Microfluidic extensional flow device to study mass transfer dynamics in the polymer microparticle formation process.

Polymer microparticles are often used to encapsulate drugs for sustained drug-release treatments. One of the ways they are manufactured is by using a solvent extraction process, in which the polymer solution is emulsified into an aqueous bulk phase using a surfactant as a stabilizing agent, followed by the removal of the solvent. The radius of a polymer drop decreases as a function of time until the polymer reaches the gelling point, after which it is separated and dried.

Low yield stress measurements with a microfluidic rheometer.

Yield stress, , is a key rheological property of complex materials such as gels, dense suspensions, and dense emulsions. While there is a range of established techniques to measure in the order of tens to thousands of pascals, the measurement of low , specifically below 1 Pa, remains underexplored. In this article, we present the measurement of low apparent using a Hele-Shaw microfluidic extensional flow device (MEFD).

The yielding behaviour of human mucus.

Mucus is a viscoelastic material with non-linear rheological properties such as a yield stress of the order of a few hundreds of millipascals to a few tens of pascals, due to a complex network of mucins in water along with non-mucin proteins, DNA and cell debris. In this review, we discuss the origin of the yield stress in human mucus, the changes in the rheology of mucus with the occurrence of diseases, and possible clinical applications in disease detection as well as cure. We delve into the domain of mucus rheology, examining both macro- and microrheology.

Affinity-controlled release of rod-derived cone viability factor enhances cone photoreceptor survival.

Retinitis pigmentosa (RP) is a group of genetic diseases that results in rod photoreceptor cell degeneration, which subsequently leads to cone photoreceptor cell death, impaired vision and eventual blindness. Rod-derived cone viability factor (RdCVF) is a protein which has two isoforms: a short form (RdCVF) and a long form (RdCVFL) which act on cone photoreceptors in the retina. RdCVFL protects photoreceptors by reducing hyperoxia in the retina; however, sustained delivery of RdCVFL remains challenging.

Pathophysiology of outer retinal corrugations: Imaging dataset and mechanical models.

This article presents high-resolution swept-source optical coherence tomography (SS-OCT) imaging data used to elaborate a mechanical model that elucidates the formation of outer retinal corrugations (ORCs) in rhegmatogenous retinal detachments (RRD). The imaging data shared in the repository and presented in this article is related to the research paper entitled "Outer Retinal Corrugations in Rhegmatogenous Retinal Detachment: The Retinal Pigment Epithelium-Photoreceptor Dysregulation Theory" (Muni et al., AJO, 2022).

A paradigm shift in retinal detachment repair: The concept of integrity.

The management of rhegmatogenous retinal detachment has rapidly evolved over recent decades. A range of surgical techniques exist, all of which can achieve retinal reattachment in most cases. In recent years there have also been vast technical advances in retinal imaging that have introduced novel ways of visualizing and studying the retinal macro and microstructural anatomy following retinal detachment repair.

Outer Retinal Corrugations in Rhegmatogenous Retinal Detachment: The Retinal Pigment Epithelium-Photoreceptor Dysregulation Theory.

Purpose: Outer retinal folds occur when outer retinal corrugations (ORCs) persist after retinal reattachment with worse functional outcomes. We investigate the pathophysiology of ORCs in vivo.

Design: Prospective cohort study.

Fibrous hydrogels under biaxial confinement.

Confinement of fibrous hydrogels in narrow capillaries is of great importance in biological and biomedical systems. Stretching and uniaxial compression of fibrous hydrogels have been extensively studied; however, their response to biaxial confinement in capillaries remains unexplored. Here, we show experimentally and theoretically that due to the asymmetry in the mechanical properties of the constituent filaments that are soft upon compression and stiff upon extension, filamentous gels respond to confinement in a qualitatively different manner than flexible-strand gels.

Emulsion characterization via microfluidic devices: A review on interfacial tension and stability to coalescence.

