Fluidic Resistance Research Articles

Developing a Flow-Resistance Module for Elucidating Cell Mechanotransduction on Multiple Shear Stresses.

Fluid shear stress plays a pivotal role in regulating cellular behaviors, maintaining tissue homeostasis, and driving disease progression. Cells in various tissues are specifically adapted to physiological levels of shear stress and exhibit sensitivity to variations in its magnitude, highlighting the requirement for a comprehensive understanding of cellular responses to both physiologically and pathologically relevant levels of shear stress. In this study, we developed an independent upstream flow-resistance module with high fluidic resistances comprising three microchannels. The validity of the flow-resistance module was confirmed via computational fluid dynamics (CFD) simulations and flow calibration experiments, resulting in the generation of steady wall shear stresses ranging from 0.06 to 11.57 dyn/cm2 within the interconnected cell culture chips. Gene expression profiles, cytoskeletal remodeling, and morphological changes, as well as Yes-associated protein (YAP) nuclear translocation, were investigated in response to various shear stresses to authenticate the reliability of our experimental platform, indicating an increasing trend as the shear stress increases, reaching its maximum at various shear stresses. Our findings suggest that this flow-resistance module can be readily employed for precise characterization of cellular responses under various shear stresses.

Separation of Lung Cancer Cells From Mixed Cell Samples Using Aptamer-Modified Magnetic Beads and Permalloy Micromagnets.

This study involved the design and fabrication of a microfluidic chip integrated with permalloy micromagnets. The device was used with aptamer-modified magnetic beads (MBs) of various sizes to successfully separate lung cancer cells from a mixture of other cells. The overall separation efficiency was evaluated based on the ratios of cells in the different outlets and inlets of the chip. The results showed efficiencies ranging from 43.4% to 50.2% for MB sizes between 1.36 and 4.50 µm. Interestingly, efficiency slightly decreased as the size of the MBs increased, contrary to predictions. Further examination revealed that larger MBs exerted gravitational force on the cell-bound MBs at low flow rates, causing the targets to settle before reaching the main microchannel region. This was attributed to fluidic resistance caused by a size mismatch between the inlet tube and the microfluidic conduit. An increase in cell accumulation at the inlet was observed with larger MB sizes due to gravity. Therefore, the definition of effective separation efficiency was revised to exclude the effect of cell accumulation at the inlet. Effective separation efficiencies were found to be 71.6%, 76.4%, and 79.4% for MB sizes of 1.36, 3.00, and 4.50µm, respectively. The study concluded that larger MBs interacted more with the magnetic force, resulting in better separation. However, cells with smaller MBs were more likely to evade the magnetic force. The investigation provides valuable insights into isolating lung cancer cells using this method, with the potential for clinical application in cancer diagnosis and treatment.

Monolayer-fluorescence counting for ultrasensitive detection of tumour cell-derived extracellular vesicles using a step-wedge microfluidic platform

Extracellular vesicles have emerged as significant noninvasive tumour biomarkers, and ultrasensitive detection methods are important for early cancer diagnosis. Here, a monolayer-fluorescence counting strategy was developed for the ultrasensitive detection of extracellular vesicles using a microfluidic platform. Extracellular vesicles were specially captured and separated from complex matrix by immune magnetic microbeads (IMBs). With an enhancing acoustic wave microfluidic channel, the magnetic-extracellular vesicles immune complex was adequately mixed and reacted with antibody-modified fluorescence microbeads (IFBs). Using a newly designed step-wedge microfluidic structure, micrometer-size particles were trapped in large numbers with monolayer in the step zone, and the fluidic resistance was reduced through the wedge structure. This detection signal of the fluorescence-labelled immune sandwich complex could be read by counting, avoiding background interference and achieving an ultrasensitive detection with a detection limit of 850 particles/mL. Moreover, this method showed strong reliability and specificity in clinic samples. In addition, a miniaturized detection device was developed based on this microfluidic platform, improving this detection automation.

