Microfluidics and Nanofluidics最新文献

Microfluidics is turning out to be essential for the advancement of scientific research, healthcare, and various other applications due to its ability to provide precise control, miniaturization, and integration of fluid samples. Existing research shows a considerable growth rate in the utilization of microfluidics-based techniques, especially in the biomedical field for disease detection, drug analysis, cell analysis, and more. However, the development of microfluidic systems for soil nutrition testing applications is still a challenging task due to the need for micro scale dimensions and a high degree of precision during the fabrication and detection of soil nutrients. The present investigation aims to find the most suitable design for the microfluidic chip that can control and detect microfluid containing soil nutrients, especially nitrites, effectively. To achieve this goal, the parameters of different microchannel (MC) specimens, such as snug height, channel width, obstacle pitch, mean mixture pressure, wall shear stress, strain rate, and total pressure, are analyzed. In addition, the Response Surface Methodology (RSM) is introduced to statistically authenticate the obtained simulation data. As a result, the present investigation proposes the optimal MC design with optimal parameters: snug height of 0.35 mm, channel width of 1.54 mm, obstacle pitch of 2.5 mm, mean mixture pressure of 0.24 MPa, wall shear stress of 1.1 Pa, strain rate of 2259 s⁻¹, and total pressure of 1.42 MPa. Moreover, the functionality of the proposed microfluidic chip was calibrated and predicted using the Deep Neural Network-based Modified Sea Horse Optimizer (DNN-MSHO) algorithm, confirming the presence of nitrites in the used soil samples in a range of 2.81–4.18 ppm, which again proves the efficiency and trustworthiness of the proposed microfluidic chip design and its usability in real soil testing applications.

Experiments on contaminated Taylor flows in a square microchannel were carried out to investigate the effects of surfactant on the bubble shape in the nose and tail regions for different surfactant properties. The nose curvature was found to be proportional to the bubble length at low surfactant concentrations, while it was independent of the concentration at high concentrations. The rate of increase in the nose curvature at the former concentrations can be expressed in terms of the surface coverage ratio. The bubble velocity decreased with increasing the nose curvature, whereas the surface tension reduced by surfactant adsorption worked better to correlate the velocity data. The curvature of the bubble tail increased steeply at low concentrations as a consequence of the early coverage due to interfacial advection. The tail curvature also had a strong correlation with the surface coverage ratio.

Boundary conditions at the surface of a layer of flexible fibers (i.e. the canopy envelope) subjected to fluid flow are proposed for uniform and non-uniform motions of the fibers, where the fibers exhibit identical and individual motions, respectively, to understand the mechanisms of the swaying motion of the canopy. By assuming small deflections, the fibers are treated as rigid rods hinged to a flat wall and the effects of the hydrodynamic force on the fibers are expressed with the moment of fluid forces by averaging the Navier–Stokes equations. For the uniformly moving case, displacement of the envelope is represented by a mass-spring-damper system driven by the hydrodynamic force. As the non-uniformity of the canopy behavior enhances, the effects of the diffusion of fiber velocities and fluid inertia along the fiber stems play a more important role in the envelope displacement equation. Numerical simulations of fluid flow are conducted with the envelope displacement models as the boundary conditions at the canopy surface. The validity of the present models is assessed by comparison with the results of fluid–structure interaction (FSI) simulation, which directly solves the interaction between individual fibers and fluid by an immersed boundary method. With the envelope model for non-uniform displacement, the grid convergence of the numerical result is about a first order rate. The comparison of the terms in the envelope model for non-uniform displacement shows that diffusion of fiber velocities dominates the motion of fibers. The applicability of the model is assessed by varying the number density of the fibers.

Passive micromixers, known for their notable mixing effectiveness and simple manufacturing, are extensively utilized in the lab on chip devices, the bio-medicinal industry, the pharma industry and chemical process. Among the various designs of passive micromixers, the simple T-junction micromixer and the vortex T-junction micromixer are basic designs. In this paper, a comparative study was performed to analyze the influence of bend structural channels on the mixing quality, pressure drop and mixing cost for simple and vortex T micromixers by using numerical simulations. Reynolds numbers (30–120) and angle of bend (θ) ranging from 0° to 180° are the crucial parameters for the investigation. The outcomes suggest that vortex T-junction micromixers with bend structural channels have a greater mixing index than simple T-junction micromixers with bend structural channels, across all the Reynolds values. The findings also suggest that increasing the angle of bend (θ) improves the mixing performance. Additionally, the degree of mixing performance and pressure reduction both exhibit a positive correlation with higher Reynolds numbers.

Contactless dielectrophoresis is an effective method for trapping and manipulating cells in microfluidic devices. However, the efficiency of these devices decreases at higher flow rates. To address the limitation of previous studies, a new pillar shape is introduced and numerically simulated to isolate THP-1 cells and efficiently separate them from red blood cells (RBCs). A comparison is made in two microchannels with the novel pillar shape of two perpendicular ellipses and the circular pillar shape as the reference case. Simulation results demonstrate that the use of two perpendicular ellipticals pillar shape improves the electric characteristics of the device, showing 92.7% higher (nabla {E}_{rms}^{2}) compared to the channel with circular pillars. The working frequency is selected based on the CM factor to isolate THP-1 cells without affecting RBCs. Additionally, the new pillar configuration exhibited 116% higher cell trap efficiency compared to the chip with circular pillars.

