Particle focusing by 3D inertial microfluidics

Three-dimensional(3D)particle focusing in microfluidics is a fundamental capability with a wide range of applications,such as on-chip flow cytometry,where high-throughput analysis at the single-cell level is performed.Currently,3D focusing is achieved mainly in devices with complex layouts,additional sheath fluids,and complex pumping systems.In this work,we present a compact microfluidic device capable of 3D particle focusing at high flow rates and with a small footprint,without the requirement of external fields or lateral sheath flows,but using only a single-inlet,single-outlet microfluidic sequence of straight channels and tightly curving vertical loops.This device exploits inertial fluidic effects that occur in a laminar regime at sufficiently high flow rates,manipulating the particle positions by the combination of inertial lift forces and Dean drag forces.The device is fabricated by femtosecond laser irradiation followed by chemical etching,which is a simple two-step process enabling the creation of 3D microfluidic networks in fused silica glass substrates.The use of tightly curving three-dimensional microfluidic loops produces strong Dean drag forces along the whole loop but also induces an asymmetric Dean flow decay in the subsequent straight channel,thus producing rapid cross-sectional mixing flows that assist with 3D particle focusing.The use of out-of-plane loops favors a compact parallelization of multiple focusing channels,allowing one to process large amounts of samples.In addition,the low fluidic resistance of the channel network is compatible with vacuum driven flows.The resulting device is quite interesting for high-throughput on-chip flow cytometry.

EVA NEXUS-Phaco performance study

AIM:To investigate a novel phacoemulsification system“EVA NEXUS”(D.O.R.C.,Dutch Opthalmic Research Center)in comparison to the existing system“EVA”in clinical use.And to compare both phacoemulsification systems in terms of efficiency,safety and postoperative inflammatory activity.METHODS:In this study standardized cataract surgery was performed on both eyes of the study participant,using the“EVA system”(control group,n=20)on one eye and the“EVA NEXUS system”(intervention group,n=20)on the other eye.Only patients with cataract LOCS Grading 1-3 and no accompanying eye diseases were included in this study.A total of 20 patients were included in this study,with each treatment arm including 20 eyes.During surgery a 0.1 mL aqueous humor sample was collected 1min after phacoemulsification to measure the total prostaglanin E2 concentrations using an enzyme-linked immunosorbent assay.The endothelial cell count,visual and refractive outcomes,and anterior chamber flare were evaluated preoperatively,and 1d,1wk,and 3mo postoperatively.RESULTS:There were no statistically significant differences between both groups regarding intraoperative safety parameters including effective phacoemulsification time(P=0.904),balanced saline solution flow(P=0.701)and total surgery time(P=0.565).Postoperative prostaglandin E2 levels,anterior chamber flare as well as endothelial cell loss tended to be lower in the NEXUS-Group,however not being statistically significant(P=0.718;0.164;0.486).Both systems provided similar clinical outcomes,regarding best corrected visual acuity and refractive parameters,showing no statistically significant differences between both groups.CONCLUSION:Both systems show a high level of safety and efficency with similar results in terms of safety parameters including postoperative inflammatory activity and endothelial cell loss as well as visual and refractive outcomes.Although statistically not significant,the EVA NEXUS system tends to cause less postoperative inflammation with lower prostaglandin E2 levels and lower anterior chamber flare values.

采用反吹、微流控技术分析原油中的轻烃组分

利用程序升温蒸发进样器、反吹技术和微流控装置分析原油中的C5-C13轻烃组分，用一根HPPONA色谱柱分离，同时得到保留时间相同的火焰离子化检测信号和质谱检测信号，为原油中轻烃组分的色谱定性提供了新的有力工具。该方法中所用的色谱柱使用寿命长，分离效果好，对平湖4井油样中C5～C13馏分的分离得到了可用质谱定性的峰约290个（尚有不少混合峰存在），较难分离的物质对t-1，2-二甲基环戊烷与2-乙基戊烷得到了较好的分离，2-乙基戊烷峰得到非常好的质谱图，是目前研究原油中轻烃组分分析的有效手段。同时应用微流控装置后可在质谱仪不停机的条件下更换色谱柱。

