Application of molecular simulations: Insight into liquid bridging and jetting phenomena
Molecular dynamics simulations have been performed on pure liquid water, aqueous solutions of sodium chloride, and polymer solutions exposed to a strong external electric field with the goal to gain molecular insight into the structural response to the field. Several simulation methodologies have be...
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irk-123456789-1535772019-06-15T01:27:48Z Application of molecular simulations: Insight into liquid bridging and jetting phenomena Nezbeda, I. Jirsák, J. Moučka, F. Smith, W.R. Molecular dynamics simulations have been performed on pure liquid water, aqueous solutions of sodium chloride, and polymer solutions exposed to a strong external electric field with the goal to gain molecular insight into the structural response to the field. Several simulation methodologies have been used to elucidate the molecular mechanisms of the processes leading to the formation of liquid bridges and jets (in the production of nanofibers). It is shown that in the established nanoscale structures, the molecules form a chain with their dipole moments oriented parallel to the applied field throughout the entire sample volume. The presence of ions may disturb this structure leading to its ultimate disintegration into droplets; the concentration dependence of the threshold field required to stabilize a liquid column has been determined. Conformational changes of the polymer in the jetting process have also been observed. Методом молекулярної динамiки виконано моделювання чистої води, водного розчину хлориду натрiю i полiмерних розчинiв, що пiддавалися дiї сильних зовнiшнiх електричних полiв з метою отримання молекулярних характеристик структурного вiдгуку на дiю цих полiв. Щоб встановити молекулярнi процеси, якi ведуть до формування рiдинних мiсткiв i струменiв (при виробництвi нановолокон), використано декiлька методологiй моделювання. Встановлено, що у структурах усталеного наномасштабу, молекули утворюють ланцюжок з дипольними моментами, орiєнтованими паралельно до прикладеного поля по всьому об’єму зразка. Присутнiсть iонiв може внести збурення в цю структуру, що приведе до її повної дезiнтеграцiї на краплини; встановлено залежнiсть порогового поля, необхiдного для стабiлiзацiї стовпця рiдини, вiд концентрацiї. Окрiм цього, спостерiгались конформацiйнi змiни полiмера в процесi формування струменя. 2015 Article Application of molecular simulations: Insight into liquid bridging and jetting phenomena / I. Nezbeda, J. Jirsák, F. Moučka, W.R. Smith // Condensed Matter Physics. — 2015. — Т. 18, № 1. — С. 13602:1-10. — Бібліогр.: 26 назв. — англ. 1607-324X DOI:10.5488/CMP.18.13602 arXiv:1504.00815 PACS: 68.03.Hj http://dspace.nbuv.gov.ua/handle/123456789/153577 en Condensed Matter Physics Інститут фізики конденсованих систем НАН України |
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Molecular dynamics simulations have been performed on pure liquid water, aqueous solutions of sodium chloride, and polymer solutions exposed to a strong external electric field with the goal to gain molecular insight into the structural response to the field. Several simulation methodologies have been used to elucidate the molecular mechanisms of the processes leading to the formation of liquid bridges and jets (in the production of nanofibers). It is shown that in the established nanoscale structures, the molecules form a chain with their dipole moments oriented parallel to the applied field throughout the entire sample volume. The presence of ions may disturb this structure leading to its ultimate disintegration into droplets; the concentration dependence of the threshold field required to stabilize a liquid column has been determined. Conformational changes of the polymer in the jetting process have also been observed. |
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Article |
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Nezbeda, I. Jirsák, J. Moučka, F. Smith, W.R. |
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Nezbeda, I. Jirsák, J. Moučka, F. Smith, W.R. Application of molecular simulations: Insight into liquid bridging and jetting phenomena Condensed Matter Physics |
| author_facet |
Nezbeda, I. Jirsák, J. Moučka, F. Smith, W.R. |
| author_sort |
Nezbeda, I. |
| title |
Application of molecular simulations: Insight into liquid bridging and jetting phenomena |
| title_short |
Application of molecular simulations: Insight into liquid bridging and jetting phenomena |
| title_full |
Application of molecular simulations: Insight into liquid bridging and jetting phenomena |
| title_fullStr |
Application of molecular simulations: Insight into liquid bridging and jetting phenomena |
