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Purpose: To examine the behavior and function of human gingival fibroblasts growing on healing abutments with or without laser-textured topography. Materials and Methods: Human primary gingival connective tissue fibroblasts were cultured on healing abutments with machined or laser-textured (Laser-Lok, BioHorizons) surfaces. Cellular and molecular responses were evaluated by a variety of tests, including cell density assay (WST-1), fluorescence microscopy, real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR), and detachment tests. Results: The machined surface showed monodirectional traces and scratches from milling, whereas the laser-textured surface showed a distinct morphology consisting of monodirectional mesoscale channels (15-µm pitch) and woven oblique microridges formed within the channels. There were no differences in initial fibroblast attachment, subsequent fibroblast proliferation, or collagen production between the machined and laser-textured surfaces. Fibroblasts growing on a laser-textured surface were found to spread in one direction along the mesochannels, while cells growing on machined surfaces tended to spread randomly. Fibroblasts on laser-textured surfaces were 1.8 times more resistant to detachment than those on machined surfaces. An adhesive glycoprotein (fibronectin) and transmembrane adhesion linker gene (integrin ß-1) were upregulated on laser-textured surfaces. Conclusions: The increased fibroblast retention, uniform growth, and increased transcription of cell adhesion proteins compellingly explain the enhanced tissue-level response to laser-created and hybrid-textured titanium surfaces. These results provide a cellular and molecular rationale for the tissue reaction to this unique surface; in addition, they support its extended use, from implants and healing abutments to diverse prosthetic components where enhanced soft tissue responses would be desirable. [ABSTRACT FROM AUTHOR]

Human parathyroid hormone (1–34) (PTH) exhibits osteoanabolic and osteocatabolic effects, with shorter plasma exposure times favoring bone formation. Subcutaneous injection (SCI) is the conventional delivery route for PTH but faces low delivery efficiency due to limited passive diffusion and the obstruction of the vascular endothelial barrier, leading to prolonged drug exposure times and reduced osteoanabolic effects. In this work, a microcurrent delivery system (MDS) based on multimicrochannel microneedle arrays (MMAs) is proposed, achieving high efficiency and safety for PTH transdermal delivery. The internal microchannels of the MMAs are fabricated using high‐precision 3D printing technology, providing a concentrated and safe electric field that not only accelerates the movement of PTH but also reversibly increases vascular endothelial permeability by regulating the actin cytoskeleton and interendothelial junctions through Ca2+‐dependent cAMP signaling, ultimately promoting PTH absorption and shortening exposure times. The MDS enhances the osteoanabolic effect of PTH in an osteoporosis model by inhibiting osteoclast differentiation on the bone surface compared to SCI. Moreover, histopathological analysis of the skin and organs demonstrated the good safety of PTH delivered by MDS in vivo. In addition to PTH, the MDS shows broad prospects for the high‐efficiency transdermal delivery of macromolecular drugs. [ABSTRACT FROM AUTHOR]

In recent years, the field of micro- and nanochannel fabrication has seen significant advancements driven by the need for precision in biomedical, environmental, and industrial applications. This review provides a comprehensive analysis of emerging fabrication technologies, including photolithography, soft lithography, 3D printing, electron-beam lithography (EBL), wet/dry etching, injection molding, focused ion beam (FIB) milling, laser micromachining, and micro-milling. Each of these methods offers unique advantages in terms of scalability, precision, and cost-effectiveness, enabling the creation of highly customized micro- and nanochannel structures. Challenges related to scalability, resolution, and the high cost of traditional techniques are addressed through innovations such as deep reactive ion etching (DRIE) and multipass micro-milling. This paper also explores the application potential of these technologies in areas such as lab-on-a-chip devices, biomedical diagnostics, and energy-efficient cooling systems. With continued research and technological refinement, these methods are poised to significantly impact the future of microfluidic and nanofluidic systems. [ABSTRACT FROM AUTHOR]

Scaffolds for bone defect treatment should ideally support vascularization and promote bone formation, to facilitate the translation into biomedical device applications. This study presents a novel approach utilizing 3D-printed water-dissolvable polyvinyl alcohol (PVA) sacrificial molds to engineer polymerized High Internal Phase Emulsion (polyHIPE) scaffolds with microchannels and distinct multiscale porosity. Two sacrificial mold variants (250 µm and 500 µm) were generated using fused deposition modeling, filled with HIPE, and subsequently dissolved to create polyHIPE scaffolds containing microchannels. In vitro assessments demonstrated significant enhancement in cell infiltration, proliferation, and osteogenic differentiation, underscoring the favorable impact of microchannels on cell behavior. High loading efficiency and controlled release of the osteogenic factor BMP-2 were achieved, with microchannels facilitating release of the growth factor. Evaluation in a mouse critical-size calvarial defect model revealed enhanced vascularization and bone formation in microchanneled scaffolds containing BMP-2. This study not only introduces an accessible method for creating multiscale porosity in polyHIPE scaffolds but also emphasizes its capability to enhance cellular infiltration, controlled growth factor release, and in vivo performance. The findings suggest promising applications in bone tissue engineering and regenerative medicine, and are expected to facilitate the translation of this type of biomaterial scaffold. This study holds significance in the realm of biomaterial scaffold design for bone tissue engineering and regeneration. We demonstrate a novel method to introduce controlled multiscale porosity and microchannels into polyHIPE scaffolds, by utilizing 3D-printed water-dissolvable PVA molds. The strategy offers new possibilities for improving cellular infiltration, achieving controlled release of growth factors, and enhancing vascularization and bone formation outcomes. This microchannel approach not only marks a substantial stride in scaffold design but also demonstrates its tangible impact on enhancing osteogenic cell differentiation and fostering robust bone formation in vivo. The findings emphasize the potential of this methodology for bone regeneration applications, showcasing an interesting advancement in the quest for effective and innovative biomaterial scaffolds to regenerate bone defects. [Display omitted] [ABSTRACT FROM AUTHOR]

The present study investigates the complexities of thermal performance in nanofluids within curved microchannels of varying radii of curvature by examining the bending effects on convective heat transfer at different flow rates. Employing the finite element method, the study assesses existing viscosity and thermal conductivity models for steady-state, non-isothermal incompressible nanofluids. A parametric analysis is conducted to determine Nusselt numbers at varying Reynolds numbers and angles of curvature, utilizing Maiga's empirical model and contrasting the findings with Batchelor's and Brinkman's theoretical models. The results consistently show that empirical models yield Nusselt numbers significantly higher than theoretical predictions. With respect to flow rate, empirical models exhibit a 4.58–6.11% enhancement in heat transfer for nanofluid concentrations ranging from 1 to 4 mass%. Instances with identical Dean's numbers but different Nusselt numbers demonstrate that higher Reynolds numbers substantially elevate the Nusselt number concerning microchannel curvature. It is also found that at Re ≤ 10, the impact of channel curvature on nanofluid thermal performance was less than 0.1%. A novel expression for the Nusselt number as a function of the Dean number is proposed. The study highlights the potential to achieve similar heat transfer outcomes by strategically adjusting the microchannel curvature and nanofluid flow rate, offering opportunities to enhance thermal efficiency in curved microchannels. [ABSTRACT FROM AUTHOR]

