Interfacial Crystals Research Articles

Non-Classical Euler Buckling and Brazier Instability in Cylindrical Liquid Droplets.

Crystalline monolayers prevalent in nature and technology possess elusive elastic properties with important implications in fundamental physics, biology, and nanotechnology. Leveraging the recently discovered shape transitions of oil-in-water emulsion droplets, upon which these droplets adopt cylindrical shapes and elongate, we investigate the elastic characteristics of the crystalline monolayers covering their interfaces. To unravel the conditions governing Euler buckling and Brazier kink formation in these cylindrical tubular interfacial crystals, we strain the elongating cylindrical droplets within confining microfluidic wells. Our experiments unveil a nonclassical relation between the Young's modulus and the bending modulus of these crystals. Intriguingly, this relation varies with the radius of the cylindrical crystal, presenting a nonclassical mechanism for tuning of elasticity in nanotechnology applications.

Different hydrophilic polyglycerol fatty acid esters interact with fat crystals and proteins at the interface to co-stabilize highly unsaturated whipped emulsions

This study investigates the impact of different hydrophilic polyglycerol fatty acid esters (SWA-10D, M-7D and M-10D) on the stability of aerated emulsions containing palm oil stearin (solid fat content of 6% w/w) under varying pressures. The study encompasses a comparative analysis of the microstructure of droplets, distribution of fat crystals, and protein at the interface within these distinct emulsions. In addition, the study evaluates the stability of the emulsions after a whipping process. The microstructure of emulsions prepared with M-7D showed discernible evident bright rings that become more pronounced as pressure increased. Furthermore, the droplet size of M-7D emulsion was consistently smaller in comparison to M-10D and SWA-10D emulsions at different pressure levels. The M-7D emulsion exhibited a higher nucleation rate, featuring a greater count of crystal nuclei at the interface. Simultaneously, the interfacial protein content in the M-7D emulsion was lower compared to the other samples, diminishing from 2.5 mg/mL to 0.6 mg/mL as pressure increased. Consequently, the interface accommodated a higher concentration of interfacial fat crystals, while the protein content decreased, resulting in increased partial coalescence. This phenomenon, in turn, promoted the formation of a sharp rosette-shaped aerated structure, leading to a diminutive reduction of less than 10% in height over 6 h. This outcome serves as a clear indicator of the formation of a stable aerated structure.

Isolating the interface of an emulsion using X-ray scattering and tensiometry to understand protein-modulated alkylglyceride crystallisation

HypothesisDairy proteins and mono- and diglycerides (MDG) are often used in unison to tailor the properties of dairy-based emulsions. However, there are significant gaps in our understanding of how proteins affect lipid crystallisation at the oil–water interface. We have used a unique combination of interfacially-sensitive techniques to elucidate the impact of dairy proteins on interfacial MDG crystal formation. ExperimentsThe formation temperature of interfacial MDG crystals was assessed through interfacial tension studies via drop shape analysis. Small and Wide-Angle X-ray Scattering measurements were performed on isolated oil–water interfaces, allowing for in-situ interrogation of MDG crystal structure and concentration at and near the interface. FindingsDairy proteins are seen to reduce the temperature at which MDG crystals form at the oil–water interface. The displacement of proteins upon interfacial crystal formation was also clearly observed in interfacial tension measurements. For the first time, lipid crystals formed at the oil–water interface have been characterised using X-ray scattering. All scattering studies showed no change to the MDG crystal structures at the oil–water interface in the presence of adsorbed proteins. The results demonstrate that informed selection of emulsifier components is critical to controlling interfacial crystallisation with concomitant impact on emulsion stability.

Effects of the Distribution Site of Crystallizable Emulsifiers on the Gastrointestinal Digestion Behavior of Double Emulsions.

Double emulsions (DEs) are promising delivery vehicles for the protective and programmed release of bioactive compounds. Herein, DEs with monoglycerides crystallized at the internal- or external interface or oil phase were fabricated. The results suggested that the crystallization site of monoglycerides exerts a significant role in retarding the structural degradation and lipid digestion of DEs by affecting the available contact area of lipase. At the initial stage of intestinal digestion, compared with noncrystalline DEs (82.1%, 3.7 min), the burst release of internal markers in the internal interface crystallized emulsions was decreased by 42.4% and the lag time of free fatty acid (FFA) release was delayed by 5.8 min in the external interface crystallized emulsions. The structural integrity and digestion kinetics of the external interface crystallized DEs were synchronized with the retention time of the interfacial crystals. Therefore, crystallizable emulsifiers exhibit unique and fine regulatory effects on the digestive properties of emulsions.

