Hydrodynamic Trapping Research Articles

Mapping hydrodynamic structure with sparse or no well data

Hydrodynamic traps are usually mapped using well pressure data to transform structural depth maps, but if well data are sparse then hydrodynamic maps produced this way may have large uncertainties. An alternative approach that does not rely on well data is described here, utilizing simplified, locally planar representation of the potentiometric surface. Ranges of hydraulic gradient magnitudes and azimuths representing different potentiometric surface orientations, together with a range of possible density contrasts between the flowing and trapped fluids, define a three-dimensional array, termed here ‘hydrodynamic space’. This array can be constrained and simplified by reasonable assumptions and the introduction of an additional new concept that combines the hydraulic gradient magnitude and fluid density contrast into a single parameter termed ‘potentiometric transform’. Ranges of these parameters yield a set of hydrodynamic structural maps. The fineness of sampling the hydrodynamic space parameters is limited only by the resources available to support the workflow. The array can be automatically assessed in terms of hydrodynamic trap volumes by applying a structural closure algorithm that isolates and characterizes dip-closed structure. Closure volumes across the map set are ranked by spatial distribution analysis that informs exploration programs relevant to any subsurface fluid management application. The method is described for the first time here and illustrated by application to a real structural dataset.

Capillarity-Driven Enrichment and Hydrodynamic Trapping of Trace Nucleic Acids by Plasmonic Cavity Membrane for Rapid and Sensitive Detections.

Small-reactor-based polymerase chain reaction (PCR) has attracted considerable attention. A significant number of tiny reactors must be prepared in parallel to capture, amplify, and accurately quantify few target genes in clinically relevant large volume, which, however, requires sophisticated microfabrication and longer sample-to-answer time. Here, single plasmonic cavity membrane is reported that not only enriches and captures few nucleic acids by taking advantage of both capillarity and hydrodynamic trapping but also quickly amplifies them for sensitive plasmonic detection. The plasmonic cavity membrane with few nanoliters in a void volume is fabricated by self-assembling gold nanorods with SiO2 tips. Simulations reveal that hydrodynamic stagnation between the SiO2 tips is mainly responsible for the trapping of the nucleic acid in the membrane. Finally, it is shown that the plasmonic cavity membrane is capable of enrichingsevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genes up to 20000-fold within 1min, amplifying within 3min, and detecting the trace genes as low as a single copy µL-1. It is anticipated that this work not only expands the utility of PCR but also provides an innovative way of the enrichment and detection of trace biomolecules in a variety of point-of-care testing applications.

Single-cell trapping and retrieval in open microfluidics

Among various single-cell analysis platforms, hydrodynamic cell trapping systems remain relevant because of their versatility. Among those, deterministic hydrodynamic cell-trapping systems have received significant interest; however, their applications are limited because trapped cells are kept within the closed microchannel, thus prohibiting access to external cell-picking devices. In this study, we develop a hydrodynamic cell-trapping system in an open microfluidics architecture to allow external access to trapped cells. A technique to render only the inside of a polydimethylsiloxane (PDMS) microchannel hydrophilic is developed, which allows the precise confinement of spontaneous capillary flow in the open-type microchannel with a width on the order of several tens of micrometers. Efficient trapping of single beads and single cells is achieved, in which trapped cells can be retrieved via automated robotic pipetting. The present system can facilitate the development of new single-cell analytical systems by bridging between microfluidic devices and macro-scale apparatus used in conventional biology.

Experimental analysis of flow topology and particle behavior in microcavities

Efficient hydrodynamic particle trapping requires the precise control of flow structures that serve as hydrodynamic traps. Microfluidic structures, such as microcavities of various shapes and sizes, can be applied as hydrodynamic traps, and the exerting force can be controlled by changing the geometrical parameters and flow regimes of the cavities. In this study, the capability of trapping microparticles in rectangular, semicircular, and triangular microcavities is experimentally investigated. The flow structure in microcavities with a length-to-depth ratio L/h of 1–4 for rectangular cavities and L/h = 1–2 for semicircular and triangular cavities at a Reynolds number ranging between 1 and 1000 is visualized using a microparticle image velocimetry system. Additionally, patches of 20 µm particles are visualized using a high-speed camera. Different flow phases, namely attached, transitional, and separated, are observed and correlated with the cavity parameters and flow regime. Additionally, qualitative flow parameters determining particle behavior, such as the vortex center location and temporal vortical stability, are analyzed. Finally, the particle behavior is correlated with the flow structure in the cavities, and guidelines for the development of the optimal design of micro- and nanofluidic devices are discussed.