The challenge of particle deposition in microchannels has consistently posed issues in nanofluids, adversely impacting the heat transfer rate. This study investigates the novel approach of employing a magnetic field to prevent deposition and enhance the heat transfer of nanoparticles in microchannels, utilizing Euler-Lagrange method. The analysis involves the coupled solution of momentum and energy equations, incorporating forces such as Brownian motion, thermophoresis, drag, and volumetric force. The findings within the explored parameters indicate that temperature variations affecting particles beyond the thermal boundary layer have a comparatively minor impact compared to those within the boundary layer. This presents an opportunity for optimizing nanoparticle consumption. Additionally, the study reveals that a non-developed flow at the inlet results in lower particle deposition compared to a developed inlet. The results show that an increase in the Reynolds number from 50 to 300 leads to a 1.75% increase in the distance of particles from the wall. The study also delves into the positioning of the current-carrying wire, demonstrating that placing the wire at the microchannel entrance significantly reduces particle deposition. Furthermore, the results indicate that with an increase in electrical current up to 4 amperes, the efficiency of non-deposition reaches 100%.

Steel containment vessels for nuclear power plants can experience gas leakage due to minute defects such as cracks, corrosion, and aging, leading to gas leakage. A gas leakage model for microchannels is established to elucidate the mechanism underlying gas leakage within microchannels caused by these defects, specifically addressing the issue of unidirectional gas flow. Computational Fluid Dynamics (CFD) and the UK R6 method are employed to calculate the gas leakage rate within microchannels. Furthermore, the characteristics of gas flow within microchannels are explored, including the factors affecting the gas leakage rate. Validation of the calculation results is verified experimentally. The results indicate that the gas mass flow rate exhibits a linear decrease with decreasing internal pressure and a non-linear decline as temperature increases. Additionally, the gas mass flow rate demonstrates a negative correlation with the microchannel length but a positive association to its hydraulic diameter. The primary influencing factors on gas leakage rates are hierarchically ranked as follows: pressure difference, microchannel cross-sectional area, temperature, microchannel length, and microchannel hydraulic diameter.

Increasing global economic development leads to a continuous increase in energy demand, considering the limited conventional resources of energy as well as the impact on the environment associated with its use. The primary disadvantage of solar energy is that it is only accessible during the day. Thermal energy storage systems can overlook this flaw since they can store energy throughout the day for use at night. This paper presents a new cooling technique for low-concentration parabolic collectors with microchannel and Phase Change Material (PCM). A test model consisting of a parabolic concentrator was designed and fabricated to test the parabolic concentrator with and without PCM in Baghdad city during January, March, and July. The solar receiver is an essential component of a solar-powered system and was manufactured from Aluminum metal with 44 microchannels (0.3 m in length, 0.02 m in width, and 0.009 m in height), where the receiver consisted of four rows of microchannels, each row consisting of 11 channels is constructed with velocity and temperature measurement facilities to achieve the experimental results. The results show that the PCM will store the energy roughly three hours after sunset at a flow rate of 0.009339 kg/s. Also, the result indicated that the two-axis tracking system would increase thermal efficiency.

The hypervapotron structure was considered to be a feasible configuration to meet the high heat-dissipating requirement of divertors in nuclear fusion devices. In this work, symmetric CuCrZr-based transverse microchannels (TMHC) and longitudinal microchannels (LMHC) with an integrated hypervapotron channel were proposed and manufactured, and subcooled flow boiling experiments were conducted using deionized water at an inlet temperature of 20 °C with a traditional flat-type hypervapotron channel (FHC) for comparison. The LMHC and TMHC obtained lower wall temperatures than the FHC for all conditions, and the TMHC yielded the lowest temperatures. The heat transfer coefficients of the LMHC and TMHC outperformed the FHC due to the enlarged heat transfer area, and the TMHC had the greatest heat transfer coefficient (maximumly increased by 132% compared to the FHC) because the transverse-arranged microchannels were conductive, promoting the convection and liquid replenishment ability by introducing branch flow between fins; however, the microchannels of the LMHC were insensible to flow velocities due to the block effect of longitudinal microchannels. The LMHC obtained the largest pressure drop, and the pressure drop for the FHC and TMHC were comparable since the transverse-placed microchannels had little effect on frictional pressure loss. The TMHC attained the greatest comprehensive thermohydraulic performance which might bring significant insight to the structural design of hypervapotron devices. [ABSTRACT FROM AUTHOR]

Continuous-flow microchannels are widely employed for synthesizing various materials, including nanoparticles, polymers, and metal-organic frameworks (MOFs), to name a few. Microsystem technology allows precise control over reaction parameters, resulting in purer, more uniform, and structurally stable products due to more effective mass transfer manipulation. However, continuous-flow synthesis processes may be accompanied by the emergence of spatial convective structures initiating convective flows. On the one hand, convection can accelerate reactions by intensifying mass transfer. On the other hand, it may lead to non-uniformity in the final product or defects, especially in MOF microcrystal synthesis. The ability to distinguish regions of convective and diffusive mass transfer may be the key to performing higher-quality reactions and obtaining purer products. In this study, we investigate, for the first time, the possibility of using the information complexity measure as a criterion for assessing the intensity of mass transfer in microchannels, considering both spatial and temporal non-uniformities of liquid's distributions resulting from convection formation. We calculate the complexity using shearlet transform based on a local approach. In contrast to existing methods for calculating complexity, the shearlet transform based approach provides a more detailed representation of local heterogeneities. Our analysis involves experimental images illustrating the mixing process of two non-reactive liquids in a Y-type continuous-flow microchannel under conditions of double-diffusive convection formation. The obtained complexity fields characterize the mixing process and structure formation, revealing variations in mass transfer intensity along the microchannel. We compare the results with cases of liquid mixing via a pure diffusive mechanism. Upon analysis, it was revealed that the complexity measure exhibits sensitivity to variations in the type of mass transfer, establishing its feasibility as an indirect criterion for assessing mass transfer intensity. The method presented can extend beyond flow analysis, finding application in the controlling of microstructures of various materials (porosity, for instance) or surface defects in metals, optical systems and other materials that hold significant relevance in materials science and engineering. Graphic Abstract [ABSTRACT FROM AUTHOR]

