Microfluidics refers to a system that manipulates a small amount of fluids using small channels with sizes ten to hundreds micrometres. It is a multidisciplinary field that involves molecular analysis, molecular biology, and microelectronics. It has practical applications in the design of systems that process low volumes of fluids to achieve multiplexing, automation, and high-throughput screening. Microfluidics emerged in the beginning of the 1980s and is used in the development of inkjet printheads, DNA chips, lab-on-a-chip technology, micro-propulsion, and micro-thermal technologies.
Digital microfluidics (DMF) is a platform for lab-on-a-chip systems that is based upon the manipulation of microdroplets. Droplets are dispensed, moved, stored, mixed, reacted, or analyzed on a platform with a set of insulated electrodes. Digital microfluidics can be used together with analytical analysis procedures such as mass spectrometry, colorimetry, electrochemical, and electrochemiluminescense.
In molecular biology, biochips are engineered substrates that can host large numbers of simultaneous biochemical reactions. One of the goals of biochip technology is to efficiently screen large numbers of biological analytes, with potential applications ranging from disease diagnosis to detection of bioterrorism agents. For example, digital microfluidic biochips are under investigation for applications in biomedical fields. In a digital microfluidic biochip, a group of (adjacent) cells in the microfluidic array can be configured to work as storage, functional operations, as well as for transporting fluid droplets dynamically.
A lab-on-a-chip (LOC) is a device that integrates one or several laboratory functions on a single integrated circuit of only millimeters to a few square centimeters to achieve automation and high-throughput screening. LOCs can handle extremely small fluid volumes down to less than pico-liters. Lab-on-a-chip devices are a subset of microelectromechanical systems (MEMS) devices and sometimes called "micro total analysis systems" (µTAS). LOCs may use microfluidics, the physics, manipulation and study of minute amounts of fluids. However, strictly regarded "lab-on-a-chip" indicates generally the scaling of single or multiple lab processes down to chip-format, whereas "µTAS" is dedicated to the integration of the total sequence of lab processes to perform chemical analysis.
Microfabrication is the process of fabricating miniature structures of micrometre scales and smaller. Historically, the earliest microfabrication processes were used for integrated circuit fabrication, also known as "semiconductor manufacturing" or "semiconductor device fabrication". In the last two decades microelectromechanical systems (MEMS), microsystems, micromachines and their subfields, microfluidics/lab-on-a-chip, optical MEMS, RF MEMS, PowerMEMS, BioMEMS and their extension into nanoscale have re-used, adapted or extended microfabrication methods. Flat-panel displays and solar cells are also using similar techniques.
A lateral flow test (LFT), is an assay also known as a lateral flow device (LFD), lateral flow immunochromatographic assay, or rapid test. It is a simple device intended to detect the presence of a target substance in a liquid sample without the need for specialized and costly equipment. LFTs are widely used in medical diagnostics in the home, at the point of care, and in the laboratory. For instance, the home pregnancy test is an LFT that detects a specific hormone. These tests are simple and economical and generally show results in around five to thirty minutes. Many lab-based applications increase the sensitivity of simple LFTs by employing additional dedicated equipment. Because the target substance is often a biological antigen, many lateral flow tests are rapid antigen tests.
Micropumps are devices that can control and manipulate small fluid volumes. Although any kind of small pump is often referred to as a micropump, a more accurate definition restricts this term to pumps with functional dimensions in the micrometer range. Such pumps are of special interest in microfluidic research, and have become available for industrial product integration in recent years. Their miniaturized overall size, potential cost and improved dosing accuracy compared to existing miniature pumps fuel the growing interest for this innovative kind of pump.
Bio-MEMS is an abbreviation for biomedical microelectromechanical systems. Bio-MEMS have considerable overlap, and is sometimes considered synonymous, with lab-on-a-chip (LOC) and micro total analysis systems (μTAS). Bio-MEMS is typically more focused on mechanical parts and microfabrication technologies made suitable for biological applications. On the other hand, lab-on-a-chip is concerned with miniaturization and integration of laboratory processes and experiments into single chips. In this definition, lab-on-a-chip devices do not strictly have biological applications, although most do or are amenable to be adapted for biological purposes. Similarly, micro total analysis systems may not have biological applications in mind, and are usually dedicated to chemical analysis. A broad definition for bio-MEMS can be used to refer to the science and technology of operating at the microscale for biological and biomedical applications, which may or may not include any electronic or mechanical functions. The interdisciplinary nature of bio-MEMS combines material sciences, clinical sciences, medicine, surgery, electrical engineering, mechanical engineering, optical engineering, chemical engineering, and biomedical engineering. Some of its major applications include genomics, proteomics, molecular diagnostics, point-of-care diagnostics, tissue engineering, single cell analysis and implantable microdevices.
