Hydrodynamic Shear Research Articles

Growth dynamic of biofilm-associated Naegleria fowleri in freshwater on various materials.

In industrial water systems, the occurrence of biofilm-associated pathogenic free-living amoebae (FLA) such as Naegleria fowleri is a potential hygienic problem, and factors associated with its occurrence remain poorly understood. This study aimed to evaluate the impact of four cooling circuit materials on the growth of N. fowleri in a freshwater biofilm formed at 42°C and under a hydrodynamic shear rate of 17 s-1 (laminar flow): polyvinyl chloride, stainless steel, brass, and titanium. Colonization of the freshwater biofilms by N. fowleri was found to be effective on polyvinyl chloride, stainless steel, and titanium. For these three materials, the ratio of (bacterial prey)/(amoeba) was found to control the growth of N. fowleri. All materials taken together, a maximum specific growth rate of 0.18 ± 0.07 h-1 was associated with a generation time of ~4 h. In contrast, no significant colonization of N. fowleri was found on brass. Therefore, the contribution of copper is strongly suspected.

Survival mechanisms of circulating tumor cells and their implications for cancer treatment.

Metastasis remains the principal trigger for relapse and mortality across diverse cancer types. Circulating tumor cells (CTCs), which originate from the primary tumor or its metastatic sites, traverse the vascular system, serving as precursors in cancer recurrence and metastasis. Nevertheless, before CTCs can establish themselves in the distant parenchyma, they must overcome significant challenges present within the circulatory system, including hydrodynamic shear stress (HSS), oxidative damage, anoikis, and immune surveillance. Recently, there has been a growing body of compelling evidence suggesting that a specific subset of CTCs can persist within the bloodstream, but the precise mechanisms of their survival remain largely elusive. This review aims to present an outline of the survival challenges encountered by CTCs and to summarize the recent advancements in understanding the underlying survival mechanisms, suggesting their implications for cancer treatment.

Self-Timed and Spatially Targeted Delivery of Chemical Cargo by Motile Liquid Crystal.

A key challenge underlying the design of miniature machines is encoding materials with time- and space-specific functional behaviors that require little human intervention. Dissipative processes that drive materials beyond equilibrium and evolve continuously with time and location represent one promising strategy to achieve such complex functions. This work reports how internal nonequilibrium states of liquid crystal (LC) emulsion droplets undergoing chemotaxis can be used to time the delivery of a chemical agent to a targeted location. During ballistic motion, hydrodynamic shear forces dominate LC elastic interactions, dispersing microdroplet inclusions (microcargo) within double emulsion droplets. Scale-dependent colloidal forces then hinder the escape of dispersed microcargo from the propelling droplet. Upon arrival at the targeted location, a circulatory flow of diminished strength allows the microcargo to cluster within the LC elastic environment such that hydrodynamic forces grow to exceed colloidal forces and thus trigger the escape of the microcargo. This work illustrates the utility of the approach by using microcargo that initiate polymerization upon release through the outer interface of the carrier droplet. These findings provide a platform that utilizes nonequilibrium strategies to design autonomous spatial and temporal functions into active materials.

Rapid, label-free, contactless measurement of membrane potential in excitable H9c2 cardiomyoblasts using ζ-potential

The measurement of cell membrane potential (V m) is important for understanding ion channel function. V m plays a role in several routine cellular functions and diseases, particularly in excitable cells such as muscle and nerve. However, measuring V m is difficult, relying either on labour-intensive direct measurement of single cells (intracellular electrodes, patch clamp) or indirect measurement of fluorescence intensity, using V m-sensitive labels. Here we demonstrate a direct measurement technique based on determination of the cell’s ζ-potential, the electrical potential at the hydrodynamic shear plane, approximately 1 nm beyond the cell surface. We demonstrate this principle using excitable H9c2 cardiomyoblasts, measured in both polarised and depolarised states, before and after extracellular intervention to alter cell ion concentration. Given widespread availability of ζ-potential measurement apparatus (most typically in chemistry and materials science settings), this offers a new method of measuring V m without the need for fluorescence measurements or calibration curves.

Biologically generated turbulent energy flux in shear flow depends on tensor geometry.

