Numerical Simulation Of The Fabrication Of Anisotropic Particles In Microfluidic Devices

Anisotropic particles are the basic blocks of functional materials and thenon-centrosymmetric features of anisotropic particles could construct a unique classof nano-and micro-colloidal with controlled internal architectures which haveextensive applications in many fields such as chemical engineering, medicine, biology,electric. Although real world applications of these materials appear to still be far fromrealization, these anisotropic particles have attracted much attention due to novelmorphologies and diverse potential applications.Droplet microfluidics based on microfluidics is a rapidly growing field applied tohandle tiny volume droplets. Droplet microfluidics has capability of precise control ofdroplet volume and reliable manipulation of individual droplets such as coalescence,mixing contents in droplet and droplet sorting. Droplet based microfluidics platformsused as microreactors have a series of advantages such as rapid mix and lowconsumption of reagents, and its applications range from fast analytical systems to thesynthesis of advanced materials, from protein crystallization to biological assays forliving cells.Boundary element method has advantages of high accuracy, reducing dimensionof calculation and high facility in describing the complex geometries or infinite field.Coupled with spectral method, we employ an explicit time-integration algorithmbased on a2D boundary element method to simulate the rheology of droplet at lowReynold number and develop a mesh reconstruction method in order to simulate thecoalescence of droplet.The process of coalescence involves short time scale and length scale whichcause difficulty to experiment study. For this reason, the mechanisms of coalescencestill need more exploration. This paper employs2D spectral boundary elementmethod to simulate the head-on collision of two equal droplets and pays attention tothe evolution of the distance between droplet centers and internal flow field. A novelmesh reconstruction is developed and applied to simulate the process of coalescence,such as two equal droplets in cross microchannel.In the paper we provide a new device to fabricate anisotropic particles with precise-designed patches. This device is a combination of a cross-slot and a MFRMwhich could generate flow fields from extensional, simple shear to rotational flows atits central cavity by varying the flow rate at the various inlets and outlets. Accordingto calculation results, we plot the velocity vectors and streamlines at different flowconditions and put forward the scheme of fabrication of anisotropic particles. Besides,we pay attention to the effects of rotation time, viscosities, radius of small droplet onthe position of patches and point out the optimal flow rate range in the fabrication.These results give a new way to manufacture anisotropic particles with precise-sitepatches and have guiding significance for utilizing microfluidic to fabricate particles.