This article discusses the significance of Soret and Dufour, non-uniform heat generation, activation energy on radiative 3D flow of trihybrid nanofluid over a sheet with Marangoni convection. The energy equation takes into consideration the impacts of the heat generation, while the concentration equation takes activation energy into account. This trihybrid nanofluid is based on ethylene glycol and contains nanoparticles of titanium dioxide ((Ti{O}_{2})), cobalt ferrite ((CoF{e}_{2}O)), and aluminum oxide ((text{A}{l}_{2}{O}_{3})). For the case of trihybrid nanoparticles, the Yamada–Ota and Xue nanofluid models have been modified. This model is helpful for optimizing heating and cooling systems in fields like energy systems, microelectronics, and aerospace engineering where exact control of thermal properties is essential. By adjusting the characteristics of nanofluids, it also enhances heat transfer rates, which is a critical component in the development of solar collectors and high-efficiency heat exchangers. By using the necessary similarity transformations, non-linear ODEs are obtained from the controlling PDEs. The shooting method (BVP4c) can be utilized to solve this system of highly nonlinear equations numerically. As the surface tension gradient parameter is increased, the velocity distribution, mass transfer, and heat transfer rates all increase but the performance of the thermal and solutal profiles is opposite.

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Microfluidic technology is widely applied in biological detection, primarily utilizing microvalves to control and regulate fluid flow. Increasing attention and research have recently been directed toward magnetic droplet valves, which use magnetic fields to control magnetic droplets in microchannels for sealing purposes. A novel droplet formation technique has been proposed, employing a permanent magnet to attract magnetic fluid through a step emulsification process, thus controllably forming the magnetic droplets required for microvalves. However, the current understanding of the generation mechanism of magnetic fluid step emulsification remains insufficiently deep, with inadequate force analysis during the expansion stage of the magnetic fluid. This shortcoming results in an unclear comprehension of the relationship between the magnetic field and step emulsification formation, impeding the accurate prediction and control of droplet size and formation rate, thereby compromising the performance and reliability of magnetic droplet valves. Therefore, the study initially analyzes the forces acting on the magnetic fluid in a non-uniform magnetic field theoretically and systematically explores the step emulsification mechanism of magnetic fluids through a combination of numerical simulations and experimental validations. The magnetic field inhomogeneity degree directly affects the microdroplet formation process. As the lateral distance between the permanent magnet and the channel outlet increases, the magnetic field inhomogeneity degree decreases, resulting in larger droplet volumes and lower formation rates. Through theoretical analysis and experimental validation, this study provides a significant theoretical foundation and practical guidance for forming magnetic fluid in microfluidic systems.

Inexpensive, autonomous, easy to fabricate and portable self-powered microfluidic pumps are urgently required especially in rapid point-of-care testing (POCT). Here, we propose a “Plug-n-Play” permeable brick-based (PB) micropump for autonomous and continuous liquid flow without any external power sources. The key advantage of this pump is that its operation only requires the user to place the PB pump on the outlet of microfluidic devices. The PB pumps are fabricated by simply slicing permeable bricks into predetermined shapes. The microcosmic morphology investigations unveil that their unique porous structures and uneven surface provide outstanding capillary force. For instance, a typical cuboid PB pump (2 × 2 × 2 cm³) can produce an average flow rate of more than 100 µL min^− 1, a working time of 10 min and a maximum liquid absorption volume of ~ 1200 µL. Also, the flow rate and absorption volume can be programmed by using the PB pumps with different shapes. Moreover, we apply hydrophobic reagents (Glaco) treatment on the PB pumps to achieve the control over the liquid flow rates. Finally, through applying the PB pumps, we can perform blood type detection in POC cases. Based on its advantages of low cost, long service life, and adjustable flow rates, brick pump can be easily integrated into microfluidic systems and has great potential for microfluidic applications, especially in developing regions or in resource-limited settings.

The activation of zebrafish sperm is essential for advancing vertebrate research, including studies in germplasm physiology and cryopreservation. In this study, a magnetic microrobot-based micromixer is developed to maximize zebrafish sperm activation through uniform micromixing and precise hydrodynamic control. Three distinct configurations of the microfluidic channel, labeled Design I, II, and III, are proposed and employed to activate zebrafish sperm cells. These configurations are distinguished by the number of microrobots utilized and their specific placement within the microfluidic channel. The fluid shear rate induced by the microrobot’s rotational motion is quantified to be 0.2 s⁻¹, falling within the lower range conducive to sperm activation. Meanwhile, zebrafish sperm activation percentage is observed to reach 88% within 10 s in an individual experiment. Additionally, the dynamics of sperm motility parameters, including VSL (straight-line velocity), VCL (curvilinear velocity), and LIN (linearity, VSL/VCL), are quantified to verify these results. The LIN value is observed to be 0.91 for Design III at the actuation time period of 10 s, indicating that the activated sperms are highly efficient and progressively motile. This study underscores the efficacy of microrobotic technologies in live cell manipulation, establishing a promising approach for future research.

Buffer exchange is a common process in manufacturing protocols for a wide range of bioprocessing applications, with a variety of technologies available to manipulate biological materials for culture medium exchange, cell washing and buffer removal. Microfluidics is an emerging field for buffer exchange and has shown promising results with both prototype research and commercialised devices which are inexpensive, highly customisable and often have the capacity for scalability to substantially increase throughput. Microfluidic devices are capable of processing biological materials and exchanging solutions without the need for conventional processing techniques like centrifugation, which are time-consuming, unsuitable for large volumes and may be damaging to cells. The use of microfluidic separation devices for cell therapy manufacturing has been under-explored despite some device designs successfully being used for diagnostic enrichment of rare circulating tumour cells from peripheral blood. This mini-review aims to review the current state of microfluidic devices for buffer exchange, provide an insight into the advantages microfluidics offers for buffer exchange and identify future developments key to exploiting the technology for this application.