Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session Q14: Microfluidic Devices: Applications and DesignMicro
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Chair: Lailai Zhu, Princeton University Room: 507 |
Tuesday, November 21, 2017 12:50PM - 1:03PM |
Q14.00001: Separation of red blood cells in deep deterministic lateral displacement devices Gokberk Kabacaoglu, George Biros Microfluidic cell separation techniques are of great interest since they help rapid medical diagnoses and tests. Deterministic lateral displacement (DLD) is one of them. A DLD device consists of arrays of pillars. Main flow and alignment of the pillars define two different directions. Size-based separation of rigid spherical particles is possible as they follow one of these directions depending on their sizes. However, the separation of non-spherical deformable particles such as red blood cells (RBCs) is more complicated than that due to their intricate dynamics. We study the separation of RBCs in DLD using an in-house integral equation solver. We systematically investigate the effects of the interior fluid viscosity and the membrane elasticity of an RBC on its behavior. These mechanical properties of a cell determine its deformability, which can be altered by several diseases. We particularly consider deep devices in which an RBC can show rich dynamics such as tank-treading and tumbling. It turns out that strong hydrodynamic lift force moves the tank-treading cells along the pillars and downward force leads the tumbling ones to move with the flow. Thereby, deformability-based separation of RBCs is possible. [Preview Abstract] |
Tuesday, November 21, 2017 1:03PM - 1:16PM |
Q14.00002: Manipulating low-Reynolds-number flow by a watermill Lailai Zhu, Howard Stone Cilia and filaments have evolved in nature to achieve swimming, mixing and pumping at low Reynolds number. Their unique capacity has inspired a variety of biomimetic strategies employing artificial slender structures to manipulate flows in microfluidic devices. Most of them have to rely on an external field, such as magnetic or electric fields to actuate the slender structures actively. In this talk, we will present a new approach of utilizing the underlying flow alone to drive these structures passively. We investigate theoretically and numerically a watermill composing several rigid slender rods in simple flows. Slender body theory with and without considering hydrodynamic interactions is adopted. The theoretical predictions agree qualitatively with the numerical results and quantitatively in certain configurations. [Preview Abstract] |
Tuesday, November 21, 2017 1:16PM - 1:29PM |
Q14.00003: Integrated high pressure manifold for thermoplastic microfluidic devices S.Ali Aghvami, Seth Fraden We introduce an integrated tubing manifold for thermoplastic microfluidic chips that tolerates high pressure. In contrast to easy tubing in PDMS microfluidic devices, tube connection has been challenging for plastic microfluidics. Our integrated manifold connection tolerates 360 psi while conventional PDMS connections fail at 50 psi. Important design considerations are incorporation of a quick-connect, leak-free and high-pressure manifold for the inlets and outlets on the lid and registration marks that allow the precise alignment of the inlets and outlets. In our method, devices are comprised of two molded pieces joined together to create a sealed device. The first piece contains the microfluidic features and the second contains the inlet and outlet manifold, a frame for rigidity and a viewing window. The mold for the lid with integrated manifold is CNC milled from aluminium. A cone shape PDMS component which acts as an O-ring, seals the connection between molded manifold and tubing. The lid piece with integrated inlet and outlets will be a standard piece and can be used for different chips and designs. Sealing the thermoplastic device is accomplished by timed immersion of the lid in a mixture of volatile and non-volatile solvents followed by application of heat and pressure. [Preview Abstract] |
Tuesday, November 21, 2017 1:29PM - 1:42PM |
Q14.00004: Microfluidic Transducer for Detecting Nanomechanical Movements of Bacteria Vural Kara, Kamil Ekinci Various nanomechanical movements of bacteria are currently being explored as an indication of bacterial viability. Most notably, these movements have been observed to subside rapidly and dramatically when the bacteria are exposed to an effective antibiotic. This suggests that monitoring bacterial movements, if performed with high fidelity, can offer a path to various clinical microbiological applications, including antibiotic susceptibility tests. Here, we introduce a robust and sensitive microfluidic transduction technique for detecting the nanomechanical movements of bacteria. The technique is based on measuring the electrical fluctuations in a microchannel which the bacteria populate. These electrical fluctuations are caused by the swimming of motile, planktonic bacteria and random oscillations of surface-immobilized bacteria. The technique provides enough sensitivity to detect even the slightest movements of a single cell and lends itself to smooth integration with other microfluidic methods and devices; it may eventually be used for rapid antibiotic susceptibility testing. [Preview Abstract] |
