Study On Surface Process And Sliding Frictionperformance Of Silicon Based Micro Device

With the development of MEMS and the size of micro devices are getting smaller and smaller,the problems of surface contact,absorption,friction and abrasion caused by size effect are more prominent than traditional machines.And the friction caused by high-speed sliding of MEMS also increase the wear of micro devices,shorten the life of micro devices and throttled the development of MEMS.Therefore,three types of silicon based micro devices with different surface texture are designed and fabricated The sliding friction performance of the silicon based micro device is studied with the help of the micro friction and wear performance test device.Three types of silicon based micro devices with different surface texture(polished surface,striped surface and rippled surface)were designed and fabricated by Deep Reaction Ion Etching(DRIE)and laser etching technology.The WD-10-APS mixed self-assembly monolayers was made on the texture surface of three silicon based micro devices by Co-adsorbed method.The dry friction and wear test,the liquid lubrication test and the friction and wear test of mixed self-assembly monolayers were carried out,and the coefficient of friction was measured during the test by using the micro friction and wear performance test device that has been improved.The surface morphology of the micro devices were measured by atomic force microscope(AFM),scanning electron microscope(SEM),and light microscope.Meanwhile,the molecular dynamics simulations of the mixing process and the energy and temperature changes of the mixed self-assembly monolayers were adopted by using Materials Studio software,and the pressure that the micro devices can bear was computed by CFD lubrication simulation analysis using the Fluent software during the Hydrodynamic Lubrication stage.The dry friction and wear test results showed that the sliding friction coefficient of three types of silicon based micro devices was almost the same,furthermore,the friction coefficient of striped surface and rippled surface were slightly smaller than that of polished surface.However the striped surface and rippled surface worn more serious than the polished surface in the edge parts.The friction and wear test with lubricant shows that the friction coefficient of the silicon based micro devices with striped surface and rippled surface is smaller than that of the polished surface in Boundary Lubrication stage and Mixed Lubrication stage,moreover,the friction coefficient of rippled surface was smaller than that of striped surface.The CFD simulation verifies that the micro devices with textured surface had higher bearing pressure than that of polished surface in the stage of Lubrication stage.The scanning electron microscope showed that the micro devices with textured surface worn obviously lighter than that of polished surface.The results of friction and wear test of mixed self-assembly monolayers showed that the friction coefficient of same type micro device with mixed self-assembly monolayers was smaller than that without mixed self-assembly monolayers.Furthermore,the molecular dynamics simulation showed that the energy of micro devices surface with mixed self-assembly monolayers was lower and stable.Besides,the atomic force microscope showed that the surface of mixed self-assembly monolayers spaced regularly and the surface roughness was small.However,the surface roughness became bagger and furrow appeared after worn.The study shows that the sliding friction performance of micro devices can be improved by texture surface,mixed self-assembly monolayers,and low viscosity liquid lubricant.