1,665 research outputs found
Phase inversion emulsification: Current understanding and applications
No full textThis review is addressed to the phase inversion process, which is not only a common, low-energy route to make stable emulsions for a variety of industrial products spanning from food to pharmaceuticals, but can also be an undesired effect in some applications, such as crude oil transportation in pipelines. Two main ways to induce phase inversion are described in the literature, i.e., phase inversion composition (PIC or catastrophic) and phase inversion temperature (PIT or transitional). In the former, starting from one phase (oil or water) with surfactants, the other phase is more or less gradually added until it reverts to the continuous phase. In PIT, phase inversion is driven by a temperature change without varying system composition. Given its industrial relevance and scientific challenge, phase inversion has been the subject of a number of papers in the literature, including extensive reviews. Due to the variety of applications and the complexity of the problem, most of the publications have been focused either on the phase behavior or the interfacial properties or the mixing process of the two phases. Although all these aspects are quite important in studying phase inversion and much progress has been done on this topic, a comprehensive picture is still lacking. In particular, the general mechanisms governing the inversion phenomenon have not been completely elucidated and quantitative predictions of the phase inversion point are limited to specific systems and experimental conditions. Here, we review the different approaches on phase inversion and highlight some related applications, including future and emerging perspectives
The effect of flow on viscoelastic emulsion microstructure
No full textEmulsions made of oil, water and surfactants are widespread soft materials with complex structures depending on composition and temperature. Emulsion phase behavior at rest has been widely investigated but flow-induced effects, which are very relevant in many applications, can still be further explored towards improved emulsion microstructural design. In this work, we use low energy emulsification processing to create small-sized emulsions. In a previous report, we showed the emulsion morphology development and the effect of flow on the microstructure of a highly viscoelastic attractive emulsion which result in a concentrated nanoemulsion after viscoelastic droplet filaments are disrupted. Here, we show that upon stopping the flow, the filaments slowly buckle, recoil and finally form clusters of randomly flocculated droplets. We thus obtain two completely different emulsion morphologies simply induced by the action of flow, where in both cases attractive interactions play a key role. The emulsion high interfacial area represents a valuable feature for several applications such as upstream operations, microreaction media and drug delivery
Emulsions in porous media: From single droplet behavior to applications for oil recovery
No full textDevelopment of model systems for in vitro investigation of transdermal transport pathways
No full textSkin is a complex structured system primarily involved in Transdermal Drug Delivery (TDD). The outer stratum corneum represents the main barrier
to the entrance of external molecules. Nowadays, none of the recognized methods, used for the investigation of penetration processes, is able to
give a complete overview of the transport mechanisms involved. Standard protocols are based on the use of human or animal skin samples, which
are difficult and expensive to obtain. Here, we present a novel experimental setup to investigate TDD by using Confocal Laser Scanning Microscopy
and image analysis. The methodology is based on diffusion experiments of fluorescent-labelled fluids (water, oil, and oil-in-water emulsions), in a
model matrix. Using an agarose gel as model for a proof of concept, different penetration efficiencies were observed, suggesting an important role of
both chemical composition and fluid microstructure on the transport mechanism. An adequate model system should be used to better mimic the
stratum corneum morphology and properties. To this aim, several bicontinuous emulsion gels, obtained from an emulsification process, were
preliminary formulated and suggested as model systems to mimic the stratum corneum. In this work, we define the key directions for the
development of an innovative approach to study the penetration of formulations through the skin
Flow-switchable morphology of concentrated emulsions
No full textSoft materials can be switched from a liquid to a gel-like state by structural re-arrangement down to the nanoscale and find application in many fields ranging from biomedical engineering to oil recovery. Here, we show that flow-switchable emulsions of oil, water and surfactants can be obtained by simple low-energy emulsification processing. By dropwise addition of water to the oil-surfactant solution under mild stirring, a striking transition from a transparent, purely viscous Newtonian fluid to a highly viscoelastic translucent material climbing onto the impeller is observed. We show that this transition is associated with the formation of elongated droplets, eventually disrupting into nanodroplets which, upon stopping the flow, slowly relax to a stable gel-like microstructure with noticeable birefringent properties. The two structures (elongated droplets and gel-like microstructure) can be reversibly switched between each other by starting/stopping the flow. This behavior can be attributed to the interplay between the cluster-disruptive effect of flow on one side, and droplets attractive interactions promoting coalescence on the other side. Our results, observed for different systems by changing oil type and surfactants chain length, highlight a flow-switchable emulsion processing method, which can be used to produce concentrated emulsions for a variety of applications
Schermi. Immagini, corpi, condivisioni
No full textIn this book the author investigates the digital image proliferation of our times from an interdisciplinary point of view. Starting from the Visual Culture theoretical frame, Valentina Mignano explores the ways in which we interact with the screen, dealing with the "screen experience" in the first years of the network societ
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