Fluid In Channel Research Articles

Brain Fluid Channels for Metabolite Removal.

The adult human brain represents only 2% of the body's total weight, however it is one of the most metabolically active organs in the mammalian body. Its high metabolic activity necessitates an efficacious waste clearance system. Besides the blood, there are two fluids closely linked to the brain and spinal cord drainage system: interstitial fluid (ISF) and cerebrospinal fluid (CSF). The aim of this review is to summarize the latest research clarifying the channels of metabolite removal by fluids from brain tissue, subarachnoid space (SAS) and brain dura (BD). Special attention is focused on lymphatic vascular structures in the brain dura, their localizations within the meninges, morphological properties and topographic anatomy. The review ends with an account of the consequences of brain lymphatic drainage failure. Knowledge of the physiological state of the clearance system is crucial in order to understand the changes related to impaired brain drainage.

Optofluidic Particle Manipulation Platform with Nanomembrane.

We demonstrate a method for fabricating and utilizing an optofluidic particle manipulator on a silicon chip that features a 300 nm thick silicon dioxide membrane as part of a microfluidic channel. The fabrication method is based on etching silicon channels and converting the walls to silicon dioxide through thermal oxidation. Channels are encapsulated by a sacrificial polymer which fills the length of the fluid channel by way of spontaneous capillary action. The sacrificial material is then used as a mold for the formation of a nanoscale, solid-state, silicon dioxide membrane. The hollow channel is primarily used for fluid and particle transport but is capable of transmitting light over short distances and utilizes radiation pressure for particle trapping applications. The optofluidic platform features solid-core ridge waveguides which can direct light on and off of the silicon chip and intersect liquid channels. Optical loss values are characterized for liquid and solid-core structures and at interfaces. Estimates are provided for the optical power needed to trap particles of various sizes.

Three-dimensional printed and fluidic dielectric material optically transparent metasurface for switchable absorption and reflection functionality in microwave frequency region

A metasurface is an artificial surface with extraordinary refraction, reflection, and absorption. These generally comprise periodic arrays of conductive patterns on dielectric materials at subwavelength scale. Various dielectric material based metasurfaces have been proposed recently, and this paper proposes a dielectric material optically transparent metasurface constructed from three-dimensionally printed and fluidic transparent materials. The proposed metasurface theoretically and experimentally demonstrates that it switches absorption and reflection at 5.3–15.2 GHz by injecting water into the fluidic channels. In addition, it is experimentally demonstrated that the proposed metasurface has transmission at 400–700 nm wavelength. The proposed metasurface could be deployed as transparent smart glasses or windows to control electromagnetic waves.

ANALYTICITY OF NON-STATIONARY PROCESSES OF CHANGE OF DIAGNOSTIC PARAMETERS OF HYDROSTATIC TRANSMISSIONS OF HARVESTERS

In this article, based on the Lagrange principle, the fundamental elements of the mechanics of continuous media with moving boundaries in relation to hydraulic drive systems of hydrostatic transmissions of combine harvesters are developed, which allows to expand the field of research and modeling diagnostics of these systems. The elements of the theory, the method of calculation of nonstationary processes of one - dimensional motions of uncompressed liquid media with moving media boundaries in hydraulic channels of complex geometric shapes of hydrostatic transmissions of combine harvesters are developed in the article. The analysis of methods of numerical solution of systems of ordinary differential equations with discontinuous coefficients is performed. It is shown that the Bless method is a more effective method of numerical solution of such systems of equations in the studied area. It is shown that for one-dimensional motions of uncompressed liquid media moving in the channel and bounded by moving boundaries, the calculation is reduced to solving the equation a a(x,t)ẍ= b(x, t)ẋ 2 + c(x, t). Here x = x (t) is the coordinate of the front or rear boundary of the liquid medium moving in the channel. It is shown that this equation is a generalized Bernoulli equation in the case of the motion of incompressible liquid media with moving boundaries. This equation is similar to the equation of motion of bodies with variable mass, and is convenient for use in CAD. The theory and method of calculation of processes of incomplete hydraulic shock arising at filling of liquid or gas-liquid environments of channels with local hydraulic support of difficult geometrical forms, for example, the centrifugal pump of hydrostatic transmissions of combine harvesters are created.The method of engineering calculation is obtained, which allows to determine the coefficient ε of compression of the liquid jet and the value of ∆p̅ = (p1 − p0 )/p0 relative shock pressure increase with incomplete hydraulic impact on local hydraulic resistance of complex geometric shape of hydrostatic transmissions of combine harvesters. Thus, the elements of the theory are created, as well as the method of calculating non-stationary processes of movement of uncompressed liquid media in the channels of complex geometric shapes of hydrostatic transmissions of combine harvesters. The method is used in the calculation of the dynamics of the start of the ampouled hydraulic system of the drive of hydrostatic transmissions of combine harvesters with minimum volumes of 1...10% of gas cavities for storage of the working fluid of the drive. The elements of the theory described above and the created calculation methods allow to expand the field of research of dynamic modes of operation of hydraulic systems of power drive of hydrostatic transmissions of combine harvesters in the process of filling working fluid channels of hydraulic systems with branches and hydraulic supports. Their application has allowed to increase the accuracy and reliability of diagnosing real processes characteristic of hydraulic drive systems of hydrostatic transmissions of combine harvesters, especially in difficult conditions of their amputation