Accommodation Coefficients (ACs) are used in slip models to determine some important parameters for flowing dilute gases on solid surfaces such as: Cercignani–Lampis–Lord (CLL) model, drag coefficient, slip velocity, shear stress, and temperature jump. These coefficients in slip, transitional, and free molecular flow regimes take values other than unity. As a result, determining these coefficients for different gases and surfaces is crucial, especially where the continuum assumption with no-slip conditions at the surface is inaccurate. These coefficients can be extracted using experimental and simulation methods with different techniques. This paper provides a review of studies that have been conducted to determine the ACs, with a particular focus on the tangential momentum accommodation coefficient (TMAC), using both experimental and simulation methods. The research mainly pertains to microfluidics and nanofluidics. The reviewed studies have concluded that there is no clear relationship between the molecular weight of a gas and it's TMAC. Also, the values of ACs depend on various factors. [ABSTRACT FROM AUTHOR]

Hot embossing is a manufacturing technique used to create microchannels on polymer substrates. In recent years, microchannel fabrication technology based on hot embossing has attracted considerable attention due to its convenience and low cost. A new evaluation method of microchannels, as well as an approach to obtaining optimal hot embossing conditions based on the Taguchi method, is proposed in this paper to fabricate precise microchannels for a flexible proton-exchange membrane fuel cell (PEMFC). Our self-made hot embossing system can be used to fabricate assorted types of micro-channel structures on polymer substrates according to various applications, whose bottom width, top width, height and cross-sectional area vary in the aims of different situations. In order to obtain a high effective filling ratio, a new evaluation method is presented based on the four parameters of channel structures, and the Taguchi method is utilized to arrange three main factors (temperature, force and time) affecting the hot embossing in orthogonal arrays, quickly finding the optimal condition for the embossing process. The evaluation method for microchannels proposed in this paper, compared to traditional evaluation methods, incorporates the area factor, providing a more comprehensive assessment of the fabrication completeness of the microchannels. Additionally, it allows for the quick and simple identification of optimal conditions. The experimental results indicate that after determining the optimal embossing temperature, pressure and time using the Taguchi method, the effective filling rate remains above 95%, thereby enhancing the power density. Through variance analysis, it was found that temperature is the most significant factor affecting the hot embossing of microchannels. The high filling rate makes the process suitable for PEMFCs. The results demonstrate that under optimized process conditions, a self-made hot embossing system can effectively fabricate columnar structure microchannels for PEMFCs. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusion The microfluidic‐based Glomerulus‐on‐Chips (GoC) are mostly cell based, that is, 3D cell culture techniques are used to culture glomerular cells in order to mimic glomerular ultrafiltration. These chips require high maintenance to keep cell viability intact. There have been some approaches to build non‐cell‐based GoCs but many of these approaches have the drawback of membrane fouling. This article presents a structural design and simulation study of a dialysate free microfluidic channel for replicating the function of the human glomerular filtration barrier. The key advancement of the current work is addressing the fouling issue by combining a pre‐filter to eliminate cellular components and performing filtration on the blood plasma.The Laminar Flow Mixture Model in COMSOL Multiphysics 5.6 has been utilized to simulate the behavior of blood flow in the microchannels. The geometrical effect of microchannels on the separation of the filtrate was investigated. The velocity at the inlet of the microchannel and pore size of the filtration membrane are varied to see the change in outflow and filtration fraction.The efficiency of the device is calculated in terms of the filtration fraction (FF%) formed. Simulation results show that the filtrate obtained is ~20% of the plasma flow rate in the channel, which resembles the glomerular filtration fraction.Given that it is not dependent on the functionality of grown cells, the proposed device is anticipated to have a longer lifespan due to its non‐cell‐based design. The device's cost can be reduced by avoiding cell cultivation inside of it. It can be integrated as a glomerular functional unit with other units of kidney model to build a fully developed artificial kidney. [ABSTRACT FROM AUTHOR]

High spatial‐resolution detection is essential for biomedical applications and human‐machine interaction. However, as the sensor array density increases, the miniaturization will lead to interference between adjacent units and deterioration in sensing performance. Here, inspired by the cochlea's sensing structure, a high‐density flexible pressure sensor array featuring with suspended sensing membrane with sensitivity‐enhanced customized channels is presented for crosstalk‐free and high‐resolution detection. By imitating the basilar membrane attached to spiral ligaments, a sensing membrane is fixed onto a high‐stiffness substrate with cavities, forming a stable braced isolation to provide an excellent crosstalk‐free capability (crosstalk coefficient: 47.24 dB) with high‐density integration (100 units within 1 cm2). Similar to the opening of ion channels in hair cells, the wedge‐type expansion of the embedded cracks introduced by stress concentration structures enables a high sensitivity (0.19 kPa−1) and a large measuring range (400 kPa). Finally, it demonstrates promising applications in distributed displays and the condition monitoring of medical‐surgical intubation. [ABSTRACT FROM AUTHOR]

This research presents the efficacy of polymeric microneedles in improving the transdermal permeation of methotrexate across human skin. These microneedles were fabricated from PLGA Expansorb® 50-2A and 50-8A and subjected to comprehensive characterization via scanning electron microscopy, Fourier-transform infrared spectroscopy, and mechanical analysis. We developed and assessed a methotrexate hydrogel for physicochemical and rheological properties. Dye binding, histological examinations, and assessments of skin integrity demonstrated the effective microporation of the skin by PLGA microneedles. We measured the dimensions of microchannels in the skin using scanning electron microscopy, pore uniformity analysis, and confocal microscopy. The skin permeation and disposition of methotrexate were researched in vitro. PLGA 50-8A microneedles appeared significantly longer, sharper, and more mechanically uniform than PLGA 50-2A needles. PLGA 50-8A needles generated substantially more microchannels, as well as deeper, larger, and more uniform channels in the skin than PLGA 50-2A needles. Microneedle insertion substantially reduced skin electrical resistance, accompanied by an elevation in transepidermal water loss values. PLGA 50-8A microneedle treatment provided a significantly higher cumulative delivery, flux, diffusion coefficient, permeability coefficient, and predicted steady-state plasma concentration; however, there was a shorter lag time than for PLGA 50-2A needles, base-treated, and untreated groups (p < 0.05). Conclusively, skin microporation using polymeric microneedles significantly improved the transdermal delivery of methotrexate. [ABSTRACT FROM AUTHOR]

Cell migration is an essential process in a number of physiological and pathological events, and known to be modulated by external microenvironment because cells may sense physical and chemical signals from the microenvironment and collectively respond to these signals. Over the past two decades, a lot of efforts have been made to study how external microenvironment can affect cell migration behaviors. Cells often migrate through confined environments in vivo, such as extracellular matrices in tissues and capillary vessels. Understanding how cells move in these constrained spaces is crucial to clarify various biological processes. For instance, during embryonic development, cells migrate through specific pathways to form tissues and organs. In wound healing, cells migrate to repair damaged tissues. In cancer, tumour cells migrate to invade surrounding tissues and metastasize to distant sites. Recent advances of bio-MEMS technologies have enabled to characterize cell mechanics and to control local cellular environment at micro-scale. In order to study cell migration under confinement, microchannels have been widely fabricated and used due to their directionality and compatibility. Thus, this study reviews recent work on fabrication of microchannels and their applications to investigate cell migration behaviors, ranging from straight channels to tortuous structures. Challenges and limitations associated with studying cell migration in microchannels are also discussed. Reviewing cell migration in confined environments may provide valuable insights into the underlying mechanisms of cell migration and aid in developing strategies for therapeutic interventions. [ABSTRACT FROM AUTHOR]

