintering technology,the preheating temperature and processing temperature were determined,and the pressure sensitive element manufactured was tested for its conductivity to verify the feasibility of the flexible pressure sensor.Prepare TPU/MCNTs composite powder materials with different ratios,perform laser sintering experiments,and study the influence law of different ratios and different process parameters on s sensing performance,molding performance and dimensional accuracy of TPU/MCNTs flexible pressure sensitive element.Through orthogonal experimental design method of three factors and four levels,the density,Z-direction dimensional accuracy and sensitivity of molded parts were taken as indicators.The molding process of MCNTs composite powder was optimized to obtain the best process parameters of laser sintering TPU/MCNTs flexible pressure sensitive components.Through the foot laser scanner combined with reverse modeling technology,a human foot model was constructed.Based on the optimized sensitive element,integrated production of a pressure-sensitive insole that fits the subject's foot were designed,and the plantar pressure distribution were studied when standing statically.According to the plantar pressure distribution,the COMSOL Multiphysics software was used to design and optimize the structure of the sole,and the sensitive insole was used to conduct experimental verification and comparative analysis of the plantar pressure distribution before and after the optimization of the sole structure,so as to manufacture the micro-structured flexible pressure-sensitive element of high performance.It is helpful to improve the testing technology of plantar pressure distribution and ensure the accuracy of health monitoring and medical diagnosis.