A multi-depth spiral milli fluidic device for whole mount zebrafish antibody staining

Whole mount zebrafish antibody staining (ABS) is a common staining technique used to localize protein information in a zebrafish embryo or larva. Like most biological assays, the whole mount zebrafish ABS is still largely conducted manually through labor intensive and time-consuming steps which affect both consistency and throughput of the assay. In this work, we develop a milli fluidic device that can automatically trap and immobilize the fixed chorion-less zebrafish embryos for the whole mount ABS. With just a single loading step, the zebrafish embryos can be trapped by the milli fluidic device through a chaotic hydrodynamic trapping process. Moreover, a consistent body orientation (i.e., head point inward) for the trapped zebrafish embryos can be achieved without additional orientation adjustment device. Furthermore, we employed a consumer-grade SLA 3D printer assisted method for device prototyping which is ideal for labs with limited budgets. Notably, the milli fluidic device has enabled the optimization and successful implementation of whole mount zebrafish Caspase-3 ABS. We demonstrated our device can accelerate the overall procedure by reducing at least 50% of washing time in the standard well-plate-based manual procedure. Also, the consistency is improved, and manual steps are reduced using the milli fluidic device. This work fills the gap in the milli fluidic application for whole mount zebrafish immunohistochemistry. We hope the device can be accepted by the zebrafish community and be used for other types of whole mount zebrafish ABS procedures or expanded to more complicated in situ hybridization (ISH) procedure.Graphical

A microfluidic device for selective pairing and electrofusion of cell-sized liposomes

Electrofusion is a rapid and straightforward method for merging natural and synthetic cells. The accuracy of the fusion process can be improved through the use of micromanipulation or by implementing microfluidic devices with micro-traps and microelectrodes. However, these approaches have their limitations, including contamination, sample evaporation, inability to exchange solutions, and difficulty in removing unwanted pairs in the traps. In this paper, we present a microfluidic device that utilizes a hydrodynamic pairing system and microelectrodes to achieve accurate electrofusion. Our hydrodynamic pairing system involves two hydrodynamic trapping units that are duplicated in a mirror-symmetric configuration and connected at the two trapping channels. We install alloy-based microelectrodes by vacuum-filling method sandwiching the pairing part. Using the fabricated device, we demonstrate accurate pairing and efficient electrofusion of cell-sized liposomes. Our device would be a valuable tool in controlling biochemical reactions in artificial cells.

A microfluidic-based In-situ investigation of swelling dynamics of superabsorbent polymer microparticles

This paper presents a novel microfluidic-based technique for in-situ time-lapse investigation of the dynamic water absorption (or swelling) of individual superabsorbent polymer (SAP) microparticles (MPs). Most prior studies were restricted to using gravimetric techniques to investigate the equilibrium state of the swelled SAP macroparticles, without considering their swelling dynamics. Time-lapse investigation of the swelling rate is essential for optimizing SAP-MPs' performance to meet the needs of different applications. Moreover, since swelling occurs through the surface of SAP particles, we hypothesize that decreasing their size to microscale (i.e., SAP-MPs) could potentially improve their performance due to the increased surface area-to-volume ratio. In this context, the proposed microfluidic device enabled hydrodynamic trapping of an array of individual SAP-MPs and in-situ investigation of their swelling behaviour under a microscope. The SAP-MPs were initially suspended in ethanol and loaded into the microfluidic device. Once they were trapped, the fluid medium was switched to water to trigger their swelling. Acrylic acid (AA)/acrylamide (Aam)-based SAP-MPs in size range of 250–300 µm were investigated to characterize the device's performance. The SAP-MPs' average trapping time and yield in the device were 9.56 s per SAP-MP and 92%, respectively, at an ethanol loading flow rate of 0.15 mL/min. A minimum water flow rate of 5 mL/min was required to achieve an average ethanol-to-water transition time of 10 s. This was needed to suppress the effect of the solution exchange on the swelling behavior of the SAP-MPs. The equilibrium volumetric swelling ratio (VSReq), swelling rate (SR), and initial SR of AA-Aam-based SAP-MPs were determined to be 5.59 ± 0.13 (m3/m3), 0.039 ± 0.002 (m3/m3.s), and 0.068 ± 0.010 (m3/m3.s), respectively. A significant effect of the neutralization degree (ND) on the swelling behavior of AA-Aam-based SAP-MPs was also observed. At 90% ND, the maximum VSReq of 79.45 ± 2.49 m3/m3 and SR of 1.11 ± 0.047 m3/m3·s were achieved. This microfluidic platform could be used to conduct parametric study and real-time characterization of various SAP-MPs in biological, chemical, medical, and agricultural applications.