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Application of molecular simulations: Insight into liquid bridging and jetting phenomena |
| title_sort |
application of molecular simulations: insight into liquid bridging and jetting phenomena |
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Інститут фізики конденсованих систем НАН України |
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2015 |
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http://dspace.nbuv.gov.ua/handle/123456789/153577 |
| citation_txt |
Application of molecular simulations: Insight into liquid bridging and jetting phenomena / I. Nezbeda, J. Jirsák, F. Moučka, W.R. Smith // Condensed Matter Physics. — 2015. — Т. 18, № 1. — С. 13602:1-10. — Бібліогр.: 26 назв. — англ. |
| series |
Condensed Matter Physics |
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2025-07-14T04:39:25Z |
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2025-07-14T04:39:25Z |
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1837595849600794624 |
| fulltext |
Condensed Matter Physics, 2015, Vol. 18, No 1, 13602: 1–10
DOI: 10.5488/CMP.18.13602
http://www.icmp.lviv.ua/journal
Application of molecular simulations: Insight into
liquid bridging and jetting phenomena
I. Nezbeda1,2, J. Jirsák1, F. Moučka1, W.R. Smith3
1 Faculty of Science, J.E. Purkinje University, 400 96 Ústín. Lab., Czech Republic
2 Institute of Chemical Process Fundamentals, Academy of Sciences, 165 02 Prague 6 – Suchdol, Czech Republic
3 Department of Mathematics and Statistics, University of Guelph, Guelph, ON N1G 2W1, Canada
Received October 22, 2014, in final form December 20, 2014
Molecular dynamics simulations have been performed on pure liquid water, aqueous solutions of sodium chlo-
ride, and polymer solutions exposed to a strong external electric field with the goal to gain molecular insight
into the structural response to the field. Several simulation methodologies have been used to elucidate the
molecular mechanisms of the processes leading to the formation of liquid bridges and jets (in the produc-
tion of nanofibers). It is shown that in the established nanoscale structures, the molecules form a chain with
their dipole moments oriented parallel to the applied field throughout the entire sample volume. The presence
of ions may disturb this structure leading to its ultimate disintegration into droplets; the concentration depen-
dence of the threshold field required to stabilize a liquid column has been determined. Conformational changes
of the polymer in the jetting process have also been observed.
Key words: electrospinning, floating liquid bridge, liquids in field, aqueous solution surfaces, polymer solution,
molecular dynamics simulations
PACS: 68.03.Hj
1. Introduction
With advance in computer technology, the development of efficient simulation techniques, and the
availability of commercial or freeware packages, molecular simulation methods [1, 2] have become the
main, and in some instances the only tool to study fluid systems at the molecular level. A primary output
of molecular simulations (and target of theories) have typically been thermophysical properties (equa-
tion of state, heat capacity, viscosity, etc.), entering macroscopic theories of the studied systems, and their
relation to various kinds of underlying intermolecular interactions. However, they make it also possible
to study various processes and this approach has become thus commonplace in many other fields, in-
cluding mechanical engineering and material design, biology, and even medicine, often shedding light
on problems that are inaccessible by other methods. Examples include the rheology of lubricants [3, 4]
and protein self-assembly [5], potentially related to Alzheimer’s and Parkinson’s diseases. In these ap-
plications, the simulations need not necessarily yield numerical values of physical quantities, but they
may help to qualitatively understand and explain the underlying molecular mechanism of the observed
phenomena.
A similar type of problems whose molecular nature is not yet fully understood involves liquid sur-
faces exposed to strong external electric fields, their disturbance and subsequent development. These
problems are encountered in a variety of fields, e.g., physics of the atmosphere (ice formation in super-
cooled water), biology (transport through biological cell membranes), and mineralogy (reactivity at the
mineral–water interface). Interesting examples of processes in which the external field is the driving
force are the floating water bridge (FWB), whose application potential has not been explored yet [6], and
the production of nanofibers using needleless electrospinning technology [7].