Emulsions have gained significant importance in many industries including foods, pharmaceuticals, cosmetics, health care formulations, paints, polymer blends and oils. During emulsion generation, collisions can occur between newly-generated droplets, which may lead to coalescence between the droplets. The extent of coalescence is driven by the properties of the dispersed and continuous phases (e.

Biodegradable nano composite reinforced with cellulose nano fiber from coconut industry waste for replacing synthetic plastic food packaging.

Environmental pollution due to the usage of non-biodegradable synthetic plastic and agro-waste disposal/burning are major issues nowadays. Hence, in the present study, agro-waste (coconut shells) was selected as raw material to synthesize cellulose nanofibers, and it was incorporated into a biodegradable packaging film to enhance its properties. Coconut shell cellulose nanofibers (CNF) were synthesized by a combination of mechanical (ball milling), chemical (acid hydrolysis), and physical (ultra-sonication) methods with an excellent yield of 41.

Understanding the mechanism of retinal displacement following rhegmatogenous retinal detachment repair: A computer simulation model.

Purpose: Retinal displacement is common following rhegmatogenous retinal detachment (RRD) repair. A computer simulation was developed to assess forces applied by a gas tamponade of various sizes in the setting of pneumatic retinopexy (PnR) versus pars plana vitrectomy (PPV).

Design: Computer simulation model.

Substrate colonization by an emulsion drop prior to spreading.

In classical wetting, the spreading of an emulsion drop on a surface is preceded by the formation of a bridge connecting the drop and the surface across the sandwiched film of the suspending medium. However, this widely accepted mechanism ignores the finite solubility of the drop phase in the medium. We present experimental evidence of a new wetting mechanism, whereby the drop dissolves in the medium, and nucleates on the surface as islands that grow with time.

IMMEDIATE SUBRETINAL FLUID DISPLACEMENT FROM THE BUOYANT FORCE OF A SMALL GAS BUBBLE IN PNEUMATIC RETINOPEXY: INSIGHTS INTO THE POTENTIAL MECHANISM OF RETINAL DISPLACEMENT AFTER RETINAL DETACHMENT REPAIR.

Purpose: To demonstrate how a small gas bubble injected into the vitreous cavity in pneumatic retinopexy for rhegmatogenous retinal detachment causes immediate displacement of subretinal fluid and to gain insights into the potential mechanism of retinal displacement.

Methods: Three patients with rhegmatogenous retinal detachment who underwent pneumatic retinopexy were enrolled and prospectively followed. All patients underwent ultra-widefield fundus photography at baseline and at 1 to 2 minutes after intravitreal gas injection.

3D Printing of Vascular Tubes Using Bioelastomer Prepolymers by Freeform Reversible Embedding.

Bioelastomers have been extensively used in tissue engineering applications because of favorable mechanical stability, tunable properties, and chemical versatility. As these materials generally possess low elastic modulus and relatively long gelation time, it is challenging to 3D print them using traditional techniques. Instead, the field of 3D printing has focused preferentially on hydrogels and rigid polyester materials.

h-FIBER: Microfluidic Topographical Hollow Fiber for Studies of Glomerular Filtration Barrier.

Kidney-on-a-chip devices may revolutionize the discovery of new therapies. However, fabricating a 3D glomerulus remains a challenge, due to a requirement for a microscale soft material with complex topography to support cell culture in a native configuration. Here, we describe the use of microfluidic spinning to recapitulate complex concave and convex topographies over multiple length scales, required for biofabrication of a biomimetic 3D glomerulus.

Interfacial Tension of the Water-Diluted Bitumen Interface at High Bitumen Concentrations Measured Using a Microfluidic Technique.

