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The in-plane packing of gold (Au), polystyrene (PS), and silica (SiO2) spherical nanoparticle (NP) mixtures at a water-oil interface is investigated in situ by UV-vis reflection spectroscopy. All NPs are functionalized with carboxylic acid such that they strongly interact with amine-functionalized ligands dissolved in an immiscible oil phase at the fluid interface. This interaction markedly increases the binding energy of these nanoparticle surfactants (NPSs). The separation distance between the Au NPSs and Au surface coverage are measured by the maximum plasmonic wavelength (λmax) and integrated intensities as the assemblies saturate for different concentrations of non-plasmonic (PS/SiO2) NPs. As the PS/SiO2 content increases, the time to reach intimate Au NP contact also increases, resulting from their hindered mobility. λmax changes within the first few minutes of adsorption due to weak attractive inter-NP forces. Additionally, a sharper peak in the reflection spectrum at NP saturation reveals tighter Au NP packing for assemblies with intermediate non-plasmonic NP content. Grazing incidence small angle X-ray scattering (GISAXS) and scanning electron microscopy (SEM) measurements confirm a decrease in Au NP domain size for mixtures with larger non-plasmonic NP content. The results demonstrate a simple means to probe interfacial phase separation behavior using in situ spectroscopy as interfacial structures densify into jammed, phase-separated NP films.

Near total reflection regime has been widely used in x-ray science, specifically in grazing incidence small angle x-ray scattering and in hard x-ray photoelectron spectroscopy (XPS). In this work, we introduce some practical aspects of using near total reflection (NTR) in ambient pressure XPS and apply this technique to study chemical concentration gradients in a substrate/photoresist system. Experimental data are accompanied by x-ray optical and photoemission simulations to quantitatively probe the photoresist and the interface with the depth accuracy of ∼1 nm. Together, our calculations and experiments confirm that NTR XPS is a suitable method to extract information from buried interfaces with highest depth-resolution, which can help address open research questions regarding our understanding of concentration profiles, electrical gradients, and charge transfer phenomena at such interfaces. The presented methodology is especially attractive for solid/liquid interface studies, since it provides all the strengths of a Bragg-reflection standing-wave spectroscopy without the need of an artificial multilayer mirror serving as a standing wave generator, thus dramatically simplifying the sample synthesis.

When surface-active molecules or particles assemble at fluid–fluid interfaces, these interfaces acquire complex rheological properties that are of importance in processes that involve flow and deformation of interfaces. Although much progress has been made, interfacial rheology measurements and, in particular, the measurement of interfacial rheological properties of polymers at the air-water interface remain challenging. These are due to weak interactions with the water subphase, the polymer backbone conformation, the glass transition of the interfacial layer, and memory effects. In the present work, we describe systematic rheological measurements of polymer-laden interfaces. The measurements were performed with four different interfacial shear rheometers that can be classified into two types: rheometers in which the surface pressure can be controlled independently, and devices based on fixtures mounted on standard rotational rheometers and lacking control of the surface pressure. We use poly(tert-butyl methacrylate) and poly(methyl methacrylate), two high glass transition temperature, hydrophobic polymers anchored to the water subphase by means of the acrylate group. Using a Langmuir–Pockels (LP) trough, we identify the transition of the polymer monolayer from a viscous to a solid elastic or soft-glassy interface as the polymer surface concentration increases by compression. Then, we compare the linear viscoelastic properties of the interface as obtained by each rheometer. Our results show poor reproducibility and comparability of the rheological data as obtained by different rheometers for the same polymer. This is mainly due to differences in the method used to prepare the layers. For LP-based devices, spreading under dilute conditions and subsequent compression yields layers of compressed glassy blobs with reproducible results. On the other hand, for devices without surface pressure control, deposition of the amount needed to reach a desired concentration may lead to the formation of ill-defined layers resulting in irreproducible data. Furthermore, we find that only when spreading the polymer to form a dilute layer and then controlling the surface pressure by compression, we can clearly distinguish the fluidlike from solidlike interfaces, and a clear correlation is observed between the surface pressure (or interfacial polymer concentration) and the rheological properties of the interface. [ABSTRACT FROM AUTHOR]

