Current Opinion in Colloid & Interface Science最新文献

Due to their environmental benefits and rich interfacial and colloidal properties, biosurfactants show promise as a platform for next-generation reagents in metal extraction using froth and foam flotation. While the development of biosurfactants as flotation bioreagents is still in its infancy, it has witnessed important progress in the past five years. Recent studies have not only demonstrated the ability of biosurfactants to compete with conventional collectors but have also provided valuable insights into the experimental parameters affecting these two separation processes. Despite this progress, the interactions of biosurfactants with mineral particles, metal ions, and air bubbles under flotation conditions remain far from being fully understood. There is growing evidence suggesting that these interactions are more complex than observed for conventional petroleum-based collectors. We summarize the recent progress and outline the main remaining knowledge gaps, aiming to generate more interest in the intriguingly complex multifunctional properties of biosurfactants as collectors.

New surfactants are not necessarily better than established surfactants; new surfactants need to be better, cheaper or have a lower environmental impact to have an advantage over existing products. Attributes like aquatoxicity, mildness, sourcing from renewable carbon and emissions of greenhouse gases during production and use of surfactants had become more and more important. Biosurfactants (BS) which are not really new to the world but which have been so far only produced at low concentrations by microorganisms or plants have attained attention in academical research and interest of industry in the last 25 years resulting in the commercial availability of Sophorolipids and Rhamnolipids by several companies. BS are dedicated to applications in PersonalCare and HouseHold Care due to their consumer-recognizable mildness; BS can, however, not simply replace established components in formulations due to their different performance profile, which makes comparison to traditional surfactants rather complicated.

The dispersion of small particles provides an inexpensive and convenient way to significantly improve various functional properties of the base fluid. Nanodispersions can be used to solve various industrial and technical problems, such as increasing the efficiency of heat generating systems, cooling electrical equipment, water desalination, control of thermal regimes of chemical processes and electronic devices, enhancing oil recovery, and so on. This review targets to highlight the recently published results that are of general importance for understanding the processes occurring during wetting and spreading of nanofluids over various surfaces, as well as the mechanisms that determine these processes.

The upper layer of our skin, the stratum corneum (SC), is a versatile material that combines mechanical strength with efficient barrier function. In this paper, we discuss these macroscopic properties of SC in relation to recent findings on molecular responses and structural diversity in SC protein and lipids. We put particular focus on the intermediate (colloidal) length scale and how the different SC substructures are organized with respect to each other, including effects of non-equilibrium conditions in the skin with respect to the gradients in water and other components.

This review provides an overview of experimental and computational results on the interaction between nanocarriers of different natures and pulmonary surfactant models that have appeared in the literature in the last five years. The purpose is to highlight the changes in the nanoscopic structure and functionality of the pulmonary surfactant layer due to the interaction with nanocarriers and nanoparticles, which are inorganic, polymeric, or consist of biomolecules. The information gathered contributes to the development of carriers' nanotechnology, thus allowing specific and controlled drug delivery while being minimally invasive by crossing pulmonary surfactant without altering its structure and function.

Biopolymer hydrogel particles provide a wide range of advantages to food applications due to their highly hydrophilic nature, the ability to tailor micro-/macro-structure, and their complex rheology as dispersions. In food, dispersions of cross-linked hydrogel particles are increasingly used to create unique appearances or textures, novel aroma experiences, and/or for controlled-release applications. Mastering food biopolymer particle dispersions requires understanding of biopolymer physicochemistry, controlled microstructure creation, particle interactions that govern flow behavior, and the characterization techniques that give insight into the structure-function relationships across the different length scales. In the present review, recent progress in cross-linked food biopolymer hydrogels across these domains is presented with a particular focus on fluid gel dispersions and controlled release. We highlight how emerging technologies/techniques might enable new microstructural understanding or designer biopolymer sequences. Finally, we highlight how these developments help to fully unlock biopolymer hydrogel dispersions for food applications.

