Regularized lattice Boltzmann Multicomponent models for low Capillary and Reynolds microfluidics flows

We present a regularized version of the color gradient lattice Boltzmann (LB) scheme for the simulation of droplet formation in microfluidic devices of experimental relevance. The regularized version is shown to provide computationally efficient access to Capillary number regimes relevant to droplet generation via microfluidic devices, such as flow-focusers and the more recent microfluidic step emulsifier devices.Comment: 9 pages, 5 figure

Design automation based on fluid dynamics

This article was accepted and presented at the 9th International Workshop on Bio-Design Automation, Pittsburgh, Pennsylvania (2017).Microfluidic devices provide researchers with numerous advantages such as high throughput, increased sensitivity and accuracy, lower cost, and reduced reaction time. However, design, fabrication, and running a microfluidic device are still heavily reliant on expertise. Recent studies suggest micro-milling can be a semi-automatic, inexpensive, and simple alternative to common fabrication methods. Micro-milling does not require a clean-room, mask aligner, spin-coater, and Plasma bonder, thus cutting down the cost and time of fabrication significantly. Moreover, through this protocol researchers can easily fabricate microfluidic devices in an automated fashion eschewing levels of expertise required for typical fabrication methods, such as photolithography, soft-lithography, and etching. However, designing a microfluidic chip that meets a certain set of requirements is still heavily dependent on a microfluidic expert, several days of simulation, and numerous experiments to reach the required performance. To address this, studies have reported random automated design of microfluidic devices based on numerical simulations for micro-mixing. However, random design generation is heavily reliant on time-consuming simulations carried out beforehand, and is prone to error due to the accuracy limitations of the numerical method. On the other hand, by using micro-milling for ultra-fast and inexpensive fabrication of microfluidic devices and Taguchi design of experiments for state-space exploration of all of the geometric parameters, we are able to generate a database of geometries, flow rates, and flow properties required for a single primitive to carry out a specified microfluidic task

Design and fabrication of chemically robust three-dimensional microfluidic valves

A current problem in microfluidics is that poly(dimethylsiloxane) (PDMS), used to fabricate many microfluidic devices, is not compatible with most organic solvents. Fluorinated compounds are more chemically robust than PDMS but, historically, it has been nearly impossible to construct valves out of them by multilayer soft lithography (MSL) due to the difficulty of bonding layers made of non-stick fluoropolymers necessary to create traditional microfluidic valves. With our new three-dimensional (3D) valve design we can fabricate microfluidic devices from fluorinated compounds in a single monolithic layer that is resistant to most organic solvents with minimal swelling. This paper describes the design and development of 3D microfluidic valves by molding of a perfluoropolyether, termed Sifel, onto printed wax molds. The fabrication of Sifel-based microfluidic devices using this technique has great potential in chemical synthesis and analysis

High-throughput on-chip DNA fragmentation

free microfluidic deoxyribonucleic acid (DNA) fragmentation chip that is based on hydrodynamic shearing. Genomic DNA has been reproducibly fragmented with 2-10 kbp fragment lengths by applying hydraulic pressure ΔP across micromachined constrictions in the microfluidic channels. The utilization of a series of constrictions reduces the variance of the fragmented DNA length distribution; and parallel microfluidic channels design eliminates the device clogging

Microfluidic DNA amplification - a review

The application of microfluidic devices for DNA amplification has recently been extensively studied. Here, we review the important development of microfluidic polymerase chain reaction (PCR) devices and discuss the underlying physical principles for the optimal design and operation of the device. In particular, we focus on continuous-flow microfluidic PCR on-chip, which can be readily implemented as an integrated function of a micro-total-analysis system. To overcome sample carryover contamination and surface adsorption associated with microfluidic PCR, microdroplet technology has recently been utilized to perform PCR in droplets, which can eliminate the synthesis of short chimeric products, shorten thermal-cycling time, and offers great potential for single DNA molecule and single-cell amplification. The work on chip-based PCR in droplets is highlighted

Molecular biology on a microfluidic chip

We have developed microfluidic chips for automating molecular biology processes such as gene ligation and gene transformation from nanolitre sample volumes with parallel architecture. Unlike conventional tube methods with cumbersome pipetting procedures, all processes, including metering of samples, ligation and transformation, were carried out in the microfluidic chips through pneumatic control of the nanofluid. The microfluidic devices presented here offer an illustration of some of the basic physics that arises when trying to miniaturize and automate biological techniques