© I. Nezbeda, J. Jirsák, F. Moučka, W.R. Smith, 2015 13602-1
http://dx.doi.org/10.5488/CMP.18.13602
http://www.icmp.lviv.ua/journal
I. Nezbeda et al.
Figure 1. Photographs of (A) the floating water bridge established between two beakers and (B) jets ema-
nating from the macroscopic drop in electrospinning.
The macroscopic floating bridge arises between two beakers filled with a liquid (not necessarily wa-
ter) and with immersed electrodes [8], see figure 1 (A). The beakers are initially in contact and a free
hanging structure is formed when they are then slowly pulled apart. A nanoscale analogue to the float-
ing bridge (a nanobridge) is observed between the tip and sample surface in atomic force microscopy
(AFM) [9]. Several scattering experiments using different techniques have been used to elucidate the
microscopic mechanism which holds the FWB together but their results were inconclusive or even con-
tradicting [10–13]. And, as for molecular simulation studies, we are aware of only two attempts. Skinner
et al. [13] used the simulation setup not fully representing the FWB but only its bulk-like interior and did
not find any preferential orientation of the water molecules in the bridge. Cramer et al. [14] studied a
drop attached to a surface and observed its deformation into a column-like structure, though never fully
developing a bridge. Their main result was the finding that whatever strength of the field was used, the
hydrogen bond network of the water molecules remained practically intact.
In needleless electrospinning, the external field destabilizes the surface of the liquid. It gives rise to
the formation of a Taylor cone which ultimately looses stability and an eruption of a jet is observed; these
stages are schematically shown in figure 2. The photograph in figure 1 (B) depicts the experimental obser-
vation of jetting. After flying through a short linear section, the jet undergoes the so-called whipping stage
and the resulting fiber is then collected at the other electrode. With the exception of a recent paper [15],
we are not aware of any other atomistic simulation study dealing directly with the above described pro-
cess. Other available simulations related to this process focus on the structure formation of polymer
Figure 2. Schematic representation of the formation of the jet: (A) the initial flat surface; (B) formation of
the cone; and (C) eruption of the jet.
13602-2
Fluid surfaces in external field
chains [16], the effect of solvent on the produced nanofibers [17], and on spraying ionic liquids [18].
In a recent paper [15] wemade the first attempt to apply molecular simulations to the electrospinning
process to examine (i) to what extent simulation can be applied to such a dynamic process and (ii) what
results it can provide. We used three different methodologies, all of which yielded qualitatively the same
results. We have continued in this research in which, in addition to the qualitative pictures, the gain of
also some quantitative characterizations has been attempted and the obtained results are reported in
this paper. We consider both the solution of sodium chloride and a model polymer solution, specifically
the solution of polyethylene glycol (PEG). For completeness and comparison, also pure water has been
included in this study. In the next section we provide the main technical details of the simulations, and in
section 3 we present the obtained results. These include the stability analysis in the dependence on the
strength of the field, an analysis of the orientational arrangement of the water molecule dipoles and the
effect of the presence of ions thereupon in dependence on the electrolyte concentration, changes in the
polymer conformation during the process, and relevant kinetic properties.
2. Methodology
For molecular dynamics simulations reported in this paper, we used the GROMACS package (versions
4.5 and 4.6) [19]. A leap-frog integrator with time steps ranging from 1 to 2 fs was employed and the
particle-mesh Ewald method [20] with cubic interpolation and tinfoil boundary conditions were used to
treat electrostatic forces whenever periodic boundary conditions were applied. The technical parameters
of the Ewald summation (cutoff, rc, separation parameter, α, grid spacing, etc.) were being adjusted for
different setups individually to optimize computational cost while maintaining reasonable accuracy. The
relative strength of the direct potential at the cutoff (GROMACS ewald-rtol parameter), i.e., erfc(αrc),
was always set to the value 10−5.