When surface-active molecules or particles assemble at fluid–fluid interfaces, these interfaces acquire complex rheological properties that are of importance in processes that involve flow and deformation of interfaces. Although much progress has been made, interfacial rheology measurements and, in particular, the measurement of interfacial rheological properties of polymers at the air-water interface remain challenging. These are due to weak interactions with the water subphase, the polymer backbone conformation, the glass transition of the interfacial layer, and memory effects. In the present work, we describe systematic rheological measurements of polymer-laden interfaces. The measurements were performed with four different interfacial shear rheometers that can be classified into two types: rheometers in which the surface pressure can be controlled independently, and devices based on fixtures mounted on standard rotational rheometers and lacking control of the surface pressure. We use poly(tert-butyl methacrylate) and poly(methyl methacrylate), two high glass transition temperature, hydrophobic polymers anchored to the water subphase by means of the acrylate group. Using a Langmuir–Pockels (LP) trough, we identify the transition of the polymer monolayer from a viscous to a solid elastic or soft-glassy interface as the polymer surface concentration increases by compression. Then, we compare the linear viscoelastic properties of the interface as obtained by each rheometer. Our results show poor reproducibility and comparability of the rheological data as obtained by different rheometers for the same polymer. This is mainly due to differences in the method used to prepare the layers. For LP-based devices, spreading under dilute conditions and subsequent compression yields layers of compressed glassy blobs with reproducible results. On the other hand, for devices without surface pressure control, deposition of the amount needed to reach a desired concentration may lead to the formation of ill-defined layers resulting in irreproducible data. Furthermore, we find that only when spreading the polymer to form a dilute layer and then controlling the surface pressure by compression, we can clearly distinguish the fluidlike from solidlike interfaces, and a clear correlation is observed between the surface pressure (or interfacial polymer concentration) and the rheological properties of the interface. [ABSTRACT FROM AUTHOR]

[Display omitted] A membrane is a thin layer or sheet at the interface of two material compartments aimed for separation and purification processes. Membranes made using nanofibers, termed as nanomembranes, are preferred at these interfaces to improve the materials and process efficiency because the extreme small size not only lowers the materials requirements but also controls the pore size and distribution. Among the nanofabrication techniques, electrospinning is an industrially viable method of preparing nanomembranes due to its tunable properties as well as affordability. Herein, techniques to modify electrospun nanomembranes (ENMs) for process improvement, such as post-heat treatment, coating, additives, interfacial polymerization, surface chemistry control, pore size and porosity control, hydrophobicity/ hydrophilicity, and flux rejection efficiency at liquid–liquid and solid–liquid interfaces are reviewed. The ENMs in desalination of seawater, textile wastewater remediation, agriculture, biomedical, renewable energy, electrical, and food industries have also been investigated. We also review ENM's potential in liquid gating, which has been cited as one of the top ten emerging technologies. This review also finds areas requiring innovation on ENMs and on the sustainability of the electrospinning technology. Thus, this review provides a one-stop center for various membrane applications at liquid–liquid and solid–liquid interfaces and areas requiring further innovation. [ABSTRACT FROM AUTHOR]

The pair interaction potentials of polymer-grafted silica nanoparticles (NPs) at liquid surfaces were determined by scanning electron microscopy, exploiting the nonvolatility of ionic liquids to stabilize the specimens against microscope vacuum. Even at near contact, individual, two-dimensionally well-dispersed NPs were resolved. The potential of mean force, reduced to the pair interaction potential for dilute NPs, was extracted with good accuracy from the radial distribution function, as both NP diameter and grafted polymer chain length were varied. While NP polydispersity somewhat broadened the core repulsion, the pair potential well-approximated a hard sphere interaction, making these systems suitable for model studies of interfacially bound NPs. For short (5 kDa) poly(ethylene glycol) ligands, a weak (< kB T) long-range attraction was discerned, and for ligands of identical length, pair potentials overlapped for NPs of different diameter; the attraction is suggested to arise from ligand-induced menisci. To understand better the interactions underlying the pair potential, NP surface-binding energies were measured by interfacial tensiometry, and NP contact angles were assessed by atomic force microscopy and transmission electron microscopy.