It has been proposed that biologically generated turbulence plays an important role in material transport and ocean mixing. Both experimental and numerical studies have reported evidence of the nonnegligible mixing by moderate Reynolds number swimmers, such as zooplankton, in quiescent water, especially at aggregation scales. However, the interaction between biologically generated agitation and the background flow, as a key factor in biologically generated turbulence that could reshape our previous knowledge of biologically generated turbulence, has long been ignored. Here, we show that the geometry between the biologically generated agitation and the background hydrodynamic shear can determine both the intensity and direction of biologically generated turbulent energy flux. Measuring the migration of a centimeter-scale swimmer-as represented by the brine shrimp Artemia salina-in a shear flow and verifying through an analog experiment with an artificial jet revealed that different geometries between the biologically generated agitation and the background shear can result in spectral energy transferring toward larger or smaller scales, which consequently intensifies or attenuates the large-scale hydrodynamic shear. Our results suggest that the long ignored geometry between the biologically generated agitation and the background flow field is an important factor that should be taken into consideration in future studies of biologically generated turbulence.

Mechanics and microstructure of blood plasma clots in shear driven rupture.

Intravascular blood clots are subject to hydrodynamic shear and other forces that cause clot deformation and rupture (embolization). A portion of the ruptured clot can block blood flow in downstream vessels. The mechanical stability of blood clots is determined primarily by the 3D polymeric fibrin network that forms a gel. Previous studies have primarily focused on the rupture of blood plasma clots under tensile loading (Mode I), our current study investigates the rupture of fibrin induced by shear loading (Mode II), dominating under physiological conditions induced by blood flow. Using experimental and theoretical approaches, we show that fracture toughness, i.e. the critical energy release rate, is relatively independent of the type of loading and is therefore a fundamental property of the gel. Ultrastructural studies and finite element simulations demonstrate that cracks propagate perpendicular to the direction of maximum stretch at the crack tip. These observations indicate that locally, the mechanism of rupture is predominantly tensile. Knowledge gained from this study will aid in the development of methods for prediction/prevention of thrombotic embolization.

Study on the mechanism of hydrodynamic manipulation of floc structure to achieve high-flux of coagulation macro-filtration for the rapid removal of Aphanizomenonflos-aquae

Coagulation-filtration hybrid process has been widely used in algae removal treatment to improve the water quality and alleviate the membrane fouling. However, the intricate interplay of how floc structure induced by coagulation hydraulic shear influences the cake layer and filtration performance in coagulation macro-filtration of microalgae remains unexplored. In this study, a novel coagulation filtration with macro-pore of 75 μm was first adopted for the rapid removal of Aphanizomenonflos-aquae, and the floc structure was artificially manipulated through various velocity gradients to explore the effect mechanism of the coagulation hydrodynamic shear on the macro-filtration performance from the perspectives of floc characteristics (size and fractal dimension) and cake layer structure (thickness and roughness). The results showed that an optimal average flux of 31257.64 ± 2776.28 L·m−2·h−1 can be achieved at a manipulated appropriate velocity gradient (19 s−1), which is 1.1–2.3 times the flux achieved at higher or non-velocity gradients. The flocs formed at low velocity gradient were large and loose, while those formed at high velocity gradient were small and compact. Subsequently, the cake layer stacked by loose flocs was thicker and coarser than that by compact flocs, and exhibited a lower specific cake resistance, yielding a higher average flux. Moreover, a theoretical model for average flux was developed by introducing the velocity gradient, which directly elucidates how hydrodynamic shear affects floc characteristic, cake structure and filtration flux for the coagulation macro-filtration of Aphanizomenonflos-aquae. This study lays a theoretical foundation for the optimization of coagulation macro-filtration performance of microalgae and provides a new solution for the large flux removal of cyanobacteria by artificially regulating the coagulation hydrodynamic shear.

Influence of hydrodynamic shear stress on activated algae granulation process for wastewater treatment

In this study, activated algae granule was formed by cultivating a mixed culture of the microalga Chlorella vulgaris and activated sludge in batch photobioreactors (PBRs). Without aeration, the granulation process was investigated through four different agitation speeds of 80, 120, 160, 200 rpm (shear stress of 0.04, 0.15, 0.35, 0.69 Pa). Hydrodynamic shear stress created by agitation affected the activated algae granulation through microeddies. The largest granule was achieved in the PBR with agitation speed of 200 rpm (R200) with shear stress of 0.69 Pa (size of 339 µm). In the other hand, lower shear stress in R160 (shear stress of 0.35 Pa) gave optimal results in terms of wastewater treatment efficiency and granule formation time (165 days of operation). Shear stress below 0.15 Pa (120 rpm) showed no granule formation during 220 days operation. While shear stress from 0.04–0.15 Pa could guarantee mass transfer for the entire co-culture without aeration, shear stress from 0.15–0.69 Pa was a suitable range for the granulation process of activated algae. This study reveals that activated algae granule formation through agitation mechanism is a promissing solution for wastewater treatment and microalgae biomass recovery to substantially increase the share of renewable energy in the global energy mix.