Room-temperature mL-to-μL quantitative liquid concentration device for cyclone flow

Highly sensitive quantitative analysis of liquids is required in various fields. Analytical instruments and devices such as chromatography, spectroscopic analysis, DNA sequencers, immunoassay, mass spectrometry, and microfluidic devices are utilized for this purpose. Typically, the sample volume is at the milliliter scale, while the analysis volume is at the microliter scale. Consequently, most of the sample is discarded. Therefore, a universal volume interface is required to quantitatively concentrate samples from milliliter to microliter volume. This study introduces a liquid quantitative function to the cyclone concentration method using a millimeter-scale channel, which is highly suitable for controlling liquids at the microliter scale due to its high fluidic resistance against cyclone flow. This method enables the effective control of liquid concentration by cyclone flow. The optimum channel structure is investigated, and a 33-fold concentration of aqueous solutions is demonstrated. Finally, the concentration device is applied to measure molybdenum ions in a river.Graphical abstract

Embedded Fluidic Sensing and Control with Soft Open‐Cell Foams

AbstractThe synthesis of soft matter intelligence with circuit‐driven logic has enabled a new class of robots that perform complex tasks or conform to specialized form factors in unique ways that cannot be realized through conventional designs. Translating this hybrid approach to fluidic systems, the present work addresses the need for sheet‐based circuit materials by leveraging the innate porosity of foam—a soft material—to develop pneumatic components that support digital logic, mixed‐signal control, and analog force sensing in wearables and soft robots. Analytical tools and experimental techniques developed in this work serve to elucidate compressible gas flow through porous sheets, and to inform the design of centimeter‐sized foam resistors with fluidic resistances on the order of 109 Pa s m−3. When embedded inside soft robots and wearables, these resistors facilitate diverse functionalities spanning both sensing and control domains, including digital logic using textile logic gates, digital‐to‐analog signal conversion using ladder networks, and analog sensing of forces up to 40 N via compression‐induced changes in resistance. By combining features of both circuit‐based and materials‐based approaches, foam‐enabled fluidic circuits serve as a useful paradigm for future hybrid robotic architectures that fully embody the sensing and computing capabilities of soft fluidic materials.

A Lego-Like Reconfigurable Microfluidic Stabilizer System with Tunable Fluidic RC Constants and Stabilization Ratios.

In microfluidic systems, it is important to maintain flow stability to execute various functions, such as chemical reactions, cell transportation, and liquid injection. However, traditional flow sources, often bulky and prone to unpredictable fluctuations, limit the portability and broader application of these systems. Existing fluidic stabilizers, typically designed for specific flow sources, lack reconfigurability and adaptability in terms of the stabilization ratios. To address these limitations, a modular and standardized stabilizer system with tunable stabilization ratios is required. In this work, we present a Lego-like modular microfluidic stabilizer system, which is fabricated using 3D printing and offers multi-level stabilization combinations and customizable stabilization ratios through the control of fluidic RC constants, making it adaptable to various microfluidic systems. A simplified three-element circuit model is used to characterize the system by straightforwardly extracting the RC constant without intricate calculations of the fluidic resistance and capacitance. By utilizing a simplified three-element model, the stabilizer yields two well-fitted operational curves, demonstrating an R-square of 0.95, and provides an optimal stabilization ratio below 1%. To evaluate the system's effectiveness, unstable input flow at different working frequencies is stabilized, and droplet generation experiments are conducted and discussed. The results show that the microfluidic stabilizer system significantly reduces flow fluctuations and enhances droplet uniformity. This system provides a new avenue for microfluidic stabilization with a tunable stabilization ratio, and its plug-and-play design can be effectively applied across diverse applications to finely tune fluid flow behaviors in microfluidic devices.

Mechanism analysis on heat transfer of supercritical LNG in horizontal U-bend tube

A comprehensive comprehension of the intricate heat transfer mechanisms pertaining to supercritical fluids within U-bend tubes holds paramount significance in the optimization design of submerged combustion vaporizers and other water-bath heating heat exchangers. This paper employs a combined approach of experimental analysis and numerical simulation to explore the complicated heat transfer processes of supercritical liquefied natural gas in the U-bend tube. For a careful consideration of similarity and safety, the N2–Ar mixture is used as the alternative experimental media. Upon validating the model's accuracy using experimental data, this study unveils the mechanism of the coupling effect between centrifugal force and buoyancy on heat transfer based on simulation results. The results show that the internal circulation flow field structure caused by centrifugal force weakens the heat transfer on the inner side within an angle range of approximately 60°. Along the entrance region of downstream straight tubing, secondary flow continues to be predominantly governed by centrifugal forces due to inertia-driven effects. Subsequently, buoyancy-driven secondary flow impels compression upon centrifugally-induced secondary flow towards the inner side, thereby instigating significant augmentation in fluidic heat transfer resistance in both the viscous sub-layer and buffer layer of the inner side. Overall, the downstream straight tube section exhibits a special heat transfer variation pattern characterized by an initial strengthening, followed by deterioration, and ultimately recovery due to the influence of centrifugal force, with a maximum influence distance extending to 175.5d.