Abstract\nHIGHLIGHTSThis study presents a numerical evaluation of the performance of low Global Warning Potential (GWP) refrigerants R600a, R290, R1270, and R134a in heat dissipation by forced convection in a microchannel heat sink. The heat sink comprises 50 parallel microchannels with a cross-sectional area equal to 123 × 494 [µm2]. The differential equations describing the physical behavior interaction between the refrigerant and the copper matrix are solved using the finite volume method and the SIMPLEC coupling algorithm. The numerical model is used to predict fluid mechanics and heat transfer for single-phase laminar conditions including the friction factor, the Nusselt number and the average wall temperatures, as well as the whole performance of the microchannel heat sink. The accuracy of the numerical model is validated by comparing the performance of R600a with experimental data, resulting in deviations within the range of the uncertainty of each parameter. The evaluation of the performance of different refrigerants reveals that the friction factor and Nusselt number are significantly influenced by the microchannel geometry and thermal conditions, exhibiting unique yet similar trends for different refrigerants. Furthermore, the analysis of the average wall temperature in the microchannels demonstrates that the hydrocarbon-based refrigerants effectively reduce the temperature of the copper matrix compared to R134a, suggesting a superior performance in the dissipation of heat flux under single-phase laminar conditions.Thermal performance of refrigerants in heat dissipation by microchannel heat sink.FVM numerical prediction of fluid mechanics and heat transfer in microchannels.Computational model for R600a flow with experimental and predictive correlations.Hydrocarbon-based refrigerants demonstrate superior performance compared to R134a.Thermal performance of refrigerants in heat dissipation by microchannel heat sink.FVM numerical prediction of fluid mechanics and heat transfer in microchannels.Computational model for R600a flow with experimental and predictive correlations.Hydrocarbon-based refrigerants demonstrate superior performance compared to R134a. [ABSTRACT FROM AUTHOR]

Several engineering systems currently use microchannel heat sinks. In order to increase the performance of these devices, optimisation according to the first and second law of thermodynamics is employed. One way to achieve the goal is to modify the geometry of the cross-section, as is done in this paper for square ducts, having the walls at a uniform temperature which is higher than that of the bulk fluid at the inlet. The effects of both the thermal entry region of the duct and the heat generation due to viscous dissipation are considered. The resulting Graetz–Brinkman problem is solved numerically to obtain the velocity and temperature fields. It is demonstrated that non-negligible viscous heating eventually causes the heat flux to reverse (from fluid to walls), and that, only after this condition is achieved, can the flow become fully developed, which makes the entry region the only useful stretch for real-life applications. The length after which the direction of the heat flux reverses due to viscous heating in the fluid is obtained as a function of the Brinkman number and of the smoothing radius. Optimisation with performance evaluation criteria and entropy generation minimisation was carried out separately, and the results were combined into a single objective function. A comparison with published models highlights how neglecting the entry region and viscous heating yields misleading results. It turns out that smoothing the corners is always profitable in the case of the constrained heated perimeter or area of the cross-section but seldom when the characteristic length or the hydraulic diameter is fixed. With few exceptions, viscous heating amplifies the trends experienced for zero-Brinkman flows. The results are in non-dimensional form, yet they have been obtained starting from plausible dimensional values and are applicable to real-life devices. [ABSTRACT FROM AUTHOR]

To investigate the microchannel liquid cooling system of 18650 cylindrical lithium battery packs, cooling systems with varying numbers of microchannels are developed and they are analyzed through numerical simulations using COMSOL software. The findings reveal that lower coolant inlet temperatures correspond to lower maximum temperatures during discharge, with temperatures decreasing closer to the inlet. When the coolant passes through a 3.6 mm diameter or at an inlet flow rate of 0.1 m s−1, an increase in Reynolds number results in a decrease in the highest temperature of the cells. However, this temperature reduction slows down when Re exceeds 400. The annular channel cooling structure demonstrates superior cooling effects and temperature uniformity. Optimization opportunities exist to reduce the number of inlets. The dual‐inlet and dual‐outlet cooling structure has been enhanced by adjusting the number of channels in the annular channel design. This modification has resulted in a maximum temperature reduction of 4.62 K and a temperature difference of less than 5 K compared to the initial reference group, demonstrating effective cooling performance. [ABSTRACT FROM AUTHOR]

This research explores fluid flow speed behavior in capillary channels using additive manufacturing, focusing on stereolithography (SLA). It aims to validate microchannels fabricated through SLA for desired fluid flow characteristics, particularly capillary-driven flow. The methodology involves designing, fabricating, and characterizing microchannels via SLA, with improvements such as an air-cleaning step facilitating the production of microchannels ranging from 300 to 1000 μ m . Experimental validation assesses fluid flow speed behavior across channels of varying dimensions, evaluating the impact of channel geometry, surface roughness, and manufacturing parameters. The findings affirm the feasibility and efficacy of SLA in producing microchannels with consistent and predictable fluid flow behavior between 300 to 800 μ m . This study contributes insights into microfluidic device fabrication techniques and enhances the understanding of fluid dynamics in capillary-driven systems. Overall, it underscores the potential of additive manufacturing, specifically SLA, in offering cost-effective and scalable solutions for microfluidic applications. The validated fluid flow speed behavior in capillary channels suggests new avenues for developing innovative microfluidic devices with improved performance and functionality, marking a significant advancement in the field. [ABSTRACT FROM AUTHOR]

Modern microtechnology methods are widely used to create neural networks on a chip with a connection architecture demonstrating properties of modularity and hierarchy similar to brain networks. Such in vitro networks serve as a valuable model for studying the interplay of functional architecture within modules, their activity, and the effectiveness of inter-module interaction. In this study, we use a two-chamber microfluidic platform to investigate functional connectivity and global activity in hierarchically connected modular neural networks. We found that the strength of functional connections within the module and the profile of network spontaneous activity determine the effectiveness of inter-modular interaction and integration activity in the network. The direction of intermodular activity propagation configures the different densities of inhibitory synapses in the network. The developed microfluidic platform holds the potential to explore function-structure relationships and efficient information processing in two- or multilayer neural networks, in both healthy and pathological states. [ABSTRACT FROM AUTHOR]

