Microfluidics and Nanofluidics

Microfluidics and nanofluidics are interdisciplinary fields that involve the science and technology of fluid flow through materials and systems with micro to nanoscale features.  Research and applications in these fields have proliferated in recent years due to unique advantages of small-scale fluidic processes combined with rapid advances in materials development and system integration. Research in the Furlani group involves modeling and simulation towards the development of novel processes and devices. Much of this work emphasizes the use of state-of-the-art computational fluid dynamic (CFD) analysis for studying fluidic phenomena involving Newtonian and Non-Newtonian fluids, conjugate heat transfer, phase change analysis, free-surface and multiphase analysis, fluid media interactions, flow through porous media, fully coupled fluid-structure and particle-fluid interactions and colloids.

Advances in microfluidics have enabled the development of Lab-on-a-Chip systems that perform multiple biochemical processes on small samples with unprecedented efficiency and reliability. However, a potential drawback of such systems is the difficulty in achieving rapid mixing of reagents. Microfluidic flow is laminar with a very low Reynolds numbers and mixing is limited to diffusion, which is slow, especially for large organic or biological molecules that have very low diffusivities. Various methods have been developed to improve micromixing and these are broadly classified as passive and active. Passive mixers are based on the perturbation of fluids caused by its flow through geometrical structures, i.e. with no moving parts. Active mixers, on the other hand, utilize external energy sources and forces to generate chaotic advection to increase the interfacial area. A promising approach to active micromixing involves the use of magnetic particles. In this approach,  a time-varying (rotating) magnetic field is applied that induces rotation of extended particle chains. The chains self-assemble in the presence of an external field due to interparticle dipole-dipole forces. This attractive force holds the chain together as it rotates, which causes a stirring and mixing of reagents. A simulation of this is shown in Figs. 1 and 2. In this model, a group of microbeads form a chain within a circular chamber that contains equal concentrations of two reagents, colored red and blue. The particles are initially collinear and spaced apart. Once the field is applied, the microbeads group into a contiguous microchain. As the field rotates counter clockwise, it imparts a torque to the chain causing it to rotate in a synchronous fashion. The rotating particle chain stirs and mixes the reagents as shown in the animation of Fig. 2.