Microscale Field-Flow Fractionation: Theory and Practice
The last decade has seen exponential growth in the development of lab-on-a-chip or micro-total-analysis system (μ-TAS) components to create better, faster, and cheaper chemical and biological analysis platforms . Lab-on-a-chip type analysis systems typically include a separation-based sample preparation unit to achieve this objective or to prepare the sample for further interrogation using orthogonal techniques. Researchers have employed a host of sample preparation techniques based on electrophoresis [2, 3], ultrasound [4, 5], flow [6, 7], mechanical ratchets [8, 9], electrokinetics [10, 11], packed bed systems , membranes  magnetics [14, 15], temperature , optics , dielectrophoresis [18, 19], and so forth. Microscale field-flow fractionation (FFF) techniques have been an integral part of these efforts. Most of these techniques are simply miniaturized versions of conventional macroscale units with the rationale being that the reduction in physical size of the instrument results in smaller sample volumes and faster analysis times. While, many of these systems work well when miniaturized, this approach proves inadequate for systems that do not scale well. FFF, at least for many subtypes, has been shown to scale very well and FFF meets many of the design challenges for a successful separation module in a μ-TAS including (a) ease of manufacturing, (b) low power, (c) wide range of sample type and size, (d) integration to fluidic components, and (e) material compatibility. Thus, FFF is potentially an important solution to many problems in microfluidic system design.
KeywordsEffective Field Channel Height Resonance Light Scattering Particle Cloud Retention Ratio
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