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Consta S. Atomistic Modeling of Jet Formation in Charged Droplets. J Phys Chem B 2022; 126:8350-8357. [PMID: 36201739 DOI: 10.1021/acs.jpcb.2c05849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The first atomistic simulations that reveal the mechanism of Rayleigh fission are presented. It is demonstrated that simple ion or macroion ejection takes place through droplet deformation from a spherical into a distinct "tear" shape that contains a conical protrusion. We assert that the latter state is a free-energy minimum along an order parameter that measures the degree of droplet asphericity. The charged droplet's long-time evolution proceeds by alternating between the two minima above and below the critical value that are reached through solvent evaporation and ion ejection, respectively. For the first time, this mechanism allows one to explain the nature of the progeny droplets and the percentage of charge lost during fission. The cone half angle is estimated and found to be in good agreement with the value predicted from the solution of the electrostatic equation for the dielectric liquid. It is found that the conical deformation is independent of the effect of electrohydrodynamic forces reported in experiments. Contrary to the experimental observations of two diametrically opposite jets for droplets suspended in the electric field, we find that a single jet is formed at the Rayleigh limit. The study provides insight into the mechanism of capture of a macroion in jets appearing in electrospray ionization mass spectrometry (ESI-MS) experiments and may explain the tolerance of the ESI-MS spectrum to salt contamination of the sample.
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Affiliation(s)
- Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, CanadaN6A 5B7.,Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EWUnited Kingdom
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2
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Ghaani MR, English NJ. Kinetic study on electro-nucleation of water in a heterogeneous propane nano-bubble system to form polycrystalline ice I c. J Chem Phys 2020; 153:084501. [PMID: 32872892 DOI: 10.1063/5.0017929] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Elucidating the underlying mechanisms of water solidification in heterogeneous systems is crucially important for a panoply of applications; gaining such an understanding has also proven to be very challenging to the community. Indeed, one such example lies in clarifying the thermodynamics and kinetics of electro-crystallization in heterogeneous systems, such as micro- and nano-bubble systems. Here, we employ non-equilibrium molecular dynamics of water in heterogeneous environments experiencing direct contact with a propane gas phase at various temperatures in externally applied static electric fields, elucidating significant external-field effects in inducing poly-crystalline cubic-ice formation. This is in stark contrast with recent work on homogeneous cubic-ice electro-nucleation to produce largely fault-free single crystals. We explore the kinetics of heterogeneous cubic-ice electro-nucleation under different field intensities and thermal conditions and provide an overview of time-dependent dynamics of evolution of polycrystallinity.
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Affiliation(s)
- Mohammad Reza Ghaani
- School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Niall J English
- School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland
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Lee SJ, Kang JY, Choi W, Kwak R. Simultaneous electric production and sizing of emulsion droplets in microfluidics. SOFT MATTER 2020; 16:614-622. [PMID: 31774108 DOI: 10.1039/c9sm01426h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Microscale emulsions are widely used in fundamental and applied sciences. To expand their utilization, various methods have been developed for manipulating and measuring the physical properties of fabricated emulsions inside microchannels. Herein, we present an electric emulsification platform that can produce emulsions and simultaneously detect their physical properties (size and production speed). The characterization of the emulsion properties during the fabrication process will broaden the application fields for microscale emulsions because it can avoid time-consuming post image processing and simplify the emulsification platform. To accomplish this, a "bottleneck" channel is implanted between two reservoirs of immiscible fluids (continuous and dispersion phases). This channel can not only confine one fluid within the other when the electric field is on, resulting in emulsification via electrohydrodynamically induced Rayleigh instability, but also act as a resistive pulse sensor (RPS). The fluctuation of the liquid/liquid interface during emulsification induces the fluctuation of the electric resistance in the bottleneck channel, as the two fluid phases have different electrical conductivities. With this simple but dual-functional channel, the emulsion size (radius of 5-10 μm) and production speed (7-12 Hz) can be controlled by adjusting the electric field and the channel-neck geometry. Additionally, the properties can be measured using the RPS; the data obtained through the RPS exhibit high correlations with the validated data obtained using a high-speed camera and microscopy (>95%). The proposed buffer-less electric emulsification with the embedded RPS is a simple and cost-effective emulsion production method that allows real-time emulsion characterization with a limited sample volume.
