Microchannel Size Research Articles

Investigation on influence factors of optically controlled electrorheological fluid damping system

Abstract Electromagnetic rheological damping control system, as an important control technology, has been widely used in braking, vibration reduction and micro-valve etc. However, the electromagnetic rheological damping control system faces issues of electromagnetic interference due to the high voltage source. To solve this problem, we proposed a novel optically controlled electrorheological fluid damping system. Previous studies have confirmed the feasibility of the optically controlled electrorheological fluid damping control system via numerical simulation and experiment. In this paper, the mechanism and mathematical model of the optically controlled electrorheological fluid damping system are established. The influence factor analyses of the optically controlled damping system, especially the impact of light intensity and microchannel size on system performance, are carried out through experimental and theoretical methods. The research findings of influence factors contribute to a deeper understanding of the working principle of the electrorheological fluid damping system, thereby promoting stability and reliability in microfluidics technology.

Design and simulation of a microfluidics-based artificial glomerular ultrafiltration unit to reduce cell-induced fouling.

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.

Enhancing Radiator Cooling with CuO Nanofluid Microchannels

The study explores in employing copper oxide (CuO) nanofluid as a cooling medium in the vehicle radiators. To simulate the heat transfer process, the microchannel is constructed using elec-tron discharge machining (EDM) and a computational fluid dynamics (CFD) modeling is em-ployed. UV-visible spectroscopy, scanning electron microscopy (SEM), and dynamic light scat-tering (DLS) are used to characterize the CuO nanofluid. CuO nanofluid surpasses water in the heat transfer capabilities, with a 40% improvement in thermal conductivity. The average size of CuO nanoparticles was determined via DLS to be 485.1 nm. The heat transfer coefficient of CuO nanofluid is 5366 W/m2K, which is 116% larger than that of water. The increased heat transfer capabilities of CuO nanofluid microchannel flow indicate to its potential as a viable replacement for conventional radiators in the automotive applications. Lower engine tempera-tures, increased fuel efficiency, and longer engine lifespan may result from improved cooling performance. Due of the small size of microchannels, more efficient and space-saving radiators for automobiles are conceivable. More research is needed to improve the microchannel design as well as to realize the practical benefits of CuO nanofluids in car cooling systems.

Fabrication of Ceramic Microchannels with Periodic Corrugated Microstructures as Catalyst Support for Hydrogen Production via Diamond Wire Sawing.

Hydrogen energy is the clean energy with the most potential in the 21st century. The microchannel reactor for methanol steam reforming (MSR) is one of the effective ways to obtain hydrogen. Ceramic materials have the advantages of high temperature resistance, corrosion resistance, and high mechanical strength, and are ideal materials for preparing the catalyst support in microchannel reactors. However, the structure of ceramic materials is hard and brittle, and the feature size of microchannel is generally not more than 1 mm, which is difficult to process using traditional processing methods. Diamond wire saw processing technology is mainly used in the slicing of hard and brittle materials such as sapphire and silicon. In this paper, a microchannel with a periodic corrugated microstructure was fabricated on a ceramic plate using diamond wire sawing, and then as a catalyst support when used in a microreactor for MSR hydrogen production. The effects of wire speed and feed speed on the amplitude and period size of the periodic corrugated microstructure were studied using a single-factor experiment. The microchannel surface morphology was observed via SEM and a 3D confocal laser microscope under different processing parameters. The microchannel samples obtained under different processing parameters were supported by a multiple impregnation method. The loading strength of the catalyst was tested via a strong wind purge experiment. The experimental results show that the periodic corrugated microstructure can significantly enhance the load strength of the catalyst. The microchannel catalyst support with the periodic corrugated microstructure was put into the microreactor for a hydrogen production experiment, and a good hydrogen production effect was obtained. The experimental results have a positive guiding effect on promoting ceramic materials as the microchannel catalyst support for the development of hydrogen energy.

Synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 to improve tribological properties of M50 bearing steel with microporous channels

Purpose This paper aims to study the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 to improve the tribological properties of M50 bearing steel with microporous channels. Design/methodology/approach M50 matrix self-lubricating composites (MMSC) were designed and prepared by filling Sn–Ag–Cu and MXene–Ti3C2 in the microporous channels of M50 bearing steel. The tribology performance testing of as-prepared samples was executed with a multifunction tribometer. The optimum hole size and lubricant content, as well as self-lubricating mechanism of MMSC, were studied. Findings The tribological properties of MMSC are strongly dependent on the synergistic lubrication effect of MXene–Ti3C2 and Sn–Ag–Cu. When the hole size of microchannel is 1 mm and the content of MXene–Ti3C2 in mixed lubricant is 4 wt.%, MMSC shows the lowest friction coefficient and wear rate. The Sn–Ag–Cu and MXene–Ti3C2 are extruded from the microporous channels and spread to the friction interface, and a relatively complete lubricating film is formed at the friction interface. Meanwhile, the synergistic lubrication of Sn–Ag–Cu and MXene–Ti3C2 can improve the stability of the lubricating film, thus the excellent tribological property of MMSC is obtained. Originality/value The results help in deep understanding of the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 on the tribological properties of M50 bearing steel. This work also provides a useful reference for the tribological design of mechanical components by combining surface texture with solid lubrication. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0381/

Three-dimensional array of microbubbles sonoporation of cells in microfluidics.

Sonoporation is a popular membrane disruption technique widely applicable in various fields, including cell therapy, drug delivery, and biomanufacturing. In recent years, there has been significant progress in achieving controlled, high-viability, and high-efficiency cell sonoporation in microfluidics. If the microchannels are too small, especially when scaled down to the cellular level, it still remains a challenge to overcome microchannel clogging, and low throughput. Here, we presented a microfluidic device capable of modulating membrane permeability through oscillating three-dimensional array of microbubbles. Simulations were performed to analyze the effective range of action of the oscillating microbubbles to obtain the optimal microchannel size. Utilizing a high-precision light curing 3D printer to fabricate uniformly sized microstructures in a one-step on both the side walls and the top surface for the generation of microbubbles. These microbubbles oscillated with nearly identical amplitudes and frequencies, ensuring efficient and stable sonoporation within the system. Cells were captured and trapped on the bubble surface by the acoustic streaming and secondary acoustic radiation forces induced by the oscillating microbubbles. At a driving voltage of 30 Vpp, the sonoporation efficiency of cells reached 93.9% ± 2.4%.

The adoption of novel cooling liquids for enhancing heat transfer performance of three-dimensional integrated circuits with embedded micro-channel

The nanofluids (including MWCNT based nanofluid and SWCNT based nanofluid) and liquid metal Ga68In20Sn12 are proposed to replace the conventional water as cooling liquid of micro-channel for enhancing heat transfer performance of three-dimensional integrated circuits (3-D ICs) in this paper. An equivalent thermal model of 3-D ICs with integrated micro-channel is established to investigate the heat transfer performances for using different cooling liquids. The results show that the steady-state temperature for MWCNT based nanofluid, SWCNT based nanofluid and Ga68In20Sn12 as cooling liquids can be reduced over 25.698%, 28.771% and 35.735% than the conventional water scheme in a four-layers stacked chip, respectively. Besides, it is found that the steady-state temperature of all die layer in 3-D ICs can be further reduced by increasing the micro-channel size and flow velocity of cooling liquid. Therefore, the proposed novel materials (i.e., nanofluids and Ga68In20Sn12) as cooling liquids have excellent application prospect in solving thermal problems of 3-D ICs.

Interface Leakage Theory of Mechanical Seals Considering Microscopic Forces

The fluid flow in the small pore throat is a nonlinear flow, and the microscopic force between the fluid and the wall cannot be ignored. However, the previously established theories about the leakage between sealing interfaces have not considered the influence of microscopic forces. Based on contact mechanics and percolation theory, the void characteristics of the sealing interface were clarified, and the influence of microscopic force on fluid flow in porous medium was analyzed. Combined with the capillary force, the concept of a critical void radius between the mechanical seal interfaces is proposed. The fluid flow resistance model and leakage rate calculation equation of the sealing interface considering the van der Waals force are established, and the leakage judgment criterion of the sealing interface is provided. Through numerical calculation and experiments, the effect of microscopic force is verified in terms of the fluid flow law and macroscopic leakage rate. The results show that van der Waals forces have an important influence on the fluid flow between the sealing interfaces. As the microchannel size decreases, the van der Waals forces between solid and liquid increase, and the influence of these van der Waals forces on the fluid flow between the sealing interfaces cannot be ignored. The calculation model of the sealing interface leakage rate proposed in this paper shows little difference with the results of the Persson model, and is in good agreement with the experimental results; the maximum relative error is 8.7%, the minimum relative error is only 3.8%.