To keep contact with the previous study [15], for simulations with pure water and sodium chloride
solutions, we used the TIP3P water model [21] and the associated Joung and Cheatham [22] ionic force
fields. The solution of polyethylene glycol (PEG) was modelled by the GROMOS 53A6OXY+D [23] force field
with SPC water.
In order to approach the proper scale of the investigated processes as closely as possible, and to make
simultaneously the simulation feasible using the available computing facilities, the number of molecules
in the simulations ranged from 3400 up to 55000. In simulations with polymer, two 10.5 kDa PEG chains
of the formula HO–[–CH2–CH2–O–]n–H, n = 239, were placed into the simulation box along with water
and ions.
The supporting square underlay in the simulations without periodic boundary conditions was real-
ized by a square grid of Lennard-Jones (LJ) atoms with fixed positions. The spacing between neighbours
in the grid was 0.14142 nm. The contact angle depends on the mutual interaction between the droplet
molecules and the underlay. We fixed, therefore, the parameters to the values corresponding to a weakly
hydrophobic material to provide a sufficiently firm attachment while preventing the undesired spread-
ing of liquid over the underlay surface. Furthermore, in order to prevent the droplet from moving over
the edge of the underlay, a repulsive rim made of sites with the ∼ r
−12 repulsive potential was added.
The parameters of the LJ potential C12r
−12
−C6r
−6 were, respectively, C12 = 1.234×10−6 kJmol−1 nm12
and C6 = 5.852×10−4 kJmol−1 nm6 for the underlay, and C12 = 4.937×10−6 kJmol−1 nm12 for the rim.
For the interaction of the underlay with the liquid, geometric mean combining rules were applied to both
constants (GROMOS default).
The intensity of the applied electric field varied within the range from 0.01 to 2 Vnm−1. The use of a
field of such strength is consistent with simulation studies on water reported in the literature [14, 24, 25].
In real electrospinning experiments, the applied voltage is, typically, between 10 and 30 kV. The exact
strength around the apex of the Taylor cone depends on the electrode separation and the geometry of
the apex. A rough estimate gives values between 1 and 100 Vnm−1 which also provides support for the
strength of the field used in the simulations.
Before the field was applied, all systems were preequilibrated in an NV T ensemble at 298.15 K using
the stochastic velocity rescaling method of Bussi et al. [26] with correlation time 0.1 ps. In simulations
involving jet formation, no thermostat was in use after the field had been turned on, while in bridge
13602-3
I. Nezbeda et al.
stability studies, a thermostat was applied during the entire simulation. Ions were excluded from velocity
scaling to avoid interference with their drift.
3. Results and discussion
A typical development of the jet observed in simulations with dilute solutions of NaCl is shown in fig-
ure 3. Qualitatively the same behavior was also observed for pure water. Without the external field, the
solution remains on the underlay in the form of a droplet, figure 3 (A). When the homogeneous external
field in the direction perpendicular to the underlay is switched on, the droplet gradually develops into a
cone, figure 3 (B), and then it forms a pillar resembling a jet in electrospinning. Apart from a small num-
ber of individual water molecules belonging to its vapor phase, the jet remained continuous. It means
that no molecular clusters broken off the jet (which is typical of electrospraying) were observed. Since
the results obtained for pure water and a dilute electrolyte were qualitatively the same, one can deduce
that ions, i.e., charge bearing particles, are not the driving force behind the origin of jetting. One can thus
speculate that the building blocks of the jet are the dipoles (either permanent or induced) of molecules.
That the dipoles do form a chain aligned along the external field has been confirmed and this is demon-
strated below. Nonetheless, the internal structure of pure water may be more complex because even at a
strong external field the hydrogen bonding network remains intact despite the alignment of a dipole as
shown by Cramer et al. [14].
