The Study On Wettability And Tribological Properties Of Bionic Microstructured Surfaces

As one of the main failure forms of materials and parts,friction and wear widely exist in the fields of optoelectronics,machinery,aviation and other related fields,and bring hundreds of billions of dollars of waste to humans every year.Especially in microfriction systems with smaller structural dimensions such as high-precision machinery,micro-electromechanical systems and micro-robots,it has the characteristics of light weight,small gap and large surface area ratio.The friction and wear problems is more prominent caused by poor contact of the lubricating medium at the friction interface.The study found that adhesion failure and friction wear under the action of microsurface forces are closely related to factors such as the gap of the friction interface,the surface micro-topography,surface energy and the mechanical properties of the surface layer,but the views are not uniform and the combined impact of various factors is rarely considered.After billions of years of evolution,some biological materials show excellent surface lubricity and friction characteristics due to special surface wettability in nature.For example,human joints show hydrophilicity and have a very low friction coefficient,lotus leaf shows superhydrophobic and has self-cleaning properties and the ultra-slip properties of nepenthes.The research object of tribology involves the mutual friction effect and wear failure of solid-solid surface,solid-liquid surface and solid-gas surface.Through the study of friction reduction,anti-adhesion and high-efficiency lubrication mechanisms of biological friction systems,the successful experience and creation rules of biological friction systems are borrowed from the perspective of structure,materials and control,which provides an important bionics revelation for tribological research of micromechanical systems.This paper is oriented to the application of micro-mechanical systems,using a biological friction system with special wettability as a prototype,using precision wire cutting,laser processing and combined with surface chemical modification to prepare different wettable surfaces,interlaced wettability surfaces and different adhesion superhydrophobic surfaces,study the influence of surface microstructure,wettability,adhesion and their interaction on surface tribological performance,reveal the relationship between surface microstructure,wettability and tribological performance,and discusses the application prospect of using mechanical imprinting technology to manufacture bionic microstructure surface.The main conclusions are as follows:(1)The micro square column structure is processed by precision wire cutting,and mixed with thiol modification and pH reagent treatment to obtain different wettable surfaces.Study the friction characteristics of different wettable surfaces.The results show that for hydrophobic surfaces(CA > 90°),as the contact angle increases,the friction coefficient shows a downward trend,for hydrophilic surfaces(0° <CA < 90 °),the friction coefficient increases with contact angle ascent,for super-hydrophilic surfaces(CA = 0 °),the friction coefficient increases significantly.Among different wetted surfaces,the super-hydrophobic surface anti-friction effect is the most significant.(2)Nanosecond lasers were used to prepare micro-square columns and microtrench structures to obtain hydrophilic surfaces of the two structures,and modified with fluorosilane to obtain the hydrophobic surfaces of the two structures,using sandpaper to polish the hydrophobic surface to obtain the upper and lower hydrophilic surfaces of the two structures respectively,and laser selective etching of the hydrophobic surfaces to obtain the upper and lower hydrophilic surfaces of the two structures respectively(The upper surface of the microstructure is defined as the upper layer,and the sides and bottom of the groove are defined as the lower layer).Comparing the adhesion characteristics and water-lubricated friction characteristics of different surfaces,the results show that for the surface of the micro square pillar structure,the hydrophobic surface and the upper hydrophobic lower surface hydrophilic surface are in low adhesion state and have excellent friction characteristics.As for the surface of the micro-grooved structure,the four surfaces are in a state of high adhesion,and the hydrophobic surface has excellent friction characteristics.(3)Nanosecond lasers were used to prepare micro-square column structures of different sizes,distributions and depths on the surface,and fluorosilane modification was used to obtain low,medium and high adhesion superhydrophobic surfaces.The results show that the low-adhesion superhydrophobic surface has a significant antifriction effect,and there is no significant difference in the friction coefficient of other adhesive superhydrophobic surfaces.(4)Micro-pit arrays of different diameters,distributions,and depths were prepared on the surface by mechanical imprinting technology.The friction characteristics of different micro-array surfaces under oil lubrication were studied.The results showed that for samples with 850 ?m and 1200 ?m center distances,as the diameter and depth of the pit increase,the friction coefficient decreases.For the sample with a center distance of 1700 ?m,the friction coefficient decreases first and then increases with the increase of the diameter and depth of the pit,where the diameter of the pit is 480 ?m and the depth is 137 ?m.The coefficient is the smallest.For the same microstructure surface,as the load increases,the friction coefficient shows a downward trend.