This paper experimentally investigates the mechanism of water droplet detachment in a confined microchannel under highly inertial (10<Re< 200) air flow conditions. Experimental observations show that as the Reynolds number of the continuous phase is increased, the droplet transitions from an elongated slug to a nearly uniform aspect ratio droplet. Supporting scaling arguments are then made that...

The objective of this research is to develop an accurate numerical method to be used in showing the deformation of a liquid fuel droplet in a convective field. To simultaneously solve the internal liquid droplet flow field as well as the external gas phase flow field, a nonstaggered rectangular grid system without any coordinate transformation is used. Transition from the gas field to the liqui...

A droplet solution characterizes the lamellar phase of a diblock copolymer when the two composing monomers maintain a skewed ratio. We study the threshold case where the free energy of a droplet solution is comparable to the free energy of the constant solution. Using a Lyapunov-Schmidt reduction approach, adapted to calculus of variations, we prove the existence of a free energy local minimize...

Droplet manipulation is comprised of techniques such as droplet generation, merging, and splitting, of which droplet merging is one of the major bottlenecks in achieving high-throughput analysis. Here we present a three dimensional electrode that improves the electric field uniformity and field strength experienced by two adjacent droplets undergoing merging. We conducted a systematic compariso...

A microfluidic device designed to generate monodispersed picoliter to femtoliter sized droplet emulsions at controlled rates is presented. This PDMS microfabricated device utilizes the geometry of the channel junctions in addition to the flow rates to control the droplet sizes. An expanding nozzle is used to control the breakup location of the droplet generation process. The droplet breakup occ...

A numerical investigation of unsteady liquid fuel droplet combustion with droplet heating and internal circulation under forced convection is presented. The droplet is burning within an airstream at atmospheric pressure and under zero-gravity conditions. Combustion is modeled using finite rate kinetics and a one-step overall reaction. The numerical model includes a new multicomponent formulatio...

Digital microfluidics (DMF) is a popular alternative to traditional in-channel microfluidics, which allows precise control of individual droplets. Most commonly used droplet manipulation methods for DMF are electrowetting on dielectric (EWOD) and magnetic actuation. Both methods require high surface hydrophobicity to facilitate droplet movement, and often superhydrophobic surfaces are used to f...

The Ohta-Kawasaki density functional theory of diblock copolymers gives rise to a nonlocal free boundary problem. Under a proper condition between the block composition fraction and the nonlocal interaction parameter, a pattern of a single droplet is proved to exist in a general planar domain. A smaller parameter range is identified where the droplet solution is stable. The droplet is a set whi...

We consider the finite-size scaling of equilibrium droplet shapes for fluid adsorption (at bulk two-phase coexistence) on heterogeneous substrates and also in wedge geometries in which only a finite domain Λ A of the substrate is completely wet. For three-dimensional systems with short-ranged forces we use renormalization group ideas to establish that both the shape of the droplet height and th...

We have demonstrated the application of low surface energy fluoropolymer coatings onto poly(dimethylsiloxane) (PDMS) microfluidic devices for droplet formation and extraction-induced merger of droplets. Initiated chemical vapor deposition (iCVD) was used to pattern fluoropolymer coatings within microchannels based on geometrical constraints. In a two-phase flow system, the range of accessible f...