Microfluidics of nanoparticles using vibration-mediated regulation of aggregates evolution

Controlling the flow of particulate matter, especially nanoparticles, requires a deep understanding of particle structure and motion. In this study, we present experimental observations and intrinsic mechanisms for controlling the nanoparticle flow using vibration-mediated regulation of aggregates evolution. Our findings demonstrate that vibration could exert significant forces on the particles, causing them held apart or would touch with less force and then leads to re-breakup process of the aggregates. Furthermore, the relationship between the vibration parameter, aggregate size, the microchannel size and flow behavior has also been revealed. Notably, the outflowing aggregates have extremely small Stokes numbers due to their high porosity, and their motion is dominated by gas drag. The relationship between particles flow rate and the size of the microchannel and vibration parameters has been identified. These results have significant implications for precise control and assembly of nanoparticles.

Three-dimensional numerical simulation of bubble dynamics and design optimization of microchannel in proton exchange membrane water electrolyzers

Proton exchange membrane (PEM) water electrolysis is considered as a promising and sustainable solution for energy storage and hydrogen production. The dynamic behaviors of gas bubble in microchannels have an important impact on the gas/liquid two-phase transport process during electrochemical reaction, consequently affect the performance and efficiency of PEM water electrolyzers. This paper aims to investigate and understand the phenomena of bubble detachment in microchannels during the operation of PEM water electrolyzers. The detachment process is captured in-situ/operando, and the four stages of bubble detachment are qualitatively analyzed. Three-dimensional numerical simulation is conducted to study the dynamics of bubble detachment in a Poiseuille flow of microchannel. A strategy of determine the critical flow velocity, pressure drop, and power consumption of bubble detachment in a microchannel with consideration of main forces acting on a bubble during detaching process is developed. The simulation results reveal that various factors, including the contact angle, microchannel size, and the shape and parameters of the upper wavy wall, significantly influence the behavior of bubble detachment and the associated power consumption. Based on these findings, a design strategy is proposed to enhance bubble detachment efficiency in microchannels. The suggested approach involves the implementation of a rectangular upper wavy wall with appropriate wavelength and amplitude, resulting in the lowest power consumption during the bubble detachment process. The present analysis results provide a better understanding of bubble dynamics behaviors and offer practical insights for optimizing the design of microchannels in PEM water electrolyzers.

Cooling and preheating behavior of compact power Lithium-ion battery thermal management system

A novel honeycomb battery thermal management system with a combination of liquid-cooling and composite phase change material has been proposed for the cylindrical power lithium-ion battery to improve the cooling effect under harsh discharge conditions and the capacity reduction in low-temperature environment. The cooling and preheating performance have been compared at a discharge rate of 4C for three different monomer battery systems without any heat dissipation elements, with passive composite phase change material, or with hybrid cooling elements. The effects of the thickness of composite phase changed material, the size of micro-channel, the channel level number, the flow velocity of inlet liquid and the heating strategy on the cooling behaviour of the monomer battery are studied and examined. Furthermore, the impacts of inlet/outlet arrangement mode and inlet liquid flow velocity on the thermal behaviour of the cell module are analysed. When the environment temperature is 40 °C, the optimal parameters on thermal performance are decided, which reliably control the highest temperature, cell–cell temperature difference and the mass fraction of liquid phase of composite phase change material within an allowable range, and save the space of the module as much as possible. At the discharge rate of 4C and the coolant inlet flow velocity of 0.06 m/s, the highest temperature and cell–cell temperature difference of the module can be controlled at 46.21 °C and 3.5 °C, respectively, and keep the mass fraction of the liquid phase of composite phase change material at around 55% after battery discharge. When the battery module is heated from −15 °C to 10 °C, there are different optimal pulse width modulation heating strategies for 20 W and 10 W heating belts and the battery module can be rapidly heated in about 6 min.

Experimental and Numerical Analysis of the Influence of Microchannel Size and Structure on Boiling Heat Transfer

Computational fluid dynamics was used and a numerical simulation analysis of boiling heat transfer in microchannels with three depths and three cross-sectional profiles was conducted. The heat transfer coefficient and bubble generation process of three microchannel structures with a width of 80 μm and a depth of 40, 60, and 80 μm were compared during the boiling process, and the factors influencing bubble generation were studied. A visual test bench was built, and test substrates of different sizes were prepared using a micro-nano laser. During the test, the behavior characteristics of the bubbles on the boiling surface and the temperature change of the heated wall were collected with a high-speed camera and a temperature sensor. It was found that the microchannel with a depth of 80 μm had the largest heat transfer coefficient and shortest bubble growth period, the rectangular channel had a larger peak heat transfer coefficient and a lower frequency of bubble occurrence, while the V-shaped channel had the shortest growth period, i.e., the highest frequency of bubble occurrence, but its heat transfer coefficient was smaller than that of the rectangular channel.

