title: Electric field mediated spraying of miniaturized droplets inside microchannel.
abstract: We report a facile and noninvasive way to disintegrate a microdroplet into a string of further miniaturized ones under the influence of an external electrohydrodynamic field inside a microchannel. The deformation and breakup of the droplet was engendered by the Maxwell's stress originating from the accumulation of induced and free charges at the oil-water interface. While at smaller field intensities, for example less than 1 MV/m, the droplet deformed into a plug, at relatively higher field intensities, e.g. ∼1.16 MV/m, a pair of droplets having opposite surface charge was formed. The charged droplets showed an interesting periodic bridging and breakup during their translation motion across the channel. For even higher field intensities, for example more than 1.2 MV/m, the entire droplet underwent dielectrophoresis toward one of the electrodes before experiencing a strong attractive force from the other electrode to deform into a shape of a Taylor cone. With progress in time, mimicking the electrospraying phenomenon, the cone tip periodically ejected a string of miniaturized water droplets to form a microemulsion inside the channel. The frequency and size of the droplet ejection could be tuned by varying the applied field intensity. A water droplet of ∼214 μm diameter could continuously eject droplets of size ∼10 μm or even smaller to form a microemulsion inside the channel.
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India.
authors.forename: Seim
authors.initials: S
authors.lastname: Timung
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India.
authors.forename: Joydip
authors.initials: J
authors.lastname: Chaudhuri
authors.affiliation: Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India.
authors.forename: Manash Pratim
authors.initials: MP
authors.lastname: Borthakur
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India.|Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati, Assam, India.
authors.forename: Tapas Kumar
authors.initials: TK
authors.lastname: Mandal
authors.affiliation: Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India.
authors.forename: Gautam
authors.initials: G
authors.lastname: Biswas
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India.|Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati, Assam, India.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Bandyopadhyay
mesh_terms: D003198:Computer Simulation; D004560:Electricity; D046209:Electrophoresis, Microchip / Q000295:instrumentation / Q000379:methods; D004867:Equipment Design; D056656:Lab-On-A-Chip Devices; D044085:Microfluidics; D008904:Miniaturization; D008962:Models, Theoretical; D010316:Particle Size; D012825:Silicon
chemical_list: D012825:Silicon
keywords: Electric field; Microchannel; Microdroplet; Miniaturization; Multiphase flow