Modulation of the spatial distribution of crystallizable emulsifiers in Pickering double emulsions

The unique role of the spatial distribution of crystallizable emulsifiers in regulating the structure and properties of double emulsions has been gradually recognized. Herein, we utilized crystallizable monoglycerides of different carbon chain length (GMS/GMP/GML) to “structuring” the intermediate oil phase of double emulsions during a two-stage emulsification process followed by a cooling treatment. A ternary eigenvector (I, M, E) based on the numerical processing of polarization images was invented to quantitatively characterize the distribution pattern of monoglycerides. Crystallization kinetics analysis and dissipative particle dynamic simulation were then employed to reveal the regulatory mechanism for the site-specific interface distribution behavior. Results suggested that the distribution pattern of monoglycerides could be pricesly tuned as the internal interface-, external interface- or oil-phase dominated one in double emulsions. The surface activity as well as crystallization rates of monoglycerides dominated the interfacial distribution kinetics, and the cooling gradient along the interface region further regulated their interfacial distribution potential. Specificly, shorter crystallization time (t1/2) made GMP molecules rapidly solidified in oil phase, leading to the oil phase domninate crystallization (0, M, 0), whereas, slow crystallization rate rendered GML and GMS with sufficient time to diffuse to the interface, thus forming interfacial crystals ((I, 0, 0) and (0, 0, E)). The sensitivity of GML to cooling gradient along the interface region led to its preferential external interface distribution under cooling treatment. The presented study explored novel strategies that can be used in characterizing and manipulating the distribution pattern of crystallizable emulsifiers in multi-interface emulsion systems.

Structuring of Edible Liquid Oil into Smart Thermo-Triggered Soft Matters for Controlled Bioactive Delivery.

Growing interest is being dedicated to smart soft matters because of their potential in controlling bioactives upon exposure to an appropriate stimulus. Herein, structuring of edible liquid oil into oleogels and emulgels as smart thermo-triggered soft vehicles for controllable release of diverse nutrients was developed. Edible liquid oil was trapped inside the crystal network structure of phytosterols and monoglycerides resulting in bicomponent solidlike oleogels. Subsequently, both water-in-oleogel (W/O) emulgels and glycerol-in-oleogel (G/O) emulgels were further fabricated by spatial distribution of the stabilizing interfacial crystals around dispersed droplets as well as the network crystals in the continuous phase. Rheological measurements showed that the gel strength of the oleogel-based emulgels depends on the fraction of the aqueous phase and is greater than that of corresponding oleogels due to a filler effect of dispersed aqueous droplets within the crystal network, offering an additional strategy to tune the structure and rheology. Comparatively, introducing glycerol endowed a higher gel strength for the oleogel-based emulgels than water, particularly at increased filler loads. In addition, these soft matters exhibited interesting thermoresponsive nature, which exhibit the flexibility for programmed release of coencapsulated bioactive components upon exposure to an appropriate thermal triggered switchable. The resulted smart thermo-triggered soft matters have emerging opportunities for application in functional active ingredient delivery by on-demand strategies.

Interfacial Defects Change the Correlation between Photoluminescence, Ideality Factor, and Open-Circuit Voltage in Perovskite Solar Cells.

The ideality factor (nid ) and photoluminescence (PL) analyses assess charge recombination characteristics in perovskite solar cells (PeSCs). However, their correlations with open-circuit voltage (Voc ) are often found to be complicated depending on the recombination types in the devices. Herein, the correlation of nid , PL characteristics and Voc is elucidated depending on the interfacial crystal quality in triple-cation mixed-halide perovskite, Cs0.05 (MA0.17 FA0.83 )0.95 Pb(I0.83 Br0.17 )3 , deposited on different hole transport layers (HTLs). In the devices with low quality interfacial crystals, Voc increases together with nid , which originates from the light intensity-dependence of majority carrier at the interface. Meanwhile, a negative correlation between Voc and nid is observed for devices with high quality interfacial crystals. The authors discuss the cases that PL enhancement by the improvement of overall crystal quality can fail to correlate with a Voc increase if interfacial crystal quality becomes worse. The study highlights that interfacial crystal quality evaluation can help to understand charge recombination via nid and PL measurements, and more importantly provide information of which defect engineering between at the interface and in the bulk would be more effective for device optimization.

