Nanometer-scale pores have demonstrated potential for the electrical detection, quantification, and characterization of molecules for biomedical applications and the chemical analysis of polymers. Despite extensive research in the nanopore sensing field, there is a paucity of theoretical models that incorporate the interactions between chemicals (i.e., solute, solvent, analyte, and nanopore). Here, we develop a model that simultaneously describes both the current blockade depth and residence times caused by individual poly(ethylene glycol) (PEG) molecules in a single α-hemolysin ion channel. Modeling polymer-cation binding leads to a description of two significant effects: a reduction in the mobile cation concentration inside the pore and an increase in the affinity between the polymer and the pore. The model was used to estimate the free energy of formation for K+-PEG inside the nanopore (≈-49.7 meV) and the free energy of PEG partitioning into the nanopore (≈0.76 meV per ethylene glycol monomer). The results suggest that rational, physical models for the analysis of analyte-nanopore interactions will develop the full potential of nanopore-based sensing for chemical and biological applications.

https://www.pnas.org/content/pnas/107/27/12080.full.pdf

Theory for polymer analysis using nanopore-based single-molecule mass spectrometry.

Particle image velocimetry (PIV) experiments were conducted to study the coalescence of single drops through planar liquid/liquid interfaces. Sequences of velocity vector fields were obtained with a high-speed video camera and subsequent PIV analysis. Two ambient liquids with different viscosity but similar density were examined resulting in Reynolds numbers based on a surface tension velocity of 10 and 26. Prior to rupture, the drops rested on a thin film of ambient liquid above an underlying interface. After rupture, which was typically off-axis, the free edge of the thin film receded rapidly allowing the drop fluid to sink into the bulk liquid below. Vorticity generated in the collapsing fluid developed into a vortex ring straddling the upper drop surface. The ring core traveled radially inward with a ring-shaped capillary wave effectively pinching the upper drop surface and increasing the drop collapse speed. The inertia of the collapse deflected the interface downward before it rebounded upward. Duri...

Drop coalescence through a liquid/liquid interface

Abstract The coalescence phenomenon of drops in liquid/liquid systems is reviewed with particular focus on its technical relevance and application. Due to the complexity of coalescence, a comprehensive survey of the coalescence process and the numerous influencing factors is given. Subsequently, available experimental techniques with different levels of detail are summarized and compared. These techniques can be divided in simple settling tests for qualitative coalescence behavior investigations and gravity settler design, single-drop coalescence studies at flat interfaces as well as between droplets, and detailed film drainage analysis. To model the coalescence rate in liquid/liquid systems on a technical scale, the generic population balance framework is introduced. Additionally, different coalescence modeling approaches are reviewed with ascending level of detail from empirical correlations to comprehensive film drainage models and detailed computational fluid and particle dynamics.

/pdf/drop-coalescence-in-technical-liquid-liquid-applications-a-1g9yygoy0z.pdf

Drop coalescence in technical liquid/liquid applications: a review on experimental techniques and modeling approaches

Toward comprehensive studies of liquids at high pressures and high temperatures: Combined structure, elastic wave velocity, and viscosity measurements in the Paris–Edinburgh cell

Polymer-modified binders are widely used for pavement construction. Among different polymers used to modify bitumen, polyolefins have shown to impart beneficial effects on the bitumen, especially to prevent some of the pavement shortcomings at high temperatures, such as rutting. The phase separation problems of these polymers from the bitumen may affect the final properties of the pavement. The determination of the polymer phase destabilization mechanism and rate are crucial to defer or delay the polymer separation from the matrix. With this aim, several HDPE-modified binders were manufactured by using a high-shear mixing device. The binders were stored in tubes at temperatures as high as 180°C. During the storage, the unstable polymer phase creamed up to the surface. The destabilization process was followed by means of optical microscopy observations through time, as the separation process proceeded. The segregation of the polymer phase is shown to be preceded by a coalescence mechanism. Enhanced mechanical properties have been obtained by HDPE modification. However, such binders may not be efficient for the pavement application, since phase separation may occur during the application of the binder on the road. Functionalized reactive polymers are envisaged to hinder the separation problems in bituminous binders. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 260–267, 2006

Destabilization mechanism of polyethylene-modified bitumen

The increase in uncertainty throughout the viscosity scale being the principal disadvantage of capillary viscometry, an absolute falling-ball viscometer has been developed, making it possible to cover a wide range of viscosities while keeping a weak uncertainty. The measurement of viscosity of a liquid then rests on the terminal velocity measurement of a falling ball, corrected by the principal identified effects (edge effects, inertial effects, etc.). An experimental bench was developed in order to reach a relative uncertainty of the order of 10−3 to the measure of viscosity. The bench, by the use of a linear camera, allows us to observe the trajectory and to obtain the variations in velocity of the ball inside a cylindrical tube filled with liquid whose viscosity is to be measured.