On Switching of a Flip-Flop Jet Nozzle with Double Ports by Single-Port Control

This research deals with the oscillation mechanism of a flip-flop jet nozzle with a connecting tube, based on the measurements of pressures and velocities in the connecting tube and inside the nozzle. The measurements are carried out varying: 1) the inside diameter d of the connecting tube;2) the length L of the connecting tube and 3) the jet velocity VPN from a primary-nozzle exit. We assume that the jet switches when a time integral reaches a certain value. At first, as the time integral, we introduce the accumulated flow work of pressure, namely, the time integral of mass flux through a connecting tube into the jet-reattaching wall from the opposite jet-un-reattaching wall. Under the assumption, the trace of pressure difference between both the ends of the connecting tube is simply modeled on the basis of measurements, and the flow velocity in the connecting tube is computed as incompressible flow. Second, in order to discuss the physics of the accumulated flow work further, we conduct another experiment in single-port control where the inflow from the control port on the jet-reattaching wall is forcibly controlled and the other control port on the opposite jet-un-reattaching wall is sealed, instead of the experiment in regular jet’s oscillation using the ordinary nozzle with two control ports in connection. As a result, it is found that the accumulated flow work is adequate to determine the dominant jet- oscillation frequency. In the experiment in single-port control, the accumulated flow work of the inflow until the jet’s switching well agrees with that in regular jet’s oscillation using the ordinary nozzle.

A deep-reinforcement learning approach for optimizing homogeneous droplet routing in digital microfluidic biochips

Over the past two decades,digital microfluidic biochips have been in much demand for safety-critical and biomedical applications and increasingly important in point-of-care analysis,drug discovery,and immunoassays,among other areas.However,for complex bioassays,finding routes for the transportation of droplets in an electrowetting-on-dielectric digital biochip while maintaining their discreteness is a challenging task.In this study,we propose a deep reinforcement learning-based droplet routing technique for digital microfluidic biochips.The technique is implemented on a distributed architecture to optimize the possible paths for predefined source–target pairs of droplets.The actors of the technique calculate the possible routes of the source–target pairs and store the experience in a replay buffer,and the learner fetches the experiences and updates the routing paths.The proposed algorithm was applied to benchmark suitesⅠand Ⅲ as two different test benches,and it achieved significant improvements over state-of-the-art techniques.

Study on hydrodynamic vibration in fluidic flowmeter

The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed.

A Twin Unidirectional Impulse Turbine for Wave Energy Conversion—Effect of Fluidic Diode on the Performance

As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. However, the average efficiency of the suggested twin turbine is considerably lower than that of a conventional unidirectional turbine in this topology because reciprocating air flow can’t be rectified adequately by a unidirectional turbine. In order to improve the efficiency, using fluidic diode is discussed. In this study, two different fluidic diodes were discussed by computational fluid dynamics (CFD) and a wind tunnel test. Further, its usefulness is discussed from a view point of the turbine efficiency. The fluidic diode was shown to improve rectification of the topology. However, it needs more improvement in regards to its energy loss in order to enhance the turbine efficiency.

Growth Enhancement of Dunaliella salina by Microbubble Induced Airlift Loop Bioreactor (ALB)—The Relation between Mass Transfer and Growth Rate

The efficiency of a novel microalgal culture system (an airlift loop bioreactor [ALB] engaged with a fluidic oscillator to produce microbubbles) is compared with both a conventional ALB (producing fine bubbles without the fluidic oscillator) and non-aerated flask culture. The impact of CO2 mass transfer on Dunaliella salina growth is assessed, through varying the gas (5% CO2, 95% N2) dosing flow rate. The results showed that approximately 6 - 8 times higher chlorophyll content was achieved in the aerated ALB cultures than in the non-aerated flasks, and there was a 20% - 40% increase in specific growth rate of D. salina in the novel ALB with microbubbles when compared with the conventional ALB cultures. The increase in chlorophyll content was found to be proportional to the total amount of CO2 mass transfer. For the same dosing time and flow rate, higher CO2 mass transfer rate (microbubble dosing) resulted in a greater growth rate.

Effect of Cilia Orientation in Metachronal Transport of Microparticles

A biomimetic approach is used to generate a directed transversal transportation of micron-sized particles in liquids based on the principle of cilia-type arrays in coordinated motion. Rows of flaps mimicking planar cilia are positioned off-centre along an array of cavities covered with membranes that support the flaps. These membranes are deflected from a concave to a convex shape and vice versa by pneumatic actuation applying positive and negative pressures (relative to the ambient) inside the cavities. As a result, the flap on top of the membrane tilts to the left or right within such a pressure cycle, performing a beat stroke. Since each cavity can be addressed in the device individually and in rapid succession, waves of coordinated flap motion can be run along the wall. Such metachronal waves are generated and transport of particles along the cilia surface is achieved in both symplectic and antiplectic direction. It is shown that the initial tilt of the flaps relative to the wall-normal determines the direction of transport.