Molecular dynamic simulation of performance of modified BAMO/AMMO copolymers and their effects on mechanical properties of energetic materials

Based on molecular dynamic method, densities, mechanical behavior and mechanical performance of P(BAMO/ AMMO) (Polymer 1) and two novel modified P(BAMO/AMMO) (Polymer 2: containing amino group, Polymer 3: containing nitro group), and their effects on mechanical properties of four energetic materials are investigated, the main results are as follow: Polymer 2 (1.235 g/cm3, 240 ± 5 K) and Polymer 3: 1.281 g/cm3, 181 ± 3 K) possess higher densities and lower glass transition temperatures than Polymer 1 (1.229 g/cm3, 247 ± 4 K). The modification makes Polymer 1 difficult to expand, improves its mechanical properties, but has few effect on its diffusion coefficient at same temperature and state. In addition, three binders are compatible with TNT, HMX and CL-20, and may react with DNTF. All polymers particularly improve rigidity of four energetic materials, and enhance their ductility except Polymer 2 on TNT. The ability of Polymer 2 and Polymer 3 improving rigidity (except Polymer 3 on HMX) and ductility of TNT and HMX is inferior to that of Polymer 1, but it is contrary for CL-20 and DNTF (except Polymer 2 on rigidity of DNTF). Moreover, Polymer 2-based interfacial crystals exhibit higher rigidity than Polymer 3-based interfacial crystals.

Interfacial Crystallization of Diacylglycerols Rich in Medium‐ and Long‐Chain Fatty Acids in Water‐in‐Oil Emulsions

AbstractThe effects of diacylglycerols rich in medium‐ and long‐chain fatty acids (MLCD) on the crystallization of hydrogenated palm oil (HPO) and formation of 10% water‐in‐oil (W/O) emulsion are studied, and compared with the common surfactants monostearoylglycerol (MSG) and polyglycerol polyricinoleate (PGPR). Polarized light microscopy reveals that emulsions made with MLCD form crystals around dispersed water droplets and promotes HPO crystallization at the oil‐water interface. Similar behavior is also observed in MSG‐stabilized emulsions, but is absent from emulsions made with PGPR. The large deformation yield value of the test W/O emulsion is increased four‐fold versus those stabilized via PGPR due to interfacial crystallization of HPO. However, there are no large differences in droplet size, solid fat content (SFC), thermal behavior or polymorphism to account for these substantial changes, implying that the spatial distribution of the HPO crystals within the crystal network is the driving factor responsible for the observed textural differences. MLCD‐covered water droplets act as active fillers and interact with surrounding fat crystals to enhance the rigidity of emulsion. This study provides new insights regarding the use of MLCD in W/O emulsions as template for interfacial crystallization and the possibility of tailoring their large deformation behavior.Practical Applications: MLCD is applied in preparing W/O emulsion. It is found that MLCD forms unique interfacial Pickering crystals around water droplets, which promote the surface‐inactive HPO nucleation at the oil‐water interface. Thus MLCD‐covered water droplets act as active fillers and interact with surrounding fat crystals, which can greatly enhance the rigidity of emulsion. This observation would provide a theoretical reference and practical basis for the application of the MLCD with appreciable nutritional properties in lipid‐rich products such as whipped cream, shortenings margarine, butter and ice cream, so as to substitute hydrogenated oil. MLCD‐stabilized emulsions can also be explored for the development of novel confectionery products, lipsticks, or controlled release matrices.

Controlling βSn grain orientations in electronic interconnects with single-crystal Cobalt substrates

The reliability of electronic solder joints is strongly influenced by βSn grain orientations. Single-crystal Cobalt substrates were used to control βSn nucleation and grain orientations in solder joints. On (0001)Co, (112¯0)Co, (101¯0)Co, and (11¯02)Co, interfacial αCoSn3 crystals that are potent to catalyze βSn nucleation exhibited strong textures with 2–5 symmetric orientations featuring reproducible orientation relationships (ORs) with the Co. Preferred ORs and orientation selections of αCoSn3 were examined by exploring i) thermodynamic stabilities of interfaces represented by interfacial atomic matches and work of adhesion and interfacial energies calculated based on density functional theory (DFT) and ii) crystal growth kinetics indicated by the angle between (100)CoSn3 and the substrate plane. In sharp contrast to the innumerable grain orientations in joints on commonly used substrates, dramatically reduced orientations are attributed to the strongly textured αCoSn3, on which βSn grains nucleated by fixed ORs. On (112¯0)Co, the total number of orientations including twinned grains were reduced to 20. On (101¯0)Co, none of the βSn orientations exhibit the c-axis perpendicular to the substrate (i.e. parallel to the electron flow direction), which should reduce fast diffusion paths across the joint and improve the reliability of solder joints.

