Spontaneous And Consecutive Fluidic Transport:Mechanism And Application

Directional fluidic transport has significant applications in daily life and industry.In nature,cactus spine,which has a geometry similar to a tapered pillar,owns the ability to transport liquid spontaneously and directionally.Inspired by this intriguing phenomenon,in this thesis,a numerical model was developed.With the help of this numerical model,the mechanism behind spontaneous and directional liquid transport were revealed and several key parameters were studied.Several thresholds(tapered angle,diameter of the tip end and contact angle)were found,which may be helpful for design and manufactory of the tapered pillar for achieving spontaneous and directional liquid transport.In order to overcome the limitation which laid on the transport distance due to the limited length of ordinary tapered pillar,a novel ladderlike tapered pillar was proposed and the corresponding numerical model was developed.Initially,a novel alternative etching and coating method developed and later,the ladderlike tapered pillar was achieved in fabrication.Subsequently,by experimental study,the mechanism for the process in which droplet overcame the joint between two sections was revealed.Also,the acceptable ranges for those key parameters were concluded.For instance,the tilt angle,contact angle and hydrophilic modification time were 0-25°,50° and 5 minutes respectively.It was proved that liquid transport distance for ladderlike tapered pillar was twice as that for ordinary tapered pillar and the maximum acceleration was 5g.When the ladderlike tapered pillars were applied in fog harvesting device,the collecting efficiency for this device was improved by 53.5% than ordinary setup.Furthermore,ladderlike tapered pillar was introduced to underwater bubble manipulation.By theoretical research and experimental study,the essential requirements for underwater bubble capture and manipulation were discovered,namely,hydrophobic group and micro-/nano-structure.According to this discovery,the bubble slippery technology was proposed to modify the surface property of the pillars.The mechanism of underwater bubble manipulation on ladderlike tapered pillar was revealed and the manipulating ability was discussed(accessible average velocity ranged from 113.9±10.3 to 309.1±5.8 mm/s).Finally,the general principles for underwater bubble manipulation were concluded and the helical ladderlike tapered pillar was designed and fabricated to achieve underwater bubble manipulation in 3D space.These results may provide a new systematic way to design and fabricate structures and devices for spontaneous and consecutive fluidic transport.Tapered pillar,ladderlike tapered pillar and helical ladderlike tapered pillar may have great potential in triboelectric nanogenerator,fog harvesting,oil-water separation,underwater gas collection and underwater gas reaction etc.