Dual hydrodynamic trap based on coupled stagnation point flows

Recent advancements in science and engineering have allowed for trapping and manipulation of individual particles and macromolecules within an aqueous medium using a flow-based confinement method. In this work, we demonstrate the feasibility of trapping and manipulating two particles using coupled planar extensional flows. Using Brownian dynamics simulations and a proportional feedback control algorithm, we show that two micro/nanoscale particles can be simultaneously confined and manipulated at the stagnation points of a pair of interconnected planar extensional flows. We specifically studied the effect of strain rate, particle size, and feedback control parameters on particle confinement. We also demonstrate precise control of the interparticle distance by manipulating the strain rates at both junctions and particle position at one of the junctions. We further discuss the advantages and limitations of the dual hydrodynamic trap in comparison to existing colloidal particle confinement methods and outline some potential applications in polymer science and biology. Our results demonstrate the versatility of flow-based confinement and further our understanding of feedback-controlled particle manipulation.

Balancing of Flow at Microfluidic Apertures

Computational fluid dynamics simulations are used to obtain a radially symmetrical flow profile at an aperture of a microfluidic channel by manually arranging flow‐directing obstacles around the aperture. For the first time, the flow profile is improved by calculating the coefficient of variation (CoV), which is applied to the flow velocity magnitude along coaxially arranged circles below the aperture in the microfluidic channel. A minimum CoV of 0.03 is obtained at the circle with the same diameter as the aperture. Channels with the optimized design are fabricated by lamination of two layers of dry film resist and patterned with UV‐lithography. The aperture is formed by using an inductively coupled plasma reactive ion etching process. Video recording of the flow behavior confirmed the simulation results experimentally. The proposed channel design and the optimization method can favorably be used for a balanced hydrodynamic trapping of particles or cells at apertures.

Iron–titanium sands of the Atlantic beaches between Tan-Tan and Tarfaya (southwest Morocco): Characterisation and origin

In Morocco, the most important placers of ferrotitanium minerals are found along the Laâouina–Cape Juby Atlantic coastline, where they accumulate in the upper parts of the foreshores. The heavy minerals would come from the dismantling of the acidic to intermediate magmatic rocks of the Precambrian Anti-Atlasic buttonholes and from the Meseta basement where crystallophyllous rocks predominate. The sands emanating from this erosion, once ejected by the rivers in the Atlantic, are transported by the littoral drift in the direction of the south before being trapped at the level of the great virgation of the shoreline of Laâouina–Cape Juby. The wind deflation, in its turn, reinforces this sorting by carrying away the white sands towards the continent and also the black sands sometimes. The cliffs along the coast of Laâouina–Sidi Akhfenir are, however, barriers against wind loss unlike the sector of Sidi-Akhfenir–Cape Juby where the continuous migration of sands to the hinterland is facilitated by the absence of cliffs. The conjunction of these factors has the consequence of weakening the retention of sands' ferrotitanium in the sector Sidi Akhfenir–Cape Juby compared with its counterpart of Laâouina–Sidi Akhfenir. In general, the Laâouina–Cape Juby coastline can be considered a morphological and hydrodynamic trap whose concentrations in ferrotitanium minerals are likely to earn the quality of a mining district despite its seasonal instability and the difficulty of estimating reserves. Indeed, in this supposed district, heavy minerals total about 95 % of the raw sediments and ilmenite predominates and its alteration state is only superficial.

