Glucocorticoids Alter Bone Microvascular Barrier via MAPK/Connexin43 Mechanisms.

Glucocorticoids (GCs) are standard-of-care treatments for inflammatory and immune disorders, and their long-term use increases the risk of osteoporosis. Although GCs decrease bone functionality, their role in bone microvasculature is incompletely understood. Herein, the study investigates the mechanisms of bone microvascular barrier function via osteoblast-endothelial interactions in response to GCs.

Flow Activation Energy of High-Concentration Monoclonal Antibody Solutions and Protein-Protein Interactions Influenced by NaCl and Sucrose.

The solution viscosity and protein-protein interactions (PPIs) as a function of temperature (4-40 °C) were measured at a series of protein concentrations for a monoclonal antibody (mAb) with different formulation conditions, which include NaCl and sucrose. The flow activation energy () was extracted from the temperature dependence of solution viscosity using the Arrhenius equation. PPIs were quantified via the protein diffusion interaction parameter () measured by dynamic light scattering, together with the osmotic second virial coefficient and the structure factor obtained through small-angle X-ray scattering.

Lignin Adhesion for High-Performance Bamboo Composites.

Bamboo composite is an attractive candidate for structural materials in applications such as construction, the automotive industry, and logistics. However, its development has been hindered due to the use of harmful petroleum-derived synthetic adhesives or low-bonding biobased adhesives. Herein, we report a novel bioadhesion strategy based on lignin bonding that can process natural bamboo into a scalable and high-performance composite.

Mechanical Regulation of Oral Epithelial Barrier Function.

Epithelial cell function is modulated by mechanical forces imparted by the extracellular environment. The transmission of forces onto the cytoskeleton by modalities such as mechanical stress and matrix stiffness is necessary to address by the development of new experimental models that permit finely tuned cell mechanical challenges. Herein, we developed an epithelial tissue culture model, named the 3D Oral Epi-mucosa platform, to investigate the role mechanical cues in the epithelial barrier.

Applicability of the Generalized Stokes-Einstein Equation of Mode-Coupling Theory to Near-Critical Polyelectrolyte Complex Solutions.

We examine whether the mode-coupling theory of Kawasaki and Ferrell (KF) [Kawasaki, K. Kinetic Equations and Time Correlation Functions of Critical Fluctuations. 1970, 61 (1), 1-56; Ferrell, R.

Microfluidic techniques for mechanical measurements of biological samples.

The use of microfluidics to make mechanical property measurements is increasingly common. Fabrication of microfluidic devices has enabled various types of flow control and sensor integration at micrometer length scales to interrogate biological materials. For rheological measurements of biofluids, the small length scales are well suited to reach high rates, and measurements can be made on droplet-sized samples.

A small-volume microcapillary rheometer.

We demonstrate a capillary device used to measure the shear rate-dependent viscosity of microliter scale volumes. Liquid samples are driven pneumatically through a microcapillary and partially fill a larger glass capillary. The glass capillary is mounted on an optical linear sensor to track the air-liquid meniscus in real time and trigger the reversal of flow direction by switching a pneumatic valve.

Blood vessel-on-a-chip examines the biomechanics of microvasculature.

We use a three-dimensional (3D) microvascular platform to measure the elasticity and membrane permeability of the endothelial cell layer. The microfluidic platform is connected with a pneumatic pressure controller to apply hydrostatic pressure. The deformation is measured by tracking the mean vessel diameter under varying pressures up to 300 Pa.

Entrance effects and high shear rate rheology of shear banding wormlike micelle fluids in a microcapillary flow.

The viscosity of a shear-banding wormlike micelle solution at high shear rates is investigated using capillary rheology and particle streak velocimetry. Measurements of the flow profile and pressure gradient show an extended entrance region, which exceeds a length to diameter ratio of 100, to reach a fully developed flow. We characterized this entrance region for capillaries with different cross-sections and use the results to select a downstream portion of the capillary where viscosity measurements can be made on fully developed flow.

Capillary RheoSANS: measuring the rheology and nanostructure of complex fluids at high shear rates.

