Design of a relaying electroosmosis pump driven by low-voltage DC

Electroosmosis pumps (EOPs) have been widely used for manipulating small amounts of reagents for chemical and biological analysis. Traditionally, a high-voltage DC has to be applied in order to achieve the required flow rate. One alternative is to use low AC voltage. Here we propose another solution, which, instead of using a high-voltage DC or low AC voltage, adds a low-voltage DC to an array of electrodes. This design of EOP is called a relaying EOP or cascade EOP. In this study, we intend to push the limit of the low-voltage further down to 2 V by patterning a dense electrode array in a straight microchannel. Two patterns of interdigitated electrodes, symmetric with equal size electrodes and asymmetric with unequal size electrodes, are proposed. Simulations are performed to optimize the distribution and geometrical parameters of the electrode array in order to achieve the maximum flow rate. The proposed low-voltage DC electroosmosis pump shows an advantage in integrating EOP into portable Lab-on-a-chip devices. In addition, the low-voltage DC EOP shows a good promise for in vivo biomedical applications such as drug delivery.     

新型双并联电渗微泵的制备与测试

设计了一个双并联电渗驱动泵,它由三条并联的主通道和叉指型电极两部分组成,其中每条主通道由若干个与电渗流形成方向成45°角的沟槽并联构成。通过选用ITO载玻片作为芯片基底并获得其最佳工艺参数,制作了带电极的PDMS-玻璃微流控芯片。最后对制作的电渗微泵进行测试,通过记录一段时间内单个主通道泵输送液体的体积,得出单个主通道的流速与微泵总流速。实验发现在5V内,微泵泵送液体的能力随着电压的增加而增大,微泵流速可以达到正常人体眼球房水生成速度,该结构在未来房水引流器件制作方面具有潜在的应用价值。     

Effects of electrophoresis and electroosmotic flow on ion enrichment in micro-nanofluidic preconcentrator

In this paper, we demonstrate the effects of electrophoresis (EP) and electroosmotic flow (EOP) on ion enrichment in micro-nanofluidic preconcentrator via numerical simulation. The difference of sample fluxes resulted from EP and EOP at the micro-nano interface is defined to distinguish the contributions of EOF and EP to ion enrichment. The influences of several parameters related to the enrichment ratio are investigated in detail. The results show that the enrichment ratio can be improved via enhancing the difference. To increase the difference, several proposals are presented, including raising imposed electric potential, increasing surface charge density and enhancing fluid viscosity.     

A Relationship between a Freely Chosen Working Pace and Energy Consumption Curves

An ergometer incorporating a car tyre pump was used to compare the physiological cost when a subject worked at a freely chosen pace with that when he worked at a series of paces from 10 to 60 strokes of the pump per minute. When the energy cost per stroke (above resting level) was plotted against the work rate, the graph suggested that there was a po i nt of minimum energy per stroke. This point appeared to agree with the freely chosen work pace.     

A chip scale nanofluidic pump using electrically controllable hydrophobicity

The traditional microfluidic systems and devices faced limitations such as power consumption and high driving force in the attempt for implementation as chemical analysis and environmental monitoring systems. The up-to-date development of chemistry and biology has generated great demand for lab-on-a-chip performing specific chemical and biological analysis, clinical diagnostics and biomedical processing. Manipulation of ultrasmall amount and great varieties of biofluids has also been a major issue challenging many researchers. Here we demonstrate in this article, a device utilizing electrically controllable surface tension as the driving force to deliver fluid flow in the order of nanoliters per minute or even smaller, without a dedicated actuator. This device is capable of pumping a continuous liquid column. This actuation mechanism of fluid flow in this device is based on electrowetting-on-dielectric (EWOD) effect and the physics of the fluid dynamics is governed by Navier–Stokes equation. It also has a built-in metering feature to precisely determine the flow rate without an additional flow sensor. The experimental results show that water can be electrically actuated successfully to flow in the microchannel at a flow rate of 18 nl/min under a potential of as low as 20 V. This is very attractive for applications which require an ultra miniaturized metering pump operated at a low power for portable environmental monitoring instruments, chemical analysis systems, implantable medical devices, drug delivery systems and clinical diagnostic systems.     