The trend toward ever‐increased speeds for microelectronics is challenged by the emergence of heat‐wall, leading to the faltering of Moore's Law. A potential solution may be integrating microfluidic channels into silicon (Si), to deliver controlled amounts of cooling fluid and regulate hot spots. Such meandering microfluidic channels within other transparent materials already played significant roles, including in biomedical and sensor applications; however, analogous channel architectures do not exist in Si. Here, a novel method is proposed to fabricate buried microchannel arrays monolithically integrated into Si, without altering the wafer surface. A two‐step, laser‐assisted subtractive removal method is exploited, enabling fully‐buried multi‐level architectures, with control on the channel port geometry, depth, curvature, and aspect ratio. The selective removal rate is 750 µm per h per channel, and the channel inner‐wall roughness is 230 nm. The method preserves top wafer surface roughness of 2 nm, with significant potential for 3D integrated systems. [ABSTRACT FROM AUTHOR]

Elevated battery temperature and its heterogeneity are responsible for many battery‐related problems such as short lifespan and thermal runaway. For longer life and safe functionality of lithium‐ion battery (LIB), both the average battery temperature and temperature heterogeneity must be controlled. The present work analyzes a modified cooling channel design that can control both the average battery temperature and its heterogeneity. The design adopts microtexturing approach for the heat transfer augmentation of the serpentine cooling channels. First, the transient thermal analysis of different geometry of microtextures, viz., microchannels (MCs) and microdimples (MDs), is carried out on an aluminum slab. The rectangular MCs and square MDs are found to be the most efficient among the other considered microtexture geometries. Further, the modified design is employed for a 19‐cell battery pack to analyze the thermal performance, pressure drop, and coolant pump power requirements. A decrease in maximum temperature difference (MTD) by 6.03 % and 3.72% is observed for 380 MCs (rectangular) and 960 MDs (squared), respectively. While MDs improve the temperature homogeneity within the LIBs, the coolant pump power requirement and pressure drop (by ≈15.42%) are higher for it compared to the MC‐based design for a given MTD. [ABSTRACT FROM AUTHOR]

Directional liquid spreading has an irreplaceable role in applications such as microfluidic devices, disposable biosensors, and point‐of‐care diagnostics. However, how to achieve directional, rapid, and complete spreading (i.e., superspreading) of liquids without external energy input is a great challenge. Herein, inspired by the peristome surface of Nepenthes pitcher, the directional superspreading of water droplets on hydrogel surfaces with predesigned microchannels by using the synergistic effect of the liquid‐like property of hydrogels and the guidance of anisotropic microstructures is reported. Compared with the smooth ones, hydrogel surfaces with isotropic microstructures can facilitate the superspreading of water droplets, which can be realized within 500 ms in the absence of external forces. Furthermore, directional superspreading and the flow of water droplets are realized under the guidance of anisotropic microgrooves. Such a unique spreading behavior can also be observed on the hydrogel surfaces with various shaped microchannels, such as periodic, bent, shunted, divergent, and confluent morphologies, which have potential for the development of open microfluidic platforms for various healthcare‐related applications. [ABSTRACT FROM AUTHOR]

The study investigated fluid dynamics in curved microchannels, exploring 3D printing parameters, channel geometry, and fluid properties, crucial for applications in medicine and energy. It highlighted the importance of microfluidics in handling small samples and enabling rapid analysis, stressing the need for precise measurement techniques to validate fluid velocity. Using 3D printing for microchannel design illustrated their utility, with microscopy aiding flow behavior comprehension. The research aimed to validate fluid velocity, covering technology analysis, microdevice design, fabrication, and measurement methodologies. It successfully fabricated microdevices confirming fluid movement via capillarity, revealing the relationship between channel radius and flow velocity. Distinct flow velocity patterns were observed, vital for design optimization. The study affirmed capillary flow as a spontaneous phenomenon, with fluid velocity variations along curved microchannels consistent with mass conservation principles in incompressible flows. [ABSTRACT FROM AUTHOR]

High-grade gliomas (HGGs) and glioblastoma multiforme (GBM) are characterized by a heterogeneous and aggressive population of tissue-infiltrating cells that promote both destructive tissue remodeling and aberrant vascularization of the brain. The formation of defective and permeable blood vessels and microchannels and destructive tissue remodeling prevent efficient vascular delivery of pharmacological agents to tumor cells and are the significant reason why therapeutic chemotherapy and immunotherapy intervention are primarily ineffective. Vessel-forming endothelial cells and microchannel-forming glial cells that recapitulate vascular mimicry have both infiltration and destructive remodeling tissue capacities. The transmembrane protein TMEM230 (C20orf30) is a master regulator of infiltration, sprouting of endothelial cells, and microchannel formation of glial and phagocytic cells. A high level of TMEM230 expression was identified in patients with HGG, GBM, and U87-MG cells. In this study, we identified candidate genes and molecular pathways that support that aberrantly elevated levels of TMEM230 play an important role in regulating genes associated with the initial stages of cell infiltration and blood vessel and microchannel (also referred to as tumor microtubule) formation in the progression from low-grade to high-grade gliomas. As TMEM230 regulates infiltration, vascularization, and tissue destruction capacities of diverse cell types in the brain, TMEM230 is a promising cancer target for heterogeneous HGG tumors. [ABSTRACT FROM AUTHOR]

This study explores and analyzes the mixing efficiency of five innovative micromixers, each featuring serpentine microchannels, through comprehensive experimentation. The mixing experiments were conducted on micromixers with distinct shapes: backward arrow, loop, square, circular, and box waves, all equipped with backward arrow-shaped inlets, using the Villermaux–Dushman protocol. The assessment of mixing performance was carried out across a range of Reynolds numbers (Re) from 100 to 700, accompanied by varying pressure drop measurements. The efficiency of mixing was determined using ultraviolet spectrophotometry to measure the absorbance values and times for mixed fluids from the five micromixers. At Re values greater than 100, the mixing performance ranked as follows: Square-wave > Circular-wave > Box-wave > Loop-wave > Backward Arrow-shaped micromixers. Factors such as repeated perturbations, the presence of crests and troughs, the angle of the channels, and the split and recombination effects played significant roles in these outcomes. With increasing Re from 100 to 700, we observed progressive and consistent results across all microchannels. Remarkably, at a broad range of Reynolds numbers, the five micromixers demonstrated superior mixing performance compared to designs based on unbalanced split and collisions, achieving an impressive mixing efficiency of over 93 %, while keeping the pressure drop under 80 kPa. This pressure drop range is suitable for a variety of lab-on-a-chip and micro-total analysis systems. Furthermore, the experimental results show that the mixing performance of microfluidic systems can be improved by incorporating the presented design method of microchannel shapes, especially the Square-wave. [ABSTRACT FROM AUTHOR]