In figure 4 we show the same sequence as above in the case of a more concentrated solution. At
the beginning, the droplet follows the same evolution pattern as discussed above but at a later instant,
instead of the development into a stable jet, small clusters formed by a central ion (hydrated ion) leave
the bulk structure and accelerate away along the field lines of the external field. Although reality may
be more complex, it is evident that the ions do disturb the structure observed in the case of pure fluids.
The interaction between the ions and water molecules (hydration) may overcome the effects of external
field on water (polarization). This intuitive deduction is confirmed in figure 5. The strong polarization
of water molecules and their alignment along the field in the jet is demonstrated in panel (A). Panel (B)
reveals that the ion Na+ makes the water molecules in its vicinity reorient with their oxygen atom to
Figure 3. (Color online) Snapshots showing the development of the jet (column structure) from a dilute
solution of NaCl: (A) the initial droplet on an underlay; (B) transformation of the droplet into a cone
structure; (C) establishing of the jet. The strength of the external electric field was 1.5 Vnm−1 and the
droplet contained 18 NaCl ion pairs and 5954 molecules of water; snapshots (B) and (C) were taken, resp.,
27 ps and 49 ps after the external electric field was switched on.
13602-4
Fluid surfaces in external field
Figure 4. (Color online) Snapshots showing the development of the jet (column structure) and its disrup-
tion from the concentrated solution of NaCl: (A) the initial droplet on an underlay; (B) transformation
of the droplet into a cone structure; (C) disrupted jet with a hydrated ion cluster leaving the jet. The
strength of the external electric field was 1.5 Vnm−1 and the droplet contained 36 NaCl ion pairs and
5954 molecules of water; snapshots (B) and (C) were taken, resp., 30 ps and 34 ps after the external elec-
tric field was switched on. The small droplet torn off the jet (C) contained 13 molecules of water and one
Na+ ion.
be closer to it. Similarly, the Cl− ion has the same effect with the difference that now it is the hydrogen
atomwhich is pulled closer to the ion (C). This reorientation of water molecules disturbs thus the original
alignment of the water dipoles which in the case of sufficiently high concentration leads to disintegration
of the column-like structure and spraying or collapse of the bridge.
In our feasibility study [15] we considered only pure water and electrolyte solutions. In real electro-
spinning, it is polymer which in the end forms the nanofiber. Another step towards real electrospinning
must also involve polymer molecules; we have also performed, therefore, simulations on a polymer solu-
tion. It is known that the majority of simulations with polymer solutions are carried out either on lattice
or considering the solvent only implicitly. This is not suitable for studying the molecular nature of the
electrospinning process and there are two questions to be answered: (i) whether a picture of the pro-
Figure 5. (Color online) Snapshots showing the orientation of the water molecules in the jet: (A) in the ion-
free region; (B) around Na+ cation; (C) around Cl− anion. The strength of the external electric field was
1.5 Vnm−1. In order to highlight the molecules around the ions, water molecules whose oxygen-to-ion
distances were greater than 0.3 nm (B) and 0.4 nm (C) are rendered in transparent colors.
13602-5
I. Nezbeda et al.
Figure 6. (Color online) Snapshots showing the development of the jet from the solution of polyethylene
glycol and NaCl in water: (A) the initial droplet on an underlay; (B) transformation of the droplet into
a cone structure; (C) establishing of the jet. The strength of the external electric field was 1.5 Vnm−1;
the droplet contained 2 chains of polyethylene glycol, 18 NaCl ion pairs, and 5954 molecules of water;
snapshots (B) and (C) were taken, resp., 25 ps and 50 ps after the external electric field was switched on.
In order to expose the polymer conformation, the same configurations are shown in the inserts where
the water molecules are not displayed.
cess can be obtained within a reasonable CPU time using explicit solvent and (ii) how large the polymer
molecule should be to make simulations feasible and yet realistic. In figure 6 we show jet development
from the polymer solution which does not differ much from the scenarios discussed above. The poly-
mer molecule changes its conformation along with deformation of the droplet, figure 6 (B). The polymer
chain uncoils when it is forced to enter the jet, figure 6 (C). A detailed investigation of the changes of
the polymer conformations in dependence on the polymer composition, its structure, the strength of the
field, electrolyte concentration, etc., is beyond the scope of this study and deserves an independent inves-
tigation. Nonetheless, the presented results show that such a study with polymer solution is nowadays
feasible.