A Study on Fluidic Diode for Wave Energy Conversion-Effect of Bypass Geometry on the Turbine Performance

A twin-impulse turbine for bi-directional flow has been developed for wave energy converter. However, the previous studies elucidated that the mean efficiency of the twin turbine is much lower than that of the impulse turbine for a unidirectional flow because a portion of airflow passes through the reverse flow turbine whose efficiency is very low. Therefore, a fluidic diode was adopted in the twin-impulse turbine in order to reduce the air flow through the reverse flow turbine. In this study, the rectification effect of the fluidic diode was investigated where a bypass is introduced into a blunt body. A computational fluid dynamics (CFD) analysis was conducted to investigate the effect of fluidic diodes on the turbine performance. In this analysis, RANS equations were used as the governing equations and the standard k-ε model was used as the turbulence model. The computational domain is composed of a circular tube and fluidic diode, and the domain meshed with an approximately 1.5 million mesh elements. As a result, it was found that the rectification effect of the fluidic diode is enhanced by installing a blunt body with a bypass hole of 5° taper angle.

A Survey on Pneumatic Muscle Actuators Modeling

The aim of this article is to provide a survey on the most popular modeling approaches for PMAs （pneumatic muscle actuators）. PMAs are highly non-linear pneumatic actuators where their elongation is proportional to the interval pressure. During the last decade, there has been an increase in the industrial and scientific utilization of PMAs, due to their advantages such as high strength and small weight, while various types of PMAs with different technical characteristics have appeared in the literature. This article will： （a） analyse the PMA＇s operation from a mathematical modeling perspective; （b） present their merits and drawbacks of the most common PMAs; and （c） establish the fundamental basis for developing industrial applications and conducting research in this field.

Characterization of a novel fluidic friction-reduction tool used in extended-reach well considering periodic particle-laden jet

Fluidic oscillators(FOs)can be used as an efficient fluidic vibration tool to solve high friction problems in extended-reach wells.However,the complex mechanism of FOs makes the design challenging,and the dynamic erosion behavior inside FOs is still unclear.In this paper,new FOs are proposed and the working characteristics under the influence of periodic particle-laden jets are investigated.Firstly,the results reveal the working mechanism of new FOs,showing that the generation of pressure pulses is closely connected with periodic jet switching and the development of vortices.Secondly,the important performance parameters,i.e.,pressure pulse and oscillation frequency,are extensively studied through numerical simulation and experimental verification.It is found that the performance can be optimized by adjusting the tool structure according to different engineering requirements.Finally,the oscillating solid-liquid two-phase flow inside FO is studied.It is demonstrated that the accumulation of particles leads to a significant reduction in performance.The results also reveal five locations that are susceptible to erosion and the erosion behavior of these locations are studied.It has been shown that the periodic jet causes fluctuations in the amount of erosion at the outlet and splitter.This research can provide valuable references for the design and optimization of vibration friction-reduction tools.

An Investigation of Bubble Motion in the Fluidic Oscillator

Enhanced gas-liquid mass transfer is significant for the desulfurization and denitration of ship exhaust gases.As a fluid device,the special structure of the fluidic oscillator generates self-excited oscillations that can effectively enhance the mass transfer process of gas-liquid.But there are few studies on the internal gas-liquid flow.The transportation of individual bubbles in the fluidic oscillator was investigated by a high-speed camera and digital image analysis.The results show that the bubble experienced a significant deceleration process in the chamber region of the fluidic oscillator.In addition,the maximum bubble offset increased with the diameter of the initial bubble.The trajectory of the bubble showed zigzag movement due to the deflecting oscillation of the fluidic oscillator.At the same time,the deformation of the bubble was intensified by the deflecting oscillation.The deformation ratio of the bubble increased with the increase of Reynolds number.By studying the transport process of a single bubble in the fluid oscillator,it is considered that the fluid oscillator has the potential to be a new bubble generator.

