| Microscale behavior of fluids Silicone rubber and glass | | | | corridors (indicated here as Ji,j) into a 1D lattice. The |
| microfluidic devices. Top: a photograph of the | | | | ecosystem service (of habitat renewal) to each MHP |
| devices. Bottom: DIC micrographs of a serpentine | | | | represented here as i (red arrows). Each MHP can |
| channel ~15 m wide. The behavior of fluids at the | | | | also hold different carrying capacity Ki for its |
| microscale can differ from 'macrofluidic' behavior in | | | | supporting local population of bacterial cells (depicted |
| that factors such as surface tension, energy | | | | in green). By combining microfluidics with landscape |
| dissipation, and fluidic resistance start to dominate the | | | | ecology and nanofluidics, a nano/micro fabricated |
| system. Microfluidics studies how these behaviors | | | | fluidic landscape can be constructed by building local |
| change, and how they can be worked around, or | | | | patches of bacterial habitat and connecting them by |
| exploited for new uses. At small scales (channel | | | | dispersal corridors. The resulting landscapes can be |
| diameters of around 100 nanometers to several | | | | used as physical implementations of an adaptive |
| hundred micrometers) some interesting and | | | | landscape , by generating a spatial mosaic of patches |
| sometimes unintuitive properties appear. In particular, | | | | of opportunity distributed in space and time. The |
| the Reynolds number (which compares the effect of | | | | patchy nature of these fluidic landscapes allows for |
| momentum of a fluid to the effect of viscosity) can | | | | the study of adapting bacterial cells in a |
| become very low. A key consequence of this is that | | | | metapopulation system. The evolutionary ecology of |
| fluids, when side-by-side, do not necessarily mix in | | | | these bacterial systems in these synthetic |
| the traditional sense; molecular transport between | | | | ecosystems allows for using biophysics to address |
| them must often be through diffusion. High specificity | | | | questions in evolutionary biology. Cellular biophysics By |
| of chemical and physical properties (concentration, | | | | rectifying the motion of individual swimming bacteria , |
| pH, temperature, shear force, etc.) can also be | | | | microfluidic structures can be use to extract |
| ensured resulting in more uniform reaction conditions | | | | mechanical motion from a population of motile |
| and higher grade products in single and multi-step | | | | bacterial cells . This way, bacteria-powered rotors can |
| reactions. Effects of micro domain laminar flow | | | | be built. Optics Tuneable Microlens Array Acoustic |
| surface tension electrowetting fast thermal relaxation | | | | droplet ejection (ADE) Acoustic droplet ejection uses |
| electrical surface charges diffusion Key application | | | | a pulse of ultrasound to move low volumes of fluids |
| areas Microfluidic structures include micropneumatic | | | | (typically nanoliters or picoliters) without any physical |
| systems, i.e. microsystems for the handling of | | | | contact. This technology focuses acoustic energy into |
| off-chip fluids (liquid pumps, gas valves, etc), and | | | | a fluid sample in order to eject droplets as small as a |
| microfluidic structures for the on-chip handling of | | | | millionth of a millionth of a liter (picoliter = 10-12 liter). |
| nano- and picolitre volumes. To date, the most | | | | ADE technology is a very gentle process, and it can |
| successful commercial application of microfluidics is | | | | be used to transfer proteins, high molecular weight |
| the inkjet printhead. Significant research has been | | | | DNA and live cells without damage or loss of viability. |
| applied to the application of microfluidics for the | | | | This feature makes the technology suitable for a |
| production of industrially relevant quantities of | | | | wide variety of applications including proteomics and |
| material. Advances in microfluidics technology are | | | | cell-based assays. Fuel cells For more details on this |
| revolutionizing molecular biology procedures for | | | | topic, see Electroosmotic pump. Microfluidic fuel cells |
| enzymatic analysis (e.g., glucose and lactate assays), | | | | can use laminar flow to separate the fuel and its |
| DNA analysis (e.g., polymerase chain reaction and | | | | oxidant to control the interaction of the two fluids |
| high-throughput sequencing), and proteomics. The | | | | without a physical barrier as would be required in |
| basic idea of microfluidic biochips is to integrate assay | | | | conventional fuel cells. See also Fluidics Nanofluidics |
| operations such as detection, as well as sample | | | | List of microfluidics research groups Lab on a chip |
| pre-treatment and sample preparation on one chip. | | | | Digital microfluidics Fluids@Home References ^ Kirby, |
| An emerging application area for biochips is clinical | | | | B.J. (2010). Micro- and Nanoscale Fluid Mechanics: |
