Particle sorting, counting, and separation are crucial precursor steps to a host of biomedical assays, and various macroscale tools have been developed over the past several decades in response. In more recent years, microfluidic technologies have gained significant popularity as a means of performing these same tasks and more, all at reduced power, reagent volume, time, and user difficulty. This raises the possibility that every fluidic, optical, and electronic system in a biomedical laboratory could soon be reduced to a microscale equivalent, and incorporated onto a single handheld device, a hypothetical lab-on-a-chip. However, while the sorting technologies at the heart of this new class of device have developed at a dramatic pace, the devices themselves remain costly to fabricate, difficult to manufacture at large scales, and poorly integrated with auxiliary systems such as power supplies and peristaltic pumps. As such, they rarely develop beyond the proof-of-concept stage and have yet to achieve any significant acceptance in the biomedical community. This work seeks to move microfluidic sorters beyond this obstacle. First, it was demonstrated that multiple components could be implemented onto a single platform, eliminating cumbersome external fluidics in the process. Next, methods from the mature microelectronics industry were used to build an electronic microfluidic cell sorter on a printed circuit board platform, yielding a dramatic improvement in device manufacturability and user friendliness, as well as ease of integration with other electronics, micro or otherwise. Finally, building on this, a method was developed to manufacture large numbers of three-dimensional microelectrodes and then incorporate them into a microfluidic device using pick-and-place methods, again a technique adapted from the microelectronics industry. Together, this shifts microfluidics away from the established standard of cumbersome devices monolithically constructed using costly materials and methods and towards a novel standard of more manufacturable and user-friendly devices, and represents a step towards this class of device gaining mainstream acceptance in the biomedical community.

Microfluidic platforms are increasingly being used for separating a wide variety of particles based on their physical and chemical properties. In the past two decades, many practical applications have been found in chemical and biological sciences, including single cell analysis, clinical diagnostics, regenerative medicine, nanomaterials synthesis, environmental monitoring, etc. In this Special Issue, we invited contributions to report state-of-the art developments in the fields of micro- and nanofluidic separation, fractionation, sorting, and purification of all classes of particles, including, but not limited to, active devices using electric, magnetic, optical, and acoustic forces; passive devices using geometries and hydrodynamic effects at the micro/nanoscale; confined and open platforms; label-based and label-free technology; and separation of bioparticles (including blood cells), circulating tumor cells, live/dead cells, exosomes, DNA, and non-bioparticles, including polymeric or inorganic micro- and nanoparticles, droplets, bubbles, etc. Practical devices that demonstrate capabilities to solve real-world problems were of particular interest.

The manipulation of cells and microparticles within microfluidic systems using external forces is valuable for many microscale analytical and bioanalytical applications. Acoustofluidics is the ultrasound-based external forcing of microparticles with microfluidic systems. It has gained much interest because it allows for the simple label-free separation of microparticles based on their mechanical properties without affecting the microparticles themselves. Microscale Acoustofluidics provides an introduction to the field providing the background to the fundamental physics including chapters on governing equations in microfluidics and perturbation theory and ultrasound resonances, acoustic radiation force on small particles, continuum mechanics for ultrasonic particle manipulation, and piezoelectricity and application to the excitation of acoustic fields for ultrasonic particle manipulation. The book also provides information on the design and characterization of ultrasonic particle manipulation devices as well as applications in acoustic trapping and immunoassays. Written by leading experts in the field, the book will appeal to postgraduate students and researchers interested in microfluidics and lab-on-a-chip applications.

Flow cytometry and fluorescence activated cell sorting (FACS) are powerful analytical techniques with applications in a variety of fields, but restricted to use in specialty settings. Realizing a microfluidic flow cytometer would greatly improve the accessibility of this technology, as this would make the device portable and easily mass producible. In this thesis cell sorting techniques are reviewed in the microfluidic domain and the feasibility of a surface acoustic wave (SAW) driven sorting technique is examined. Standard soft lithography techniques were used to fabricate PDMS channels and standard surface micromachining techniques were used to fabricate inter-digitated transducers (IDT) on a piezoelectric substrate for surface acoustic wave (SAW) generation. A 3-D focused flow system with focused IDT was characterized for its particle sorting abilities with microbeads, analogous to blood cells in size and density, at varying power levels from -1dBm to 0.5 dBm. The results indicated the particles displace proportionally to the applied power. Theoretical calculations about forces and particle displacement were also considered to further understand the device functionality. The device demonstrated the ability to laterally displace particles and could ultimately be used for cell sorting purpose in a fully integrated microfluidic flow cytometer.

Cilia are tiny hairs covering biological cells to generate and sense fluid flow. Millions of years of evolution have inspired a novel technology which is barely a decade old. Artificial cilia have been developed to control and sense fluid flow in microscopic systems, presenting new and interesting options for flow control in lab-on-a-chip devices. This appealing link between nature and technology has seen rapid development in the last few years, and this book presents a review of the state-of-the-art in the form of a professional reference book. The editors have pioneered the field, having initiated a major European project on this topic soon after its inception. Active researchers in academia and industry will benefit from the comprehensive nature of this book, while postgraduates and those new to the field will gain a clear understanding of the theory, techniques and applications of artificial cilia.

Microdroplet technology has recently emerged to provide new and diverse applications via microfluidic functionality, especially in various areas of biology and chemistry. This book, then, gives an overview of the principle components and wide-ranging applications for state-of-the-art of droplet-based microfluidics. Chapter authors are internationally-leading researchers from chemistry, biology, physics and engineering that present various key aspects of micrdroplet technology -- fundamental flow physics, methodology and components for flow control, applications in biology and chemistry, and a discussion of future perspectives. This book acts as a reference for academics, post-graduate students, and researcher wishing to deepen their understand of microfluidics and introduce optimal design and operation of new droplet-based microfluidic devices for more comprehensive analyte assessments.

Now in its Third Edition, the Artech House bestseller, Fundamentals and Applications of Microfluidics, provides engineers and students with the most complete and current coverage of this cutting-edge field. This revised and expanded edition provides updated discussions throughout and features critical new material on microfluidic power sources, sensors, cell separation, organ-on-chip and drug delivery systems, 3D culture devices, droplet-based chemical synthesis, paper-based microfluidics for point-of-care, ion concentration polarization, micro-optofluidics and micro-magnetofluidics. The book shows how to take advantage of the performance benefits of microfluidics and serves as an instant reference for state-of-the-art microfluidics technology and applications. Readers find discussions on a wide range of applications, including fluid control devices, gas and fluid measurement devices, medical testing equipment, and implantable drug pumps. Professionals get practical guidance in choosing the best fabrication and enabling technology for a specific microfluidic application, and learn how to design a microfluidic device. Moreover, engineers get simple calculations, ready-to-use data tables, and rules of thumb that help them make design decisions and determine device characteristics quickly.