The Study Of Micro-structure Array Machining Based On Lithography

The structured surface of shark skin and lotus after natural evolution show good anti-friction and drag reduction performance. Micro-groove array under the above prototype also has good prospect in reactor, cooler and biomedical area. The photochemical and electrochemical micro-machining methods have great advantages, such as the applicability regardless of material’s mechanical properties and high machining efficiency. All these advantages make it great superiority in the fabrication of micro-groove array.BN308-300CP negative photoresist was chosen to study its preparation parameters to obtain insulating patterned layer with high pattern precision. The photo-chemical etching experiments were conducted to study the effects of temperature and machining time on the morphology of micro-groove array. Optimized parameters were chosen as follows:solution temperature T=30 ℃, machining time t=30 min, pattern width L0=130 μm. The micro-groove array with average width of 276.8 μm, average depth of 168.7 μm and surface roughness of Ral.82 μm were acquired under optimized parameters in 1.5 mol/L FeCl3 solutions.In order to improve the regularity of micro-groove array, electro-chemical micro-machining with photoresist mask experiments were conducted to fabricate micro-groove array on aluminum surface. Finite element analysis was carried out to find out the influence of photoresist layer thickness and machining gap on the distribution of electric field intensity. Flow fixture and testing devices were set up before the beginning of experiments. The relationship between current density and machining time with micro-groove’s morphology were studied and the optimized parameters were chosen as follows:current density i=8 A/cm, machining time t=60 s,15wt% NaNO3 solution and the photoresist pattern width L0=130 μm. The micro-groove array with average width of 272.3 μm, average depth of 104 μm and surface roughness of Ra1.62 μm were acquired under optimized parameters.Trial and error, we found that the mixed electrolyte of 15wt% NaNO3 and 0.1 mol/L H2SO4 solutions can solve the passivation when machining 304-stainless steel with electro-chemical micro-machining method. Optimized the current density and machining time to improve machining localization ability. The optimized parameters were chosen as follows: current density i=8 A/cm2, machining time t=60 s. The micro-groove array with average width of 223.6 μm, average depth of 72.6 μm and surface roughness of Ra0.16 μm were acquired under optimized parameters, also the localization parameter EF was calculated as 1.97. Pulsed power was used to carry out the tests of fabricating micro-grooves array with electro-chemical micro-machining method. Orthogonal tests were done to study the influence of current density, pulse frequency and duty circle on micro-grooves’ morphology. The micro-groove array with average width L=213.8μm, average height h=97.7μm , surface roughness as Ra0.14 μm and radius r=32.1 μm were got under the parameters as follows: current density i=8 A/cm2, pulse frequency f=30 kHz, duty circle q=30%. After calculation, we found that the machining localization ability parameter (EF) is 2.33. When contrasted with DC power, pulsed power improved the machining localization ability of electro-chemical micro-machining experiments.