Wastewater Treatment Using Shear Enhanced Flotation Separation Technology: A Pilot Plant Study for Winery Wastewater Processing

The agricultural sector is one that requires and consumes enormous amounts of fresh water globally. Commercial wine production in particular uses large volumes of fresh water and, through various processes, generates significant quantities of wastewater. The wastewater produced by wineries typically exhibits elevated levels of chemical oxygen demand (COD), total suspended solids (TSS), an acidic pH, and varying salinity and nutrient contents. The overall characteristics of winery wastewater indicate that it is a potential environmental hazard if not processed and disposed of appropriately. Due to significant variations in wastewater contaminant levels among wineries, the implementation of a universally applicable, environmentally friendly, and sustainable waste management system seems practically unattainable. This study investigated the design, fabrication, and modification of a shear enhanced flotation separation (SEFS) pilot plant to be used as a primary treatment stage during winery wastewater processing. This technology combines the synergistic advantages of hydrodynamic shear, coagulation, flocculation, and dissolved air flotation. To date, there have been only limited publications on the feasibility and application of hydrodynamic shear and its potential to assist with coagulation/flocculation and flotation efficiencies specifically for winery wastewater treatment. The results obtained indicate that the SEFS pilot plant may well be able to process winery wastewater to a quality level where reuse of the water for irrigation of crops may be considered.

Housing of electrosynthetic biofilms using a roll-up carbon veil electrode increases CO2 conversion and faradaic efficiency in microbial electrosynthesis cells

Electrode-driven microbial electron transfer enables the conversion of CO2 into multi-carbon compounds. The electrosynthetic biofilms grow slowly on the surface and are highly susceptible to operational influences, such as hydrodynamic shear stress. In this study, a cylindrical roll-up carbon felt electrode was developed as a novel strategy to protect biofilms from shear stress within the reactor. The fabricated electrode allowed hydrogen bubble formation inside the structure, which enabled microbes to uptake hydrogen and convert CO2 to multi-carbon organic compounds. The roll-up electrode exhibited faster start-up and biofilm formation than the conventional linear shape carbon felt. The acetate yield and cathodic faradaic efficiency increased by 80% and 34%, respectively, and the bioelectrochemical stability was improved significantly. The roll-up structure increased biofilm development per unit electrode surface by three to five-fold. The roll-up configuration improved biofilm formation on the electrode, which enhanced the performance of microbial electrosynthesis-based CO2 valorization.

Integrating shear flow and trypsin treatment to assess cell adhesion strength.

Cell adhesion is of fundamental importance in cell and tissue organization and for designing cell-laden constructs for tissue engineering. Prior methods to assess cell adhesion strength for strongly adherent cells using hydrodynamic shear flow either involved the use of specialized flow devices to generate high shear stress or used simpler implementations like larger height parallel plate chambers that enable multihour cell culture but generate low wall shear stress and are, hence, more applicable for weakly adherent cells. Here, we propose a shear flow assay for adhesion strength assessment of strongly adherent cells that employs off-the-shelf parallel plate chambers for shear flow as well as simultaneous trypsin treatment to tune down the adhesion strength of cells. We implement the assay with a strongly adherent cell type and show that wall shear stress in the 0.07-7 Pa range is sufficient to dislodge the cells with simultaneous trypsin treatment. Imaging of cells over a square centimeter area allows cell morphological analysis of hundreds of cells. We show that the cell area of cells that are dislodged, on average, does not monotonically increase with wall shear stress at the higher end of wall shear stresses used and suggest that this can be explained by the likely higher resistance of high circularity cells to trypsin digestion. The adhesion strength assay proposed can be used to assess the adhesion strength of both weakly and strongly adherent cell types and has the potential to be adapted for substrate stiffness-dependent adhesion strength assessment in mechanobiology studies.

Effects of subgrid‐scale turbulence parametrization on the representation of clear‐air turbulence using kilometre‐ to hectometre‐scale numerical simulations