Densely grafted comb-like macromolecules (bottlebrushes) with alternating solvophobic and solvophilic side chains were studied in a selective solvent and at the liquid interface using mesoscopic computer simulations. The effects of backbone length and copolymer composition were considered. While self-assembly in solution revealed only spherical aggregates for all ar-chitectures studied, adsorption onto the liquid interface in particular cases resulted in morpho-logical changes, with worm-like aggregates or a continuous monolayer observed. In turn, the compression of macromolecules at the interface also leads to morphological transitions, includ-ing the formation of a mesh-like percolated structure. The obtained results may be useful for the preparation of solid nanoparticles of anisotropic shape or nanostructured ultra-thin copolymer films. [ABSTRACT FROM AUTHOR]

This study presents a proof of concept to demonstrate the ability of ultrasounds to perform acoustophoretic processes in hybrid millifluidic resonators that include channels laterally embedded in extremely soft media with physical properties close to those of liquids. In our experiments, particles are driven by acoustic radiation forces toward hydrodynamic/acoustic equilibrium positions in a similar way to that produced in conventional microfluidic resonators with solid structures; 20 um-sized polystyrene beads immersed in deionized water flow channelized throughout an aqueous-based gel between an inlet and outlet in a resonant chamber while being exposed to ultrasounds at a frequency of 1.54 MHz. The liquid channel formed presents irregular walls and variable geometry defined by the sample injection pressure. Particles collect rapidly along a central line equidistant from the walls, regardless of whether they are parallel or not, as observed for different channel geometries and cross-sectional dimensions. Only when the flow stops, the particles collect in acoustic pressure nodes established with the 2D spatial distribution. These results break the paradigm of solid structures as essential physical elements to support acoustophoresis, demonstrating the ability to produce these processes in media without a consolidated structure. It opens a door to bioprinting applications.

The present investigation envisages on the Mathematical modeling of waves propagating in a porous micropolar fibre-reinforced structure in a half-space and liquid interface. The harmonic method of wave analysis is utilized, such that, the reflection and transmission of waves in the media were modelled and it's equations of motion analytically derived. It was deduced that incident longitudinal wave in the solid structure yielded four reflected waves given as; quasi--P wave (qLD), quasi--SV wave, quasi--transverse microrotational (qTM) wave and a wave due to voids and one transmitted wave known as the quasi-longitudinal transmitted (qLT) wave. The phase velocity in the liquid medium is independent of angle of propagation as observed. The corresponding amplitude ratios of propagations for both reflected and transmitted waves are analytically derived by employing Snell's law. The model would prove to be of relevance in the understanding of modeling of the behavior of propagation phenomena of waves in micropolar fibre-reinforecd machination systems resulting in solid/liquid interfaces especially in earth sciences and in particular seismology, amongst others. [ABSTRACT FROM AUTHOR]

The contact angle was used to estimate the rate of evaporation of liquid droplets on bare glass or gold (Au) sputtered glass surfaces. The rate of evaporation of water (a pure liquid) was higher than non-pure liquid composed of a 3 wt% solution of silica nanoparticles (SNP) on these two solid supports. Despite using the same initial drop volume (1 µL) throughout the experiment, the base diameter of the liquid droplet after evaporation on the different surfaces interestingly showed variations. While the liquid–solid interface displayed slip-length and contact angle variations throughout the evaporation time, the slip-length variations were more pronounced with colloidal SNP on Au-sputtered glass surfaces than pure liquid on bare glass surface. Potential application of this study was also investigated in the surface control of uniform silica microwires from colloidal SNP on Au-sputtered glass surface under low temperature conditions. The kinetics of liquid drop evaporation from glass surfaces was evaluated. Differential evaporation rates were compared between Au coated and bare glass surfaces. The contact angle was used to quantify the diameter of the water drop as a measure of evaporation rate. Potential applications in the control of silica-microwires have been discussed. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effects of femtosecond laser‐assisted keratoplasty using a liquid patient interface (L‐PI) as opposed to an applanated interface (A‐PI) on graft quality and functionality markers. Methods: Pressure measurements during femtosecond laser‐assisted trephination were performed using two groups of 10 porcine eyes. Trephination was performed either in an L‐PI or in an A‐PI setting. Pressure sensor needles placed intravitreally continuously recorded intraocular pressure during trephination. Twenty paired human donor eyes were used to test the morphological quality of donor tissue after trephination in L‐PI and A‐PI settings. Optical coherence tomography (OCT) scans were performed before and after trephination. Images were processed using ImageJ and pixel2. Results: During trephination, pressure measurements with an L‐PI were significantly lower than with an A‐PI (p = 0.0121). Mean pressure during trephination was 78.1 mmHg ± 37.6 mmHg with L‐PI and 188.6 mmHg ± 17.7 mmHg with A‐PI. Trephination in A‐PI produced a significantly larger increase (p < 0.00001) in donor pachymetry than trephination in L‐PI. Significantly lower areas of Descemet folds were achieved in L‐PI trephination than in A‐PI trephination (p < 0.01). There was no significant difference in circularity between A‐PI and L‐PI (p = 0.27). Total time required for trephination was comparable between L‐PI and A‐PI (p = 0.45). Time taken to reach working vacuum was achieved significantly more quickly in L‐PI (p < 0.05). Conclusion: Femtosecond laser‐assisted L‐PI keratoplasty appears to be a promising method to decrease stress to donor and recipient tissue during femtosecond laser‐assisted trephination. Results showed favourable donor tissue morphology markers after L‐PI trephination. [ABSTRACT FROM AUTHOR]