Tuesday, November 21, 2017 1:42PM - 1:55PM |
Q14.00005: Novel and facile viscometer using a paper-based microfluidic device Hyunwoong Kang, Ilhoon Jang, Simon Song In clinical applications, it is important to rapidly estimate the blood viscosity of a patient with a high accuracy and a small sample consumption. Unfortunately, ordinary mechanical viscometers require long analysis time, large volume of sample and skilled person. To address this issue, silicon-based viscometers have been developed, but they are still far from prevail usage in clinical environments due to complexity in process and analysis. Recently, a paper-based microfluidic device is emerged as a new platform for a facile point-of-care diagnostic device due to low cost, disposability and ease of use. Thus, we propose a novel and facile method of measuring a viscosity with a paper-based microfluidic devices and a smartphone. This viscometer utilizes mixing characteristics of two fluid flows in a T-shape channel: one for reference and the other for test fluid. The mixing strongly depends on viscosity difference between the two fluids. Also, the fluids are dyed for colorimetric analysis with a smartphone. We found that the accuracy of viscometer is about 3 percent when it was tested for various glycerin aqueous solutions. More detailed information will be discussed in the presentation. [Preview Abstract] |
Tuesday, November 21, 2017 1:55PM - 2:08PM |
Q14.00006: Simulatng Sawtooth Mixers For Biofouling Mitigation James Waters, Anna Balazs We demonstrate how a ridged surface can be used to generate vortices that will break up clusters of cells as they form. This offers an appealing avenue for fouling mitigation, as it relies on a physical mechanism without unintended environmental consequences. By adjusting the shape of these ridges, we can increase the effectiveness of the surface across a range of shear values. We represent such a system computationally using a hybrid of bulk fluid simulated via the lattice Boltzmann method, and deformable vesicles, representing cells, simulated via that lattice spring method. This simulation methodology allows us to rapidly implement and test different surface patterns, and explore how their parameters can most effectively deter the accumulation of biofilms. [Preview Abstract] |
Tuesday, November 21, 2017 2:08PM - 2:21PM |
Q14.00007: Inertial instabilities in a mixing-separating microfluidic device Allysson Domingues, Robert Poole, David Dennis Combining and separating fluids has many industrial and biomedical applications. This numerical and experimental study explores inertial instabilities in a so-called mixing-separating cell micro-geometry which could potentiality be used to enhance mixing. Our microfluidic mixing-separating cell consists of two straight square parallel channels with flow from opposite directions with a central gap that allows the streams to interact, mix or remain separate (often referred to as the `H' geometry). A stagnation point is generated at the centre of symmetry due to the two opposed inlets and outlets. Under creeping flow conditions (Reynolds number [$Re \sim 0$]) the flow is steady, two-dimensional and produces a sharp symmetric boundary between fluids stream entering the geometry from opposite directions. For $Re>30$, an inertial instability appears which leads to the generation of a central vortex and the breaking of symmetry, although the flow remains steady. As $Re$ increases the central vortex divides into two vortices. Our experimental and numerical investigations both show the same phenomena. The results suggest that the effect observed can be exploited to enhance mixing in biomedical or other applications. [Preview Abstract] |
Tuesday, November 21, 2017 2:21PM - 2:34PM |
Q14.00008: Droplet Breakup in Asymmetric T-Junctions at Intermediate to Large Capillary Numbers Reza Sadr, Way Lee Cheng Splitting of a parent droplet into multiple daughter droplets of desired sizes is usually desired to enhance production and investigational efficiency in microfluidic devices. This can be done in an active or passive mode depending on whether an external power sources is used or not. In this study, three-dimensional simulations were done using the Volume-of-Fluid (VOF) method to analyze droplet splitting in asymmetric T-junctions with different outlet lengths. The parent droplet is divided into two uneven portions the volumetric ratio of the daughter droplets, in theory, depends on the length ratios of the outlet branches. The study identified various breakup modes such as primary, transition, bubble and non-breakup under various flow conditions and the configuration of the T-junctions. In addition, an analysis with the primary breakup regimes were conducted to study the breakup mechanisms. The results show that the way the droplet splits in an asymmetric T-junction is different than the process in a symmetric T-junction. A model for the asymmetric breakup criteria at intermediate or large Capillary number is presented. The proposed model is an expanded version to a theoretically derived model for the symmetric droplet breakup under similar flow conditions. [Preview Abstract] |