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Affiliation(s)
- Sang Jun Lee
- Center for BioMicrosystems, Korea Institute of Science and Technology, Seoul, 02792, Korea
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Malevanets A, Oh MI, Sharawy M, Consta S. Landau–Ginzburg theory for ‘star’-shaped droplets. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1513174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Anatoly Malevanets
- Department of Electrical and Computer Engineering, The University of Western Ontario, London, Ontario, Canada
| | - Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
| | - Mahmoud Sharawy
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
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Nandi PK, Burnham CJ, English NJ. Electro-nucleation of water nano-droplets in No Man's Land to fault-free ice I c. Phys Chem Chem Phys 2018. [PMID: 29513305 DOI: 10.1039/c7cp07406a] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Elucidating water-to-ice freezing, especially in "No Man's Land" (150 K < T < 235 K), is fundamentally important (e.g., predicting upper-troposphere cirrus-cloud formation) - and elusive. An oft-neglected aspect of tropospheric ice-crystallite formation lies in inevitably-present electric fields' role. Exploring nucleation in No Man's Land is technically demanding, owing to rapid nucleation rates, to mention nothing of difficulties of applying relevant electric fields thereto. Here, we tackle these intriguing open questions, via non-equilibrium molecular-dynamics simulations of sub-microsecond formation of rhombus-shaped ice Ic nano-crystallites from aggressively-quenched supercooled water nano-droplets in the gas phase, in external static electric fields. We explore droplets' nano-confined geometries and the entropic-ordering agent of external electric fields as a means of realising cubic-ice formation, especially with very few stacking faults and defects.
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Affiliation(s)
- Prithwish K Nandi
- School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland. and Irish Centre for High-End Computing, Grand Canal Quay, Dublin 2, Ireland.
| | - Christian J Burnham
- School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Niall J English
- School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland.
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Nandi PK, Burnham CJ, English NJ. Electro-suppression of water nano-droplets’ solidification in no man’s land: Electromagnetic fields’ entropic trapping of supercooled water. J Chem Phys 2018; 148:044503. [DOI: 10.1063/1.5004509] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Prithwish K. Nandi
- Irish Centre for High-End Computing, Grand Canal Quay, Dublin 2, Ireland
- School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Christian J. Burnham
- School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Niall J. English
- School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland
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In Oh M, Paliy M, Consta S. “Star” morphologies of charged nanodrops comprised of conformational isomers. J Chem Phys 2018; 148:024307. [DOI: 10.1063/1.5011989] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Affiliation(s)
- Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Maxim Paliy
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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Pillai R, Berry JD, Harvie DJE, Davidson MR. Electrolytic drops in an electric field: A numerical study of drop deformation and breakup. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:013007. [PMID: 26274270 DOI: 10.1103/physreve.92.013007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Indexed: 06/04/2023]
Abstract
The deformation and breakup of an axisymmetric, conducting drop suspended in a nonconducting medium and subjected to an external electric field is numerically investigated here using an electrokinetic model. This model uses a combined level set-volume of fluid formulation of the deformable surfaces, along with a multiphase implementation of the Nernst-Planck equation for transport of ions, that allows for varying conductivity inside the drop. A phase diagram, based on a parametric study, is used to characterize the stability conditions. Stable drops with lower ion concentration are characterized by longer drop shapes than those achieved at higher ion concentrations. For higher drop ion concentration, greater charge accumulation is observed at drop tips. Consequently, such drops break up by pinching off rather than tip streaming. The charge contained in droplets released from unstable drops is shown to increase with drop ion concentration. These dynamic drop behaviors depend on the strength of the electric field and the concentration of ions in the drop and result from the interplay between the electric forces arising from the permittivity jump at the drop interface and the ions in the bulk.