Nowadays, the demand for obtaining high heat flux values in small volumes has increased with the development of technology. Condensing flow inside mini- and microchannels has been becoming a promising solution for refrigeration, HVAC, air-conditioning, heat pumps, heat pipes, and electronic cooling applications. In these applications, employing mini/microchannels in the condenser design results in the working fluid, generally refrigerant, undergoing a phase change inside the mini/microchannels. On the other hand, the reduction in the hydraulic diameter during condensation gives rise to different flow regimes and heat transfer mechanisms in the mini- and microchannels compared to the conventional channels. Therefore, the understanding of fluid flow and heat transfer characteristics during condensation of refrigerant inside mini- and microchannels has been gaining importance in terms of condenser design. This study presents a state-of-the-art review of condensation studies on refrigerants inside mini- and microchannels. The review includes experimental studies as well as correlation models, which are developed to predict condensation heat transfer coefficients and pressure drop. The refrigerant type, thermodynamical performance, and compatibility, as well as the environmental effects of refrigerant, play a decisive role in the design of refrigeration systems. Therefore, the environmental impacts of refrigerants and current regulations against them are also discussed in the present review. [ABSTRACT FROM AUTHOR]

In this numerical study, the heat transfers of two types of fuels, namely kerosene and gasoline, were studied within a wavy channel with pulsed flow. The CFD module at COMSOL Multiphysics was used in this study. Several variables were used and applied to both types of fuel and compared between them. These variables included the values of Reynolds numbers between 200 to 800, as well as several values of Strouhal Numbers between 0 to 0.25. Different variable values were also used for the wavy channel, including the wave numbers (0, 2, 4, 6, 8, 10) as well as variable values of the wave amplitude (0, 0.1, 0.2, 0.3). Through this study, it was observed that as Strouhal Numbers increase, there is an increase in the Nusselt Number value. It was also observed that as the number of waves increases, there is an improvement in the heat transfer values. The numerical results showed that the values of heat transfer improved with an increase in the amplitude of the wave.. [ABSTRACT FROM AUTHOR]

Abstract High spatial‐resolution detection is essential for biomedical applications and human‐machine interaction. However, as the sensor array density increases, the miniaturization will lead to interference between adjacent units and deterioration in sensing performance. Here, inspired by the cochlea's sensing structure, a high‐density flexible pressure sensor array featuring with suspended sensing membrane with sensitivity‐enhanced customized channels is presented for crosstalk‐free and high‐resolution detection. By imitating the basilar membrane attached to spiral ligaments, a sensing membrane is fixed onto a high‐stiffness substrate with cavities, forming a stable braced isolation to provide an excellent crosstalk‐free capability (crosstalk coefficient: 47.24 dB) with high‐density integration (100 units within 1 cm2). Similar to the opening of ion channels in hair cells, the wedge‐type expansion of the embedded cracks introduced by stress concentration structures enables a high sensitivity (0.19 kPa−1) and a large measuring range (400 kPa). Finally, it demonstrates promising applications in distributed displays and the condition monitoring of medical‐surgical intubation.

The study investigated fluid dynamics in curved microchannels, exploring 3D printing parameters, channel geometry, and fluid properties, crucial for applications in medicine and energy. It highlighted the importance of microfluidics in handling small samples and enabling rapid analysis, stressing the need for precise measurement techniques to validate fluid velocity. Using 3D printing for microchannel design illustrated their utility, with microscopy aiding flow behavior comprehension. The research aimed to validate fluid velocity, covering technology analysis, microdevice design, fabrication, and measurement methodologies. It successfully fabricated microdevices confirming fluid movement via capillarity, revealing the relationship between channel radius and flow velocity. Distinct flow velocity patterns were observed, vital for design optimization. The study affirmed capillary flow as a spontaneous phenomenon, with fluid velocity variations along curved microchannels consistent with mass conservation principles in incompressible flows.

Modern Electric Vehicles (EVs) require high power and high efficient powertrains to extend their power range. A key element of the electric powertrain is its drive with an electric motor controlled by a traction inverter. A cooling system dissipates heat generated due to the losses in this inverter and keeps its temperature within limits, i.e. below the operational maximum value. Indirect cooling systems are often the preferred solution due to their easy implementation and robust separation of the electric/electronic parts and the coolant circuit. Indirect cooling comes with additional surface interfaces, hence thermal barriers and increased thermal resistance for the losses’ heat flow path. One way to increase the system’s heat transfer coefficient is by implementing power electronics with dual-sided cooling (DSC) solutions and by enhancing surface structures for the cold plates. Manufacturing complex cold plate solutions with internal surface-enhancing structures by way of classical techniques (e.g. aluminum extrusion with CNC machining) can be difficult, costly, or even not possible. Sealed one-piece solutions are preferred, without the need to weld parts or to use screws, glue, gaskets, etc. 3D metal printing allows to manufacture of a one-unit compact, light, and reliable cold plate. This study shows the advantages and limitations of a 3D metal-printed inverter cold plate by presenting the microchannel design, numerical thermal simulations, and experimental results for the liquid cooled DSC SiC and Si inverters. This work explores the compatible use of 3D metal printing solutions, which will aid the development of modern high-power density EVs.

A significant heat flux affects the efficacy and durability of most equipment. Cooling these devices is the primary concern, prompting specialists to propose and investigate various solutions. For these applications, microchannels are regarded as a possibility. Experiments were conducted in this study to determine the effect of an electroplating coating on the characteristics of a single-phase flow. As the working fluid for the experiments, deionized water was used. During the investigations, a microchannel of 0.3mm width and 0.7mm depth with an average roughness of 18.64 nm was machined; the inlet temperature was maintained at 30°C, and the Reynolds number ranged from 109.2 to 2599. According to the results, the correlation between the fanning friction factor and laminar and turbulent flows can predict experimental findings with high precision. In addition, an increase in the Nusselt number correlates with an increase in the Reynolds number.When compared to a conventional microchannel, the models with an Al2O3 cladding have a fanning friction factor that is much greater. According to the results, a reliable correlation can be used to precisely estimate the friction factor of typical Al2O3-coated microchannels. The results demonstrated that the average value of the maximum thermal performance value was approximately 1.19 at low Reynolds numbers between 240-480 and then decreased as Reynolds numbers increased.

In recent years, the field of micro- and nanochannel fabrication has seen significant advancements driven by the need for precision in biomedical, environmental, and industrial applications. This review provides a comprehensive analysis of emerging fabrication technologies, including photolithography, soft lithography, 3D printing, electron-beam lithography (EBL), wet/dry etching, injection molding, focused ion beam (FIB) milling, laser micromachining, and micro-milling. Each of these methods offers unique advantages in terms of scalability, precision, and cost-effectiveness, enabling the creation of highly customized micro- and nanochannel structures. Challenges related to scalability, resolution, and the high cost of traditional techniques are addressed through innovations such as deep reactive ion etching (DRIE) and multipass micro-milling. This paper also explores the application potential of these technologies in areas such as lab-on-a-chip devices, biomedical diagnostics, and energy-efficient cooling systems. With continued research and technological refinement, these methods are poised to significantly impact the future of microfluidic and nanofluidic systems.