Improved Interfacial Crystallization by Synergic Effects of Precursor Solution Stoichiometry and Conjugated Polyelectrolyte Interlayer for High Open-Circuit Voltage of Perovskite Photovoltaic Diodes.

The open-circuit voltage (Voc) of perovskite photovoltaic diodes depends largely on the selection of charge transport layers (CTLs) and surface passivation, which makes it important to understand the physical processes occurring at the interface between the perovskite and a CTL. We provide a direct correlation between Voc and the interfacial characteristics of perovskites tuned through stoichiometry engineering of precursor solutions and surface modification of the underlying poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) layer. Poor quality interfacial perovskite crystals were observed on top of the PEDOT:PSS layer, resulting in strong interfacial recombination and a low Voc. In contrast, the growth of the interfacial perovskite crystals was significantly improved by the synergic effects of varying the precursor solution composition and covering the surface with a pH-neutral conjugated polyelectrolyte, poly[2,6-(4,4-bis(potassium butanylsulfonate)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (CPE-K), which possesses potassium ions as counter ions. The influence of the energy-level alignment at the interface on Voc was also discussed. Our findings highlight that improved perovskite crystallization at the interface can facilitate bulk growth of perovskite grains in the vertical direction and effectively suppress nonradiative surface charge recombination, thus enhancing the short-circuit current and Voc.

Multi-Scale Investigation of Body-Glaze Interface in Ancient Ceramics

Bernard Palissy is a French Renaissance ceramist renowned for his masterpieces called Rustiques Figulines on which dozens of glazes of different chemistries (and thus firing behaviors) coexist harmoniously. This study aims at gathering information on the master procedure -never revealed- by investigating the body-glaze interface region (focusing on iron-colored honey transparent glaze-white body system). Optical and electron microscopies including transmission electron microscopy (TEM) are used to characterize the micro and nanostructure of both archaeological and replicas interfaces elaborated in controlled conditions (firing time, cooling rate, addition of Al in the glazing mixture). Both types of interfaces are comparable: a modified paste area from which are growing a relatively continuous layer of interfacial crystals identified as lead feldspars (K,Ca)PbAl2Si2O8 micro-sized single-crystals incorporating mullite 3Al2O3.2SiO2 nano-sized single-crystals. Modification of the firing parameters and removal of Al from the glazing mixture change essentially the interface extension and the micro-crystals morphology. By comparing archaeological and replica interfaces and considering previous studies, we can now state that Palissy was very likely adding clay (Al) in his frit. Moreover, he was probably working with a firing time of more than 1 h followed by slow cooling in the oven.

Ultrastable Water-in-Oil High Internal Phase Emulsions Featuring Interfacial and Biphasic Network Stabilization.

In this work, we present gel-in-gel water-in-oil (W/O) high internal phase emulsions (HIPEs) that feature high stability by structuring both phases of the emulsion. Compared to significant advances made in oil-in-water (O/W) HIPEs, W/O HIPEs are extremely unstable and difficult to generate without introducing high concentrations of surfactants. Another main challenge is the low viscosity of both water and oil phases which promotes the instability of W/O HIPEs. Here, we demonstrate ultrastable W/O HIPEs that feature biphasic structuring, in which hydrogels are dispersed in oleogels, and self-forming, low-concentration interfacial Pickering crystals provide added stability. These W/O HIPEs exhibit high tolerance toward pH shock and destabilizing environments. In addition, this novel ultrastable gel-in-gel W/O HIPE is sustainable and made solely with natural ingredients without the addition of any synthetic stabilizers. By applying phase structuring within the HIPEs through the addition of various carrageenans and beeswax as structurants, we can increase the emulsion's stability and viscoelastic rheological properties. The performance of these gel-in-gel W/O HIPEs holds promise for a wide range of applications. As a proof of concept, we demonstrated herein the application as a gelled delivery system that enables the co-delivery of hydrophilic and hydrophobic materials at maximized loads, demonstrating high resistance to gastrointestinal pHs and a controlled-release profile.