A simple catch: Fluctuations enable hydrodynamic trapping of microrollers by obstacles.

It is known that obstacles can hydrodynamically trap bacteria and synthetic microswimmers in orbits, where the trapping time heavily depends on the swimmer flow field and noise is needed to escape the trap. Here, we use experiments and simulations to investigate the trapping of microrollers by obstacles. Microrollers are rotating particles close to a bottom surface, which have a prescribed propulsion direction imposed by an external rotating magnetic field. The flow field that drives their motion is quite different from previously studied swimmers. We found that the trapping time can be controlled by modifying the obstacle size or the colloid-obstacle repulsive potential. We detail the mechanisms of the trapping and find two remarkable features: The microroller is confined in the wake of the obstacle, and it can only enter the trap with Brownian motion. While noise is usually needed to escape traps in dynamical systems, here, we show that it is the only means to reach the hydrodynamic attractor.

Using Numerical Reservoir Simulation to Assess CO2 Capture and Underground Storage, Case Study on a Romanian Power Plant and Its Surrounding Hydrocarbon Reservoirs

During current times, it is acknowledged that there is the often presence of extreme meteorological phenomena including floods and landslides, due to heavy rains, large wildfires, due to heat or droughts, permafrost melting, etc. At this stage, the world admits that anthropic activities have an important impact on these phenomena and considers that greenhouse gases are at the core of this climate change. The most common greenhouse gasses have general formulae COX and/or NOX, and they are released during different energy generating/conversion processes such as electric energy generation from fossil fuels or mechanical energy obtained from by-products of fossil fuels. Once acknowledged, the world’s countries have developed long-term strategies to eliminate gradually the release of these gases directly into Earth’s atmosphere. E.g., the EU aims to be climate-neutral by 2050; i.e., its economy will have net-zero greenhouse gas emissions. For this to happen, different effective methodologies have been drafted and implemented with underground gas storage in hydrocarbon depleted geological formations and/or saline aquifers being ones of significance when it comes to electric energy generation from fossil fuels in controlled spaces. The paper presents the simulation of capturing and injecting of these greenhouse gases through injection wells in neighboring depleted natural gas reservoirs using commercial numerical simulators for the Iernut natural gas (CH4) burning power plant which is one of Romania’s most important gas plants. Within this simulation study, the total CO2 quantity that can be stored via the proposed carbon capture and sequestration study and the proportion of each of the three CO2 storage mechanisms involved in the process (physical trapping, hydrodynamic trapping, and geochemical trapping) were determined and presented. Even though previous local studies investigated the potential of CO2 storage and sequestration into the Romanian underground reservoirs, none of it considered using the depleted hydrocarbon reservoirs surrounding the Iernut power plant for this process.

Microfluidic aspiration-assisted electrical impedance spectroscopy system is a reliable tool for the characterization of oocyte hardening

The fertilization rate in assisted reproduction depends significantly on the quality of the oocyte, especially on the hardening of the zona pellucida, which is a gelatinous layer of extracellular matrix surrounding the oocyte. Current reproduction techniques use elaborated and frequent manual manipulation steps, which are expensive, non-standardized, and observer dependent. However, a technically simple to perform, reliable and robust, indisputable and observer independent method is needed to characterize the biophysical properties of the oocyte, especially the hardening state of the zona pellucida. Therefore, a microfluidic-based cell trap technique is proposed, which offers a simple oocyte handling through hydrodynamic trapping. The zona pellucida aspiration at an aperture was measured observer-independently by electrical impedance spectroscopy for the first time. Impedance spectra were fitted by an appropriate equivalent electrical circuit model. A numerical in combination with an analytical model correlated the impedance changes with the aspiration length changes, from which Young’s modulus of the zona pellucida was calculated. As a proof-of-concept, the setup was applied to three different genetic mouse oocyte models owing a super soft, a normal and a stiff zona pellucida structure, respectively. The presented measurement technique can either be used for human and animal reproductive medicine to assist artificial fertilization, for the development of contraceptives using the zona pellucida as a barrier or, in general, for all kinds of characterization of rheological properties of single cells.