A turbulence event arising in a jet exit region above the Belgium–Luxembourg area, determined from airliner in‐situ measurements, is reproduced using the meteorological models Application de la Recherche à l'Opérationnel à Méso‐Echelle (AROME) and Meso‐NH at horizontal resolutions of 1.3 km and 260 m. The behaviour of the subgrid turbulence scheme at 1.3 km and its sensitivity to various parameters are analysed, with results being evaluated using measurements. An increase of the vertical resolution around the tropopause levels with m is shown to greatly enhance the turbulence representation. The use of a non‐local formulation of the mixing length in the current parametrization at 1.3 km allows reproduction of a turbulence signal in agreement with the observations. On the contrary, the use of a fully three‐dimensional formulation has no impact on the simulation at this resolution (1.3 km). Using the 260 m runs, this turbulence event is linked to hydrodynamical wind shear instabilities characterized by horizontal wavelength of 4.5 km, sub‐resolved at the operational resolution. At these small grid‐size scales, turbulence evolution and equation budgets reflect an equilibrium between dynamical production and turbulence dissipation, and highlight the importance of horizontal gradients. Subgrid turbulence intensities are assessed to be underestimated by the current parametrization at 1.3 km when compared with this high‐resolution reference simulation. Finally, different tests on the turbulence parametrization illustrate a transfer between resolved and subgrid kinetic energy in the model. This transfer stresses the importance of a trade‐off between mixing intensity and the representation of wind at resolved scales for the upper troposphere.

Structure-Activity Relationships of Low Molecular Weight Alginate Oligosaccharide Therapy against Pseudomonas aeruginosa.

Low molecular weight alginate oligosaccharides have been shown to exhibit anti-microbial activity against a range of multi-drug resistant bacteria, including Pseudomonas aeruginosa. Previous studies suggested that the disruption of calcium (Ca2+)-DNA binding within bacterial biofilms and dysregulation of quorum sensing (QS) were key factors in these observed effects. To further investigate the contribution of Ca2+ binding, G-block (OligoG) and M-block alginate oligosaccharides (OligoM) with comparable average size DPn 19 but contrasting Ca2+ binding properties were prepared. Fourier-transform infrared spectroscopy demonstrated prolonged binding of alginate oligosaccharides to the pseudomonal cell membrane even after hydrodynamic shear treatment. Molecular dynamics simulations and isothermal titration calorimetry revealed that OligoG exhibited stronger interactions with bacterial LPS than OligoM, although this difference was not mirrored by differential reductions in bacterial growth. While confocal laser scanning microscopy showed that both agents demonstrated similar dose-dependent reductions in biofilm formation, OligoG exhibited a stronger QS inhibitory effect and increased potentiation of the antibiotic azithromycin in minimum inhibitory concentration and biofilm assays. This study demonstrates that the anti-microbial effects of alginate oligosaccharides are not purely influenced by Ca2+-dependent processes but also by electrostatic interactions that are common to both G-block and M-block structures.

Interfacial Adsorption Controls Particle Formation in Antibody Formulations Subjected to Extensional Flows and Hydrodynamic Shear

During their manufacturing and delivery to patients, therapeutic proteins are commonly exposed to various interfaces and to hydrodynamic shear forces. Although adsorption of proteins to solid–liquid interfaces is known to foster formation of protein aggregates and particles, the impact of shear remains controversial, in part because of experimental challenges in separating the effects of shear from those caused by simultaneous exposure to interfaces. Extensional flows (occurring when solutions flow through sudden contractions) exert localized elongational forces that have been suspected to be damaging to proteins. In this work, we measured aggregation and particle formation in formulations of polyclonal and monoclonal antibodies subjected to extensional flow, high shear (105 s−1) and exposure to stainless-steel/water interfaces. Modification of the surface charge at the stainless steel/water interface changed protein adsorption characteristics without altering shear profiles, enabling shear and interfacial interactions to be separated. Even under conditions where antibodies were subjected to high hydrodynamic shear and extensional flow, production of subvisible particles could be inhibited by modifying the stainless-steel surface charge to minimize antibody adsorption. Digital images of particles recorded by flow imaging microscopy (FIM) and analyzed with machine learning algorithms were consistent with a particle formation mechanism by which antibodies adsorb and aggregate at the stainless-steel/water interface and subsequently form particles when shear displaces the interfacial aggregates, transporting them into the bulk solution. Topographical differences measured using atomic force microscopy (AFM) supported the proposed mechanism by showing reduced levels of protein adsorption on surface-charge-modified stainless-steel.

Development of a scale-up strategy for an aerated coaxial mixer containing a non-Newtonian fluid: A mass transfer approach

Coaxial mixers have been shown to be effective in enhancing the hydrodynamic stress and shear environment inside the aerated systems. However, the scale-up study of the aerated coaxial mixing reactors based on a constant mass transfer coefficient has never been reported in the literature. In this study, for the first time, a practical technique is suggested to evaluate the scalability of these systems in terms of a constant mass transfer coefficient. The effects of impeller speed, impeller type, aeration rate, and pumping direction on the mass transfer, power consumption, gas holdup profile, fluid hydrodynamics, and energy dissipation rate were explored for gas dispersion in non-Newtonian fluids inside coaxial mixers through tomography, dynamic gassing-in, and computational fluid dynamics. It was found that a practical approach to preserve the mass transfer coefficient of the large-scale coaxial mixer the same as its small-scale counterpart was to maintain the volumetric aeration rate per working fluid volume constant.