A new self-adjustable glaucoma valve.

Introduction: Glaucoma, the leading cause of irreversible blindness globally, affects more than 70 million people across the world. When initial treatments prove ineffective, especially for cases with high intraocular pressure (IOP), the preferred approach involves employing glaucoma drainage devices (GDDs). Methods: This study introduces a novel self-adjustable glaucoma drainage device (SAGDD) designed to maintain IOP within the desired biological range (10mmHg < IOP <18mmHg) by dynamically modulating its fluidic resistance. Inspired by the starling resistor, we designed a circular valve with a thin, flexible membrane placed over the valve's inlet and outlet. To achieve the ideal design for the SAGDD and optimize its parameters, we utilized fluid-solid interaction (FSI) numerical models and conducted parametric studies, wherein simulations demonstrated the validity of the concept. Subsequently, to confirm and validate the numerical results, we fabricated a SAGDD at a 3:1 scale and subjected it to in vitro testing. Results: Our findings demonstrate that, on a 3:1 scale, a circular SAGDD with a diameter of 8.1mm and a stainless-steel membrane with a thickness of 10µm effectively maintained IOP within the target range when the membrane exposed to external pressures of 7.5 or 10mmHg. Discussion: In summary, our study establishes a strong foundation for further exploration of the potential efficacy of SAGDD as a promising treatment for glaucoma. The cost-effectiveness and simplicity of its design, devoid of costly instrumentation, hold considerable promise in addressing the challenges associated with glaucoma.

Buoyancy-Driven Micro/-Nanomotors: From Fundamentals to Applications.

The progression of self-powered micro/-nanomotors (MNMs) has rapidly evolved over the past few decades, showing applications in various fields such as nanotechnology, biomedical engineering, microfluidics, environmental science, and energy harvesting. Miniaturized MNMs transduce chemical/biochemical energies into mechanical motion for navigating through complex fluidic environments with directional control via external forces fields such as magnetic, photonic, and electric stimuli. Among various propulsion mechanisms, buoyancy-driven MNMs have received noteworthy recognition due to their simplicity, efficiency, and versatility. Buoyancy force-driven motors harness the principles of density variation-mediated force to overcome fluidic resistance to navigate through complex environments. Restricting the propulsion in one direction helps to control directional movement, making it more efficient in isotropic solutions. The changes in pH, ionic strength, chemical concentration, solute gradients, or the presence of specific molecules can influence the motion of buoyancy-driven MNMs as evidenced by earlier reports. This review aims to provide a fundamental and detailed analysis of the current state-of-the-art in buoyancy-driven MNMs, aiming to inspire further research and innovation in this promising field.

Microfluidic viscometer using capillary pressure sensing

Blood viscosity is considered as a vital determinant of the efficiency of blood flow in blood-vessel networks. The coflowing method is considered as a promising technique for measuring blood viscosity. However, it requires two precise syringe pumps to supply two fluids (i.e., the reference fluid and blood), calibration in advance, and long waiting time for securing steady blood flow. To solve these problems, a single syringe pump is adopted to supply blood into a microfluidic device without requiring a reference fluid. Two key parameters—fluidic resistance and compliance coefficient—are suggested and obtained by analyzing the fluid velocities in a microfluidic channel and calculating the air pressure in the air compliance unit. Using a discrete fluidic circuit model, the pressure difference is analytically derived and utilized as the nonlinear regression formula. The two key parameters are then obtained through nonlinear regression analysis. According to experimental results, the air cavity and flow rate contribute to increasing the compliance coefficient. The fluidic resistance increases significantly at higher concentrations of glycerin solution ranging from 20% to 50%. The proposed method underestimates the values by approximately 27.5% compared with the previous method. Finally, the proposed method is adopted to detect the effects of hematocrit and red blood cell sedimentation in the driving syringe based on two vital parameters. Regarding the fluidic resistance, the normalized difference between the proposed and previous methods is less than 10%. Therefore, two key parameters can be considered as effective for quantitatively monitoring the hematocrit variation in blood flow. In conclusion, from a biomechanical perspective, the proposed method is highly promising for quantifying blood flow in a microfluidic channel.

Blood component separation in straight microfluidic channels.

