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Summary: NEST Scientific Report 2007-2009
Surface-acoustic-wave driven lab-on-chip technologies
71
T
he increasing demand for low-cost and portable devices for biomedical applications
has stimulated the development of advanced micro-total-analysis systems (µTAS). The
miniaturization of these devices led to better performance with respect to traditional
analytical methods, since it involved smaller quantities of samples and reagents, allowing
more reactions to occur in parallel on the same chip, more quickly and effectively, and with
reduced manual intervention[1]. For a full exploitation of the advantages of microfluidics
one needs highly controlled liquid flows into biochips. In the common case of hydrophobic
capillaries, polar fluids must be forced into microchannels by means of active pumping
elements, overcoming the large resistance to flow due to small microchannel sections. The
existing pumping systems typically rely on external pressurized lines, which severely limit
the portability of microfluidic systems. In the last years, the interaction between surface
acoustic waves (SAWs) and liquids began to be studied as a pumping approach, relying
on the streaming effect that drives the fluid flow in the direction of SAW propagation[2].
SAW methods have been mainly limited to mixing, localization or transport of droplets
deposited on planar substrates, preferably patterned by regions of different wettability. The
main issues of such open digitalized microfluidic architectures are the liquid evaporation
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