Tuesday, November 21, 2017 2:34PM - 2:47PM |
Q14.00009: Three-dimensional investigations of the threading regime in a microfluidic flow-focusing channel. Krishne Gowda.V, Christophe Brouzet, Thibault Lefranc, L.Daniel Soderberg, Fredrik Lundell We study the flow dynamics of the threading regime in a microfluidic flow-focusing channel through 3D numerical simulations and experiments. Making strong filaments from cellulose nano-fibrils (CNF) could potentially steer to new high-performance bio-based composites competing with conventional glass fibre composites. CNF filaments can be obtained through hydrodynamic alignment of dispersed CNF by using the concept of flow-focusing. The aligned structure is locked by diffusion of ions resulting in a dispersion-gel transition. Flow-focusing typically refers to a microfluidic channel system where the core fluid is focused by the two sheath fluids, thereby creating an extensional flow at the intersection. In this study, threading regime corresponds to an extensional flow field generated by the water sheath fluid stretching the dispersed CNF core fluid and leading to formation of long threads. The experimental measurements are performed using optical coherence tomography (OCT) and 3D numerical simulations with OpenFOAM. The prime focus is laid on the 3D characteristics of thread formation such as wetting length of core fluid, shape, aspect ratio of the thread and velocity flow-field in the microfluidic channel. [Preview Abstract] |
Tuesday, November 21, 2017 2:47PM - 3:00PM |
Q14.00010: Non-perturbative manipulation through a 3D microfluidic treadmill Jeremias Gonzalez, Bin Liu Our capabilities of micromanipulation have evolved with advances in contact-free trapping techniques under various disciplines, such as optical, magnetic, and microfluidic traps. In these techniques, a microscale particle is held in place under compression due to electromagnetic or hydrodynamic forces. In this work, we present a trap-free design of a microfluidic ``treadmill'' (MFC), realized by a uniform flow along arbitrary directions in a 3D microfluidic device, which is composed of a central chamber and pairs of $x-$ and $y-$channels at different elevations. Through boundary element simulations, we demonstrate that 3D background flows along any direction can be generated in the middle of the chamber, controlled by a set of syringe pumps. By tuning the detailed geometry of the MFC, we show the optimized shape of the device that leads to minimized strain rate, allowing for manipulation of the suspended particles with negligible perturbations. We also show an experimental realization of the MFC device, using laser stereolithography. The $x-$, $y-$, and $z-$ manipulation modes are obtained independently by a syringe pump with push/pull mechanisms, and are compared with the above simulation results. [Preview Abstract] |
Tuesday, November 21, 2017 3:00PM - 3:13PM |
Q14.00011: Ultrahigh throughput microfluidic platform for in-air production of microscale droplets John Healy, Pooyan Tirandazi, Carlos H. Hidrovo In-air droplet formation inside microfluidic networks is an alternative technique to the conventional in-liquid systems for creating uniform, microscale droplets. Recent works have highlighted and quantified the use of a gaseous continuous phase for controlled generation of droplets in the Dripping regime in planar structures. Here we demonstrate a new class of non-planar droplet-based systems which rely on controlled breakup of a liquid microjet within a high speed flow of air inside a confined microfluidic flow-focusing PDMS channel. We investigate the physics of confined gas-liquid flows and the effect of geometry on the behavior of a liquid water jet in a gaseous flow. Droplet breakup in the Jetting regime is studied both numerically and experimentally and the results are compared. We show droplet production capability at rates higher than 100 KHz with droplets ranging from 15-30$\mu $m in diameter and a polydispersity index of less than 15{\%}. This work represents an important investigation into the Jetting regime in confined microchannels. The ability to control jet behavior, generation rate, and droplet size in gas-liquid microflows will further expand the potential applications of this system for high throughput operations in material synthesis and biochemical analysis. [Preview Abstract] |
Tuesday, November 21, 2017 3:13PM - 3:26PM |
Q14.00012: Separation and filtration systems with an array of anchored liquid-bridges as stationary phase Siqi Du, German Drazer We first present a novel deterministic lateral displacement (DLD) system in which the standard array of cylindrical posts is replaced by an equivalent array of anchored liquid-bridges. The water bridges are created between two parallel plates and anchored to the bottom one by means of a square array of cylindrical wells. We present results demonstrating that, similar to traditional DLD systems, anchored-liquid DLD arrays lead to size-based separation of suspended particles. We will also discuss cases in which liquid-bridge deformation leads to separation by density. Finally, we discuss the possible use of such arrays to filtrate particulate matter in air. [Preview Abstract] |
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