[Display omitted] Microgels are soft colloidal particles constituted by cross-linked polymer networks with a high potential for applications. In particular, after adsorption at a fluid interface, interfacial tension provides two-dimensional (2D) confinement for microgel monolayers and drives the reconfiguration of the particles, enabling their deployment in foam and emulsion stabilization and in surface patterning for lithography, sensing and optical materials. However, most studies focus on systems of fluids with a high interfacial tension, e.g. alkanes/ or air/water interfaces, which imparts similar properties to the assembled monolayers. Here, instead, we compare two organic fluid phases, hexane and methyl tert-butyl ether, which have markedly different interfacial tension (γ) values with water and thus tune the deformation of adsorbed microgels. We rationalize how γ controls the single-particle morphology, which consequently modulates the structural and mechanical response of the monolayers at varying interfacial compression. Specifically, when γ is low, the microgels are less deformed within the interface plane and their polymer networks can rearrange more easily upon lateral compression, leading to softer monolayers. Selecting interfaces with different surface energy offers an additional control to customize the 2D assembly of soft particles, from the fine-tuning of particle size and interparticle spacing to the tailoring of mechanical properties. [ABSTRACT FROM AUTHOR]

[Display omitted] Stabilization of water-in-water (W/W) emulsions resulting from the separation of polymeric phases such as dextran (DEX) and poly(ethyleneoxide) (PEO) is highly challenging, because of the very low interfacial tensions between the two phases and because of the interface thickness extending over several nanometers. In the present work, we present a new type of stabilizers, based on bis-hydrophilic, thermoresponsive microgels, incorporating in the same structure poly(N -isopropylacrylamide) (pNIPAM) chains having an affinity for the PEO phase and dextran moieties. We hypothesize that these particles allow better control of the stability of the W/W emulsions. The microgels were synthesized by copolymerizing the NIPAM monomer with a multifunctional methacrylated dextran. They were characterized by dynamic light scattering, zeta potential measurements and nuclear magnetic resonance as a function of temperature. Microgels with different compositions were tested as stabilizers of droplets of the PEO phase dispersed in the DEX phase (P/D) or vice-versa (D/P), at different concentrations and temperatures. Only microgels with the highest DEX content revealed excellent stabilizing properties for the emulsions by adsorbing at the droplet surface, thus demonstrating the fundamental role of bis-hydrophilicity. At room temperature, both pNIPAM and DEX chains were swollen by water and stabilized better D/P emulsions. However, above the volume phase transition temperature (VPTT ≈ 32 °C) of pNIPAM the microgels shrunk and stabilized better P/D emulsions. At all temperatures, excess microgels partitioned more to the PEO phase. The change in structure and interparticle interaction induced by heating can be exploited to control the W/W emulsion stability. [ABSTRACT FROM AUTHOR]

