Studies Of Ultra-fast Directional Liquid Transfer On Concave Curved Conical Fibers

Directional liquid transport is widely used in daily production and life,such as fog collection,oil-water separation,micro-fluids,filtration,and so on.There are many kinds of system to realize directional transport,among them,tapered fiber has become an ideal system for directional transport due to its unique structure.However,the study is limited to the surface of the conical fiber,in which the transport velocity is slow and the transport distance is short.Besides,the volume of liquid will be lost during the process of movement,which will be hard to reach a high efficiency of collection and utilization.Therefore,how to achieve efficient and ultra-fast transport is still an urgent problem to be solved.Inspired by the collection and directional transport on the surface of the conical fiber,we adopt the special-shaped fibers by optimizing the structure and introducing new driving factors to observe the collection and directional transport of liquid,which has achieved the ultra-fast transport under the synergistic effect of the concave structure and the tapered structure.In our study,the velocity of liquid transport on the surface of different shaped fibers was observed and compared when different numbers of concave structures were introduced in conical fiber.The force analysis of the liquid transported on the surface of different tapered fibers was carried out to explore and verify the mechanism of liquid directional transport.And the corresponding mechanism model was established finally.This study is significant for the development of simple,efficient and low-cost directional transport.The main contents of this dissertation are as follows:1 Ultra-fast directional liquid transfer on concave curved conical fibersFour kinds of fibers were obtained by PDMS.The mechanism diagram of the complex process was drawn by characterizing the surface morphology and cross-section morphology of these fibers.The fiber was placed horizontally after its surface was modified into hydrophilic.And then,0.05 ?L of deionized water was added by using the static contact angle instrument to observe the movement of liquid on the surface of these fibers.The velocities of liquid on cone fiber,concave tri-pyramid fiber,concave tetra-pyramid fiber,and concave penta-pyramid fiber are 0.97 mm/s,28.79 mm/s,14.42 mm/s,8.78 mm/s,respectively.The result shows that the velocity on concave pyramid is faster than it on cone fiber.Among them,the velocity on concave tri-pyramid is the highest,which is about 30 times faster than it on the cone fiber.Moreover,the liquid was added to observe the movement on wet fibers after the surfaces of these fibers were pre-wetted.Comparing the velocities of liquid moving on dry fibers,we found the velocities on wet fibers were larger than the velocity on dry fibers.The velocity on the concave tri-pyramid with wet surface is the largest,which can achieve up to 47.34 mm/s.In this part,the conclusion of this experiment provides a new idea for ultrafast directional transport.2 The research of ultra-fast directional transport mechanism and applicationIn the second chapter,we proved that the velocities of liquid moving on the concave fibers are larger than it on cone fibers.In the third chapter,we analyzed the influence of the force during the movement on four fibers and the influence of the structure on the velocity of the liquid that moving on different fibers.Finally,the mechanism model was established,and the ultra-fast directional transport was extended to transport other liquids.In the study,we observed the process of silicone oil moving on the surface of concave pyramid and cone fiber under microscope and found the precursor film on the concave pyramid fibers was longer than it on the cone fiber.Moreover,there is a significant difference in meniscus at the front of liquid during it moving on concave pyramid fiber and cone fiber.The shape of advancing meniscus on the concave pyramid fiber is “?”,while the movement of liquid on the convex cone fiber with the “?” shape of advancing meniscus.We simplified the tapered fibers into the following structure,that is,rectangular,rectangular with concave structure,triangle and triangular with concave structure.The height of silicone oil climbing on these samples were measured to determine the effect of structures on liquid transport.In our study,we found the height of the liquid is the highest under the synergistic effect of the concave structure and the tapered structure.The mechanism of ultra-fast liquid transport is expected to have broad application prospects in high-efficiency collection of fog,ultra-fast detection or microfluidic chips.