Fat Crystals Influence Methylcellulose Stabilization of Lipid Emulsions

AbstractOil‐in‐water emulsions stabilized with methylcellulose (MC) varied in stability depending on the composition of the fat phase. When droplets were composed entirely of liquid oil, MC was able to form a continuous, protective film around the droplets. Therefore, when two liquid oil droplets were brought into contact, they underwent extreme shape deformation but did not coalesce, even when excess force was used. Subsequently, interfacial crystals extending into the aqueous phase from palm kernel oil droplets were aimed into an entirely liquid oil droplet. The MC‐coated droplet would deform wherever the crystal contacted; however, the protruding crystals could not penetrate into the liquid oil droplet. Conversely, when the target droplet was composed of a small amount of solid fat that resulted in localized crystalline regions and the interfacial crystals of the second droplet were aimed at this region, they then easily pierced the droplet. This demonstrates that MC is an excellent stabilizer for liquid oil droplets but internal lipid crystals within fat globules can alter MC surface conformation to allow for crystal penetration and arrested coalescence.

Graphene-Induced Oriented Interfacial Microstructures in Single Fiber Polymer Composites.

Interfacial interactions between the polymer and graphene are pivotal in determining the reinforcement efficiency in the graphene-enhanced polymer nanocomposites. Here, we report on the dynamic process of graphene-induced oriented interfacial crystals of isotactic polypropylene (iPP) in the single fiber polymer composites by means of polarized optical microscopy (POM) and scanning electron microscopy (SEM). The graphene fibers are obtained by chemical reduction of graphene oxide fibers, and the latter is produced from the liquid crystalline dispersion of graphene oxide via a wet coagulation route. The lamellar crystals of iPP grow perpendicular to the fiber axis, forming an oriented transcrystalline (TC) interphase surrounding the graphene fiber. Various factors including the diameter of graphene fibers, crystallization temperature, and time are investigated. The dynamic process of polymer transcrystallization surrounding the graphene fiber is studied in the temperature range 124-132 °C. The Lauritzen-Hoffman theory of heterogeneous nucleation is applied to analyze the transcrystallization process, and the fold surface free energy is determined. Study into microstructures demonstrates a cross-hatched lamellar morphology of the TC interphase and the strong interfacial adhesion between the iPP and graphene. Under appropriate conditions, the β-form transcrystals occur whereas the α-form transcrystals are predominant surrounding the graphene fibers.

Forces acting on dielectric colloidal spheres at a water/nonpolar-fluid interface in an external electric field. 1. Uncharged particles

Here, we calculate the electric forces acting on uncharged dielectric colloidal particles, which are attached to the interface between a nonpolar fluid (air, oil) and water, in the presence of an applied uniform external electric field directed normal to the interface. The uncharged particle becomes a source of dipolar electric field because it is polarized by the external field. Our goal is to calculate the normal (electrodipping) force acting on each separate particle, and the force of interaction between two identical particles. An exact analytical solution is obtained by solving the Laplace equation in toroidal coordinates and by separating the variables using the Mehler–Fock integral transform. The results show that the dependence of the normal force on particle contact angle is non-monotonic, with a maximum and a minimum. This force can be directed upward or downward depending on the particle contact angle and dielectric constant. An analytical asymptotic expression is derived for the force of interaction between two floating particles in external field. The magnitude of the latter force depends strongly on the particle contact angle α. At a certain value of α, the leading dipolar term becomes zero, and the interaction force is determined by the short-range octupolar term. Then, the attractive lateral capillary forces and van der Waals forces can overcome the electrostatic repulsion and can induce two-dimensional coagulation of the particles at the interface. The effects of the external electric field could find applications for control of the distances between particles in non-densely packed interfacial colloid crystals used in lithographic masks for the production of antireflective coatings, microlens arrays, etc. The case of charged particles in external field is considered in the second part of this study.

Forces acting on dielectric colloidal spheres at a water/nonpolar fluid interface in an external electric field. 2. Charged particles

Here, we calculate the electric forces acting on charged dielectric colloidal particles, which are attached to the interface between a nonpolar fluid (air and oil) and water in the presence of applied uniform external electric field, E0, directed normal to the interface. Electric charges are present on the particle–nonpolar fluid interface. The solution to the problem represents a superposition of the solutions of two simpler problems: (i) charged particle in the absence of external field and (ii) uncharged particle in the presence of external field. Because the external field can be directed upward or downward, it enhances or opposes the effect of the particle surface charges. As a result, the vertical (electrodipping) force vs. E0 may have a maximum or minimum and can be positive or negative depending on the particle contact angle and dielectric constant. In contrast, the lateral electric force between two identical charged floating particles is always positive (repulsive), but it can vary by many orders of magnitude with E0. This is because at a certain value of E0, the net dipolar moment of the particle becomes zero. Then, the interparticle force is governed by the octupolar moment, which leads to a much weaker and short-range repulsion. In the vicinity of this special value of E0, the interparticle repulsion is very sensitive to the variations in the external field. These effects can be used for a fine control of the lattice spacing in non-densely packed interfacial colloidal crystals of regular hexagonal packing for producing lithographic masks with various applications in nanotechnology.