Cell sorting is the process through which a particular cell type is separated from others contained in a sample on the basis of its physical or biological properties, such as size, morphological parameters, viability and both extracellular and intracellular protein expression. The homogeneous cell population obtained after sorting can be used for a variety of applications including research, diagnosis, and therapy.
Nanofluidic circuitry is a nanotechnology aiming for control of fluids in nanometer scale. Due to the effect of an electrical double layer within the fluid channel, the behavior of nanofluid is observed to be significantly different compared with its microfluidic counterparts. Its typical characteristic dimensions fall within the range of 1–100 nm. At least one dimension of the structure is in nanoscopic scale. Phenomena of fluids in nano-scale structure are discovered to be of different properties in electrochemistry and fluid dynamics.
The centrifugal micro-fluidic biochip or centrifugal micro-fluidic biodisk is a type of lab-on-a-chip technology, also known as lab-on-a-disc, that can be used to integrate processes such as separating, mixing, reaction and detecting molecules of nano-size in a single piece of platform, including a compact disk or DVD. This type of micro-fluidic biochip is based upon the principle of microfluidics; to take advantage of non-inertial pumping for lab-on-a-chip devices using non-inertial valves and switches under centrifugal force and Coriolis effect to distribute fluids about the disks in a highly parallel order.
Microfluidic whole genome haplotyping is a technique for the physical separation of individual chromosomes from a metaphase cell followed by direct resolution of the haplotype for each allele.
An organ-on-a-chip (OOC) is a multi-channel 3-D microfluidic cell culture, integrated circuit (chip) that simulates the activities, mechanics and physiological response of an entire organ or an organ system. It constitutes the subject matter of significant biomedical engineering research, more precisely in bio-MEMS. The convergence of labs-on-chips (LOCs) and cell biology has permitted the study of human physiology in an organ-specific context. By acting as a more sophisticated in vitro approximation of complex tissues than standard cell culture, they provide the potential as an alternative to animal models for drug development and toxin testing.
Microfluidics in chemical biology is the application of microfluidics in the study of chemical biology.
Multiplexed point-of-care testing (xPOCT) is a more complex form of point-of-care testing (POCT), or bedside testing. Point-of-care testing is designed to provide diagnostic tests at or near the time and place that the patient is admitted. POCT uses the concentrations of analytes to provide the user with information on the physiological state of the patient. An analyte is a substance, chemical or biological, that is being analyzed using a certain instrument. While point-of-care testing is the quantification of one analyte from one in vitro sample, multiplexed point-of-care testing is the simultaneous on-site quantification of various analytes from a single sample.
Droplet-based microfluidics manipulate discrete volumes of fluids in immiscible phases with low Reynolds number and laminar flow regimes. Interest in droplet-based microfluidics systems has been growing substantially in past decades. Microdroplets offer the feasibility of handling miniature volumes of fluids conveniently, provide better mixing, encapsulation, sorting, sensing and are suitable for high throughput experiments. Two immiscible phases used for the droplet based systems are referred to as the continuous phase and dispersed phase.
Andrew James deMello is a British chemist and Professor of Biochemical Engineering at ETH Zürich.
Paper-based microfluidics are microfluidic devices that consist of a series of hydrophilic cellulose or nitrocellulose fibers that transport fluid from an inlet through the porous medium to a desired outlet or region of the device, by means of capillary action. This technology builds on the conventional lateral flow test which is capable of detecting many infectious agents and chemical contaminants. The main advantage of this is that it is largely a passively controlled device unlike more complex microfluidic devices. Development of paper-based microfluidic devices began in the early 21st century to meet a need for inexpensive and portable medical diagnostic systems.
Cho Yoon-Kyoung is an interdisciplinary researcher involved in basic science to translational research in microfluidics and nanomedicine. She is a group leader in the Center for Soft and Living Matter at the Institute for Basic Science (IBS) and a full professor in Biomedical Engineering at the Ulsan National Institute of Science and Technology (UNIST), Ulsan, Korea. Cho is a member of the National Academy of Engineering of Korea and a Fellow of the Royal Society of Chemistry.
Aaron R. Wheeler is a Canadian chemist who is a professor of chemistry and biomedical engineering at the University of Toronto since 2005 with cross-appointment at Institute of Biomedical Engineering and Terrence Donnelly Centre for Cellular and Biomolecular Research. His academic laboratory is located at Lash Miller Chemical Laboratories and Terrence Donnelly Centre for Cellular and Biomolecular Research at the University of Toronto. In 2005, Wheeler was appointed as assistant professor and Tier II Canada Research Chair then promoted to associate professor in 2010, full professor in 2013, and in 2018 he became the Tier I Canada Research Chair in Microfluidic Bioanalysis.