Characterisation of hydrodynamic trapping in microfluidic cross-slot devices for high strain rate applications.

Hydrodynamic trapping of a particle or cluster of particles based on contact and non-contact approaches has brought prominent insights to micro-nano scale applications. Of the non-contact methods, image-based real-time control in cross-slot microfluidic devices is one of the most promising potential platform for single cellular assays. Here, we report results from experiments conducted in two cross-slot microfluidic channels of different widths, with varying real-time delay of the control algorithm and different magnification. Sustained trapping of 5 μm diameter particles was achieved with high strain rates, of order 102 s-1, higher than in any previous studies. Our experiments show that the maximum attainable strain rate is a function of the real-time delay of the control algorithm and the particle resolution (pixel/μm). Therefore, we anticipate that with further reduced time delays and enhanced particle resolution, considerably higher strain rates can be attained, opening the platform to single cellular assay studies where very high strain rates are required.

Microfluidic device combining hydrodynamic and dielectrophoretic trapping for the controlled contact between single micro-sized objects and application to adhesion assays.

The understanding of cell-cell and cell-matrix interactions via receptor and ligand binding relies on our ability to study the very first events of their contact. Of particular interest is the interaction between a T cell receptor and its cognate peptide-major histocompatibility complex. Indeed, analyzing their binding kinetics and cellular avidity in large-scale low-cost and fast cell sorting would largely facilitate the access to cell-based cancer immunotherapies. We thus propose a microfluidic tool able to independently control two types of micro-sized objects, put them in contact for a defined time and probe their adhesion state. The device consists of hydrodynamic traps holding the first type of cell from below against the fluid flow, and a dielectrophoretic system to force the second type of object to remain in contact with the first one. First, the device is validated by performing an adhesion frequency assay between fibroblasts and fibronectin coated beads. Then, a study is conducted on the modification of the cellular environment to match the dielectrophoretic technology requirements without modifying the cell viability and interaction functionalities. Finally, we demonstrate the capability of the developed device to put cancer cells and a population of T cells in contact and show the discrimination between specific and non-specific interactions based on the pair lifetime. This proof-of-concept device lays the foundations for the development of next generation fast cell-cell interaction technologies.

Enhanced single-nanoparticle collisions for the hydrogen evolution reaction in a confined microchannel

Single nanoparticle (NP) collisions technique has been widely employed in electrocatalysis. However, the short collision duration of single NPs hinders the further improvement in their electrocatalytic performance. Here, to increase the dynamic collision duration of single NPs in the electron tunneling region, enhanced near-wall hindered diffusion is introduced in the stochastic collision process by coupling a Au ultramicroelectrode (UME) with a confined microchannel. In the case of single palladium nanoparticle (Pd NP) collisions for the hydrogen evolution reaction (HER), the hydrodynamic trapping confined in the microchannel effectively permits the activation of the HER on the single Pd NPs. The microchannel-based Au UME is promising in the application of single-NP collisions to energy conversion.

Microfluidics combined with fluorescence in situ hybridization (FISH) for Candida spp. detection.

One of the most prevalent healthcare-associated infection is the urinary tract infection (UTI), caused by opportunistic pathogens such as Candida albicans or non-albicans Candida species (NACS). Urine culture methods are routinely used for UTI diagnostics due to their specificity, sensitivity and low-cost. However, these methods are also laborious, time- and reagent-consuming. Therefore, diagnostic methods relying on nucleic acids have been suggested as alternatives. Nucleic acid-based methods can provide results within 24 h and can be adapted to point-of-care (POC) detection. Here, we propose to combine fluorescence in situ hybridization (FISH) with a microfluidic platform for the detection of Candida spp. As a case study we used C. tropicalis, which is reported as the second most common NACS urine isolate obtained from patients suspected with UTI. The microfluidic platform proposed in this study relies on hydrodynamic trapping, and uses physical barriers (e.g., microposts) for the separation of target cells from the suspension. Using a specific peptide nucleic acid (PNA) probe, the FISH procedure was applied onto previously trapped C. tropicalis cells present inside the microfluidic platform. Fluorescence signal intensity of hybridized cells was captured directly under the epifluorescence microscope. Overall, the PNA probe successfully detected C. tropicalis in pure culture and artificial urine (AU) using FISH combined with the microfluidic platform. Our findings reveal that FISH using nucleic acid mimics (PNA) in combination with microfluidics is a reliable method for the detection of microorganisms such as C. tropicalis. As such, this work provides the basis for the development of a POC detection platform in the future.