Separation of blood components is required in many diagnostic applications and blood processes. In laboratories, blood is usually fractionated by manual operation involving a bulk centrifugation equipment, which significantly increases logistic burden. Blood sample processing in the field and resource-limited settings cannot be readily implemented without the use of microfluidic technology. In this study, we developed a small footprint, rapid, and passive microfluidic channel device that relied on margination and inertial focusing effects for blood component separation. No blood dilution, lysis, or labeling step was needed as to preserve sample integrity. One main innovation of this work was the insertion of fluidic restrictors at outlet ports to divert the separation interface into designated outlet channels. Thus, separation efficiency was significantly improved in comparison to previous works. We demonstrated different operation modes ranging from platelet or plasma extraction from human whole blood to platelet concentration from platelet-rich plasma through the manipulation of outlet port fluidic resistance. Using straight microfluidic channels with a high aspect ratio rectangular cross section, we demonstrated 95.4% platelet purity extracted from human whole blood. In plasma extraction, 99.9% RBC removal rate was achieved. We also demonstrated 2.6× concentration of platelet-rich plasma solution to produce platelet concentrate. The extraction efficiency and throughput rate are scalable with continuous and clog-free recirculation operation, in contrast to other blood fractionation approaches using filtration membranes or affinity-based purification methods. Our microfluidic blood separation method is highly tunable and versatile, and easy to be integrated into multi-step blood processing and advanced sample preparation workflows.

On-demand delivery of therapeutic extracellular vesicles by encapsulating in monodispersed photodegradable hydrogel microparticles using a droplet microfluidic device

Mesenchymal stem cells (MSCs)-derived extracellular vesicles (EVs) have been studied for therapeutic applications due to easier endocytosis and fewer adverse effects than MSCs. However, EVs injected medicinally are diluted by body fluids and inefficiently delivered to the therapeutic target, limiting original therapeutic effects. Therefore, biocompatible carriers such as hydrogels are needed in EVs delivery systems to enhance EVs retention and release EVs sustainably at therapeutic targets. In addition to the advantages of delivering EVs using hydrogels, photodegradable hydrogels provide a controllable degradation process via ultraviolet (UV) irradiation. However, long-term UV irradiation to degrade the photodegradable hydrogel may potentially damage EVs and targets; therefore, a carrier that can be degraded with shorter UV irradiation is required. Herein, we generate photodegradable hydrogel microparticles (PHMPs) that can release encapsulated EVs sustainably within 2 min of UV irradiation by droplet-based microfluidics. By regulating the fluidic resistance of the channels, monodisperse PHMPs, which can avoid undesired variations in EVs release kinetics, were generated. EVs were successfully retained in PHMPs in the absence of external stimuli, and EVs were released from PHMPs and enhanced cell proliferation following UV irradiation. Therefore, PHMPs can overcome the limitations of conventional EVs delivery, including their inability to deliver EVs sustainably and on-demand, and low EVs retention.

Asymmetric lung increases particle filtration by deposition

Human lung is known to be an asymmetric dichotomously branched network of bronchioles. Existing literature on the relation between anatomy and air-flow physics in the tracheobronchial trees has discussed the results of asymmetry. We discuss a secondary (but an important) lung function to seek asymmetry: to protect the acinus from a high pathogen load. We build morphometric parameter-based mathematical models of realistic bronchial trees to explore the structure-function relationship. We observe that maximum surface area for gas exchange, minimum resistance and minimum volume are obtained near the symmetry condition. In contrast, we show that deposition of inhaled foreign particles in the non-terminal airways is enhanced by asymmetry. We show from our model, that the optimal value of asymmetry for maximum particle filtration is within 10% of the experimentally measured value in human lungs. This structural trait of the lung aids in self-defence of the host against pathogen laden aerosols. We explain how natural asymmetric design of typical human lungs makes a sacrifice away from gas exchange optimality to gain this protection. In a typical human lung, when compared to most optimal condition (which is associated with symmetric branching), the fluidic resistance is 14% greater, the gas exchange surface area is about 11% lower, the lung volume is about 13% greater to gain an increase of 4.4% protection against foreign particles. This afforded protection is also robust to minor variations in branching ratio or variation in ventilation, which are both crucial to survival.

