Droplet-Based Microfluidics as a Biomimetic Principle: From PCR-Based Virus Diagnostics to a General Concept for Handling of Biomolecular Information

Abstract

The ability of lithographic fabrication of microchannels for fluid transport on the one hand and the continuously decreasing critical dimensions during the development of microlithography over the last decades generated high expectations on the progress of automated processing of small amounts of substances. In particular, it was expected that large numbers of well distinguished chemical entities-atoms, molecules, nano particles-could become manipulated highly parallel and with high speed. This hope was fed by the imagination of an analogy between the electron transport in integrated circuits and the transport of chemical objects inside microfluidic networks. The experiences of the last both decades had shown that such ideas of a complete analogy are not realistic. The progress of handling of substance-coupled information is much slower as the progress of hard ware development in the electronic devices. But, beside this general disappointment, microfluidics is still promising the arise and growth-up of very important new strategies for organizing chemical systems at the microscale and for supplying functional interfaces between the complex information inside the world of molecules and particles on the one hand and electronic systems on the other hand.Whereas clouds of electrons are manipulated in digital electronic devices, clouds of molecules are transported through microchannels by a convective flow. But, the special conditions in microfluidics cause low Reynolds numbers which reflect the small ratio of channel diameter and volume flow rate to the viscous forces. The microfluidic conditions cause always a laminary structure of flow with steep flow velocity gradients and results in to very high fluidic dispersion of concentration signals if homogeneous fluids are applied. So, the principle high potential of J.M. K€ ohler