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Affiliation(s)
- R Pillai
- Department of Chemical and Biomolecular Engineering, The University of Melbourne, Melbourne, Victoria 3000, Australia
| | - J D Berry
- Department of Chemical and Biomolecular Engineering, The University of Melbourne, Melbourne, Victoria 3000, Australia
- CSIRO Mineral Resources Flagship, Clayton, Victoria 3169, Australia
| | - D J E Harvie
- Department of Chemical and Biomolecular Engineering, The University of Melbourne, Melbourne, Victoria 3000, Australia
| | - M R Davidson
- Department of Chemical and Biomolecular Engineering, The University of Melbourne, Melbourne, Victoria 3000, Australia
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King LB, Meyer E, Hopkins MA, Hawkett BS, Jain N. Self-assembling array of magnetoelectrostatic jets from the surface of a superparamagnetic ionic liquid. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:14143-14150. [PMID: 25372842 DOI: 10.1021/la503341p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Electrospray is a versatile technology used, for example, to ionize biomolecules for mass spectrometry, create nanofibers and nanowires, and propel spacecraft in orbit. Traditionally, electrospray is achieved via microfabricated capillary needle electrodes that are used to create the fluid jets. Here we report on multiple parallel jetting instabilities realized through the application of simultaneous electric and magnetic fields to the surface of a superparamagnetic electrically conducting ionic liquid with no needle electrodes. The ionic liquid ferrofluid is synthesized by suspending magnetic nanoparticles in a room-temperature molten salt carrier liquid. Two ILFFs are reported: one based on ethylammonium nitrate (EAN) and the other based on EMIM-NTf2. The ILFFs display an electrical conductivity of 0.63 S/m and a relative magnetic permeability as high as 10. When coincident electric and magnetic fields are applied to these liquids, the result is a self-assembling array of emitters that are composed entirely of the colloidal fluid. An analysis of the magnetic surface stress induced on the ILFF shows that the electric field required for transition to spray can be reduced by as much as 4.5 × 10(7) V/m compared to purely electrostatic spray. Ferrofluid mode studies in nonuniform magnetic fields show that it is feasible to realize arrays with up to 16 emitters/mm(2).
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Affiliation(s)
- Lyon B King
- Department of Mechanical Engineering, Michigan Technological University , 1400 Townsend Drive, Houghton, Michigan 49931, United States
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Raut JS, Akella S, Singh A, Naik VM. Catastrophic drop breakup in electric field. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:4829-4834. [PMID: 19334721 DOI: 10.1021/la803740e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report novel observations revealing the catastrophic breakup of water drops containing surfactant molecules, which are suspended in oil and subjected to an electric field of strength approximately 10(5) V/m. The observed breakup was distinctly different from the gradual end pinch-off or tip-streaming modes reported earlier in the literature. There was no observable characteristic deformation of the drop prior to breakup. The time scales involved in the breakup and the resultant droplet sizes were much smaller in the phenomenon observed by us. We hypothesize that this mode of drop breakup is obtained by the combined effect of an external electric field that imposes tensile stresses on the surface of the drop, and characteristic stress-strain behavior for tensile deformation exhibited by the liquid drop in the presence of a suitable surfactant, which not only lowers the interfacial tension (and hence the cohesive strength) of the drop but also simultaneously renders the interface nonductile or brittle at high enough concentration. We have identified the relevant thermodynamic parameter, viz., the sum of interfacial tension, sigma, and the Gibbs elasticity, epsilon, which plays a decisive role in determining the mode of drop breakup. The parameter (epsilon + sigma) represents the internal restoration stress of a liquid drop opposing rapid, short-time-scale perturbations or local deformations in the drop shape under the influence of external impulses or stresses. A thermodynamic "state" diagram of (epsilon + sigma) versus interfacial area per surfactant molecule adsorbed at the drop interface shows a "maximum" at a critical transition concentration (ctc). Below this concentration of the surfactant, the drop undergoes tip streaming or pinch off. Above this concentration, the drop may undergo catastrophic disintegration if the external stress is high enough to overcome the ultimate cohesive strength of the drop's interface.
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Affiliation(s)
- Janhavi S Raut
- Unilever Research India, 64 Main Road, Whitefield, Bangalore-560066, India.
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Bormashenko E, Whyman G. Variational approach to wetting problems: Calculation of a shape of sessile liquid drop deposited on a solid substrate in external field. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.08.049] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Stone HA, Lister JR, Brenner MP. Drops with conical ends in electric and magnetic fields. Proc Math Phys Eng Sci 1999. [DOI: 10.1098/rspa.1999.0316] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Howard A. Stone
- Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - John R. Lister
- Institute of Theoretical Geophysics, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 9EW, UK
| | - Michael P. Brenner
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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