An On-Wall-Rotating Strategy for Effective Upstream Motion of Untethered Millirobot: Principle, Design, and Demonstration

Untethered miniature robots that can access narrow and harsh environments in the body show great potential for future biomedical applications. Despite the many types of millirobot that have been developed, swimming against the fast blood flow remains a big challenge due to lack of the ability to stay still and the large fluidic resistance from blood. This article proposes an on-wall-rotating strategy and a streamlined millirobot to achieve effective upstream motion in the lumen. First, the principle of on-wall-rotating strategy and the dynamic motion model of the millirobot is established. Then, a critical safety angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta _{s}$</tex-math></inline-formula> is theoretically and experimentally analyzed for the safe and stable control of the robot. After that, a series of experiments are conducted to verify the proposed driving strategy. The results suggest that the robot is able to move at a speed of 5 mm/s against flow velocity of 138 mm/s, which is comparable to the blood flow of 2700 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{3}$</tex-math></inline-formula> /s and several times faster than other reported driving strategies. This work offers a new strategy for the untethered magnetic robot construction and control for blood vessels, which would promote the application of millirobot for biomedical engineering.

Design and Characterization of an Adjustable Passive Flow Regulator and Application to External CSF Drainage

Passive valves that deliver a constant flow rate regardless of inlet pressure changes have numerous applications in research, industry, and medical fields. The present article describes a passive spring valve that can be adjusted manually to deliver the required flow rate. The valve consists of a movable rod with an engraved microchannel. The fluidic resistance of the device varies together with the inlet pressure to regulate the flow rate. A prototype was made and characterized. Flow-rate adjustment up to +/-30% of the nominal flow rate was shown. A simple numerical model of the fluid flow through the device was made to adapt the design to external ventricular drainage of cerebrospinal fluid (CSF). Some insights about the implementation of this solution are also discussed.

Lower fluidic resistance of double-layer droplet continuous flow PCR microfluidic chip for rapid detection of bacteria

BackgroundRapid diagnosis of harmful microorganisms demonstrated its great importance for social health. Continuous flow PCR (CF-PCR) can realize rapid amplification of target genes by placing the microfluidic chip on heaters with different temperature. However, bubbles and evaporation always arise from heating, which makes the amplification not stable. Water-in-oil droplets running in CF-PCR microfluidic chip with uniform height takes long time because of the high resistance induced by long meandering microchannel. To overcome those drawbacks, we proposed a double-layer droplet CF-PCR microfluidic chip to reduce the fluidic resistance, and meanwhile nanoliter droplets were generated to minimize the bubbles and evaporation. ResultsExperiments showed that (1) fluidic resistance could be reduced with the increase of the height of the serpentine microchannel if the height of the T-junction part was certain. (2) Running speed, the size and the number of generated droplets were positively correlated with the cross-sectional area of the T-junction and water pressure. (3) Droplet fusion happened at higher water pressure if other experimental conditions were the same. (4) 0.032 nL droplet was created if the cross-sectional area of T-junction and water pressure were 1600 μm2 (40 × 40 μm) and 7 kPa, respectively. Finally, we successfully amplified the target genes of Porphyromonas gingivalis within 11′16″ and observed the fluorescence from droplets. Significance and noveltySuch a microfluidic chip can effectively reduce the high resistance induced by long meandering microchannel, and greatly save time required for droplets CF-PCR. It offers a new way for the rapid detection of bacterial.

An Automated Hardware-in-Loop Testbed for Evaluating Hemorrhagic Shock Resuscitation Controllers.

Hemorrhage remains a leading cause of death, with early goal-directed fluid resuscitation being a pillar of mortality prevention. While closed-loop resuscitation can potentially benefit this effort, development of these systems is resource-intensive, making it a challenge to compare infusion controllers and respective hardware within a range of physiologically relevant hemorrhage scenarios. Here, we present a hardware-in-loop automated testbed for resuscitation controllers (HATRC) that provides a simple yet robust methodology to evaluate controllers. HATRC is a flow-loop benchtop system comprised of multiple PhysioVessels which mimic pressure-volume responsiveness for different resuscitation infusates. Subject variability and infusate switching were integrated for more complex testing. Further, HATRC can modulate fluidic resistance to mimic arterial resistance changes after vasopressor administration. Finally, all outflow rates are computer-controlled, with rules to dictate hemorrhage, clotting, and urine rates. Using HATRC, we evaluated a decision-table controller at two sampling rates with different hemorrhage scenarios. HATRC allows quantification of twelve performance metrics for each controller configuration and scenario, producing heterogeneous results and highlighting the need for controller evaluation with multiple hemorrhage scenarios. In conclusion, HATRC can be used to evaluate closed-loop controllers through user-defined hemorrhage scenarios while rating their performance. Extensive controller troubleshooting using HATRC can accelerate product development and subsequent translation.