Simultaneous enrichment and separation based on ion concentration polarization effect on a paper based analytical device

In this paper, simultaneous enrichment and separation of ions and amphoteric components were successfully demonstrated by using electric field (E) and pH gradient (double gradient) in the ion depletion zone of anion concentration polarization interface established on a paper fluid channel. Experimental results were visualized with colored ions (bright blue and amaranth) and protein probes (phycocyanin and cytochrome C). With optimization, colored phycocyanin and bovine hemoglobin with similar pI as that of albumin and immunoglobulin respectively were well separated in 900 s with 10-fold enrichment effect. Based on the separation and enrichment function of this paper-based analytical device (PAD) and rapid selective staining of human serum albumin (HSA) with bromophenol blue, a rapid colorimetric detection of HSA was implemented with smartphone camera. A limit of detection (LOD) of 5.2 mg·L−1 was achieved in the clinically significant range of 10–300 mg·L−1 (R2 = 0.99). This method was applied to real human urine samples with good agreement (ɑ = 0.01) to clinical detection method (immunoturbidimetry). With the separation and enrichment functions of PAD, both the specificity and sensitivity were enhanced, which provides a solid basis for point-of-care test of microalbuminuria. Therefore, this PAD device is potential for sample pretreatment and detection of target components from complex physiological samples.

Mimicry of the plant leaf with a living hydrogel sheet of cellulose nanofibers

Here, we composite an artificial leaf comprising a transparent hydrogel sheet, vein structures, and a photosynthetic system using cellulose nanofibers (CNFs) which can be produced from a biomass. A simple imprinting using a 3D printed stamp enabled the formation of fluidic channels in the hydrogel, embedding living cells without toxic chemistry or a drying process. Microalgae in the hydrogel grows and proliferates under ambient condition for a long period because of the continuous supply of nutrient from the channels, which is more effective for metabolic bioactivity than a flat sheet cultured in a bulk solution. This mimicry of the plant leaf provides a potential for a whole artificial plant. In addition, the simple fabrication of fluidic channels in the hydrogel can be applied to diverse living organisms, including bacteria, animal, and plant cells.

Dip-and-Read, Organic Solvent-Compatible, Paper-Based Analytical Devices Equipped with Chromatographic Separation for Indole Analysis in Shrimp.