This paper describes an inexpensive, non-invasive and highly adaptable surface reconstruction device for opaque liquids. The instrument was developed to study the lateral sloshing of ferrofluids in microgravity as part of the UNOOSA DropTES 2019 StELIUM project. Its design is driven by the geometrical and mechanical constraints imposed by ZARM's drop tower, where the experiment was launched in November 2019. The launch catapult and deceleration systems impose strong axial g-loads to a system that is confined in the reduced capsule environment. Redundant procedures are implemented to measure the first two lateral sloshing frequencies and damping ratios of the magnetic liquid, as well as its equilibrium surface in microgravity. Ideal vertical resolutions between 0.25 and 0.4 mm/px can be achieved with the configuration here proposed. The final performance depends, among other factors, on the correct application of the robust calibration procedure that is documented in this work. • A simple, inexpensive and adaptable liquid surface reconstruction device is presented. • Laser projections are employed to compute the free surface elevation profile. • The device was developed to study the sloshing of ferrofluids in microgravity. • The meniscus shape and oscillation frequencies are easily measured. [ABSTRACT FROM AUTHOR]

This paper addresses the operation in microgravity of the surface reconstruction device whose design is detailed in the first part of the manuscript. The system, employed during the drop tower campaign of the UNOOSA DropTES 2019 StELIUM experiment, studies the axisymmetric and lateral oscillations of a ferrofluid solution in microgravity. The free liquid surface is reconstructed in a cylindrical tank and relevant metrics of the magnetic sloshing problem, such as contact angles, hysteresis parameters, natural oscillation frequencies, or damping ratios, are derived. The result is a rich and unique database where several phenomena of scientific and technological interest are reported for the first time. The dependence of the fundamental axisymmetric and lateral modal frequencies with the applied magnetic field is consistent with the literature and past experiments. Although the detection system was designed and built using low-cost hardware, high-quality results are obtained. • Microgravity measurements from a novel surface reconstruction device are presented. • The system successfully reconstructs the movement of a free ferrofluid surface. • Relevant metrics of the magnetic sloshing problem are measured for the first time. • Modal shapes and frequencies are identified as a function of the magnetic environment. [ABSTRACT FROM AUTHOR]

In sharp contrast to conventional solid/hydrogel platforms, water-immiscible liquids, such as perfluorocarbons and silicones, allow the adhesion of mammalian cells via protein nanolayers (PNLs) formed at the interface. However, fluorocarbons and silicones, which are typically used for liquid cell culture, possess only narrow ranges of physicochemical parameters and have not allowed for a wide variety of cell culturing environments. In this paper, it is proposed that water-immiscible ionic liquids (ILs) are a new family of liquid substrates with tunable physicochemical properties and high solvation capabilities. Tetraalkylphosphonium-based ILs are identified as non-cytotoxic ILs, whereon human mesenchymal stem cells are successfully cultured. By reducing the cation charge distribution, or ionicity, via alkyl chain elongation, the interface allows cell spreading with matured focal contacts. High-speed atomic force microscopy observations of the PNL formation process suggest that the cation charge distribution significantly altered the protein adsorption dynamics, which are associated with the degree of protein denaturation and the PNL mechanics. Moreover, by exploiting dissolution capability of ILs, an ion-gel cell scaffold is fabricated. This enables to further identify the significant contribution of bulk subphase mechanics to cellular mechanosensing in liquid-based culture scaffolds., (© 2024 Wiley‐VCH GmbH.)

Flow regimes of two immiscible liquids at the cross junction within a rectangular microchannel are experimentally investigated. Characteristics of the flow regimes including critical conditions and interfacial deformations are presented. It is found that the occurrence of the tubing regime is favored by increased viscosity of the dispersed phase or reduced cross-sectional aspect ratio, leading to the shrinkage of the flow rate range that could produce droplets. In order to reveal the physical mechanism, the force analysis is carried out based on the tunnel structure formed between the interface and channel side walls within the rectangular cross-section. The reshaping stage and pinch-off stage are mainly driven by the interfacial tension, leading to far larger neck thinning rate compared to the superficial velocity of either phase. The filling stage and squeezing stage are dominated by the pressure drop across the dispersed tip while the role of the shear force becomes more important with increasing tunnel width. The filling period is estimated as t2≈kHwn02/Qd with k = 1.34 and the squeezing period is expressed as t3/Tc = 0.3Cac−1. According to the force analysis, the critical tip velocity under dripping scales with three key parameters, which can be expressed as (utip/U)* ~ QcLtip/wtunnel3. Flow regimes of two immiscible liquids at the cross junction within a rectangular microchannel are experimentally investigated. Distribution maps and critical conditions of four flow regimes are presented. Interfacial deformations during the droplet generation at regimes of squeezing and dripping are compared. Force analysis is carried out based on the different tunnel shape confined by the rectangular cross-section. [ABSTRACT FROM AUTHOR]