In vitro circulation model driven by tissue-engineered dome-shaped cardiac tissue

The heart is an essential organ for animals and humans. With the increased availability of pluripotent stem cells, the use of three-dimensional cardiac tissues consisting of cultured cardiomyocytes in in vitro drug evaluation has been widely studied. Several models have been proposed for the realization of the pump function, which is the original function of the heart. However, there are no models that simulate the human circulatory system using cultured cardiac tissue. This study shows that a dome-shaped cardiac tissue fabricated using the cell sheet stacking technique can achieve a heart-like pump function and circulate culture medium, there by mimicking the human circulatory system. Firstly, human induced pluripotent stem cells were differentiated into autonomously beating cardiomyocytes, and cardiomyocyte cell sheets were created using temperature-responsive culture dishes. A cardiomyocyte sheet and a human dermal fibroblast sheet were stacked using a cell sheet manipulator. This two-layered cell sheet was then inflated to create a dome-shaped cardiac tissue with a base diameter of 8 mm. The volume of the dome-shaped cardiac tissue changed according to the autonomous beating. The stroke volume increased with the culture period and reached 21 ± 8.9 μl (n = 6) on day 21. It also responded to β-stimulant and extracellular calcium concentrations. Internal pressure fluctuations were also recorded under isovolumetric conditions by dedicated culture devices. The peak heights of pulsatile pressure were 0.33 ± 0.048 mmHg (n = 3) under a basal pressure of 0.5 mmHg on day 19. When the tissue was connected to a flow path that had check valves applied, it drove a directional flow with an average flow rate of approximately 1 μl s−1. Furthermore, pressure–volume (P–V) diagrams were created from the simultaneous measurement of changes in pressure and volume under three conditions of fluidic resistance. In conclusion, this cardiac model can potentially be used for biological pumps that drive multi-organ chips and for more accurate in vitro drug evaluation using P–V diagrams.

Elastic membrane enabled inward pumping for liquid manipulation on a centrifugal microfluidic platform.

Nowadays, centrifugal microfluidic platforms are finding wider acceptance for implementing point-of-care assays due to the simplicity of the controls, the versatility of the fluidic operations, and the ability to create a self-enclosed system, thus minimizing the risk of contamination for either the sample or surroundings. Despite these advantages, one of the inherent weaknesses of CD microfluidics is that all the sequential fluidic chambers and channels must be positioned radially since the centrifugal force acts from the center of the disk outward. Implementation of schemes where the liquid can be rerouted from the disk periphery to the disk center would significantly increase the utility of CD platforms and increase the rational utilization of the real estate on the disk. The present study outlines a novel utilization of elastic membranes covering fluidic chambers to implement inward pumping whereby the fluid is returned from the disk periphery to the center of the disk. When the disk revolves at an angular velocity of 3600 rpm, liquid enters the chamber covered by the elastic membrane. This membrane is deflected upward by liquid, storing energy like a compressed spring. When the angular velocity of the disk is reduced to 180 rpm and thus the centrifugal force is diminished, the elastic membrane pushes the liquid from the chamber inward, closer to the center of the disk. There are two channels leading from the elastic membrane-covered reservoir-one channel has a higher fluidic resistance and the other (wider) has a lower fluidic resistance. The geometry of these two channels determines the fluidic path inward (toward the center of the disk). Most of the liquid travels through the recirculating channel with lower resistance. We demonstrated an inward pumping efficiency in the range of 78%-89%. Elastic membrane-driven inward pumping was demonstrated for the application of enhanced fluid mixing. Additionally, to demonstrate the utility of the proposed pumping mechanism for multi-step assays on the disk, we implemented and tested a disk design that combines plasma separation and inward pumping.

Revamping SiO2 Spheres by Core–Shell Porosity Endowment to Construct a Mazelike Nanoreactor for Enhanced Catalysis in CO2 Hydrogenation to Methanol (Adv. Funct. Mater. 47/2021)

Mazelike Nanoreactors In article number 2102896, Sergey M. Kozlov, Armando Borgna, Hua Chun Zeng, and co-workers show that premade Stöber silica spheres can be endowed with multimodal porosity, creating maze-like nanoreactors that possess numerous long travelling paths for reactants with low fluidic resistance and thus result in longer residence times within these spheres. Furthermore, complex catalytic components can be housed inside interior pores and voids, ensuring long-term performance of the nanoreactors in the hydrogenation of CO2 to methanol.