Research On Pumpless And Directed Transportation Of Bubbles On Wedge Patterned Surface

The pumpless and directed transportation of bubbles means that the transportation of bubbles along a specific transportation track under water can be realized without external power source.It has a very wide application prospect in the fields of bioengineering,chemical engineering,microfluidics and so on.However,the current existing pumpless and directed transport surfaces generally have the problems of short transport distance,small transport volume,and complicated transport structure.Moreover,it still lacks a simple and efficient bubble transport surface.In this paper,the method combining dual electrochemical etching and low surface energy modification was used to prepare the superaerophobic/superaerophilic wedge patterned surface,and the characterization of the patterned surface was analyzed.In order to clarify the mechanism of pumpless and directed transportation of bubbles,the forces acting on the bubbles during their transportation on the patterned surface were analyzed,and the related parameters of the pattern which had an influence on bubble transportation were investigated.In addition,and the related research of oxygen jet transportation based on the pattern surface was also carried out.The main contents include:According to the wettability principle,the patterned surface consisting of a peripheral superaerophobic region and a middle superaerophilic wedge region was prepared by dual electrochemical etching and low surface energy modification.Herein,the aluminum surface was chosen as the manufacturing object.After the first electrochemical etching and the low surface energy modification by fluorosilane,the superaerophilic surface was obtained.After the wedge-shaped mask was pasted on the superaerophilic surface,the superaerophilic wedge-shaped region and peripheral superaerophobic region could be obtained after the second electrochemical etching.A series of characterizations of the surface morphologies,crystal structures and element compositions were carried out on the prepared patterned surface,and the wettability state of the surface to water droplets and bubbles after each process was analyzed.Through the force analysis of the bubble on the wedge patterned surface,it was found that the main driving force during the pumpless and directed transportation process was the Laplace gradient force of the wedge region to the bubble,the main resistances were the flow resistance of the water to the bubble and the adhesion force of the wedge region to bubble.When the buoyancy component along the direction of the centerline of wedge region was the same as the bubble transport direction,it was the driving force.On the contrary,it was the resistance.Research on the related parameters of the patterned surface shows that increasing the wedge angle,covering the wedge region with gas film,and tilting the patterned surface upward can improve the bubble transportation efficiency.The developed wedge patterned surface can not only realize the pumpless and directed transportation of single bubble,but also can realize the pumpless and directed transportation of large flow of gas jet.Therefore,the wedge patterned surface is feasible in practical application.