In figure 7 we show the results on the dynamics of the onset of jetting: the average mass flow (MF) in
its dependence on the distance from the axis running through the jet’s center-of-mass and parallel to the
external field and also on the distance from the underlay. As it is seen, (A), deep in the bulk solution and
far from the bottom of the jet, the effect of the external field on MFz is negligible. However, as soon as
the solution enters the region of the jet, it sharply accelerates in the direction of the field. In figure 7 (B)
we show the motion of the solution in the direction towards the jet’s axis. Despite a large statistical noise,
we see that on the surface of the solution in the vicinity of the base of the jet there is a region where the
solution is more strongly drawn into the jet. We may thus gather that a relatively large part of the jet
mass originates from the surface layer around the jet.
All results commented on above correspond to situations where the external electric field is strong
enough to initiate transformation of the liquid surface into a jet. If the field was suddenlyweakened under
the jetting threshold at any instant during the simulation, the jet would eventually vanish. However, one
can use quite a different setup, where we anchor a liquid pillar on both ends, forming a liquid bridge. In
contrast to a jet, being a dynamical phenomenon, the bridge can exhibit a thermodynamic (meta)stability
(in the absence of drifting ions) and can exist under much a weaker field than that needed for its build-up
from the liquid surface. An illustration of this phenomenon is given in figure 8 showing snapshots from
the simulation of the NaCl aqueous solution, which initially forms a column continuous in the z-direction,
13602-6
Fluid surfaces in external field
Figure 7. (Color online) Average mass flow (MF) in the jet erupted from a flat layer of pure water at the ex-
ternal field of 2 Vnm−1. The profile is shown as a function of the squared distance r
2 from the axis of the
jet and the distance z from the supporting underlay: (A) flow in the direction along the external electric
field; (B) flow in the direction towards the axis of the jet. The axis of the jet is considered parallel with the
external electric field and going through the center of mass of the jet. The mass flow was averaged over
the interval of 10 ps and it was expressed as a relative value in arbitrary units (the same in both panels).
i.e., in the direction of the applied field, through periodic boundary conditions, see panel (A). This setup
elegantly avoids attaching the ends of the bridge to a particular material by simulating only the middle
portion of the bridge self-anchored by its periodic images. The bridge was originally formed from a liquid
slab by a strong field perpendicular to the liquid surface, in a way similar to all the above-described
simulations. Subsequently, a column was subjected to a series of weakened fields, while the stability of
the structure, i.e., whether a column remains continuous or breaks, was assessed. When the field was
weak enough, increasingly prominent bulging appeared along the column, see figure 8 (B), resulting in
Figure 8. (Color online) Sequence of snapshots showing the disintegration of a cylindrical nanobridge of
aqueous solution of NaCl: (A) the established water nanobridge at the external field of 2 Vnm−1; (B) its
gradual deformation at 0.1 Vnm−1; (C) its final collapse into a droplet. The solution contained 64 ion pairs
and 6784 water molecules; snapshots (B) and (C) were taken, resp., 750 ps and 900 ps after the external
electric field was switched on.
13602-7
I. Nezbeda et al.
Figure 9. Dependence of the electric field strength necessary for a stable bridge of aqueous NaCl solution
to be formed on its concentration. All the initial bridges were 4 nm in diameter. Circles denote the stable
bridge and crosses mark its breakup.
the ultimate disintegration of the continuous liquid column into droplets, see panel (C).
