Study On Droplet Manipulation Behavior And Mechanism

Droplet manipulation technology plays a key role in the fields of biomedicine,chemical materials,energy,printing and surface cleaning.Scientists realize the collection,transportation and storage of droplets by studying the removal,mixing,reaction and transport behavior of single droplets.With the development of intelligent processing technology,scientists have prepared surfaces that can manipulate droplets through various surface processing techniques.However,the existing control methods have problems such as complex preparation,high cost,and contaminated droplets,which limit the development of microdroplet control technology.Therefore,the development of multifunctional wettability surface with excellent comprehensive performance is still of great concern.This paper systematically summarizes the latest research progress of droplet manipulation dependent on passive modification and external field intervention.Based on this,the droplet manipulation behavior dependent on microstructure and external field intervention is explored.The main contents and conclusions are as follows :(1)The hydrophobic integrated grid was prepared by simple ammonia alkali etching and chemical modification on the surface of bionic rice leaves and pitcher grass.The anisotropic transport behavior of droplets on the integrated grid surface was studied and its mechanism was analyzed.By changing the mesh aperture,inclination angle and droplet size,the critical conditions for anisotropic manipulation of droplets are explored.The experimental results show that the anisotropic integrated grid has chemical stability and mechanical durability.When immersed in water for 1 h,the anisotropic integrated grid still maintains its good performance after 50 times of sand impact and 50 times of sandpaper wear.(2)Densely stacked ZnO nanoarrays were constructed by formamide etching.Under the action of capillary force,the magnetic fluid was locked in the gap between the nanoarrays to prepare a magnetic composite surface.The intelligent control of droplet and bubble transport under the action of magnetic field is realized.ZnO nanoarrays with different densities were prepared to explore the effect of locked magnetic fluid on droplet operation efficiency.In addition,magnetic response composite surfaces with different magnetic particle contents were prepared,and the effects of magnetic particle content,magnetic field strength,droplet and bubble volume on surface morphology and fluid behavior were studied.The motion behavior of droplets and bubbles is analyzed.The prepared magnetic response composite surface has a wide range of applications in droplet and bubble transport,chemical reaction,bubble mixing and so on.(3)Magnetic liquid metal droplets were prepared by magnetic modification of carbonyl iron powder.The prepared magnetic liquid metal has good magnetic deformation ability,passive deformation ability and conductivity.The controllable motion of liquid metal under the action of magnetic field and electric field is realized.This method does not depend on the surface of a specific substrate.It has wide applicability in confined space and various substrate surfaces.