Heat transfer characteristics of supercritical CO2 in horizontal rectangular microchannels

Due to the micro-channel size effect and thermophysical property variations, the heat transfer characteristics of S-CO2 are unclear which are crucial for the design of printed circuit heat exchanger (PCHE). This study experimentally investigated the heat-transfer phenomenon and heat-transfer coefficient of supercritical carbon dioxide (S-CO2) heated in horizontal rectangular microchannels. The effects of different parameters, including an operating pressure of 9–12 MPa, mass flow rate of 290–1200 kg/m2·s, and heat flux of 25–50 kW/m2, on the S-CO2 heat-transfer characteristics were analysed. The experimental results show that the peak value of the heat-transfer coefficient appears near the pseudo-critical point, and the peak value moves in the direction of high temperature and decreases as the operating pressure increases. Compared with the 2-mm-diameter channel, the buoyancy has a smaller effect on heat transfer in the 1-mm-diameter channel. Consequently, a new heat transfer correlation was developed wherein the microchannel size effect and thermophysical property variations are fully considered.

High-Precision and Low-Damage Microchannel Construction via Magnetically Assisted Laser-Induced Plasma Ablation for Micro-Thermoelectric Devices.

Thermoelectric devices are developing toward high density and miniaturization with a large filling factor for new applications in chip thermal management and microenergy harvesting. Pulsed laser etching has become one of the most effective tools for the patterning construction of highly integrated micro-thermoelectric devices. However, the laser spot size and Gaussian laser energy distribution restrict the processing size and accuracy of microchannels. Moreover, the rapid temperature rise caused by laser energy injection would also raise serious problems such as element volatilization, cracks, and recast layers. Herein, a liquid-assisted nanosecond laser ablation technology with magnetically controlled plasma is proposed to etch microchannels on thermoelectric thick films. By evaluating the size and shape of microchannels, we theoretically investigated the influence of cavitation bubbles on the laser optical path and surface roughness in laser-induced plasma ablation. In addition, the energy criterion for high-precision ablation is revealed, and the effect of magnetic field on ablation threshold is explained by magnetic constraint on energy and kinetic properties of the laser-induced charged plasma plume. Finally, the high-precision and low-damage microchannels are achieved on Bi2Te3 thermoelectric thick films with a minimum line width of 19.12 μm and a small sidewall inclination degree of tan θ = 0.085. This work provides a promising alternative for the fabrication of high-density three-dimensional (3D) patterning in semiconductor microdevices.

Experimental study on the pressure drop characteristics of supercritical CO2 in horizontal rectangular microchannels

The pressure drop characteristics of supercritical carbon dioxide (S-CO2) are experimentally studied in horizontal rectangular microchannels with hydraulic diameters of 1 and 2 mm, which are used in printed circuit heat exchangers. The operating conditions include an operating pressure of 9–12 MPa, a mass flux of 290–1200 kg/m2 s, and a heat flux of 25–50 kW/m2. The four contributors to pressure drop in the S-CO2 microchannels were investigated. The results indicate that the total pressure drop decreases for lower operating pressures and mass fluxes, whereas the heat flux has little impact. The most significant contributor to the total pressure drop is the frictional pressure drop. The accelerational pressure drop increases with the heat flux. Eventually, a new frictional resistance correlation is proposed where the microchannel size and thermophysical property variations are considered.

The Significant Effect of Mechanical Treatment on Ceramic Coating for Biomedical Application

Titanium and its alloys are commonly preferred materials used for biomedical implants. However, these alloys have issues related to corrosion resistance as a result of the aggressive attack of human body fluids. Several researchers have attempted to produce a ceramic coating via physical vapour deposition (PVD). A PVD layer consists of pores, pinholes, and columnar growth that attack the substrate as an aggressive medium. The aim of this research is to evaluate the influence of ultrasonic vibration parameters on a TiN-coated biomedical Ti-13Zr-13Nb alloy. This study used TiN to formulate and coat disk-type samples in a fixed condition. Ultrasonic vibration at fixed frequencies was applied to TiN-coated samples for three sets of exposure times. The findings revealed that all TiN-coated samples exposed to ultrasonic vibration had improved corrosion resistance compared to untreated samples. Field emission scanning electron microscopy (FESEM) was employed to analyse sample’s microstructures. The top parameter (16 kHz and 11 min) yielded the most compact coating. Ultrasonic vibration’s hammering effect decreased the size of microchannels in the lining and reduced the rate of corrosion attack. The nanoindentation test showed that coated ultrasonic treated samples had a higher hardness/elasticity (H/E) ratio than untreated samples.

