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Microfluidics: Fluid physics at the nanoliter scale

Squires, Todd M. and Quake, Stephen R. (2005) Microfluidics: Fluid physics at the nanoliter scale. Reviews of Modern Physics, 77 (3). pp. 977-1026. ISSN 0034-6861. http://resolver.caltech.edu/CaltechAUTHORS:SQUrmp05

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Abstract

Microfabricated integrated circuits revolutionized computation by vastly reducing the space, labor, and time required for calculations. Microfluidic systems hold similar promise for the large-scale automation of chemistry and biology, suggesting the possibility of numerous experiments performed rapidly and in parallel, while consuming little reagent. While it is too early to tell whether such a vision will be realized, significant progress has been achieved, and various applications of significant scientific and practical interest have been developed. Here a review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena. Specifically, this review explores the Reynolds number Re, addressing inertial effects; the Péclet number Pe, which concerns convective and diffusive transport; the capillary number Ca expressing the importance of interfacial tension; the Deborah, Weissenberg, and elasticity numbers De, Wi, and El, describing elastic effects due to deformable microstructural elements like polymers; the Grashof and Rayleigh numbers Gr and Ra, describing density-driven flows; and the Knudsen number, describing the importance of noncontinuum molecular effects. Furthermore, the long-range nature of viscous flows and the small device dimensions inherent in microfluidics mean that the influence of boundaries is typically significant. A variety of strategies have been developed to manipulate fluids by exploiting boundary effects; among these are electrokinetic effects, acoustic streaming, and fluid-structure interactions. The goal is to describe the physics behind the rich variety of fluid phenomena occurring on the nanoliter scale using simple scaling arguments, with the hopes of developing an intuitive sense for this occasionally counterintuitive world.


Item Type:Article
Additional Information:©2005 The American Physical Society (Published 6 October 2005) We are grateful to Armand Ajdari, W. French Anderson, Martin Bazant, John Brady, Gary Leal, Gareth McKinley, and Howard Stone for critical readings of the manuscript, and their many detailed comments and suggestions. Helpful conversations with Jian Gong, Carl Hansen, Eric Lauga, and Aaron Wheeler are gratefully acknowledged. T.M.S. gratefully acknowledges support from a Lee A. Dubridge Prize Postdoctoral Fellowship at Caltech and an NSF Mathematical Sciences Postdoctoral Fellowship.
Subject Keywords:microfluidics; convection; deformation; laminar flow; viscosity; reviews; acoustic streaming; liquid structure
Record Number:CaltechAUTHORS:SQUrmp05
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:SQUrmp05
Alternative URL:http://dx.doi.org/10.1103/RevModPhys.77.977
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1310
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:09 Jan 2006
Last Modified:26 Dec 2012 08:43

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