AbstractThe predictability of the mathematical models on the details and the phenomenology for microscale flow conditions is an open topic in the literature. In this sense, this work evaluates the capacity of the following turbulence models: standard  k−ε, RNG k−ε, k−ω standard, k−ω SST, Realizable k−ε, and Low-Re k−ε to predict the fluid mechanics and heat transfer characteristics of low Global Warming Potential (GWP) fluid flow in a 1.1 mm ID microchannel. These turbulence models are evaluated for Reynolds Numbers up to 104. The numerical results for velocity profile, friction factors, and Nusselt Numbers are validated with analytical and experimental data published in previous works for R134a, R1234yf, R1234ze(E), and R600a. Parametric behaviors of pressure drop and heat transfer coefficient are presented and analyzed. The results indicate that each of the models describes the qualitative behavior of flow and heat transfer processes. On the other hand, the quantitative results indicate that the Low-Re k−ε,k−ω, and k−ω SST models demonstrate an acceptable prediction of some variable’s behavior. Numerically, the Low-Re k−ε model presents an accurate prediction with the lowest mean absolute. [ABSTRACT FROM AUTHOR]

Stretchable strain sensors are widely used in the fields of wearable devices, soft robotics, healthcare monitoring, and more. Despite tremendous efforts, strain sensors capable of detecting large‐scale soil deformation for urban geological hazard prevention have not yet been demonstrated. In this paper, a soft strain sensor of a highly stretchable Ecoflex‐0030 elastomeric matrix with microchannel‐confined environmentally benign conductive Chinese ink as the liquid‐state strain‐sensitive material that can reliably detect a wide range of working strain up to 300% is demonstrated. The sensor exhibits a negligible hysteresis error of 2.1%, with a considerably good gauge factor of 1.95. The sensor performance is evaluated under both creep and cyclic loading tests, indicating superior stability (0.65% fluctuation), and repeatability (0.28% variation in 1000 cycles), even under a lower underground environment temperature of 18°C. As a proof‐of‐concept demonstration, a liquid‐state strain sensor array with a strain amplification mechanism capable of accurately monitoring the formation of various underground cavities and providing timely demanded information for early warning of catastrophic road collapse is demonstrated and verified by the computer vision‐based particle image velocimetry (PIV) method. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) has become the prime imaging technique for in vivo examination of the brain. In addition to anatomical and functional MRI, diffusion MRI (dMRI) is widely used in both clinics and research to assess tissue structure and fiber directions, particularly in the nervous system. While diffusion tensor imaging is the most widespread approach for assessing orientation measures, other, more sophisticated models have also been proposed. Validation of dMRI is, however, a challenging endeavor that requires specialized test samples. Here it is shown that two‐photon polymerization (2PP) 3D printing allows for manufacturing such test objects, a.k.a. phantoms. After upscaling the 2PP fabrication process, 3D structures at high spatial resolution and sufficient size to image in a human 7T MRI scanner are created. These phantoms reliably mimic human white matter and thus enable the systematic validation and verification of dMRI data and their analyses. The 3D‐printed structures include up to 51 000 microchannels that mimic the diffusion behavior of larger axons, with a cross‐section of 12 × 12 µm2 each, in parallel and crossing arrangements. The acquired dMRI data demonstrates and verifies the utility of these novel brain phantoms. [ABSTRACT FROM AUTHOR]

In this study, a micropowder blasting system with varying processing temperatures was proposed to control the cross-sectional shape of a channel processed on a glass substrate. Based on an analysis of the processing temperature-dependence of the dynamic viscoelastic properties of a commercial mask material for micropowder blasting, a processing temperature control system that can be installed in a micropowder blasting machine was designed. The erosion of the mask during micropowder blasting depended on the loss tangent in dynamic viscoelasticity, and showed a maximum value at a processing temperature of 100 °C. Moreover, we confirmed that the maximum decrease in the width of the processed microchannel was 30 µm (12%) by mask erosion, and this change was large compared with the maximum change in the thickness of the eroded mask. These results clarified that varying the processing temperature using a mask could control the cross-section of the processed line pattern profile on glass, and a small-width channel was realized at a processing temperature of 109 °C. [ABSTRACT FROM AUTHOR]

A microchannel with a groove and rib composite structure is designed to satisfy the heat dissipation needs of microelectronic devices. Rectangular microchannels with four different structures, namely, rectangular groove–rib, triangular groove–rib, scalloped groove–rib, and trapezoidal groove–rib, are studied, with a smooth channel as comparison. The thermohydraulic performance of the microchannels with four different structures are studied, and how the temperature and velocity fields of fluid interact synergistically is explored. Moreover, the influences of rib height and groove depth on the microchannel are investigated. The results indicated that the trapezoidal structures had larger Nusselt number and frictional resistance, the synergistic relationship was better and the average synergistic angle was 1°–2° lower compared to that of smooth microchannel. The comprehensive assessment revealed that the trapezoidal groove–rib structure exhibited the highest performance evaluation criterion (PEC). Furthermore, a detailed analysis was carried out to investigate this specific structure further. Various rib heights and groove depths were studied, and the findings demonstrate that the maximum PEC of 1.51 was achieved at a rib height of 0.03 mm and groove depth of 0.05 mm. [ABSTRACT FROM AUTHOR]

Atmospheric pressure plasma jets (APPJs) are increasingly being used to functionalize polymers and dielectric materials for biomedical and biotechnology applications. Once such application is microfluidic labs-on-a-chip consisting of dielectric slabs with microchannel grooves hundreds of microns in width and depth. The periodic channels, an example of a complex surface, present challenges in terms of directly and uniformly exposing the surface to the plasma. In this paper, we discuss results from computational and experimental investigations of negative APPJs sustained in Ar/N2 mixtures flowing into ambient air and incident onto a series of microchannels. Results from two-dimensional plasma hydrodynamics modeling are compared to experimental measurements of electric field and fast-camera imaging. The propagation of the plasma across dry microchannels largely consists of a sequence of surface ionization waves (SIWs) on the top ridges of the channels and bulk ionization waves (IWs) crossing over the channels. The IWs are directed into electric field enhanced vertices of the next ridge. The charging of these ridges produce reverse IWs responsible for the majority of the ionization. The propagation of the plasma across water filled microchannels evolve into hopping SIWs between the leading edges of the water channels, regions of electric enhancement due to polarization of the water. Positive, reverse IWs follow the pre-ionized path of the initial negative waves. [ABSTRACT FROM AUTHOR]