A review on active techniques in microchannel heat sink for miniaturization problem in electronic industry

With continuous miniaturization of modern electronic components, the need of better cooling devices also keeps on increasing. The improper thermal management of these devices not only hampers the efficiency but can also cause permanent damage. Among various techniques, microchannel heat sink has shown most favourable performance. To further enhance the performance, two techniques i.e., active and passive are used. In passive technique, no external power source is required like heat sink design alteration and working fluid modification. External power source is necessary for heat transfer augmentation in the microchannel heat sink when using the active approach. Due to compact size of microchannel, active techniques are not used more often. However, the present work highlights the different active technique used in microchannel i.e., Electrostatic forces, flow pulsation, magnetic field, acoustic effects, and vibration active techniques. Above mentioned techniques have been analysed in detail.

Particularities of R134a Refrigerant Temperature Variations in a Transient Convective Regime during Vaporization in Rectangular Microchannels.

An analysis of the R134a (tetrafluoroetane) coolant’s non-stationary behavior in rectangular microchannels was conducted with the help of a newly proposed miniature refrigerating machine of our own design and construction. The experimental device incorporated, on the same plate, a condenser, a lamination tube and a vaporizer, all of which integrated rectangular microchannels. The size of the rectangular microchannels was determined by laser profilometry. R-134a coolant vapors were pressurized using a small ASPEN rotary compressor. Using the variable soft spheres (VSS) model, the mean free path, Knudsen and Reynolds numbers, as well as the dimensionless velocity profile can be assessed analytically. In order to determine the average dimensionless temperature drop in the vaporizer’s rectangular microchannels, in non-stationary regime, an analytical solution for incompressible flow with slip at the walls, fully developed flow and laminar regime was used, by aid of an integral transform approach. In the experimental study, the transitional distribution of temperature was tracked while modifying the R134a flow through the rectangular microchannels. Coolant flow was then maintained at a constant, while the amount of heat absorbed by the vaporizer was varied using multiple electric resistors. A comparative analysis of the analytical and experimental values was conducted.

The Phenomenon of Drug Emulsion Carriers Compaction during Their Movement in Microstructures.

The greatest challenges of modern pharmacology are the design of drugs with the highest possible efficacy of an active substance and with the lowest possible invasiveness for the whole organism. A good solution features the application of a bioactive substance in different carriers. The effectiveness of such preparations is determined not only by the properties of the drug, but primarily by the dynamics of carrier movement in the body. This is the reason why studies on the dispersed systems transport in micro- and nanostructures are becoming important. This paper presents a study of emulsion systems transport in microcapillaries. A dispersed phase thickening effect was observed during the process, which resulted in a concentration increase of the flowing emulsion, in some cases up to 10 times. This phenomenon directly influences transport dynamics of such substances in microstructures and should be taken into account when designing drug parameters (concentration, release time, and action range). The effect was investigated for three different emulsions concentrations and presented quantitatively. The scales of this phenomenon occurrence at different flow conditions were investigated, and their magnitudes were modelled and described. This allows the prediction of the flow resistance in the movement of given dispersion systems, as a function of the flow rate, the emulsion parameters, and the microchannel size.

Experimental study of Taylor bubble flow in non-Newtonian liquid in a rectangular microchannel

The flow characteristics of gas and non-Newtonian fluid in a rectangular T-microchannel with cross section of 150 μm × 50 μm are experimentally studied. Four flow patterns are observed, including bubble flow, Taylor flow, transitional flow and annular flow. The effects of two-phase flowrate, the CMC/SDS concentration, and microchannel size on the flow pattern maps and Taylor bubble/liquid slug length are compared. The bubble length increases with gas/liquid flowrates ratio, whilst the change of slug length is opposite. The bubble length decreases with liquid viscosity or surface tension. The slug length increases with the liquid viscosity, but decreases with surface tension. Experimental data is analyzed in relationship to JG/JL, Re and Ca using dimensional analysis. Two empirical equations are given respectively to predict the Taylor bubble/slug lengths. Predictions are largely consistent with the experimental results with maximum 25% variance. This provides an important reference for the controllable operation of two-phase flow in rectangular microchannels.