We developed an organic solvent-compatible paper-based analytical device (PAD) for the quantitative analysis of indole, which is an indicator of shrimp freshness. Although indole is insoluble in water, ethyl acetate is a suitable solvent to dissolve and extract indole from shrimp. The PADs are fabricated using a cutting method that allows the use of an organic solvent because no hydrophobic barrier is needed to form fluidic channels. Ehrlich's reagent consists of 4-(dimethylamino)benzaldehyde and p-dimethylaminobenzaldehyde and was deposited onto the reaction zone of the PAD followed by lamination to prevent evaporation of the ethyl acetate. Samples are introduced into the PAD via immersion in organic sample solutions. When the PAD is immersed into an indole solution of ethyl acetate in a closed bottle, the sample solution penetrates the channel of the PAD and successively flows into the detection zone to form a hydrophilic colored product. The PADs provide a linear relationship between the logarithm of the indole concentration and the color intensity within a range of 1.0-20 ppm with correlation coefficients of r2 > 0.99. The limits of detection and quantification are 0.36 and 0.71 ppm, respectively. Relative standard deviations for both the intraday (n = 2) and interday (n = 3) precision were less than 2.5%. In the indole analysis of shrimp, the PADs separated the interfering orange-colored astaxanthin in the extract from the colored product of indole via the paper chromatographic principle. We used the PADs to investigate the degradation of shrimp, and the results showed a rapid increase in the indole level after 7 days. High-performance liquid chromatography verified the accuracy of the PADs by showing good agreement with the obtained indole levels.

Electrocapillary Actuation of Liquid Metal in Microchannels.

Controllable deformation of liquid metal by electrocapillary actuation (ECA) is empirically characterized in fluidic channels at the sub-millimeter-length scale. In 100-µm-deep channels of varying widths, the Galinstan liquid metal could move at velocities of more than 40 mm/s. The liquid metal could extend more than 2.5 mm into the channels at an electrocapillary actuation voltage of 3 V DC. The dynamic behavior of the liquid metal as it moves in the microchannels is described. These results are useful for designing microsystems that use liquid metal as a functional material.

In vivo acoustic manipulation of microparticles in zebrafish embryos.

In vivo micromanipulation using ultrasound is an exciting technology with promises for cancer research, brain research, vasculature biology, diseases, and treatment development. In the present work, we demonstrate in vivo manipulation of gas-filled microparticles using zebrafish embryos as a vertebrate model system. Micromanipulation methods often are conducted in vitro, and they do not fully reflect the complex environment associated in vivo. Four piezoelectric actuators were positioned orthogonally to each other around an off-centered fluidic channel that allowed for two-dimensional manipulation of intravenously injected microbubbles. Selective manipulation of microbubbles inside a blood vessel with micrometer precision was achieved without interfering with circulating blood cells. Last, we studied the viability of zebrafish embryos subjected to the acoustic field. This successful high-precision, in vivo acoustic manipulation of intravenously injected microbubbles offers potentially promising therapeutic options.

Analytical Study of Unsteady Boiling Characteristics of Steam Generator

Currently, research on the efficiency of the film heater, which is a surface heating element, is being actively conducted as it is a potential alternative to the sheath heater. However, research on the heat transfer phenomenon and the performance of the film heater is insufficient. In this study, the performance of the sheath heater and the film heater were compared and analyzed, and the heat transfer pattern according to the arrangement of the heating wire was analyzed. To inspect the heat transfer performance, the external heat transfer and internal flow characteristics of the steam generator were determined, and a study on the performance of the steam generator according to each design variable was conducted. The Eulerian multiphase model was used to conduct the multiphase flow analysis, and the wall boiling model was used to conduct the phase change analysis. Among the models analyzed in this study, the model in which the heating wire was arranged along the flow path and the length of the induction was extended by 50% showed the best performance. Compared to the base model, the steam generation time was improved by 33.3% and the steam ejection time was improved by 17%. These times were improved because the heating wire arrangement of the film heater was optimized along the fluid channel. The U-shaped heating wire arrangement enabled a stable steam injection, and in the case of the normal film heater and fluid channel following heater, a large portion of the heating wire was located around the center. Consequently, steam was formed at the center of the housing. We believe that the results of this study can be applied to various fields in consideration of the advantages of the film heater package, free pattern design of printing, and economy.