The present study aimed to determine the impact of sperm capacitation on sperm rheotaxis and sperm kinematics within microfluidics of buffalo cryopreserved semen. semen straws (n = 24) were obtained from 3 fertile buffalo bulls. Each straw was divided into three aliquots: control aliquot, caffeine aliquot and heparin aliquot. Sperm rheotaxis and all sperm kinematics were determined through a computer-assisted sperm analysis (CASA) system using the microfluidic platform with controlled flow velocity. The results showed that the positive rheotaxis % (PR%) of caffeine and heparin were significantly higher (PR% = 49.4±1 and 48.8±1, respectively) than control (45.1±1) (p<0.0001). Sperm kinematics show a significant variation among the three aliquots. Results show no significant differences in VCL of caffeine and heparin compared to control. While VCL of caffeine aliquot was significantly higher than that of heparin (p=0.01). The VAP of the caffeine aliquot was significantly higher than that of heparin and control (p=0.05). VSL and BCF of caffeine and heparin aliquots were significantly higher than control (p<0.001 and p<0.0001, respectively). In conclusion, this study confirms that PR% and most sperm kinematics in buffalo frozen semen improved during invitro capacitation using caffeine and heparin. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive numerical simulation study focused on the cooling of integrated toroidal octagonal inductor using nanofluids within a microchannel heat sink. The investigation utilizes COMSOL Multiphysics 6.0 integrated with the Fluid Flow and Conjugate Heat Transfer Module. The primary objective is to explore and understand fluid flow and heat transfer characteristics within the integrated inductor. The study involves testing three distinct fluids, water, CuO-water nanofluid, and Al2O3-water nanofluid, under laminar flow conditions within microchannels. The choice of fluid plays a significant role in heat transfer, interacting with the microchannel geometry to optimize performance. Three-dimensional computational fluid dynamics (CFD) models are meticulously developed; focusing on toroidal inductors equipped with micro pin fins heat sinks. The study commences by detailing the geometry of the micro coil and the integrated heat sink. The simulation encompasses a mathematical model that captures the intricate interplay between the governing Navier-Stokes equations for fluid dynamics and the heat transfer equations within the integrated inductor. As φ increases, temperature, viscosity, and pressure decrease. CuO-water and Al2O3-water nanofluids play a significant role in influencing laminar flow and key thermal parameters in the toroidal inductor. These nanofluids, which consist of base fluids (water) with dispersed nanoparticles (CuO or Al2O3), are employed as cooling agents to enhance heat transfer. The presence of nanoparticles in the fluid alters its thermal properties, leading to changes in the flow dynamics and overall heat dissipation within the toroidal inductor.The laminar flow characteristics are affected by the nanofluid's viscosity, density, and thermal conductivity. Additionally, the Nusselt number, Reynolds number, and thermal resistance are key thermal parameters that reflect the performance of the cooling system. The nanofluid's influence on these parameters is crucial for understanding and optimizing the thermal management of the integrated toroidal inductor. The enhancement of heat dissipation in the toroidal inductor is achieved through improved thermal properties of the nanofluid. Higher nanoparticle concentrations result in better heat transfer rates, leading to lower temperatures in the toroidal inductor. This, in turn, improves the overall efficiency and performance of the cooling system. The viscosity of the nanofluid is influenced by the presence of nanoparticles. The pressure within the microchannels is also affected by the nanoparticle concentration. An increase in φ can lead to changes in pressure drop along the microchannels. Understanding these variations is crucial for designing an effective cooling system. [ABSTRACT FROM AUTHOR]

Neuron-on-chip (NoC) systems—microfluidic devices in which neurons are cultured—have become a promising alternative to replace or minimize the use of animal models and have greatly facilitated in vitro research. Here, we review and discuss current developments in neuron-on-chip platforms, with a particular emphasis on existing biological models, culturing techniques, biomaterials, and topologies. We also discuss how the architecture, flow, and gradients affect neuronal growth, differentiation, and development. Finally, we discuss some of the most recent applications of NoCs in fundamental research (i.e., studies on the effects of electrical, mechanical/topological, or chemical stimuli) and in disease modeling. [ABSTRACT FROM AUTHOR]

In the present work, the effects of various parameters (capillary size, shape, flow ratio, presence of additives, and presence of wall film) on KLa both reactive and non‐reactive LLE systems are presented and analyzed. The literature data for a constant liquid flow ratio of 1 (Qc/QD = 1) has been correlated to give rise to two empirical correlations relating the Sherwood number (Sh), Reynolds number (Re), capillary number (Ca), and Schmidt number (Sc) have been developed for 0.1 < Re < 10 and 10 < Re < 200. The concept of j‐factor for micro‐channels has been introduced and named as Pandit–Kunzru–Ganguli analogy. Three new dimensionless numbers have been introduced, namely Pandit number (Pa=KLσμu2), Ganguli number Gn=Sh/CaM, and Kunzru number (Ku=ScM/Tm). The j‐factor is found to be a strong function of Capillary number for 10 < Re < 200 while it is a strong function of surface renewal for 0.1 < Re < 10. Empirical correlations to calculate j‐factor as a function of Re or Weber number (We) are also presented. Recommendations for future work have been presented based on the review in the present work. [ABSTRACT FROM AUTHOR]

We consider the formation of an electric spark from a point anode in atmospheric air when the primary spark channel from a very early stage of its evolution immediately begins to develop in the form of a cluster of highly ionized plasma microchannels. Using laser probing at a wavelength of 1064 nm, spark microchannels are resolved in the near-anode region of the discharge, and the data on the magnitude and distribution of the plasma electron density of single microchannels are obtained. It is shown that during the first nanoseconds after the discharge gap breakdown, the electron density in individual microchannels is distributed nonuniformly and ranges from 1018 to 5 × 1019 cm–3, with characteristic microchannel diameters being of 20–50 μm. [ABSTRACT FROM AUTHOR]

Vortex generators and pin fins are conventionally used to deliver fluid mixing and improved convective heat transfer. The increased pressure loss following a fractional increase in heat transfer, as well as the complex manufacturing design, leave room for improvement. The present work proposes a novel diverging–converging base corrugation model coupled with vortex generation using simple geometrical modifications across rectangular microchannels to ensure a superior performance. The Nusselt number, friction factor, and flow phenomenon were numerically studied across a Reynolds number range of 50–1000. The optimum cross-section of the microchannel-generating vortices was determined after thorough study, and base corrugation was further added to improve heat transfer. For the vortex–corrugation modeling, the heat transfer enhancement was verified in two optimized cases: (1) curved corrugated model, (2) interacting corrugated model. In the first case, an optimized curve generating Dean vortices was coupled with base corrugation. An overall increase in the Nusselt number of up to 32.69% and the thermal performance of "1.285 TPF" were observed at a high Reynolds number. The interacting channels with connecting bridges of varying width were found to generate vortices in the counter-flow configuration. The thermal performance of "1.25 TPF" was almost identical to the curved corrugated model; however, a major decrease in pressure, with a loss of 26.88%, was observed for this configuration. [ABSTRACT FROM AUTHOR]