Complex fluids containing micelles, proteins, polymers and inorganic nanoparticles are often processed and used in high shear environments that can lead to structural changes at the nanoscale. Here, capillary rheometry is combined with small-angle neutron scattering (SANS) to simultaneously measure the viscosity and nanostructure of model complex fluids at industrially-relevant high shear rates. Capillary RheoSANS (CRSANS) uses pressure-driven flow through a long, flexible, silica capillary to generate wall shear rates up to 10 s and measure pressure drops up to 500 bar.

Three-dimensional structures and symmetry breaking in viscoelastic cross-channel flow.

Using holographic particle tracking, we report the three-dimensional flow structure organizing the viscoelastic instability in cross-channel flow. Beyond a critical Wi, the advective core flow undergoes an out-of-plane instability marked by the emergence of tertiary flow, resembling that of the toroidal vortices in Taylor-Couette geometry. The out-of-plane flow component distorts the separatrix between the impinging inflow streams, triggering symmetry breaking normal to the extension plane.

Flow Resistance and Structures in Viscoelastic Channel Flows at Low Re.

The flow of viscoelastic fluids in channels and pipes remains poorly understood, particularly at low Reynolds numbers. Here, we investigate the flow of polymeric solutions in straight channels using pressure measurements and particle tracking. The flow friction factor f_{η} versus flow rate exhibits two regimes: a transitional regime marked by rapid increase in drag, and a turbulentlike regime characterized by a sudden decrease in drag and a weak dependence on flow rate.

Upstream vortex and elastic wave in the viscoelastic flow around a confined cylinder.

The viscoelastic flow past a cylinder is a classic benchmark problem that is not completely understood. Using novel 3D holographic particle velocimetry, we report three main discoveries of the elastic instability upstream of a single cylinder in viscoelastic channel flow. First, we observe that upstream vortices initiate at the corner between the cylinder and the wall and grow with increasing flow rate.

Flow fluctuations in wormlike micelle fluids.

We investigate the unstable flow of wormlike micelle solutions in pressure driven capillary flow, with a focus on the effect of entrance geometry on the fluid fluctuations. The flow is measured at different points in the capillary using particle image velocimetry while simultaneously measuring the pressure drop across the entire capillary. The fluctuations are characterized by rapid flow rate jumps that correspond with a decrease in the pressure drop followed by a longer recovery period.

Jetting of a shear banding fluid in rectangular ducts.

Non-Newtonian fluids are susceptible to flow instabilities such as shear banding, in which the fluid may exhibit a markedly discontinuous viscosity at a critical stress. Here we report the characteristics and causes of a jetting flow instability of shear banding wormlike micelle solutions in microfluidic channels with rectangular cross sections over an intermediate volumetric flow regime. Particle-tracking methods are used to measure the three-dimensional flow field in channels of differing aspect ratios, sizes, and wall materials.

Reversible Adsorption Kinetics of Near Surface Dimer Colloids.

We investigate the effect of shape on reversible adsorption kinetics using colloidal polystyrene dimers near a solid glass surface as a model system. The interaction between colloid and wall is tuned using electrostatic, depletion, and gravity forces to produce a double-well potential. The dwell time in each of the potential wells is measured from long duration particle trajectories.

A colloid model system for interfacial sorption kinetics.

Particle adsorption to an interface may be a complicated affair, motivating detailed measurements of various processes involved, to discover better understanding of the role of particle characteristics and solution conditions on adsorption coverage and rate. Here we use micron size colloids with a weak interfacial interaction potential as a model system to track particle motion and measure the rates of desorption and adsorption. The colloid-interface interaction strength is tuned to be less than 10 kBT so that it is comparable to many nanoscale systems of interest such as proteins at interfaces.

Vesicle deformation in DC electric pulses.

The transient deformation of giant vesicles in square DC electric pulses is investigated. We experimentally observe the theoretically predicted transition from an oblate to prolate ellipsoidal shape in the case of a quasi-spherical vesicle encapsulating solution less conducting than the suspending medium. The transition is detected by utilizing a two-step pulse in order to avoid electroporation and vesicle collapse.

Electrohydrodynamic rotations of a viscous droplet.

We report a fluid system which exhibits chaotic dynamics under creeping flow conditions. A droplet in a uniform dc electric field deforms into an ellipsoid that can undergo irregular rotational motions. The nonlinear drop electrohydrodynamics is explained by a theoretical model which includes anisotropy in the polarization relaxation due to drop asphericity and charge convection due to rotational drop flow.