Analysis of the thermal performance of a flat-plate type rotary regenerator depending on the matrix material

A rotary regenerator made of polymer can reduce the operation cost and maintenance time of a thermal system due to its lightweight and high corrosion-resistivity, compared to a metal regenerator. This study investigates the heat transfer performance of a flat-plate type rotary regenerator made of polymer or metal through a numerical simulation. The effects of the matrix material, rotary generator's flow channel and wall thicknesses on the temperature profiles of the fluid channel and matrix wall were analyzed. The calculation results were compared with the theoretical effectiveness–number of transfer units relation and were verified. A sensitivity analysis on the effectiveness was conducted to show that the thermal mass of the matrix had more than 7 times higher influence on the thermal performance of a regenerator compared to the thermal conductivity of the matrix. Finally, correlations of Nusselt number as functions of the Reynolds number, non-dimensional matrix wall thickness, and non-dimensional thermal mass parameters were developed for the hot and the cold periods. Deviation of Nusselt number between the correlation and CFD simulation was found to be less than ±13%.

Experimental and Numerical Analysis of a Novel Flow Conditioner for Accuracy Improvement of Ultrasonic Gas Flowmeters

The flow field is one of the key factors that affect the measuring accuracy of ultrasonic gas flowmeters. The present work demonstrates that the designed novel flow conditioner can enhance the measurement accuracy by homogenizing the velocity profile in the acoustic transmission area. The main objective of this study is to reduce the non-uniformity of flow on velocity distribution. To accomplish this objective, a combination of theoretical analysis and numerical simulations is implemented, and the results indicate that the 10:1 aspect ratio rectangular fluid channel is better applied in ultrasonic gas flowmeters. Thus, a Computational Fluid Dynamics (CFD) model of novel flow conditioner based on the 10:1 fluid channel is simulated and validated by an experimental study. The results verify that the ultrasonic gas flowmeter composed of designed flow conditioner can reduce indication errors by up to 6%; moreover, the repeatability of all the tested standard flow rates can meet the national standard and even be enhanced by 0.15%.

A Nonintrusive Flow Rate Sensor Based on Microwave Split-Ring Resonators and Thermal Modulation

Microwave sensors offer noncontact solutions for flow rate measurements, central to various applications in pharmaceutics, chemical analysis, and biomedicine. The challenge, however, remains for microwave flow rate sensing of uniform liquids, where different flow rates do not lead to any permittivity or conductivity variations. In this work, we propose a noncontact, nonintrusive microwave sensor, capable of measuring the flow rate of uniform liquids. This sensor comprises a microwave split-ring resonator (SRR) integrated with a temperature modulation technique. The sensor operates based on the change in the dielectric properties of the liquid inside the channel, induced by local delivery of thermal energy. Different flow rates affect the exposure time of the liquid to thermal energy, which alters its permittivity and loss tangent, consequently changing the response of the SRR. The SRR with the integrated fluidic channel is designed to operate at 4.6 GHz with a resonant amplitude of &#x2212;6.8 dB and a <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula>-factor (&#x2212;3 dB) of 98. By monitoring the <inline-formula> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> (dB) response, flow rates ranging from 1 to 40 mL/h are differentiated. The <inline-formula> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> (dB) response&#x2019;s achieved sensitivity to different flow rates is <inline-formula> <tex-math notation="LaTeX">$\vert 0.02\vert $ </tex-math></inline-formula> dB/mL/h. The proof of concept is successfully evaluated using water and isopropanol as two standard liquids. The results indicate the potential of the proposed nonintrusive flow rate sensing method in various applications, such as drug delivery and chemical sample preparation.

Stability of a plane Poiseuille flow in a channel bounded by anisotropic porous walls

Linear stability of a plane Poiseuille flow in a channel bounded by anisotropic permeable walls supported by rigid walls is studied. Characteristic instability features due to two-dimensional infinitesimal disturbances of the most unstable wall mode are investigated in detail. A detailed parametric study displays the existence of wall modes, porous modes, and center modes in both the presence and absence of inertial effects. The results reveal that an increase in mean permeability decreases the critical Reynolds number, destabilizing smaller wavenumbers. Although anisotropy has no significant effect on the growth rate at smaller wavenumbers, the impact is substantial at larger wavenumbers, particularly destabilizing short-wave modes and enlarging the bandwidth of unstable wavenumbers. Furthermore, in relation to the configuration with isotropic permeability, the one with larger (smaller) relative wall-normal permeability is more (less) unstable with a large bandwidth of unstable wavenumbers covering short-wave lengths when mean permeability is high and when the fluid channel thickness is the same as the thickness of each of the porous walls. The critical Reynolds number increases with an increase in anisotropic permeability, while the critical wavenumber decreases with an increase in anisotropic permeability. This demonstrates the possibility of enhancing (suppressing) instability by designing the channel walls as one with anisotropic permeability and appropriately tuning the relative wall-normal permeability to be higher (lower). Furthermore, anisotropic permeability can be used to control instabilities for any arbitrary relative thickness of the porous medium beyond a minimum relative thickness that depends on the relative magnitude of wall normal anisotropic permeability.

