Recent advances in microparticle continuous separation.

Heriot-Watt University, MIcroSystems Engineering Centre, School of Engineering and Physical Sciences, Edinburgh, UK.
IET Nanobiotechnology (Impact Factor: 1.72). 04/2008; 2(1):1-13. DOI: 10.1049/iet-nbt:20070025
Source: PubMed

ABSTRACT Recent advances in microparticle separation in continuous flow are presented. It is intended for scientists in the field of separation science in biology, chemistry and microsystems engineering. Recent techniques of micron-sized particle separation within microsystems are described with emphasis on five different categories: optical, magnetic, fluidic-only, electrical and minor separation methods. Examples from the growing literature are explained with insights on separation efficiency and microengineering challenges. Current applications of the techniques are discussed.

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    ABSTRACT: Free-flow magnetophoresis provides a fast and efficient means of continuous flow magnetic separation for the detection of biological analytes, due to the wide variety of magnetic particle surface properties available for binding specific targets. Here, we investigate the effect of temperature changes on the deflection behaviour of magnetic particles in a microfluidic magnetophoresis separation chamber. It was found that the extent of deflection was greatly increased at higher temperatures due to decreased solution viscosity and thus reduced resistance against particle motion. This concept was used to improve the resolution of the separation of 2.8 µm and 1 µm diameter magnetic particles. Hence, controlling the temperature of the separation system provides a simple but highly effective means of enhancing magnetic separation efficiency. This concept could also be applied to the temperature-based tuning of microparticle trajectories in many others types of continuous flow processes, such as those using optical, electrical or acoustic forces.
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    ABSTRACT: Separation and sorting of micron-sized particles has great importance in diagnostics, chemical and biological analyses, food and chemical processing and environmental assessment. By employing the unique characteristics of microscale flow phenomena, various techniques have been established for fast and accurate separation and sorting of microparticles in a continuous manner. The advancements in microfluidics enable sorting technologies that combine the benefits of continuous operation with small-sized scale suitable for manipulation and probing of individual particles or cells. Microfluidic sorting platforms require smaller sample volume, which has several benefits in terms of reduced cost of reagents, analysis time and less invasiveness to patients for sample extraction. Additionally, smaller size of device together with lower fabrication cost allows massive parallelization, which makes high-throughput sorting possible. Both passive and active separation and sorting techniques have been reported in literature. Passive techniques utilize the interaction between particles, flow field and the channel structure and do not require external fields. On the other hand, active techniques make use of external fields in various forms but offer better performance. This paper provides an extensive review of various passive and active separation techniques including basic theories and experimental details. The working principles are explained in detail, and performances of the devices are discussed.
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