A Fluid Multivalent Magnetic Interface for High-Performance Isolation and Proteomic Profiling of Tumor-Derived Extracellular Vesicles.

Isolation and analysis of tumor-derived extracellular vesicles (T-EVs) are important for clinical cancer management. Here, we develop a fluid multivalent magnetic interface (FluidmagFace) in a microfluidic chip for high-performance isolation, release, and protein profiling of T-EVs. The FluidmagFace increases affinity by 105-fold with fluidity-enhanced multivalent binding to improve isolation efficiency by 13.9% compared with a non-fluid interface. Its anti-adsorption property and microfluidic hydrodynamic shear minimize contamination, increasing detection sensitivity by two orders of magnitude. Moreover, its reversibility and expandability allow high-throughput recovery of T-EVs for mass spectrometric protein analysis. With the chip, T-EVs are detected in all tested cancer samples with identification of differentially expressed proteins compared with healthy controls. The FluidmagFace opens a new avenue to isolation and release of targets for cancer diagnosis and biomarker discovery.

A Fluid Multivalent Magnetic Interface for High‐Performance Isolation and Proteomic Profiling of Tumor‐Derived Extracellular Vesicles

AbstractIsolation and analysis of tumor‐derived extracellular vesicles (T‐EVs) are important for clinical cancer management. Here, we develop a fluid multivalent magnetic interface (FluidmagFace) in a microfluidic chip for high‐performance isolation, release, and protein profiling of T‐EVs. The FluidmagFace increases affinity by 105‐fold with fluidity‐enhanced multivalent binding to improve isolation efficiency by 13.9 % compared with a non‐fluid interface. Its anti‐adsorption property and microfluidic hydrodynamic shear minimize contamination, increasing detection sensitivity by two orders of magnitude. Moreover, its reversibility and expandability allow high‐throughput recovery of T‐EVs for mass spectrometric protein analysis. With the chip, T‐EVs were detected in all tested cancer samples with identification of differentially expressed proteins compared with healthy controls. The FluidmagFace opens a new avenue to isolation and release of targets for cancer diagnosis and biomarker discovery.

Elongation enhances migration through hydrodynamic shear

Elongation enhances migration through hydrodynamic shear

Fluid Flow Templating of Polymeric Soft Matter with Diverse Morphologies.

It is challengingto find a conventional nanofabrication technique that can consistently produce soft polymeric matter of high surface area and nanoscale morphology in a way that is scalable, versatile, and easily tunable. Here, the capabilities of a universal method for fabricating diverse nano- and micro-scale morphologies based on polymer precipitation templated by the fluid streamlines in multiphasic flow are explored. It is shown that while the procedure is operationally simple, various combinations of its intertwined mechanisms can controllably and reproducibly lead to the formation of an extraordinary wide range of colloidal morphologies. By systematically investigating the process conditions, 12distinct classes of polymer micro- and nano-structures including particles, rods, ribbons, nanosheets, and soft dendritic colloids (dendricolloids) are identified. The outcomes are interpreted by delineating the physical processes into three stages: hydrodynamic shear, capillary and mechanical breakup, and polymer precipitation rate. The insights into the underlying fundamental mechanisms provide guidance toward developing a versatile and scalable nanofabrication platform. It is verified that the liquid shear-based technique is versatile and works well with many chemically diverse polymers and biopolymers, showing potential as a universal tool for simple and scalable nanofabrication of many morphologically distinct soft matter classes.

Mechanistic aspects of nanocellulose–cationic starch–colloidal silica systems for papermaking

Optimization of a chemical additive program for a paper machine can require attention to both colloidal charges and kinetic effects. This work considered an additive program with two negatively charged substances (nanofibrillated cellulose [NFC] and colloidal silica) and two positively charged items (cationic starch and cationic acrylamide copolymer retention aid). Results were shown to depend on charge interactions; however, that clearly was not the whole story. Some findings related to cationic demand, dewatering, fine-particle retention, and flocculation among fibers were best explained in terms of at least partly irreversible complexation interactions between the charged entities. Adjustments in ratios between oppositely charged additives, their sequences of addition, and effects of hydrodynamic shear levels all affected the results. In general, the most promising results were obtained at a cationic starch level of 0.25% to 0.5% based on sheet solids in systems where the cationic starch was used as a pretreatment for NFC.