Research On Special Infiltration Surface Droplet Positioning And Transport Technology Based On Gradient Effect

The operation of droplets,such as transfer,separation,mixing and transportation,has high practical application value.The location transportation of droplets on special infiltrating surface has high research value and application prospect in biochemical analysis,microfluidics system,clinical diagnosis and other fields because of its rapid and repeatable effective control of droplets.However,at present,the special wetting surface liquid positioning transportation methods have some problems,such as cumbersome preparation method,high cost,extra energy or system input,etc.,which cannot meet the requirements of practical application.In view of the above problems,this paper first introduces the basic theory and classical model of solid surface wettability,and the principle of transport of droplets on the superhydrophobic-superhydrophobic orbital and superhydrophobic-superhydrophilic orbits of gradient depth is studied separately.Based on the above theories,this paper studies the motion of droplets on the depth gradient orbit of different parameters through simulation.The simulation results show that when the droplets are transported on the superhydrophobic-superhydrophobic orbit,the wider the orbital width and the deeper the maximum depth of the orbit,the less likely the droplet is to get out of the orbit.When the droplets are transported on the super-hydrophobic and super-hydrophilic orbit,the orbital width should not be too large.At this time,the wider the orbit,the deeper the maximum depth of the orbit,the stronger the capillary force is absorbed by the droplets,and the less likely the droplet is to get out of the orbit.Then three kinds of surface microstructures,such as "maze" microstructures,"tree" microstructures and hierarchical micronanostructures,were prepared on aluminum alloy substrate by different methods of special wetting surface preparation.By comparing the properties of contact Angle,rolling Angle and surface flatness,the method of chemical etching combined with anodic oxidation was finally selected as the main method to prepare aluminum superhydrophobic surface in this project,the prepared superhydrophobic surface has a contact angle of 164° and a roll angle of 1.5°.Then,the liquid droplet positioning and transport orbits with superhydrophobicsuperhydrophobic and superhydrophobic-superhydrophilic with depth gradient were prepared on aluminum alloy substrate by using ultraviolet laser fine processing equipment,the linear,curved and circular transport orbits were prepared respectively,on which the location transport experiment of liquid droplets was carried out.The experimental results show that for the gradient superhydrophobic-superhydrophobic orbit,the droplet can transport at any speed in the linear orbit with appropriate width,when the droplets are in a curved orbit,when the orbital width is 1 mm and the maximum depth of the orbit is 450 ?m,the droplets have good transport capacity and are not easily separated.track For the gradient superhydrophobic-super-hydrophilic orbit,the transport effect is better when the orbital width is 100?m,and the curved orbit with a curvature radius of 12 mm can withstand the critical critical velocity of the droplet,and the droplet is less likely to get out of the orbit;The straight segment path will cause the droplet to achieve a greater velocity of movement,and for curved orbits of the same radius of curvature,the droplet will more likely to detach.Finally,the positioning and transport of the droplets on a circular gradient superhydrophobicsuperhydrophilic orbit with a width of 100 ?m,a maximum depth of 200 ?m and a radius of curvature of 10 mm was achieved.