Gas flow meter for application in medical equipment for respiratory control: study of the housing

The study of the housing of a gas flow meter for use in medical equipment for respiratory control will be presented in this paper. The sensor is of the thermal type with dimensions 1.4 mm×0.9 mm. The housing is developed so as to assure conditions of laminar flow in a flow range from −200 to +200 standard liters per minute (SLPM). An analytical approach is first used to determine the main housing configuration. The type and the position of a bypass tube, which is fixed to the main flow tube, are studied in detail. Extensive simulations of the flow in different housing configurations and different conditions at the inlet and outlet of the housing were performed, using the finite element analysis (FEA) software package ANSYS. The optimum housing was finally fabricated and evaluated in oxygen flow. Excellent agreement of experimental results with simulation was obtained.     

加速度传感器在气体微流量检测中的应用

根据MEMsic(微电子机械系统集成芯片)加速度传感器的工作原理及特点,提出把加速度传感器作为流量传感器应用于气体微流量检测中,为了验证,建立了一套实验装置用于MEMSic加速度传感器检测气体的流动变化,利用PIC单片机对数据进行采集和处理,经过具体实验验证,在不同温度下,经过一定的温度补偿,当气体流量从0到50sccm发生变化,加速度传感器是能够精确的测量出流量的变化,说明了MEMSic加速度传感器对微流量的检测具有较高的灵敏度和稳定性.     

Black box modeling and multiobjective optimization of electrochemical ozone production process

In this paper, simultaneous maximization of generated ozone concentration and minimization of electrical energy consumption is investigated in a laboratory-scale electrochemical ozone production system (EOP). Neural network simulation of EOP was carried out for generated ozone concentration prediction by Abbasi et al. (Chem Eng Res Des 92(11):2618–2625, 2014). In this study, neural network models (as black box models) were developed to predict both generated ozone concentration and electrical energy consumption. The models then were used for optimization. Altruistic non-dominated sorting genetic algorithm with jumping gene variant and termination criterion was used for MOO. Generational distance and spread were used in the termination criterion in order to stop algorithm after the right number of generations. Moreover, several optimal solutions from the Pareto-optimal set are chosen and then validated experimentally.

     

Unsteady flow behaviors in an obstacle-type valveless micropump by micro-PIV

In this paper, a PZT micropump excited by amplified squarewave signals with various frequencies was used to study the transient flow behaviors in an obstacle-type valveless micropump. A micro-particle-image-velocimetry (micro-PIV) with an external trigger was developed to obtain flow fields at the outlet and around the obstacle with various phases in a cycle. In comparison with previous studies on the pump performance, such as pump pressure and volume flow rate, more detailed information about the pump was obtained. The velocity profiles and periodic sectional mean velocities exhibited the unsteady flow nature. The total net flow generation efficiency per cycle was obtained experimentally by integrating the phase-dependent velocities. The flow recirculation around the obstacle was observed and quantified to investigate the influence on the pump performance. The duration, circulation, and the size of the recirculation regions indicated that this flow behavior could enhance the flow-directing capability. These results are very useful for the design and improvement of obstacle-type valveless micropumps.     