Microbubble dispersions are now commonly deployed in industrial applications ranging from bioprocesses to chemical reaction engineering, at full scale. There are five major classes of microbubble generation devices that are scalable. In recent years, some of these approaches have been explicitly studied for the influence of wetting properties on microbubble performance, for which the major proxy is the bubble-size distribution. In this piece, the methodologies for inferring bubble-size distribution are explored, with several recent advances as well as their potential pitfalls. Subsequently, studies where microbubble generation has been under investigation for wetting effects are assessed and in some cases, those that were not allowed the deduction that wetting is a significant factor. Two particular studies are highlighted: (i) systematic variation of wetting effects within a venturi with removable walls substituted with coated walls of known contact angle with hydrodynamic cavitation induced microbubbles and (ii) variation of ionic liquids with staged fluidic oscillation before steady flow. The first study shows that even in scenarios where high inertial effects would be expected to dominate, wetting influences are significant. The second study shows that transient effects are strongly influenced by both imbibition into pores and surface wetting but that viscous resistance is always a key factor. From the exploration of these recent studies, specific recommendations are made about how to assess the influence of wetting in those mechanisms/devices where it has not been explicitly studied, via deduction from those mechanisms/devices where the effects are demonstrably significant and indeed in some cases, controlling. In study (ii), which is the first to blow micro/bubbles into ionic liquids, wetting and transient effects are reasonable for between 25% and 50% reduction in average bubble size, although up to 70% reduction is observable when viscous effects are dominant, relative to the control of steady flow with the same pressure drop. Indeed, staging transient operations shows both bubble-size reduction and increased volumetric throughput are simultaneously possible.

The membrane of Gram-negative bacteria (GNB) is especially robust due to the additional, unique, highly asymmetric outer membrane, with lipopolysaccharides (LPSs) as the main component. This LPS layer serves as a protective barrier against antibiotics, host immune responses, and other environmental stresses. However, constructing model membranes containing LPS that capture the structural asymmetry for fundamental studies of the GNB cell wall remains an open challenge. In this context, we discuss how recent physicochemical studies of Langmuir monolayers incorporating LPS help us better understand the elastic properties and structural integrity of model LPS bacterial membranes. The classic Langmuir–Blodgett trough has been used to reveal different lipid phase behaviors of monolayers containing LPS mutants with different molecular architectures to mimic the outer leaflet of the GNB outer membrane, shedding light on the underpinning molecular interactions. Permeation and penetration of antimicrobial peptides are shown to alter the viscoelastic properties of LPS monolayers. The LPS-containing Langmuir monolayer can also be transferred to a substrate as the outer leaflet of an asymmetric solid-supported bilayer, and we will discuss the limitations and potential optimization of this method. Finally, we highlight how different physicochemical methods can corroborate and contribute to unravelling the structural characteristics of model bacterial membranes.

The wetting and dewetting of solid surfaces is ubiquitous in physical systems across a range of length scales, and it is well known that there are maximum speeds at which these processes are stable. Past this maximum, flow transitions occur, with films deposited on solids (dewetting) and the outer fluid entrained into the advancing one (wetting). These new flow states may be desirable, or not, and significant research effort has focused on understanding when and how they occur. Up until recently, numerical simulations captured these transitions by focussing on steady calculations. This review concentrates on advances made in the computation of the time-dependent problem, utilising dynamical systems theory. Facilitated via a linear stability analysis, unstable solutions act as ‘edge states’, which form the ‘point of no return’ for which perturbations from stable flow cease decaying and, significantly, show the system can become unstable before the maximum speed is achieved.

Neutron scattering techniques provide detailed information on the structure of and dynamics occurring within materials across multiple length and time scales. When combined with traditional characterisation techniques used in food materials science, they can generate unique insight and understanding that can assist in the development of new and improved ingredients and formulations. This review describes recent examples of the application of neutron scattering techniques across a broad range of food hydrocolloids as well as outlining future opportunities in the field.