Continuous and discontinuous transitions between two types of capillary bridges on a beaded chain pulled out from a liquid.

Capillary bridges can be used for fabricating new materials and structures. Here, we describe theoretically and validate experimentally the mechanism of formation of capillary bridges during a process in which a beaded chain is being pulled out from a liquid with a planar surface. There are two types of capillary bridges present in this system, namely the sphere-planar liquid surface bridge initially formed between the spherical bead leaving the liquid bath and the initially planar liquid surface, and the sphere-sphere capillary bridge formed between neighbouring beads in the part of the chain above the liquid surface.

Formation of printable granular and colloidal chains through capillary effects and dielectrophoresis.

One-dimensional conductive particle assembly holds promise for a variety of practical applications, in particular for a new generation of electronic devices. However, synthesis of such chains with programmable shapes outside a liquid environment has proven difficult. Here we report a route to simply 'pull' flexible granular and colloidal chains out of a dispersion by combining field-directed assembly and capillary effects.

Nano-liter droplet libraries from a pipette: step emulsificator that stabilizes droplet volume against variation in flow rate.

Many modern analytical assays, for example, droplet digital PCR, or screening of the properties of single cells or single mutated genes require splitting a liquid sample into a number of small (typically ca. nano-liter in volume) independent compartments or droplets. This calls for a method that would allow splitting small (microliter) samples of liquid into libraries of nano-liter droplets without any dead volume or waste.

The influence of van der Waals forces on droplet morphological transitions and solvation forces in nanochannels.

The morphological phase transition between sessile and lenticular shapes of a droplet placed in a nanochannel is observed upon increasing the droplet volume. The phase diagram for this system is discussed within both macroscopic and mesoscopic approaches. On the mesoscopic level, the van der Waals forces are taken into account via the effective interface potential acting between the channel walls and the droplet.

Curvature of capillary bridges as a competition between wetting and confinement.

We consider the shape evolution of non-axisymmetric capillary bridges in slit pore geometry as the pore height is increased at constant volume. Experiments and finite element simulations using Surface Evolver have shown that as the height of the pore is increased the mean curvature of the bridge, and hence Laplace pressure, changes its sign from negative to positive. Here we propose an intuitive explanation of this surprising phenomenon.

Mesoscopic analysis of Gibbs' criterion for sessile nanodroplets on trapezoidal substrates.

By taking into account precursor films accompanying nanodroplets on trapezoidal substrates we show that on a mesoscopic level of description one does not observe the phenomenon of liquid-gas-substrate contact line pinning at substrate edges. This phenomenon is present in a macroscopic description and leads to non-unique contact angles which can take values within a range determined by the so-called Gibbs' criterion. Upon increasing the volume of the nanodroplet the apparent contact angle evaluated within the mesoscopic approach changes continuously between two limiting values fulfilling Gibbs' criterion, while the contact line moves smoothly across the edge of the trapezoidal substrate.

Communication: The influence of line tension on the formation of liquid bridges.

The formation of liquid bridges between planar and conical substrates is analyzed macroscopically taking into account the line tension. Depending on the value of the line tension coefficient tau and geometric parameters of the system one observes two different scenarios of liquid bridge formation upon changing the fluid state along the bulk liquid-vapor coexistence. For tau > tau* (tau* < 0) there is a first-order transition to a state with infinitely thick liquid bridge.

Effective Hamiltonian for fluid membranes in the presence of long-ranged forces.

If the constituent particles of fluid phases interact via long-ranged van der Waals forces, the effective Hamiltonian for interfaces between such fluid phases contains--in lateral Fourier space--nonanalytic terms approximately q4ln q. Similar nonanalytic terms characterize the effective Hamiltonian for two interacting interfaces which can emerge between the three possible coexisting fluid phases in binary liquid mixtures. This is in contrast with the structure of the phenomenological Helfrich Hamiltonian for membranes, which does not contain such nonanalytic terms.

Formation of capillary bridges in two-dimensional atomic force microscope-like geometry.

We discuss the phase diagram of a fluid confined in a two-dimensional atomic force microscope-like geometry which allows the formation of liquid bridges connecting the opposite walls. The corresponding phase behavior of the fluid is influenced by the phenomenon of complete filling of a wedge.

Selectivity and sensitivity of some thin-layer chromatographic detection systems.

The selectivity and sensitivity of some thin-layer chromatographic detection systems widely used internationally and developed in our laboratory were studied. Halogenated organophosphorus pesticides were found to interfere with the detection of organochlorine pesticides when using silver nitrate-2-phenoxyethanol. The stability of colours formed by the 4-(4'-nitrobenzyl)pyridine-tetraethylenepentamine system was enhanced by spraying with acetic acid and allowed densitometric evaluation.

Surgical aspects of regional myocardial blood flow and myocardial pressure.

The surgical technique of cardiopulmonary bypass with either an empty beating or an empty fibrillating ventricle produces marked changes in the regional blood flow and oxygen demand of the left ventricle. This paper describes the changes which occurred in the regional perfusion of both the normal and the hypertrophied left ventricle during these conditions and relates them to the known changes in oxygen demand. It also correlates the changes in flow with the measurable changes in myocardial tissue pressure-systolic when the heart is beating and continuous when fibrillating.