Optimization of design and characterization of a novel micro-pumping system with peristaltic motion

In this work, we present a novel design of peristalsis based micro pump with optimized fluid chambers possessing improved discharge efficiency per unit volume of the pumping architecture and reduced reverse flow. Such designs are very often important from the standpoint of blood cell sorting assays where a full delivery of fluid containment within the pumping chamber is critical. The paper uses FLUENT and COMSOL simulations to look at the fluid flow within the pumping chamber due to the deflecting actuator membrane during pumping cycle. The resulting effect of fluid-membrane interaction has been evaluated on different chamber designs for observing the lateral velocity distribution profile of fluid in the connecting channels. It has been observed through particle image velocimetry (PIV) that the optimized design has minimized chamber retainability with maximum deflection of the actuator membrane and minimum reverse flow component. Optimized geometrical profile formulated above was seen to allow the maximum contact area between actuating membrane and fluid containment thus reducing the problem of fluid retainability. Other experimental studies show that the new design has much lower percentage retainability of biological and other fluids contained within the chambers which makes it a comparatively high efficiency micropumping system with respect to the conventional design with circular membrane and chambers. The experimental evaluation of the new micro pump design has shown its least count to be 0.1 μl/min which is very well comparing with some of the other micropumping mechanisms like electro-osmotic, magneto-hydrodynamic mechanisms (Laser and Santiago in J Micromech Microeng 14:35, 2004; Iverson et al. 2008) and additionally provides better discharge efficiency per unit volume of the pumping architecture, lower retainability, minimized reverse flow and precise pumping of fluids.     

Pneumatically bidirectional microfluidic regulation using Venturi pumps by deep RIE and bonding technology

 A novel design for bidirectional fluidic motion has been demonstrated which is widely used in the biochip or microfluidic component. Two miniaturized Venturi pumps as well as pneumatic servo system are designed to easily control the bidirectional fluidic motion by simple fabrication. The pumping velocity is 0.86 μl/min at a 2.75 slpm (standard liter per minute) air flow read from mass flow controller (MFC) for totally 4.3 μl blue ink in a 300 μm wide by 300 μm deep channel. The higher airflow, the faster fluidic pumping speed. Numerical simulation is performed to correlate the experimental data of fluidic speed and air flow in microchannel. The test chip with two Venturi pumps and channel was batchedly fabricated by silicon deep reactive ion etching (RIE) and glass anodic bonding. The ICP LIGA process is also investigated after deep RIE followed the electroforming and hot embossing. Received: 10 August 2001/Accepted: 24 September 2001     

The edge-orientation problem and some of its variants on weighted graphs

Let G(V, E) be a connected undirected graph with n vertices and m edges, where each vertex v is associated with a cost C(v) and each edge e = (u, v) is associated with two weights, W(u → v) and W(v → u). The issue of assigning an orientation to each edge so that G becomes a directed graph is resolved in this paper. Determining a scheme to assign orientations of all edges such that max_x∈V{C(x)+∑_x→zW(x→z)} is minimized is the objective. This issue is called the edge-orientation problem (the EOP). Two variants of the EOP, the Out-Degree-EOP and the Vertex-Weighted EOP, are first proposed and then efficient algorithms for solving them on general graphs are designed. Ascertaining that the EOP is NP-hard on bipartite graphs and chordal graphs is the second result. Finally, an O(n log n)-time algorithm for the EOP on trees is designed. In general, the algorithmic results in this paper facilitate the implementation of the weighted fair queuing (WFQ) on real networks. The objective of the WFQ is to assign an effective weight for each flow to enhance link utilization. Our findings consequently can be easily extended to other classes of graphs, such as cactus graphs, block graphs, and interval graphs.     

Numerical analysis of the unsteady flow in the near-tongue region in a volute-type centrifugal pump for different operating points

An investigation is presented on the unsteady flow behaviour near the tongue region of a single-suction volute-type centrifugal pump with a specific speed of 0.47. For this study, the flow through the test pump, which was available at laboratory, was simulated by means of a commercial CFD software that solved the Navier-Stokes equations for three-dimensional unsteady flow (3D-URANS). A sensitivity analysis of the numerical model was performed in order to impose appropriate parameters regarding grid size, time step size and turbulence model. The predictions of the numerical model were contrasted with experimental results of both global (flow-head curve and static pressure distribution at volute front side) and unsteady variables (unsteady pressure distribution at the volute front side filtered at the blade-passing frequency). Once validated, the model was used to study the flow pulsations associated to the interaction between the impeller blades and the volute tongue as a function of the flow rate, for several flow rates ranging from 20% to 160% of the nominal flow rate. The study allowed relating the blade passage with the pulsations of pressure and tangential and radial velocity at a number of reference locations in the near-tongue region. The numerical model was also used to evaluate the evolution of the leakage flow between the impeller-tongue gap and of the flow exiting the impeller through some specific angular intervals, during one single-blade passage.     