Densely grafted comb-like macromolecules (bottlebrushes) with alternating solvophobic and solvophilic side chains were studied in a selective solvent and at the liquid interface using mesoscopic computer simulations. The effects of backbone length and copolymer composition were considered. While self-assembly in solution revealed only spherical aggregates for all ar-chitectures studied, adsorption onto the liquid interface in particular cases resulted in morpho-logical changes, with worm-like aggregates or a continuous monolayer observed. In turn, the compression of macromolecules at the interface also leads to morphological transitions, includ-ing the formation of a mesh-like percolated structure. The obtained results may be useful for the preparation of solid nanoparticles of anisotropic shape or nanostructured ultra-thin copolymer films.

A pixelated complementary split‐ring resonator (PCSRR)‐loaded microstrip line is proposed for the detection of different liquid interfaces and its potential applications are described. The proposed sensor operation is based on the magnitude measurement, the transmission coefficient (S21) and resonance frequency (Fr) that depend on the electrical properties of the liquid. The PCSRR was designed to allow electromagnetic waves to interact with different layers of liquid inside a container. The sensor device and experiment system were fabricated and evaluated and water‐vegetable oil‐alcohol interfaces were measured. The sensors were capable of detecting noncontact liquid interfaces and have potential applications in the chemical, oil, and medical industries. [ABSTRACT FROM AUTHOR]

Local laser heating of the liquid film leads to simultaneous self-organization of both cellular convective structures and a cluster of micron-scale particles. The cluster is formed on the free surface of the layer and consists of hexagonal structures with a size of 50-100 μm. The height of the liquid film (0.5 mm) is ten times the diameter of the convective cells. Experimental data on the distribution of particle sizes and sizes of hexagonal cells in the cluster are presented. The cluster shape may be either a circle with a diameter of 110-140 μm, or an ellipse. Due to the instability of the velocity field, the toroid is not formed, and convective cells are formed only near the heating center. Self-organization of a cluster of particles and cellular structures using local heating can be effectively used to create new promising materials, as well as in micro-biology and medicine. Unlabelled Image • Convective cells and a cluster of particles are studied at laser heating. • Perturbations at a micro-scale control the average flow at a macro-scale. • The integral convection scale reflects the intensity of heat and mass transfer. [ABSTRACT FROM AUTHOR]

The behavior of self-organization of convective flows in a thin layer of liquid under point (local) heating is investigated experimentally. The interaction of thermocapillary and thermogravitational-free convection can lead both to self-organization of a cluster of micro-vortices in the form of hexagonal structures and to its partial disintegration. Correlation analysis of the velocity field shows that the characteristic convection scales change continuously over time. The largest size of the vortex flow corresponds to the layer diameter (20 mm); the integral convection scale (2.5 mm) characterizes the established interaction of vortex structures in a wide range of sizes; and the dimensions of hexagonal convective cells (80–100 µm) show the lower limit of the characteristic scale of vortex structures. The observed flow macrostructure is determined by the complex nonlinear interaction of vortices of the specified scales. The resulting value of the average integral convection scale can be effectively used to predict the convection velocity. [ABSTRACT FROM AUTHOR]

Measurement in liquid media is a major challenge in real-time detection using resonant cantilevers. This is addressed in the present study by fabricating sub-micron thick cantilevers followed by functionalization for biomolecule detection. The fabricated cantilever resonator beams of thickness 165 nm were used for measurements in two systems: (i) human immunoglobulin (HIgG) as the antibody on the cantilever sensing mouse immunoglobulin (MIgG) as corresponding antigen, and (ii) detection of triglyceride (TG) based on the enzymatic hydrolysis with lipase, using tributyrin as a model. In both cases, the beams were functionalized for covalent bonding of the protein receptor. The label-free detection was carried out by measuring the shift in resonance frequency at higher modes, using a laser Doppler vibrometer in liquid and in air. The calibration showed a linear correlation between the bioanalyte concentration and change in the resonance frequency. Notably, detection of antigen mass as low as 434 ± 59fg and triglyceride concentration in the nM range with limit of detection as 7 nM in liquid interface was achieved, greatly improving the sensitivity of bioanalyte detection in liquid samples. Although frequency-based methods are highly sensitive, the issues with measurement liquid medium limit their application. In the present report, these issues were addressed by fabricating sub-micron thick cantilever beam, choosing an appropriate functionalization method without affecting the sensitivity, and measurement at higher modes. These have resulted in circumventing issues like damping and hydrodynamic loading thus improving its potential as real-time sensor. [ABSTRACT FROM AUTHOR]