| pathology, especially the immediate point-of-care | | | | Transport in Microfluidic Devices. Cambridge University |
| diagnosis of diseases. In addition, microfluidics-based | | | | Press. ^ Karniadakis, G.M., Beskok, A., Aluru, N. (2005). |
| devices, capable of continuous sampling and real-time | | | | Microflows and Nanoflows. Springer Verlag. ^ Bruus, |
| testing of air/water samples for biochemical toxins | | | | H. (2007). Theoretical Microfluidics. Oxford University |
| and other dangerous pathogens, can serve as an | | | | Press. ^ Tabeling, P. (2005). Introduction to |
| always-on "bio-smoke alarm" for early warning. | | | | Microfluidics. Oxford University Press. ^ J |
| Continuous-flow microfluidics These technologies are | | | | Shestopalov, J. D. Tice and R. F. Ismagilov,"Multi-step |
| based on the manipulation of continuous liquid flow | | | | synthesis of nanoparticles performed on millisecond |
| through microfabricated channels. Actuation of liquid | | | | time scale in a microfluidic droplet-based system" Lab |
| flow is implemented either by external pressure | | | | Chip, 2004, 4, 316 - 321, DOI: 10.1039/b403378g. ^ |
| sources, external mechanical pumps, integrated | | | | Nguyen, N.T., Wereley, S. (2006). Fundamentals and |
| mechanical micropumps, or by combinations of | | | | Applications of Microfluidics. Artech House. ^ Wei Li, |
| capillary forces and electrokinetic mechanisms. | | | | Jesse Greener, Dan Voicu and Eugenia Kumacheva |
| Continuous-flow microfluidic operation is the | | | | "Multiple modular microfluidic (M3) reactors for the |
| mainstream approach because it is easy to implement | | | | synthesis of polymer particles" Lab Chip, 2009, 9, |
| and less sensitive to protein fouling problems. | | | | 2715 - 2721, DOI: 10.1039/b906626h. ^ Herold, KE; |
| Continuous-flow devices are adequate for many | | | | Rasooly, A (editor) (2009). Lab-on-a-Chip Technology: |
| well-defined and simple biochemical applications, and | | | | Fabrication and Microfluidics. Caister Academic Press. |
| for certain tasks such as chemical separation, but | | | | ISBN 978-1-904455-46-2. ^ a b Herold, KE; Rasooly, |
| they are less suitable for tasks requiring a high | | | | A (editor) (2009). Lab-on-a-Chip Technology: |
| degree of flexibility or complicated fluid manipulations. | | | | Biomolecular Separation and Analysis. Caister |
| These closed-channel systems are inherently difficult | | | | Academic Press. ISBN 978-1-904455-47-9. ^ Chang, |
| to integrate and scale because the parameters that | | | | H.C., Yeo, Leslie (2009). Electrokinetically Driven |
| govern flow field vary along the flow path making | | | | Microfluidics and Nanofluidics. Cambridge University |
| the fluid flow at any one location dependent on the | | | | Press. ^ Fan et al. (2009). "Two-Dimensional |
| properties of the entire system. Permanently-etched | | | | Electrophoresis in a Chip". Lab-on-a-Chip Technology: |
| microstructures also lead to limited reconfigurability | | | | Biomolecular Separation and Analysis. Caister |
| and poor fault tolerance capability. Process monitoring | | | | Academic Press. ISBN 978-1-904455-47-9. ^ |
| capabilities in continuous-flow systems can be | | | | Bontoux et al. (2009). "Elaborating Lab-on-a-Chips for |
| achieved with highly sensitive microfluidic flow | | | | Single-cell Transcriptome Analysis". Lab-on-a-Chip |
| sensors based on MEMS technology which offer | | | | Technology: Biomolecular Separation and Analysis. |
| resolutions down to the nanoliter range. Digital | | | | Caister Academic Press. ISBN 978-1-904455-47-9. ^ |
| (droplet-based) microfluidics Alternatives to the | | | | Cady, NC (2009). "Microchip-based PCR Amplification |
| above closed-channel continuous-flow systems include | | | | Systems". Lab-on-a-Chip Technology: Biomolecular |
| novel open structures, where discrete, independently | | | | Separation and Analysis. Caister Academic Press. ISBN |
| controllable droplets are manipulated on a substrate | | | | 978-1-904455-47-9. ^ Keymer J.E., P. Galajda, C. |
| using electrowetting. Following the analogy of digital | | | | Muldoon R., and R. Austin (November 2006). "Bacterial |
| microelectronics, this approach is referred to as digital | | | | metapopulations in nanofabricated landscapes". PNAS |
| microfluidics, which was pioneered as the "fluid | | | | 103 (46): 17290-295. doi:10.1073/pnas.0607971103. ^ |
| transistor" by Cytonix and subsequently | | | | Galajda P, J.E. Keymer, P Chaikin, R. Austin |
| commercialized by Duke University. By using discrete | | | | (December 2007). "A Wall of Funnels Concentrates |
| unit-volume droplets, a microfluidic function can be | | | | Swimming Bacteria". Journal of Bacteriology 189 (23): |
| reduced to a set of repeated basic operations, i.e., | | | | 8704-8707. doi:10.1128/JB.01033-07. ^ Angelani L., R. |
| moving one unit of fluid over one unit of distance. | | | | Di Leonardo, G. Ruocco (2009). "Self-Starting |