Electronic control of elastomeric microfluidic circuits with shape memory actuators

Recently, sophisticated fluidic circuits with hundreds of independent valves have been built by using multi-layer soft-lithography to mold elastomers. However, this shrinking of microfluidic circuits has not been matched by a corresponding miniaturization of the actuation and interfacing elements that control the circuits; while the fluidic circuits are small (~10–100 micron wide channels), the Medusa's head-like interface, consisting of external pneumatic solenoids and tubing or mechanical pins to control each independent valve, is larger by one to four orders of magnitude (mm to cm). Consequently, the dream of using large scale integration in microfluidics for portable, high throughput applications has been stymied. By combining multi-layer soft-lithography with shape memory alloys (SMA), we demonstrate electronically activated microfluidic components such as valves, pumps, latches and multiplexers, that are assembled on printed circuit boards (PCBs). Thus, high density, electronically controlled microfluidic chips can be integrated alongside standard opto-electronic components on a PCB. Furthermore, we introduce the idea of microfluidic states, which are combinations of valve states, and analogous to instruction sets of integrated circuit (IC) microprocessors. Microfluidic states may be represented in hardware or software, and we propose a control architecture that results in logarithmic reduction of external control lines. These developments bring us closer to building microfluidic circuits that resemble electronic ICs both physically, as well as in their abstract model

Elastomeric microfluidic diode and rectifier work with Newtonian fluids

We report on two microfluidic elastomeric autoregulatory devices—a diode and a rectifier. They exhibit physically interesting and complex nonlinear behaviors (saturation, bias-dependent resistance, and rectification) with a Newtonian fluid. Due to their autoregulatory properties, they operate without active external control. As a result, they enable increased microfluidic device density and overall system miniaturization. The demonstrated diode and rectifier would also be useful components in future microfluidic logic circuitry

A reverse predictive model towards design automation of microfluidic droplet generators

This work has been presented in the 10th IWBDA workshop.Droplet-based microfluidic devices in comparison to test tubes can reduce reaction volumes 10^9 times and more due to the encapsulation of reactions in micro-scale droplets [4]. This volume reduction, alongside higher accuracy, higher sensitivity and faster reaction time made droplet microfluidics a superior platform particularly in biology, biomedical, and chemical engineering. However, a high barrier of entry prevents most of life science laboratories to exploit the advantages of microfluidics. There are two main obstacles to the widespread adoption of microfluidics, high fabrication costs, and lack of design automation tools. Recently, low-cost fabrication methods have reduced the cost of fabrication significantly [7]. Still, even with a low-cost fabrication method, due to lack of automation tools, life science research groups are still reliant on a microfluidic expert to develop any new microfluidic device [3, 5]. In this work, we report a framework to develop reverse predictive models that can accurately automate the design process of microfluidic droplet generators. This model takes prescribed performance metrics of droplet generators as the input and provides the geometry of the microfluidic device and the fluid and flow settings that result in the desired performance. We hope this automation tool makes droplet-based microfluidics more accessible, by reducing the time, cost, and knowledge needed for developing a microfluidic droplet generator that meets certain performance requirement

Microfluidic method for rapid turbidimetric detection of the DNA of Mycobacterium tuberculosis using loop-mediated isothermal amplification in capillary tubes

We describe a microfluidic method for rapid isothermal turbidimetric detection of the DNA of Mycobacterium tuberculosis. Loop-mediated isothermal amplification is accomplished in capillary tubes for amplifying DNA in less than 15 min, and sensitivity and specificity were compared to conventional loop-mediated isothermal amplification (LAMP). The method can detect as little as 1 pg mL−1 DNA in a sample. Results obtained with clinical specimens indicated 90 % sensitivity and 95 % specificity for microfluidic LAMP in comparison to culture methods. No interference occurred due to the presence of nonspecific DNAs. The findings demonstrate the power of the new microfluidic LAMP test for rapid molecular detection of microorganisms even when using bare eyes. © 2014, Springer-Verlag Wien