Droplet actuation in an electrified microfluidic network

Abstract

This work demonstrates that liquid droplet emulsions in a microchannel can be deformed, decelerated and/or pinned by applying a suitable electrical potential. By concentrating a potential gradient at the corners, we show that different droplets can be passively binned by size and on demand in a branched microfluidic device. The deformation, deceleration, squeezing and release of droplets in a three-dimensional numerical simulation are qualitatively verified by experiments in a PDMS microfluidic device. The forces required for pinning or binning a droplet provide a delicate balance between hydrodynamics and the electric field, and are obtained using appropriate non-dimensional parameters.

Dynamics of ferrofluid drop deformations under spatially uniform magnetic fields

“…Drop formation facilitated by electric (Notz & Basaran 1999) and magnetic (Chen, Chen & Lee 2009) fields, and dynamics and instabilities of pendent drops under an electric field (Acero et al 2013;Ferrera et al 2013;Corson et al 2014) were also explored. Other works addressed simultaneous motion and deformation of free drops under magnetic fields (Nguyen, Ng & Huang 2006;Shi, Bi & Zhou 2014), electrified drops in a microfluidic channel (Wehking & Kumar 2015), and drops on a solid surface by electric (Datta, Das & Das 2015) and rotating magnetic (Zakinyan, Nechaeva & Dikansky 2012) fields. The response of free ferrofluid drops to rotating magnetic fields (Bacri, Cebers & Perzynski 1994;Rhodes et al 2006;Cebers & Kalis 2012), and the formation of complex drop shapes due to AC and rotating magnetic fields (Rhodes et al 2006) were also considered.…”

Electrospray mode transition of microdroplets with semiconductor nanoparticle suspension

“…3a that the dropsize for different suspensions spreads over a wide band as a function of voltage. The spread in the data can be collapsed into a single curve as a function of a nondimensional parameter called the electric capillary number, Ca e 32, 33 . The data in both Fig.…”

Non-dimensional groups for electrospray modes of highly conductive and viscous nanoparticle suspensions

“…The electric force on the droplet is estimated as, F Electric = Sε 0 ε r E 2 /2, where S, ε 0 , ε r , and E are the surface area of the droplet (S = 4πr 2 ), electric permittivity of vacuum, characteristic relative permittivity of each aqueous suspension, and the externally applied electric field 32 . The characteristic relative permittivity is defined as ε r = 1 + σ/(ε 0 ω) based on the Lorentz model for the interaction of electromagnetic waves in dielectric materials 32,33 , where σ and ω are the electrical conductivity of each aqueous suspension and characteristic frequency taken as c/L where c and L are the speed of light in the air and the distance from the center of the capillary tip and the inner edge of the extractor electrode.…”