Experimental Investigation of Nonlinear Vibration Isolator with Fluidic Actuators (NLVIFA)

This paper elaborates a nonlinear fluidic low frequency vibration isolator designed with the characteristics of quasi-zero stiffness(QZS).The existing model of QZS vibration isolator enhances amplitude of vibration and attenuating vibration frequencies.This concern with displacement plays a vital role in the performance and instability of oblique spring setup reduces the isolator performance in horizontal non-nominal loads,in this accordance;this paper associates double acting hydraulic cylinder(fluidic actuators in short)in oblique and helical coil spring.An approximate expression of unique analytical relationship between the stiffness of vertical spring and bulk modulus of the fluid is derived for Quasi–Zero Stiffness Non-Linear Vibration Isolator with Fluidic Actuators(NLVIFA in short)system and the force transmissibility is formulated and damping ratio are discussed for characteristic analysis.Modal analysis carried out and compared with analytical results and an experimental prototype is developed and investigated.The performance of the NLVIFA reduces the external embarrassment more at low frequencies and the series of experimental studies showing that the soft nonlinearity causes limitation in the resonant frequency thereupon the isolation will be enhanced and NLVIFA greatly outperform some other type of nonlinear isolators.

Cooling of the Vulcain Nozzle＇s Divergent Wall

Rocket engine nozzle is a propelling nozzle used to expand and accelerate the combustion gases produced by burning propellants to supersonic exit velocities. To furnish high performance and thrust, a maximum of the energy which is released inside the combustion chamber due to the reaction of the propellant and the oxidizer has to be converted into kinetic energy. This converted energy emits high heat fluxes that damage the nozzle that is so expansive to realize. For this matter, lots of researches were established to invent multiple cooling techniques in a way to avoid the damage of the nozzle, so recovering it for to be operative again. This work aims to identify the quality of cooling using the method of film injection. A numerical simulation is run on a scale model of a BKE propulsive nozzle. A parietal injection is conducted in the divergent section where the heat fluxes are enormous what allows us to predict the static temperature ＆ pressure on the walls without parietal injection ＆ then we include it in the parameters in order to see the efficiency of the film cooling technique in the nozzles. For this study, we used two different calculation codes： Ansys-Fluent was used to realize the simulation of the supersonic flow ＆ the parietal injection, where Solidworks simulation was used in the thermal study. The effects of the thermal fluxes ＆ pressure after ＆ before the fluidic injection on the wall are discussed.

Modular Soft Robotic Crawlers Based on Fluidic Prestressed Composite Actuators

Soft robotic crawlers have limited payload capacity and crawling speed.This study proposes a high-performance inchworm-like modular robotic crawler based on fluidic prestressed composite(FPC)actuators.The FPC actuator is precurved and a pneumatic source is used to flatten it,requiring no energy cost to maintain the equilibrium curved shape.Pressurizing and depressurizing the actuators generate alternating stretching and bending motions of the actuators,achieving the crawling motion of the robotic crawler.Multi-modal locomotion(crawling,turning,and pipe climbing)is achieved by modular reconfiguration and gait design.An analytical kinematic model is proposed to characterize the quasi-static curvature and step size of a single-module crawler.Multiple configurations of robotic crawlers are fabricated to demonstrate the crawling ability of the proposed design.A set of systematic experiments are set up and conducted to understand how crawler responses vary as a function of FPC prestrains,input pressures,and actuation frequencies.As per the experiments,the maximum carrying load ratio(carrying load divided by robot weight)is found to be 22.32,and the highest crawling velocity is 3.02 body length(BL)per second(392 mm/s).Multi-modal capabilities are demonstrated by reconfiguring three soft crawlers,including a matrix crawler robot crawling in amphibious environments,and an inching crawler turning at an angular velocity of 2/s,as well as earthworm-like crawling robots climbing a 20 inclination slope and pipe.

Thin-film flow technology in controlling the organization of materials and their properties Special Collection:Distinguished Australian Researchers

Centrifugal and shear forces are produced when solids or liquids rotate.Rotary systems and devices that use these forces,such as dynamic thin-film flow technology,are evolving continuously,improve material structure-property relationships at the nanoscale,representing a rapidly thriving and expanding field of research high with green chemistry metrics,consolidated at the inception of science.The vortex fluidic device(VFD)provides many advantages over conventional batch processing,with fluidic waves causing high shear and producing large surface areas for micro-mixing as well as rapid mass and heat transfer,enabling reactions beyond diffusion control.Combining these abilities allows for a green and innovative approach to altering materials for various research and industry applications by controlling small-scale flows and regulating molecular and macromolecular chemical reactivity,self-organization phenomena,and the synthesis of novel materials.This review highlights the aptitude of the VFD as clean technology,with an increase in efficiency for a diversity of top-down,bottom-up,and novel material transformations which benefit from effective vortex-based processing to control material structure-property relationships.