Studying coalescence at different lengthscales: from films to droplets

The hydrodynamics of thin films is an important factor when it comes to the stability and rheology of multiphasic materials, such as foams, emulsions, and polymer blends. However, there have so far been only limited experimental studies addressing the dynamics of individual free-standing thin films at conditions similar to those encountered on macroscopic scales. In this article, we study a well-characterized system of a water-in-oil emulsion stabilized by a non-ionic surfactant (SPAN80) close to its CMC. We employ a dynamic thin film balance, to study the dynamics of freestanding films under both constant and time-varied pressure drops. We compare with the recently published results of Narayan et al. (2020) on colliding droplets of the same system with a hydrodynamic microfluidic trap, and show for the first time that agreement between the two lengthscales is possible, which indicates that the coalescence is indeed dominated by the dynamics in the film. We then address the scatter in the coalescence times and show that it can be affected by extrinsic factors, as well as by variations in the collision angle. Finally, we discuss the difficulties of extracting insight on the coalescence mechanism from coalescence time distributions when different effects such as impurities, small pressure variations, collision angle variations, and possible Marangoni-related instabilities are at play.

Laser light-induced deformation of free surface of oil due to thermocapillary Marangoni phenomenon: Experiment and computational fluid dynamics simulations

Remote light-induced free liquid surface deformation has been studied in various systems for decades. One of the mechanisms able to do this task is driven by the thermocapillary Marangoni effect. The strength of the light–matter interaction, which is usually weak, here is amplified by the light absorption and heat production that changes surface tension. Here, we report on an experimental study aimed at dynamical aspects of the deformation induced under conditions of chopped laser excitation light. The light-induced deformations are usually in the range of several micrometers. Therefore, we applied the interferometric technique to measure deformation profiles in real time. Experiments were performed in the shallow bath of the rapeseed oil with an azo-dye and excited with 514.5 nm and probed with 650 nm coherent laser beams, respectively. The mechanism of deformation driven by Marangoni effect was carefully modeled in 3D by computational fluid dynamic numerical simulations within the COMSOL Multiphysics package. The adaptive mesh technique used in the simulation together with solving the time-dependent coupled Navier–Stokes and heat transport differential equations allowed us to replicate the experimental findings. A satisfactory agreement between the results of the simulations and those of the experiment in terms of the dynamics, shape, and depth of the deformation has been obtained. The toroidal-like whirls accompanying the thermocapillary Marangoni effect were identified by the simulation results. We then experimentally proved that these toroidal-like vortices, which accompany laser heating in dyed oil, formed a kind of novel hydrodynamic trap, in the center of their quiet zone, in which microcrystals can be trapped.

Gas Distribution and Its Geological Factors in the No.5 Coal Seam of the Weibei Field, Southeastern Ordos Basin, North China

The distribution of gas contents in the No.5 coal seams of the Weibei Field of southeastern Ordos Basin, North China, is highly variable and its mechanism remains unclear. In this study, systematic evaluation of the gas content and its geological control factors are conducted based on the field investigation together with 16 coalbed methane (CBM) wells in the Weibei Field, southeastern Ordos Basin, North China. The gas content variability is determined from the perspectives of gas generation, migration, and preservation. The results indicate that the gas generation is largely relevant with the subsidence and fluctuation of the coal seam during the middle-late Yanshanian orogeny, which controls the gas content variability of the Weibei Field. Besides, gas migration and preservation determine the gas content on a regional scale, significantly related to fault types, roof lithology, burial depth, and hydrodynamic conditions, but scarcely affected by the roof thickness. In the Weibei Field, the geological models controlling gas content are identified as (1) hydrodynamic trapping of gas in the deep burial depth and thrust faults, and (2) gas loss by groundwater flushing and normal faults. Basically, the first mechanism causes the high gas content of the east zone, whereas the other one is responsible for the low gas content in the west zone of the study area.