The interfacial tension (IFT) is a critical parameter to inform our understanding of the phenomena of drop breakup and droplet-droplet coalescence in sheared water-in-diluted bitumen (dilbit) emulsions. A microfluidic extensional flow device (MEFD) was used to determine the IFT of the dilbit-water emulsion system for bitumen concentrations of 33%, 50%, and 67% by weight (solvent to bitumen ratio (S/B) = 2, 1, and 0.5, respectively) and two different pH values of water: 8.

Novel Activated Microbubbles-based Strategy to Coat Nanoparticles on Root Canal Dentin: Fluid Dynamical Characterization.

Introduction: Activated microbubbles (MBs) have the potential to deliver nanoparticles in complex microspaces such as root canals. The objective of the study is to determine the fluid dynamical parameters associated with ultrasonic, sonic, and manual activation of MBs in simulated root canals and to assess the effectiveness of surface coating formed by delivering chitosan nanoparticles using activated MBs within root canals in extracted teeth.

Methods: In stage 1, polydimethylsiloxane models were fabricated to determine the physical effects of MBs agitated manually (MM), sonically (MS), and ultrasonically (MU).

Mass transfer dynamics in the dissolution of Taylor bubbles.

The knowledge of thermodynamic and mass transfer parameters in gas-liquid systems is critical for the design of macroscale units for separation and reaction processes. The phenomenon of shrinkage of Taylor bubbles upon dissolution has the capability of supplying these design parameters, provided a reliable mathematical model is available for data deconvolution. Unfortunately, the existing models in the literature suffer from at least one of the following three major limitations.

Near-infrared incoherent broadband cavity enhanced absorption spectroscopy (NIR-IBBCEAS) for detection and quantification of natural gas components.

The principle of near-infrared incoherent broadband cavity enhanced absorption spectroscopy was employed to develop a novel instrument for detecting natural gas leaks as well as for testing the quality of natural gas mixtures. The instrument utilizes the absorption features of methane, butane, ethane, and propane in the wavelength region of 1100 nm to 1250 nm. The absorption cross-section spectrum in this region for methane was adopted from the HITRAN database, and those for the other three gases were measured in the laboratory.

An exploration of the reflow technique for the fabrication of an in vitro microvascular system to study occlusive clots.

Embolic ischemia and pulmonary embolism are health emergencies that arise when a particle such as a blood clot occludes a smaller blood vessel in the brain or the lungs, and restricts flow of blood downstream of the vessel. In this work, the reflow technique (Wang et al. Biomed.

The hydrodynamics of segmented two-phase flow in a circular tube with rapidly dissolving drops.

This article discusses boundary integral simulations of dissolving drops flowing through a cylindrical tube for large aspect ratio drops. The dynamics of drop dissolution is determined by three dimensionless parameters: λ, the viscosity of the drop fluid relative to the suspending fluid; Ca, the capillary number defining the ratio of the hydrodynamic force to the interfacial tension force; and k, a dissolution constant based on the velocity of dissolution. For a single dissolving drop, the velocity in the upstream region is greater than the downstream region, and for sufficiently large k, the downstream velocity can be completely reversed, particularly at low Ca.

The suppression of droplet-droplet coalescence in a sheared yield stress fluid.

Efforts to stabilize emulsions against coalescence in flow have often focused on modifying properties of the interface between the continuous and dispersed phases, to create a repulsive barrier against coalescence. But prior to experiencing any interaction force, the liquid film between two colliding drops has to drain, and if this drainage process is arrested, coalescence will be suppressed. In this work, scaling analyses and thin-film lubrication simulations are used to study the hydrodynamic drainage properties of thin films of a Bingham fluid (a yield stress fluid, which flows only when a critical stress is exceeded) created between two drops colliding under the action of a constant force.

Dispersion of a passive tracer in the pressure-driven flow of a non-colloidal suspension.

This paper numerically quantifies the dispersion of a solute, and in particular, the Taylor dispersion, in the pressure-driven flow of a non-colloidal suspension at moderately high volume fractions (0.2 to 0.5) through conduits of different cross-sectional shapes.