Study On Directional Transport And Adhesion Performances Of Bubbles On Tapered Cavity Surface

The underwater bubble directional transport and the adhesion improvement of the solid surface are of practical importance in the fields of gas collection,catalytic reaction,wastewater treatment and underwater drag reduction.However,the developed surfaces for underwater bubble transport and adhesion generally have several shortages,such as limited transport velocity,insufficient surface adhesion and poor mechanical stability,which severely limit their practical applications.Here,the superaerophilic tapered cavity(STC)surface was designed and prepared,and the bubble transport performances,adhesion abilities and mechanical stabilities were studied.The details are as follows:(1)The superaerophilic tapered cavity(STC)surface is designed and prepared,and the wettability,micromorphology and element composition of the STC were characterized.The STC was designed inspired by the heron’s beak and fabricated by micro-milling,hydrochloric acid etching,superhydrophobization and laser treatment.The wettability shows that the inside section of the STC exhibits superhydrophobicity and superaerophilicity,and the outside section exhibits superhydrophilicity and superaerophobicity.The micromorphology indicates that the inside section of the STC is densely packed with micro-scale particles,while there are few particles on the inside section.The EDS proves that the components of Si and O elements on the inside section of the STC are much higher than that on the outside section,which indicates that the hydrophobic particles on the outside section of the STC were removed by the laser treatment.(2)The bubble transport performances of the STC were studied.It was found that,the STC can transport small bubbles in faster velocity compared with other underwater bubble directional transport surfaces.It was concluded that the asymmetries of intra-bubble and inter-bubbles on the STC lead to greater driving forces,therefore realize bubble directional transport in a higher velocity.Further studies indicated that the v increases with the decrease ofαand the increase of V_bon the two surfaces;the bubbles can transport from the tip to the root directionally only.Meanwhile,the mechanical stability test revealed that the STC can transport bubbles after several friction cycles.Finally,the STC is used for underwater bubble upsidedown transport,barrier-jumping transport and S-shaped trajectory directional transport.(3)The adhesion abilities of the STC was studied.It was found that the adhesion abilities of the STC are better than the SVP,the bubble retention time(t),the adhesion volume(V_a),and the retention efficiency(η)of the STC increase with the increase of theαin different extent;the surface adhesion abilities remain stable after several adhesion cycles.Meanwhile,the mechanical stability test revealed that the t,V_aandηof the STC reduce in different extent after several friction cycles.The developed superaerophilic tapered cavity(STC)surface by mimicking the beak of heron can not only directionally transport underwater bubbles at a higher velocity,but also performs better surface adhesion abilities and mechanical stability,which is significant reference for the design and manufacture of underwater bubble directional transport surface in complicated working conditions.