Droplet Based Microfluidic Systems

Droplet microfluidics has dramatically developed in the past decade and has been established as a microfluidic technology that can translate into commercial products. Its rapid development and adoption have relied not only on an efficient stabilizing system (oil and surfactant), but also on a library of modules that can manipulate droplets at a high-throughput. Droplet microfluidics is a vibrant field that keeps evolving, with advances that span technology development and applications. Recent examples include innovative methods to generate droplets, to perform single-cell encapsulation, magnetic extraction, or sorting at an even higher throughput. The trend consists of improving parameters such as robustness, throughput, or ease of use. These developments rely on a firm understanding of the physics and chemistry involved in hydrodynamic flow at a small scale. Finally, droplet microfluidics has played a pivotal role in biological applications, such as single-cell genomics or high-throughput microbial screening, and chemical applications. This Special Issue will showcase all aspects of the exciting field of droplet microfluidics, including, but not limited to, technology development, applications, and open-source systems.

Responding to the need for an affordable, easy-to-read textbook that introduces microfluidics to undergraduate and postgraduate students, this concise book will provide a broad overview of the important theoretical and practical aspects of microfluidics and lab-on-a-chip, as well as its applications.

This book describes automatic methods for the design of droplet microfluidic networks. The authors discuss simulation and design methods which support the design process of droplet microfluidics in general, as well as design methods for a dedicated droplet routing mechanism, namely passive droplet routing. The methods discussed allow for simulating a microfluidic design on a high-abstraction level, which facilitates early validation of whether a design works as intended, automatically dimensioning a microfluidic design, so that constraints like flow conditions are satisfied, and automatically generating meander designs for the respective needs and fabrication settings. Dedicated methods for passive droplet routing are discussed and allow for designing application-specific architectures for a given set of experiments, as well as generating droplet sequences realizing the respective experiments. Together, these methods provide a comprehensive “toolbox" for designers working on droplet microfluidic networks in general and an integrated design flow for the passive droplet routing mechanism in particular. Provides both a comprehensive “toolbox" for designers working on droplet microfluidic networks in general and an integrated design flow for the passive droplet routing mechanism in particular; Describes for the first time CAD methods for droplet microfluidic networks, along with the first integrated design process; Includes open source implementations, in order to reach the largest possible user group within the domain of microfluidics.

Microfluidics have aroused a new surge of interest in recent years in environmental and energy areas, and inspired novel applications to tackle the worldwide challenges for sustainable development. This book aims to present readers with a valuable compendium of significant advances in applying the multidisciplinary microfluidic technologies to address energy and environmental problems in a plethora of areas such as environmental monitoring and detection, new nanofluid application in traditional mechanical manufacturing processes, development of novel biosensors, and thermal management. This book will provide a new perspective to the understanding of the ever-growing importance of microfluidics.

Droplet-based microfluidics has proven to be a useful tool to investigate heterogeneous reactions that occur between multiple phases due to the reproducible flow patterns and effective mass transport between phases. Nowadays, droplet-based microfluidics is showing its potential for systematic study of the transport across interfaces between different micro reactors since the surfactant layers around micro droplets are in principle permeable to small molecules. In order to study such bio/chemical assays and medium transfer from one droplet to another, droplet paring system in continuous-flow channels and even static arrays has been developed and demonstrated. However, a more desirable, but more difficult unit operation for complex assays is to cluster multiple-droplet containing different reagents/samples for various biological and chemical experiments. The objective of this thesis is to study clustering of multiple-droplet in a double-layered microfluidic device integrating multiple functions such as droplet generation, manipulation, trapping, guiding, and storing. The use of guiding tracks and simple forward/backward flows has been incorporated to improve trapping/storing efficiency. The primary goal is to investigate the fluid dynamics and adopt a method to design and simulate the device. The secondary goal is to learn the ability to fabricate the device and demonstrate a large array of different multiple-droplet clustering. Finally, the future goal is to apply the tested device for a wide range of biomedical applications. We expect the proposed strategy will be valuable to study transfer of molecules across the droplets, enzymatic reaction and high throughput bioassay reaction.