Wetting and reactive wetting during hot-dip galvanizing of high Mn alloyed steel with Zn–Al–Mg baths

This present study discusses hot-dip galvanizing of a Fe–23%Mn–0.6%C–0.3%Si steel and concentrates on the impact of a Mg addition to the galvanizing bath on wetting and reactive wetting. Steel samples were conventionally annealed (800°C/60s in 5%H2–N2) and hot-dipped in ternary Zn–Al–Mg baths with 0.17–1.2wt.% of Al and 0.8–1.0wt.% of Mg for measuring wetting forces and contact angles. To characterize the impact of Mg on interface formation in more detail other samples were bright annealing (1100°C/60s in 5%H2–N2) or subjected to a oxidation/reduction treatment – so-called pre-oxidation – (600°C/10s in 1.8%O2–N2+800°C/60s in 5%H2–N2) prior to hot-dipping into a Zn–1.5%Al–5.0%Mg bath. The key findings are: adding Mg to the galvanizing bath will improve wetting and reactive wetting of high Mn alloyed steel if the amount of dissolved bath—Al is appropriately set. Furthermore, high-oxygen affine Mg is obviously able to support the dissolution of external oxides on the steel surface during hot-dipping. Morphology of Fe2Al5Znx interfacial crystals will change from globular to plate-shaped if Mg is alloyed to the galvanizing bath. Based on these observations, decreased surface tension of the galvanizing bath and intensified MnO reduction were proposed leading to this improved galvanizability of high Mn alloyed steel when hot-dipping in Zn–Al–Mg ternary baths.

Thermally Induced Gelling of Oil-in-Water Emulsions Comprising Partially Crystallized Droplets: The Impact of Interfacial Crystals

We produced triglyceride-in-water emulsions comprising partially crystallized droplets, stabilized by a mixture of protein and low molecular weight surfactant. The emulsions were emulsified in the melted state of the oil phase and stored at low temperature (4 degrees C) right after fabrication to induce oil crystallization. The systems were then warmed to room temperature for a short period of time and cooled again to 4 degrees C. Owing to this treatment referred to as temperature cycling or "tempering", the initially fluid emulsions turned into hard gels. We followed the bulk rheological properties of the materials during and after tempering. The storage modulus, G', exhibited a dramatic increase when tempering was applied. We showed that the systems evolved following two distinct regimes that depend on the average droplet size and on the surfactant-to-protein molar ratio. Gelling may involve partial coalescence of the droplets, i.e., film rupturing with no further shape relaxation because of the solid nature of the droplets. Alternatively, gelling may occur without film rupturing, and is reminiscent of a jamming transition induced by surface roughness. We discussed the origin of these two mechanisms in terms of the properties (size and protuberance) of the interfacial oil crystals.

Foot-and-Mouth Disease: The Fixed Virus Types

Here, we calculate the electric forces acting on charged dielectric colloidal particles, which are attached to the interface between a nonpolar fluid (air and oil) and water in the presence of applied uniform external electric field, E0, directed normal to the interface. Electric charges are present on the particle–nonpolar fluid interface. The solution to the problem represents a superposition of the solutions of two simpler problems: (i) charged particle in the absence of external field and (ii) uncharged particle in the presence of external field. Because the external field can be directed upward or downward, it enhances or opposes the effect of the particle surface charges. As a result, the vertical (electrodipping) force vs. E0 may have a maximum or minimum and can be positive or negative depending on the particle contact angle and dielectric constant. In contrast, the lateral electric force between two identical charged floating particles is always positive (repulsive), but it can vary by many orders of magnitude with E0. This is because at a certain value of E0, the net dipolar moment of the particle becomes zero. Then, the interparticle force is governed by the octupolar moment, which leads to a much weaker and short-range repulsion. In the vicinity of this special value of E0, the interparticle repulsion is very sensitive to the variations in the external field. These effects can be used for a fine control of the lattice spacing in non-densely packed interfacial colloidal crystals of regular hexagonal packing for producing lithographic masks with various applications in nanotechnology.