/pdf/design-of-a-high-precision-falling-ball-viscometer-1pinw8973u.pdf

Design of a high precision falling-ball viscometer

The study of coalescence of polymer droplets is presented in the viscosity ratio range (p) going from 0.1 to 10. It is shown that the determination of the characteristic time of coalescence is a good way to estimate the interfacial tension. Polydimethylsiloxane (PDMS) is mixed with polyisobutylene (PIB) and the temperature change provides a way to modify the interfacial tension of the PDMS/PIB system significantly, as measured using a pendant drop apparatus. We obtain a dependence of the reduced coalescence time as a function of p–1/2 which gives access to the interfacial tension. This technique can be an interesting choice for estimating interfacial tension without requiring sophisticated techniques. In a further attempt to correlate these observations with a theoretical model (Verdier C (2001) Polymer 42), the flow field inside and outside the droplets is investigated. PIV measurements are carried out where the evidence of elongational regimes is demonstrated. Such experiments are also interesting for future comparisons with numerical results.

/pdf/understanding-droplet-coalescence-and-its-use-to-estimate-t9fpvssctd.pdf

Understanding droplet coalescence and its use to estimate interfacial tension

To reduce the uncertainties in measurements obtained by means of capillary viscometers, we developed an absolute falling-ball viscometer. The metrological characterization of this experimental bench is presented for a mineral oil with a viscosity of 30 Pa s by means of two distinct methods described in the GUM (Guide to the Expression of Uncertainty in Measurement). First, the calculation is performed using the law of propagation of uncertainties. Then, because of the increasing use of the techniques of propagation of distributions in metrology, we calculated the measurement uncertainties by a numerical Monte Carlo simulation. Both results were then compared for a confidence interval of 95%. Finally, the viscosity measurements and uncertainties obtained by the falling-ball viscometer were compared against those obtained by a capillary viscometer.

/pdf/absolute-falling-ball-viscometer-evaluation-of-measurement-hbek2os0d0.pdf

Absolute falling-ball viscometer: evaluation of measurement uncertainty

L'incertitude sur les constantes des viscosimetres, celle des fluides de references viscosimetriques, augmentent tout le long de l'echelle de viscosite lors de la mise en oeuvre de la methode step up a partir de la viscosite de l'eau a 20 °C. C'est le principal inconvenient de la viscosite capillaire. Pour palier cela, un viscosimetre a chute de bille a ete developpe pour couvrir une large gamme de viscosite avec une faible incertitude. La mesure de viscosite repose alors sur celle de la vitesse limite de chute d'une bille. Un banc experimental a ete developpe afin de pouvoir obtenir une incertitude relative de 10 -3 . Il permet d'observer la trajectoire de la bille a l'interieur d'un tube cylindrique rempli du liquide etudie et d'obtenir l'evolution de la vitesse. La caracterisation metrologique de la premiere partie du viscosimetre (dote de la camera lineaire) est presentee avec les incertitudes obtenues sur la determination de la viscosite dynamique de plusieurs fluides en utilisant la loi de propagation des incertitudes. Les viscosites et les incertitudes associees, obtenues avec le viscosimetre a chute de bille, sont confrontees a celles obtenues avec la viscosite capillaire.

Un viscosimètre absolu pour la mesure de la viscosité des fluides

L'incertitude sur les constantes des viscosimetres, celle des fluides de references viscosimetriques, augmentent tout le long de l'echelle de viscosite lors de la mise en oeuvre de la methode step up a partir de la viscosite de l'eau a 20 °C. C'est le principal inconvenient de la viscosite capillaire. Pour palier cela, un viscosimetre a chute de bille a ete developpe pour couvrir une large gamme de viscosite avec une faible incertitude. La mesure de viscosite repose alors sur celle de la vitesse limite de chute d'une bille. Un banc experimental a ete developpe afin de pouvoir obtenir une incertitude relative de 10–3. Il permet d'observer la trajectoire de la bille a l'interieur d'un tube cylindrique rempli du liquide etudie et d'obtenir l'evolution de la vitesse. La caracterisation metrologique de la premiere partie du viscosimetre (dote de la camera lineaire) est presentee avec les incertitudes obtenues sur la determination de la viscosite dynamique de plusieurs fluides en utilisant la loi de propagation des incertitudes. Les viscosites et les incertitudes associees, obtenues avec le viscosimetre a chute de bille, sont confrontees a celles obtenues avec la viscosite capillaire.

https://hal.archives-ouvertes.fr/hal-00202020/document

Matthieu Brizard

Papers

Design of a high precision falling-ball viscometer

Understanding droplet coalescence and its use to estimate interfacial tension

Absolute falling-ball viscometer: evaluation of measurement uncertainty

Un viscosimètre absolu pour la mesure de la viscosité des fluides

Un viscosimètre absolu pour la mesure de la viscosité des fluides (Absolute falling-ball viscometer for the viscosity measurement of liquids).