Discharge improvement of a phase change material‐air‐based thermal energy storage unit for space heating applications using metal foams in the air sides

AbstractThis study examines the energy discharge of a phase‐changing material (PCM)‐based air heat exchanger using a metal foam inside the heat transfer fluid (HTF) channel. Such systems have various potential applications in the heating space and building ecosystem. Thermal energy storage (TES) often utilizes air as the HTF, which limits the heat transfer performance due to the low thermal conductivity. This paper aims to address this drawback via incorporating a metal foam into the HTF channel to enhance the thermal performance between the heat transfer fluid (air) and the PCM, which is considered as the novel side of this study. The combined system is mathematically modeled with an symmetrical, three‐dimensional computational fluid dynamics method for various flow rates and inlet temperatures of the HTF with different geometric parameters of the metal foam. This study indicates the advantage of utilizing the porous medium in the air channel. The results show the HTF flow rate has a great influence on the discharging rate. The presence of the porous medium in the system improves the discharging process by 116% compared with a non‐porous medium system at the same flow rate. The discharging time decreases by increasing the porosity, and the value of 90% is found as the best porosity value at the flow rate of 0.005 kg/s in this system. The solidification rate is proportional to the pore density because of the surface area impacts of the porous medium, also the pressure‐drop and the pumping required are highly affected by the mentioned dependent parameters.

Constructal design for tree-shaped compound heat transfer channel in a disc heat generation body

In this basic theoretical research paper, structure design of a tree-shaped compound heat transfer channel (CHTC) model in a disc heat generation body (HGB) is performed based on constructal theory. A complex function consisting of maximum temperature difference and pumping power consumption is minimized first based on the exhaustive method and Nelder-Mead optimization algorithm, and the optimal structure of the CHTC model is gained. The multi-objective optimization is further performed based on the non-dominated sorted genetic algorithm-II to obtain the Pareto optimal set, and the optimal results gained by the decision making approaches (DMAs) of LINMAP, TOPSIS and Shannon Entropy are compared. It reveals that the complex function of the HGB can approach its minimum when the reasonable radius, volume ratio and length ratio of the fluid channel in the CHTC are equal to 1.33 mm, 0.55 and 0.2, respectively. The thermal and fluid flow performances are increased by 11.6% and 30.3%, and the complex function is decreased by 21.0% after constructal design, which illustrates that the optimization effect is obvious. The thermal and fluid flow performances gained by the first two DMAs are increased by 29.60% and 5.10% after constructal design, and their deviation indexes are the same and the smallest one. Therefore, the optimal structure gained by the first two DMAs is recommended in the optimal design of the CHTC for disc HGB. Different optimal design schemes for different design requirements of the electronic devices can be offered by this paper, which aims to improve the thermal and fluid flow performances and theoretically solve the heat dissipation problem of the electronic devices. The contribution of this paper is to establish a tree-shaped CHTC model in a disc HGB, and introduce constructal theory into its structure design to obviously elevate the performance of the disc HGB.

Thermally Responsive Alkane Partitions for Assay Automation.