Effect of Fluidic Diode on Performance of Unidirectional Impulse Turbine

A pair of unidirectional turbines(UT)can operate in oscillatory airflow without additional units.However,this arrangement suffers from poor flow rectification.A fluidic diode(FD)offers variable hydrodynamic resistance based on the flow direction,and this can be coupled with UT to improve flow rectification.In this work,a numerical investigation on the effect of FD with UT is presented using the commercial fluid dynamics software ANSYS Fluent 16.1 with k-ωSST turbulence closure model.Periodic domains of UT and FD are numerically validated individually with experimental results.Later,both are coupled to obtain the combined effect,and these results are compared with the analytical approach.It was observed that coupling FD with UT improved the unit's performance at the lower flow coefficient(<1),but its performance decreased as the flow coefficient increased.Due to the diode's presence,fluid leaving the turbine experiences higher resistance at a higher flow coefficient,which decreases the overall performance of the combined unit.

Effect of IOP based infusion system with and without balanced phaco tip on cumulative dissipated energy and estimated fluid usage in comparison to gravity fed infusion in torsional phacoemulsification

Background:To evaluate the effect of three different combinations of tip designs and infusion systems in torsional phacoemulsification(INFINITI and CENTURION)in patients with cataract.According to the manufacturer,two unique improvements in the Centurion are:active fluid dynamic management system and use of an intrepid balanced tip.The study specifically aimed to evaluate the beneficial effects,if any,of change in tip design and infusion system individually and in combination on both per-operative parameters as well as endothelial health over 6 months.Methods:One hundred and twenty six consenting patients of grade 4.0-6.9 senile cataract were randomized into three groups for phacoemulsification:Group A(n=42):Gravity fed infusion system and 45° Kelman miniflared ABS phaco tip;Group B(n=42):intraocular pressure(IOP)based infusion system and 45° Kelman miniflared ABS phaco tip;Group C(n=42):IOP based infusion system and 45° Intrepid balanced phaco tip.The cumulative dissipated energy(CDE),estimated fluid usage(EFU)and total aspiration time(TAT)were compared peroperatively.The endothelial parameters were followed up postoperatively for six months.Results:The three arms were matched for age(p=0.525),gender(p=0.96)and grade of cataract(p=0.177).Group C was associated with significant reductions in CDE(p=0.001),EFU(p<0.0005)as well as TAT(p=0.001)in comparison to the other groups.All three groups had comparable baseline endothelial cell density(p=0.876)and central corneal thickness(p=0.561).On post-operative evaluation,although all groups were comparable till 3 months,by 6 months,the percentage losses in endothelial cell density were significantly lower in group C as compared to the other groups.Conclusions:Use of an IOP based phacoemulsification system in association with use of the Intrepid balanced tip reduces the CDE,EFU and TAT in comparison to a gravity fed system with a mini flared tip or IOP based system with a mini flared tip while also providing better endothelial preservation thus favouring the use of an IOP fed system with a balanced tip.

Cellular fluidic-based vascular networks for tissue engineering

Artificial organs are devices implanted into the living body as a substitute for damaged or diseased organs.Current efforts focus on the construction of fully functionalized artificial tissues/organs with vascular networks.Although engineering efforts have been made in creating artificial vessels with simple or complex configurations,building vascular networks with hierarchical architectures approximating native counterparts remains challenging.Herein,we give a perspective of cellular fluidics-based construction of vascular networks for tissue engineering,with inspirations drawn from a novel concept of 3D fluidic control platform based on unit-cell constructs.Through architected design of the unit cells,it enables programmed control over gas-liquid-solid interfaces and fluid flow processes in open-cell structures.This cellular-fluidics concept and the associated platform provide lots of inspirations for constructing artificial vascular networks.We believe that cellular fluidics opens a new avenue for fluid control and deterministic delivery,and would find vast opportunities in tissue engineering.