Figure 9 maps the stability of the established bridge with respect to the strength of the field and the
electrolyte concentration. In accord with the above-given explanation of the effect of ions on the jet sta-
bility (discussion pertaining to figure 4), one can see that as concentration increases, the critical intensity
of the electric field needed to maintain a stable bridge also increases. It is to be expected that this behav-
ior also depends on the dimensions of the bridge; however, this was not investigated within the present
study. All the bridges used in the stability assessment had diameters around 4 nm. The resulting field in-
tensities are substantially larger than those usually applied in experiments with the FWB of macroscopic
scales. One can thus expect that the critical field strength will decrease with increasing bridge diameter.
However, a proper molecular study of this trend will require further extensive simulations.
4. Conclusions
Our study has shown that it is possible to model complex field-induced processes at liquid surfaces,
such as the formation of the electrospinning jet or the collapse of the water bridge, at the atomistic level
bymolecular simulation. We have shown how such simulations can be performed and have given several
examples of the microscopic phenomena which are experimentally inaccessible whilst being important
for proper understanding of the behavior of aqueous solutions in electric fields. In contrast to intuitive
views on the mechanism of the origin of jetting and bridging phenomena, our simulations show that
the essential building blocks of the liquid column are the water molecules, and that this is qualitatively
independent of the presence of ions in solutions. The ions, such as Na+ and Cl−, destabilize both the
growing jet and the water bridge. The primarymechanism leading to the destabilization is the disruption
of thewater orientational polarization in the ions’ vicinity. The stability thus decreases with growing ionic
concentration. As regards the dynamics of jetting, the simulations indicate that the particles are drawn
into the jet preferentially from the liquid surface near the base of the jet and subsequently accelerate in
the direction of the field. Each of the above conclusions, however, provokes new questions, which can be
reliably answered only after further extensive simulations are performed as well as thorough analysis.
13602-8
Fluid surfaces in external field
Acknowledgement
This work was supported by the Czech Science Foundation (Grant No. P208/12/0105). Access to com-
puting facilities provided under the program ‘Projects of Large Infrastructure for Research, Development,
and Innovations’ (LM2010005) is appreciated. The authors also would like to thank Professor Ronald
G. Larson (University of Michigan) and the members of his group, especially Mr. Kyle Huston, for provid-
ing the parameter files for the PEG force field.
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I. Nezbeda et al.
Застосування молекулярного моделювання: погляд на
явища формування рiдинних мiсткiв i струменiв
I. Незбеда1,2, Ї. Їрсак1, Ф. Моучка1, У.Р. Смiт3
1 Факультет природничих наук, Унiверситет Я.Е. Пуркiне, Устi над Лабом, Чеська республiка
2 Iнститут фундаментальних основ хiмiчних процесiв, Академiя наук, Прага, Чеська республiка
3 Факультет математики i статистики, Унiверситет Гуелфа, Гуелф, Канада
Методом молекулярної динамiки виконано моделювання чистої води, водного розчину хлориду натрiю
i полiмерних розчинiв, що пiддавалися дiї сильних зовнiшнiх електричних полiв з метою отримання мо-
лекулярних характеристик структурного вiдгуку на дiю цих полiв. Щоб встановити молекулярнi проце-
си, якi ведуть до формування рiдинних мiсткiв i струменiв (при виробництвi нановолокон), використано
декiлька методологiй моделювання. Встановлено, що у структурах усталеного наномасштабу, молекули
утворюють ланцюжок з дипольними моментами, орiєнтованими паралельно до прикладеного поля по
всьому об’єму зразка. Присутнiсть iонiв може внести збурення в цю структуру, що приведе до її повної
дезiнтеграцiї на краплини; встановлено залежнiсть порогового поля, необхiдного для стабiлiзацiї стовпця
рiдини, вiд концентрацiї. Окрiм цього, спостерiгались конформацiйнi змiни полiмера в процесi формува-
ння струменя.
Ключовi слова: електрообертання, мiсток плаваючої рiдини, рiдини у полi, поверхнi водного розчину,
полiмерний розчин, молекулярна динамiка
13602-10
Introduction
Methodology
Results and discussion
Conclusions
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