For point-of-care diagnostic tools to be impactful, they must be inexpensive, equipment-free, and sample-to-answer (i.e., require no user intervention). Here, we report a new approach to enable sample-to-answer diagnostics that utilizes thermally responsive alkane partitions (TRAPs) as automated pseudo-valves. When combined with the magnetic manipulation of microbeads, TRAPs enable the pumpless automation of all steps in complex assays. We demonstrate that in relatively narrow channel geometries, liquified alkane partitions continue to separate reagents on each side of the partition while enabling the transition of magnetic beads from one reagent to the next, replacing manual pipetting steps in conventional assays. In addition, we show that in relatively broader geometries, liquified partitions breach, enabling the addition/mixing of preloaded reagents. Through calculation and experimentation, we determine the geometric design rules for implementing the stationary and removable partitions in fluidic channels. In addition, we demonstrate that magnetic microbeads can be pulled through liquified stationary TRAPs without disrupting partition integrity and without disrupting bound protein complexes attached at the microbead surface. The TRAP technology introduced here can enable a new low-cost and equipment-free approach for fully automated sample-to-answer diagnostics.

Ionic heat dissipation in solid-state pores.

Energy dissipation in solid-state nanopores is an important issue for their use as a sensor for detecting and analyzing individual objects in electrolyte solution by ionic current measurements. Here, we report on evaluations of heating via diffusive ion transport in the nanoscale conduits using thermocouple-embedded SiNx pores. We found a linear rise in the nanopore temperature with the input electrical power suggestive of steady-state ionic heat dissipation in the confined nanospace. Meanwhile, the heating efficiency was elucidated to become higher in a smaller pore due to a rapid decrease in the through-water thermal conduction for cooling the fluidic channel. The scaling law suggested nonnegligible influence of the heating to raise the temperature of single-nanometer two-dimensional nanopores by a few kelvins under the standard cross-membrane voltage and ionic strength conditions. The present findings may be useful in advancing our understanding of ion and mass transport phenomena in nanopores.

Experimental Assessment of the Influence of the Design on the Performance of Novel Evaporators with Latent Energy Storage Ability

This study was carried out within the HYBUILD project, as part of the task aimed at developing novel evaporators for compact and direct integration of phase-change materials (PCM) into air-conditioning systems for efficient utilization of solar energy. To achieve this, novel evaporators were designed to contain PCM between refrigerant and heat transfer fluid (HTF) channels, allowing a three-media heat exchange mechanism. This paper experimentally assesses the influence of the configuration/arrangement of the channels on the performance of the evaporators, using three different lab-scale prototypes. Key performance indicators (KPI) relevant for thermal energy storage (TES) and heat exchangers (HEX) were used to study the influence of the design on the performance of the different designs of the novel evaporators. The results show that the change in the PCM, refrigerant, and HTF channel configuration affects the performance of the novel evaporators independently. The coefficient of performance (COP) of the refrigeration system and the energy storage density of the modules are the least affected KPIs (less than 16%), whereas the state of charge (SOC) at thermal equilibrium is the most affected KPI (about 44%). A discussion on how these effects provide unique strength for specific applications is included.

Truly 3D microfluidic heating system with iterative structure of coil heaters and fluidic channels

A microfluidic chip, in which both the coil heater and the fluidic channel are designed in a 3D iterative structure, is developed and experimentally demonstrated. Using the empty surrounding 3D space, the microfluidic chip increases the heat transfer area, thereby increasing the fluid temperature by 51.3%, with the same power consumption, compared to heaters and channels typically designed on a 2D plane. After casting polydimethylsiloxane (PDMS) into a sacrificial mold printed using a 3D printer and dissolving the mold, the 3D coil Joule heater is fabricated by filling the interior part of the coil with liquid gallium by vacuuming. By adding an insulation wall filled with air having low thermal conductivity, an additional heating of 8.7% is achieved; this demonstrates the advantage of the 3D-printed soluble-mold technique, which can allow faster prototyping than the typical microfabrication based on soft lithography. Thus, this technique enables convenient design modifications with high priority for performance improvement. As all the components are manufactured simultaneously within a biocompatible, single PDMS body (because of the absence of bonding process between the devices), the risk of leakage in the device is inherently avoided, and the device can be bent without causing any fracture. Therefore, the reported fabrication process and devices are expected to contribute to miniaturization and performance enhancement of microfluidics; this will lead to the development of wearable 3D lab-on-a-chip devices in future.