Extensive effort and research are currently channeled towards the implementation of SERS (Surface Enhanced Raman Spectroscopy) as a standard analytical tool as it has undisputedly demonstrated a great potential for trace detection of various analytes. Novel and improved substrates are continuously reported in this regard. It is generally believed that plasmonic nanostructures with plasmon resonances close to the excitation wavelength (on-resonance) generate stronger SERS enhancements, but this finding is still under debate. In the current paper, we compared off-resonance gold nanobones (GNBs) with on-resonance GNBs and gold nanorods (GNRs) in both colloidal dispersion and as close-packed films self-assembled at liquid-liquid interface. Rhodamine 6G (R6G) was used as a Raman reporter in order to evaluate SERS performances. A 17-, 18-, and 55-fold increase in the Raman signal was observed for nanostructures (off-resonance GNBs, on-resonance GNBs, and on-resonance GNRs, respectively) assembled at liquid-liquid interface compared to the same nanostructures in colloidal dispersion. SERS performances of off-resonance GNBs were superior to on-resonance nanostructures in both cases. Furthermore, when off-resonance GNBs were assembled at the liquid interface, a relative standard deviation of 4.56% of the recorded signal intensity and a limit of detection (LOD) of 5 × 10−9 M could be obtained for R6G, rendering this substrate suitable for analytical applications.

To introduce a methodical description and to investigate first clinical safety of a novel liquid interface technology for femtosecond laser-assisted perforating keratoplasty, maintaining the corneal curvature without applanation of the cornea. In this pilot study six patients received a femtosecond laser keratoplasty using a new liquid interface providing a non-applanating trephination. Clinical outcomes were evaluated 1, 3 and 6 months after surgery. All procedures were performed without complications and donor and recipient corneas could be aligned without problems, even in cases of advanced keratoconus. Although this initial pilot study investigated clinical safety, a positive effect on postoperative astigmatism was observed. We could show in this first pilot study that a hand-held liquid patient interface in combination with a femtosecond laser has a preliminary safety and reliability in penetrating keratoplasty. [ABSTRACT FROM AUTHOR]

The nonlinear dynamics of the interface between two immiscible dielectric liquids at the regime of suppressed Kelvin-Helmholtz instability by external horizontal electric field is studied theoretically. The initial equations of the fluids motion are reduced to a single weakly nonlinear integro-differential equation that describes the interaction of solitary waves (rational solitons) propagating along the interface. The dynamics of two interacting solitons is regular and integrable; they can combine into a stable wave packet (breather). It is shown that the interaction of three solitons becomes complex and, for a wide rang of initial conditions, chaotic. The numerically obtained Poincaré sections demonstrate the destruction of toroidal trajectories in the phase space during the transition of the system to a chaotic regime of fluid motion. Such a behaviour is consistent with the Kolmogorov-Arnold-Moser theory describing quasi-periodic chaotic motion in Hamiltonian systems. At the developed chaotic state, the system fast loses the information on its initial state; the corresponding estimate for Lyapunov exponent is obtained. From the physical point of view, the chaotic behavior of the system is related with structural instability of the soliton triplet. The triplet can decay into a solitary wave and stable breather consisting of two interacting solitons.

• Turbulent vortex motion on the water surface is excited by standing gravity waves. • The energy decay process of vortex motion occurs in the quasi-adiabatic mode. • Direct energy cascade proportional to k−5/3 is maintained during vortices decay. The decay of the developed energy cascade of vortex motion on the water surface excited by perpendicular standing waves at a frequency of 6 Hz is investigated experimentally. It is shown that after the pumping is switched off, the relaxation process begins from the large wave vectors k and occurs in the quasi-adiabatic mode: the Kolmogorov energy distribution proportional to k−5/3 is maintained for a long time due to the nonlinear interaction of vortices. [ABSTRACT FROM AUTHOR]

