Magnetic Beads in Microfluidic Systems – Towards New Analytical Applications

Key advantages of using microfluidic systems of reduced dimension for analytical applications are known to be (a) the possibility of using minute quantities of sample and reagents (down to picoliters), (b) relatively fast reaction times, when molecular diffusion lengths are of the order of the microchannel dimension, and (c) a large surface-to-volume ratio offering an intrinsic compatibility between the use of a microfluidic system and surface-based assays. Reviews of various fluidic operations in microfluidic systems, like sample preparation, sample injection, sample manipulation, reaction, separation and detection, published in the period 1998–2004, were presented by Auroux et al. [1] and Vilkner et al. [2].

Also nanomaterials and nanoparticles have become a hot topic in research. Functional nano- and microparticles (‘beads’) offer a large specific surface for chemical binding and a polymer colloid or microsphere solution has a low viscosity compared to solutions having the same amount of solid, giving it special properties. Such small particles can be advantageously used as a ‘mobile substrate’ for bio-assays or even for in vivo applications; they can be easily recovered from a dispersion, reversibly re-dispersed etc. Several reviews on the preparation and use of polymer particles and polymer colloids for medical, biological and optical applications exist [3, 4].