In this book, the latest tools available for functional metagenomics research are described.This research enables scientists to directly access the genomes from diverse microbial genomes at one time and study these “metagenomes”. Using the modern tools of genome sequencing and cloning, researchers have now been able to harness this astounding metagenomic diversity to understand and exploit the diverse functions of microorganisms. Leading scientists from around the world demonstrate how these approaches have been applied in many different settings, including aquatic and terrestrial habitats, microbiomes, and many more environments. This is a highly informative and carefully presented book, providing microbiologists with a summary of the latest functional metagenomics literature on all specific habitats.

Droplet and Digital Microfluidics: Ideation to Implementation is a detailed introduction to the dynamics of droplet and digital microfluidics, also featuring coverage of new methods and applications. The explosion of applications of microelectromechanical systems (MEMS) in recent years has driven demand for expertise and innovation in fluid flow in the microchannels they contain. In this book, detailed descriptions of methods for biological and chemical applications of microfluidics are provided, along with supporting foundational knowledge. In addition, the principles of droplet and digital microfluidics are explained, along with their different applications and governing physics. New additions to the technological knowledgebase that enable advances in droplet and digital microfluidics include machine learning and exciting future avenues for research. Provides step-by-step fabrication, testing, and characterization instructions in each chapter to support implementation Includes explanations of applications and methods in biological and chemical settings Describes the path to automation of digital and droplet microfluidic platforms

The droplet based microfluidic technology has become indispensable in many chemical, biomedical research and high-throughput assay applications. The ability to controllably merge droplets within flow systems is of high importance when performing complex chemical or biological analysis. However, in order to perform controlled fusion reaction one needs to perform controlled droplet trapping and pairing. Recent microfluidic systems are capable of pairing the droplets by using unstabilized flow pattern. Controlled droplet pairing and fusion, especially for same-sized droplet pairing, is still a challenge, mostly because of the difficulty to manipulate droplets. It is also seen that it requires to control the droplet generation along with the flow rate control simultaneously which is also difficult to realize.^In our research, a serial flowing microfluidic system and an obstruction based microfluidic system are presented for checking the droplet flow pattern along the system using hydrodynamic resistance phenomenon. In addition to this, we also checked the device working for droplet generation along with sequential trapping and pairing of aqueous micro-droplets of different liquids. It is more robust as compared to the prior research done in this area. These systems are competent of accomplishing multiple functions including droplet generation, transportation, trapping and merging on a single integrated device. These devices consist of three different functional regions: flow focusing droplet generator; a single droplet trap region and pairing region. Our designs were based on the principle of exploiting hydrodynamic resistance of the columnar structure in the microfluidic channel. The device designs include two inlets for oil and water.^Similar structure was embedded at the outlet for the generation of second droplet of different liquid. In a typical scenario, droplets would be generated at the T-junction and would travel through the microfluidic channel to enter the single droplet trapping area. During the reverse flow, the trapped droplets in the first phase would be released and would enter the pairing chamber. These droplets would be held until another droplet of different liquid to combine with it. Second droplet would travel in the reverse flow direction and would be trapped in the pairing chamber along with the first droplet to combine with it. Deionized water and gel were used as the aqueous phase and mineral oil as the oil phase. 2% (w/w) Span-80 was used as surfactant. These devices were also simulated using PSpice and COMSOL Multiphysics to verify the droplet trapping and pairing sequences before fabrication.^Finally, we designed and tested the double droplet trapping system in a serial flowing microfluidic device along with the obstruction based microfluidic device. The efficiency for single droplet trapping in forward flow was about 99%, single droplet trapping in reverse flow direction was about 90-95% for both serial and obstruction based microfluidic device. For droplet pairing, the serial microfluidic device had an efficiency of 40-45% where as the obstruction based microfluidic had 60-65% efficiency. These devices were very simple and could very efficiently trap two different liquid droplets in a chamber without merging and with the help of an external electric field they could be selectively merged.

Edited by two leaders, this book has drawn together expertise from around the globe to form a unified, cohesive resource for the droplet microfluidics community. Starting with the basic theory of droplet microfluidics before introducing its use as a tool, the reader is treated to chapters on important techniques, including robust passive and active droplet manipulations and applications such as single cell analysis, which is key for drug discovery. This book is a go-to resource for the community yearning to adopt and promote droplet microfluidics into different applications.