Highlights • A non-contact liquid interface sensor based on a hollow coaxial cable Fabry-Perot resonator is for the first time reported. • The proposed sensor also has the ability for contactless measurement of liquid dielectric constant. • The sensor offers a robust, cost-effective, and real-time configuration for contactless liquid interface detection. Abstract This paper reports a contactless liquid interface sensor based on a microwave Fabry-Perot resonator. A hollow coaxial cable is employed as the sensing platform, in which air serves as the dielectric layer. By shorting the inner and outer conductors of the hollow coaxial cable, two reflectors with high reflectivity (>70%) are created to form a microwave Fabry-Perot resonator. An open groove is engineered on the resonator allowing the electromagnetic wave to interact with the medium outside the cavity. When a container, filled with different layers of liquids, is placed near the groove edge of the sensor, the leaked electromagnetic wave will interact with the liquids inside the container. By correlating the relative permittivity of the liquid mixture to the resonant frequency of the Fabry-Perot resonator, the interface between different liquids can be unambiguously determined. In the demonstration experiment, the water-oil interface and oil-ethanol interface were measured. Meanwhile, the sensor could also be employed to measure the relative permittivity of different liquids in a non-contact fashion. The presented sensor offers a robust, cost-effective, and real-time configuration for contactless liquid interface detection, which has potential applications in the oil and chemical industries. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A molecular thermodynamic model is derived for an uncharged delocalized surfactant monolayer adsorbed at a liquid interface, taking explicit account for the solvent molecules present in the monolayer. The model is based on the scaled particle theory of hard-disc mixtures, and is also extended to sticky discs (i.e. attraction between the adsorbed molecules). Upon compression of the adsorbed layer, the solvent is expelled from it. The respective osmotic effect on the equation of state is shown to be equivalent to an effective lateral depletion attraction between the surfactant molecules. This effective osmotic cohesion causes an increase of the value of the attraction parameter β of the monolayer. The smaller the size of the surfactant polar head group is, the larger the effective attraction the model predicts. This trend is verified with data for the adsorption at water|air surface of alcohols, undissociated acids, and hexaethylenglycol monoalkyl ethers. The proposed theory allows the amount of solvent in the monolayer to be estimated, which is shown to be important for the neutron reflectivity of the surface. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a novel method to collect fine and coarse particles dispersed in the air using magnetic fluid to improve atmospheric environment. Magnetic fluids are set in the 50 × 50 × 10 mm rectangular channel. Plain flour particles ranging from 2.5 to 450 μm are used as model particles. Then, filtration efficiency of 40% is obtained as a maximum value. We propose a unique method to visualize and quantitatively evaluate the interaction between wind and magnetic fluid which found to be an important factor for the enhancement of the particle-collecting efficiency. Generally, it is difficult to measure the magnetic fluid flow since it is not transparent against light. In our developed method, we use LED light sheet which is low cost unlike lasers. Furthermore, there is no need to add anything into the magnetic liquid and no need to dilute the liquid. It is found that the spikes are flown by the stream depending on the magnetic field strength.Graphical abstract: [ABSTRACT FROM AUTHOR]

Directional solidification of the Fe - 4,3 wt % C alloy was performed with the pulling rate equal to v=83 μm/s. Sample was frozen during solidification to reveal the shape of the solid/liquid interface. Structures eutectic pyramid and spherolitic eutectic were observed. The solidification front of ledeburite eutectic was revealed. The leading phase was identified and defined.

The ubiquity of micro-/nanoplastics poses a visible threat to the environment, aquatic organisms, and human beings and has become a global concern. Here, we proposed a liquid interface-based strategy using surface-enhanced Raman spectroscopy to coassemble nanoplastics and gold nanoparticles into a dense and homogeneous plasmonic array, thereby enabling the rapid and sensitive detection of trace nanoplastics. In addition, due to the uniqueness of the oil-water immiscible two-phase interface, we achieved ideal results for the detection of nanoplastics in a complex matrix (e.g., aqueous environment and edible oil) with a detection limit of μg/mL. With the aid of the principal component analysis algorithm, the differentiation and identification of multiple nanoplastic components (e.g., polystyrene, polyethylene, and polyethylene terephthalate) in aqueous environments and common hazards (e.g., Bap and Phe) in edible oil were achieved. Therefore, our self-assembled plasmonic arrays are expected to be used for monitoring environmental pollution and food safety.