Recent advances in studying crystallisation of mono- and di-glycerides at oil-water interfaces.

This review focuses on the current understanding regarding lipid crystallisation at oil-water interfaces. The main aspects of crystallisation in bulk lipids will be introduced, allowing for a more comprehensive overview of the crystallisation processes within emulsions. Additionally, the properties of an emulsion and the impact of lipid crystallisation on emulsion stability will be discussed.

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

Hypothesis: Dairy 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.

The effect of emulsifier type on the secondary crystallisation of monoacylglycerol and triacylglycerols in model dairy emulsions.

Dairy emulsions contain an intrinsically heterogeneous lipid phase, whose components undergo crystallisation in a manner that is critical to dairy product formulation, storage, and sensory perception. Further complexity is engendered by the diverse array of interfacially-active molecules naturally present within the serum of dairy systems, and those that are added for specific formulation purposes, all of which interact at the lipid-serum interface and modify the impact of lipid crystals on dairy emulsion stability. The work described in this article addresses this complexity, with a specific focus on the impact of temperature cycling and the effect of emulsifier type on the formation and persistence of lipid crystals at lipid-solution interfaces.

Inside the ensemble: unlocking the potential of one-at-a-time experiments with lab-on-a-chip automation.

The advent of technologies that allow the interactions of microscopic particles to be probed "" has paved the way for new experimental avenues of enquiry in colloidal systems. For example, investigating whether a particular pair of colloidal particles isolated from a macroscopic sample might adhere to each other when brought into close proximity is certainly possible. However, given the probabilistic nature of the process (different particles within the ensemble may have slightly different surface charge distributions and asperities, and interaction energies involved can be close to thermal values), it is important that many hundreds or thousands of pairs of particles are tested under each set of experimental conditions of interest.

Aggregation and coalescence of partially crystalline emulsion drops investigated using optical tweezers.

The solid content of viscoelastic emulsion drops is known to affect their propensity for aggregation and their subsequent coalescence behaviour, where the balance between the drive to reduce surface tension and the straining of an internal viscoelastic network is able to create a plethora of stable partially-coalesced states. The latter has previously been elegantly demonstrated in synthetic systems, generated using oil containing different phase volumes of added solids, with micro-pipette experiments carried out on emulsion drops of several tens of microns in size. Herein we carry out experiments in the same spirit but aided by optical tweezers (OT) and using smaller micron-sized emulsion drops generated from milk fat.

Fractionation and characterisation of hard milk fat crystals using atomic force microscopy.

The hard milk fat (HMF) fraction of milk fat was isolated via dry, thermal fractionation, followed by a solvent washing process. The resulting HMF crystals were visibly free of entrapped liquid fat, and subsequently characterised by thermal analysis, X-ray diffraction, and electron microscopy. The HMF crystals were found to be mostly β' and β' crystalline structures, with a lamellar thickness of 42.

The use of a smartwatch as a prompting device for people with acquired brain injury: a single case experimental design study.

Prompting-based memory compensation is a potential application for smartwatches. This study investigated the usability and efficacy of a Moto360 smartwatch as a memory aid. Four community dwelling adults with memory difficulties following acquired brain injury (ABI) were included in an A-B-A single case experimental design study.

Attractive and repulsive electrostatic forces between positively charged latex particles in the presence of anionic linear polyelectrolytes.

The interaction forces between individual positively charged amidine functionalized latex particles with adsorbed negatively charged sodium poly(styrene sulfonate) were studied with the colloidal probe technique based on atomic force microscopy (AFM). When the polymer dose is progressively increased, the strength of the repulsive force between the particles decreases as the charge neutralization point is approached, then increases again due to overcharging, and finally reaches a plateau. Surface potentials obtained from fits of the force profiles to Poisson-Boltzmann theory agree well with potentials measured with electrophoresis.

Attractive electrostatic forces between identical colloidal particles induced by adsorbed polyelectrolytes.

Polyelectrolytes adsorb strongly at oppositely charged surfaces, thereby dramatically influencing the corresponding interaction forces. In this letter, we report on direct force measurements with the atomic force microscope (AFM) between two individual particles in an aqueous colloidal suspension in the presence of polyelectrolytes near the isoelectric point. From systematic variations of the molecular mass, the ionic strength, and analysis of adhesion events, we conclude that the observed attractive forces are mainly due to electrostatic patch-charge interactions.

Charging and aggregation of positively charged latex particles in the presence of anionic polyelectrolytes.

Charging behavior and colloidal stability of amidine latex particles are studied in the presence of poly(sodium styrene sulfonate) (PSS) and KCl. Detailed measurements of electrophoretic mobility, adsorbed layer thickness, and aggregation (or coagulation) rate constant on varying the polymer dose, molecular mass of the polymer, and ionic strength are reported. Polyelectrolyte adsorption leads to the characteristic charge reversal (or overcharging) of the colloidal particles at the isoelectric point (IEP).

Simple, one-step synthesis of gold nanowires in aqueous solution.

A simple procedure to synthesize gold nanowires based on the reduction of hydrogen tetrachloroaurate by 2-mercaptosuccinic acid in aqueous solution is presented. This procedure requires no additional capping or reduction agent and produces wires with an apparent curly morphology several micrometers in length with diameters as thin as 15 nm. Some of the wires produced end in a ribbonlike structure, finally terminated by a flat triangular prism.

Colloid probe AFM investigation of the influence of cross-linking on the interaction behavior and nano-rheology of colloidal droplets.

The repulsive forces between a glass sphere and immobilized colloidal droplets of poly(dimethylsiloxane) (PDMS) (with various levels of internal cross-linking) have been determined in aqueous solution using colloid probe atomic force microscopy. On initial surface approach, droplet deformation is negligible and interaction forces resemble those expected for electrical double layer interaction of rigid spheres. Upon further approach, droplet flattening results in forces that deviate below rigid body electrical double layer interaction.

Surface and capillary forces encountered by zinc sulfide microspheres in aqueous electrolyte.

The colloid probe technique was used to investigate the interactions between individual zinc sulfide (ZnS) microspheres and an air bubble in electrolyte solution. Incorporation of zinc ions into the electrolyte solution overcomes the disproportionate zinc ion dissolution and mimics high-volume-fraction conditions common in flotation. Determined interaction forces revealed a distinct lack of long-ranged hydrophobic forces, indicated by the presence of a DLVO repulsion prior to particle engulfment.

Direct measurements of particle-bubble interactions.

The essence of mineral flotation is the formation of strong particle-bubble aggregates. Hydrodynamics and DLVO forces hinder the particle-bubble approach, however the presence of a hydrophobic surface results in hydrophobic attraction and strong aggregate formation. In this article we review literature where the colloid probe technique has been used to investigate flotation, primarily particle-bubble interactions in aqueous solution.

Interaction forces, deformation and nano-rheology of emulsion droplets as determined by colloid probe AFM.

Atomic force microscopy (AFM) has been used to determine the interaction forces between a spherical silica probe and immobilised colloidal droplets of polydimethylsiloxane (PDMS) in aqueous solution. Under mildly alkaline conditions where PDMS droplets and the silica probe are both negatively charged, a repulsive force is evident that increases less rapidly on surface approach than expected for electrical double layer interaction of rigid particles. The departure from hard-sphere behaviour enables the extent of droplet deformation to be determined and by varying the extent of internal cross-linking within the PDMS droplets, the influence of bulk rheology and interfacial tension on droplet deformation and nano-rheology has been isolated.