| This "digitization" method facilitates the use of a | | | | Micromotors in a Bacterial Bath". Phys. Rev. Let. 102: |
| hierarchical and cell-based approach for microfluidic | | | | 048104. doi:10.1103/PhysRevLett.102.048104. ^ Di |
| biochip design. Therefore, digital microfluidics offers a | | | | Leonardo R, L. Angelani , G. Ruocco, V. Iebba, M.P. |
| flexible and scalable system architecture as well as | | | | Conte, S. Schippa, F. De Angelis, F. Mecarini, E. Di |
| high fault-tolerance capability. Moreover, because | | | | Fabrizio (October 2009). "A bacterial ratchet motor". |
| each droplet can be controlled independently, these | | | | arXiv:Condensed Matter.Statistical Mechanics. ^ |
| systems also have dynamic reconfigurability, whereby | | | | Sokolova A., M.M. Apodacac, B.A. Grzybowskic, I.S. |
| groups of unit cells in a microfluidic array can be | | | | Aransona (December 2009). "Swimming bacteria |
| reconfigured to change their functionality during the | | | | power microscopic gears". PNAS 107 (3): 969-974. |
| concurrent execution of a set of bioassays. Although | | | | doi:10.1073/pnas.0913015107. ^ Liquid micro-lens |
| droplets are manipulated in confined microfluidic | | | | array activated by selective electrowetting on lithium |
| channels, since the control on droplets is not | | | | niobate substrates S. Grilli, L. Miccio, V. Vespini, A. |
| independent, it should not be confused as "digital | | | | Finizio, S. De Nicola, and P. Ferraro Optics Express 16, |
| microfluidics". One common actuation method for | | | | 8084-8093 (2008). ^ P. Ferraro, L. Miccio, S. Grilli, A. |
| digital microfluidics is electrowetting-on-dielectric | | | | Finizio, S. De Nicola, and V. Vespini, "Manipulating Thin |
| (EWOD). Many lab-on-a-chip applications have been | | | | Liquid Films for Tunable Microlens Arrays," Optics |
| demonstrated within the digital microfluidics paradigm | | | | & Photonics News 19, 34-34 (2008) ^ Water |
| using electrowetting. However, recently other | | | | Management in PEM Fuel Cells ^ Building a Better Fuel |
| techniques for droplet manipulation have also been | | | | Cell Using Microfluidics ^ Fuel Cell Initiative at MnIT |
| demonstrated using Surface Acoustic Waves, | | | | Microfluidics Laboratory Further reading Review |
| optoelectrowetting etc. DNA chips (microarrays) Early | | | | Papers Whitesides, G. M.; "The origins and the future |
| biochips were based on the concept of a DNA | | | | of microfluidics"; Nature 2006, 442, 368-373. Squires, |
| microarray, e.g., the GeneChip DNAarray from | | | | T. M.; Quake, S. R.; Reviews of Modern Physics 2005, |
| Affymetrix, which is a piece of glass, plastic or silicon | | | | 77, 977-1026. Microfluidics: Fluid physics at the |
| substrate on which pieces of DNA (probes) are | | | | nanoliter scale Books Herold, KE; Rasooly, A (editor) |
| affixed in a microscopic array. Similar to a DNA | | | | (2009). Lab-on-a-Chip Technology: Fabrication and |
| microarray, a protein array is a miniature array where | | | | Microfluidics. Caister Academic Press. ISBN |
| a multitude of different capture agents, most | | | | 978-1-904455-46-2. Herold, KE; Rasooly, A (editor) |
| frequently monoclonal antibodies, are deposited on a | | | | (2009). Lab-on-a-Chip Technology: Biomolecular |
| chip surface; they are used to determine the | | | | Separation and Analysis. Caister Academic Press. ISBN |
| presence and/or amount of proteins in biological | | | | 978-1-904455-47-9. External links Wikibooks has a |
| samples, e.g., blood. A drawback of DNA and protein | | | | book on the topic of Microfluidics Biomicrofluidics, an |
| arrays is that they are neither reconfigurable nor | | | | open access, peer reviewed journal published by the |
| scalable after manufacture. Digital microfluidics has | | | | American Institute of Physics MEMSuniverse, a |
| been described as a means for carrying out Digital | | | | Videos and animations of Microfluidic devices and their |
| PCR. Molecular biology In addition to microarrays | | | | applications Supercool microfluidics - Our |
| biochips have been designed for two-dimensional | | | | understanding of life and technology at extreme |
| electrophoresis, transcriptome analysis, and PCR | | | | temperatures could become clearer thanks to a |
| amplification. Other applications include various | | | | microfluidic device that studies ice formation reported |
| electrophoresis and liquid chromatography applications | | | | in Chemical Technology from the Royal Society of |
| for proteins and DNA, cell separation, in particular | | | | Chemistry From microfluidic applications to nanofluidic |
| blood cell separation, protein analysis, cell manipulation | | | | phenomena - a Chem Soc Rev themed issue |
| and analysis including cell viability analysis and | | | | showcasing the latest advances in microfluidic and |
| microorganism capturing. Evolutionary biology Three | | | | nanofluidic research, guest edited by Albert van den |
| Micro Habitat Patches MHPs connected by dispersal | | | | Berg, Harold Craighead and Peidong Yang. |