Extraction of fluvial networks from SPOT panchromatic data in a low relief,arid basin

Abstract

Euclidean distance classification of SPOT panchromatic data was used to delineate ephemeral, fluvial networks on low-relief, alluvial fan surfaces in an arid basin in the southwestern United States. The SPOT classified channel network was registered to a Universal Transverse Mercator (UTM) projection and compared to areas of channelized flow and a Strahler-ordered channel network extracted from U.S. Geological Survey 7½ minute topographic maps and black-and-white aerial photographs. One-pixel and two-pixel proximity searches of the SPOT classified image correctly classified over 80 per cent of the areas of channelized flow, 77 per cent of the second order and greater channel network, and 98 per cent of the fourth order and greater channel network. The SPOT channel network was simplified by elimination of lower-order channel segments to produce a network closely resembling (in terms of number of channel segments and total channel length) a network created for hydrological modelling from topographic maps. This suggests that SPOT panchromatic data can be used to delineate fluvial network for hydrological investigations in similar physiographic settings without existing topographic map or aerial photographic coverage.     

Gap Flow Simulation Methods in High Pressure Variable Displacement Axial Piston Pumps

High pressure variable displacement axial piston pumps are subject to complex dynamic phenomena. Their analysis is difficult, additionally complicated by leakage of the working fluid. Analytically gap flow is calculated with the Reynolds equation which describes the pressure distribution in a thin lubricating layer. The paper presents various approaches to analyze gap flow both in traditional axial piston pump and novel type of hydraulic pump, designed at the Polish Gdansk Institute of Technology. Because of large aspect ratio between the height of the gap and the size of pump elements, the authors present the numerical simulation approach using a local model to define a lubrication gap, linked to a global model of a pump from which boundary conditions were imported. User defined functions implemented in Fluent and Excel were used to calculate the pressure and velocity fields and assess the fluid flow rate.     

A fast numerical method for flow analysis and blade design in centrifugal pump impellers

A numerical methodology is developed to simulate the turbulent flow in a 2-dimensional centrifugal pump impeller and to compute the characteristic performance curves of the entire pump. The flow domain is discretized with a polar, Cartesian mesh and the Reynolds-averaged Navier-Stokes (RANS) equations are solved with the control volume approach and the k-ε turbulence model. Advanced numerical techniques for adaptive grid refinement and for treatment of grid cells that do not fit the irregular boundaries are implemented in order to achieve a fully automated grid construction for any impeller design, as well as to produce results of adequate precision and accuracy. After estimating the additional hydraulic losses in the casing and the inlet and outlet sections of the pump, the performance of the pump can be predicted using the numerical results from the impeller section only. The regulation of various energy loss coefficients involved in the model is carried out for a commercial pump, for which there are available measurements. The predicted overall efficiency curve of the pump was found to agree very well with the corresponding experimental data. Finally, a numerical optimization algorithm based on the unconstrained gradient approach is developed and combined with the evaluation software in order to find the impeller geometry that maximizes the pump efficiency, using as free design variables the blade angles at the leading and the trailing edge. The results verified that the optimization process can converge very fast and to reasonable optimal values.     

Electroosmotic pumps and their applications in microfluidic systems

Electroosmotic pumping is receiving increasing attention in recent years owing to the rapid development in micro total analytical systems. Compared with other micropumps, electroosmotic pumps (EOPs) offer a number of advantages such as creation of constant pulse-free flows and elimination of moving parts. The flow rates and pumping pressures of EOPs matches well with micro analysis systems. The common materials and fabrication technologies make it readily integrateable with lab-on-a-chip devices. This paper reviews the recent progress on EOP fabrications and applications in order to promote the awareness of EOPs to researchers interested in using micro- and nano-fluidic devices. The pros and cons of EOPs are also discussed, which helps these researchers in designing and constructing their micro platforms.     

A micro PDMS flow sensor based on time-of-flight measurement for conductive liquid

Transdermal extraction of interstitial fluid (ISF) offers an attractive method for non-invasive blood glucose monitoring. In order to calculate blood glucose concentration accurately, precise volume measurement of transdermally extracted ISF is required due to human skin’s varying permeability. In this paper, we presented a novel flow sensor fabricated from polydimethylsiloxane (PDMS), designed to measure the volume of conductive liquid. The flow sensor consists of two pairs of metal electrodes, which are fabricated in the PDMS channel. The volume of liquid is measured utilizing the time-of-flight of the two electrode pairs’ resistance while the liquid is flowing through the flow sensor. 1–14 μL normal saline solution was measured, the flow sensor measured volumes correlate very well (R ² = 0.9996 and R ² = 0.9975 for vacuum pump and syringe pump situations respectively) with the actual volumes. And the coefficient of variation for 10 times 10 μL normal saline solution measurement is 0.0077 (vacuum pump) and 0.0381 (syringe pump), respectively. The demonstrated flow sensor provides excellent functionality for conductive liquid.     

A cross-junction channel valveless-micropump with PZT actuation

A gas-jet micro pump with novel cross-junction channel has been designed and fabricated using a Si micromachining process. The valveless micro pump is composed of a piezoelectric lead zirconate titanate (PZT) diaphragm actuator and fluidic network. The design of the valveless pump focuses on a cross-junction formed by the neck of the pump chamber and one outlet and two opposite inlet channels. The structure of cross-junction allows differences in fluidic resistance and fluidic momentum inside the channels during each PZT diaphragm vibration cycle, which leads to the gas flow being rectified without valves. The flow channels were easily fabricated by using silicon etching process. To investigate the effects of the structure of the cross-junction on the gas flow rate, two types of pump with different cross-junction were studied. The design and simulation were done using ANSYS-Fluent software. The simulations and experimental data revealed that the step-nozzle structure is much more advantageous than the planar structure. A flow rate of 5.2 ml/min was obtained for the pump with step structure when the pump was driven at its resonant frequency of 7.9 kHz by a sinusoidal voltage of 50 V_p–p.     

Exploration on relationship between flow rate and sound pressure level of piezoelectric pump

This study presents the relationship between flow rate and sound pressure level of piezoelectric pump. It also presents the analysis and theoretical calculation for umbrella valve piezoelectric pump on the sound pressure level. Sound pressure level of umbrella valve piezoelectric pump in composite field (medium are air and water) was simulated by software Actran. Simulation results reveal that: The sound pressure level of Piezoelectric actuator in air field is bigger than that in water field. This result means that pump chamber with air and water has a higher sound pressure level than pump chamber with water. The flow rate and sound pressure level characteristics of umbrella valve piezoelectric pump with different pump chamber depths (d = 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm) is obtained by experiments in a voltage range of 160–220 V and a frequency range of 160–340 Hz. Experimental results show that: At different pump chamber depth (d), the range of flow rate is from 173.4 to 271.0 mL/min at 0.5 mm chamber depth, 75.0 to 149.0 mL/min at 1.0 mm chamber depth, 3.4 to 57.0 mL/min at 1.5 mm chamber depth, 2.8 to 32.8 mL/min at 2.0 mm chamber depth, the sound pressure level is from 57.52 to 65.14 dB, 54.54 to 60.05 dB, 55.26 to 69.24 dB, 53.39 to 61.19 dB. For piezoelectric pump with different pump chamber depths (d), flow rate and sound pressure level of piezoelectric pump increase as voltage increases. It is a great method to monitoring flow rate by monitoring the sound pressure level.