Virus filters for medical diagnosis( This release is available in A HREF h...),Health

Providing reliable evidence of viruses in human blood presently requires time- and labor-intensive molecular-biological procedures. Established methods are particularly hard pushed to produce evidence when the viral burden is very low, for example during a phase of therapy. This could soon change. While developing new types of micro-pumps without movable parts, scientists from the Fraunhofer Institute for Biomedical Engineering IBMT came across an unexpected phenomenon: stable turbulence structures formed in the microscale pump channels. The nano- and microparticles actually intended to verify the pump effect accumulated in large quantities in the channels. The vortex patterns completely filled the whole microchannel, creating a virtually 100% trap for the particles that followed the generated flow profile, although there is a very large cross-section to flow through. "The development of flow vortices is nothing unusual on the macroscopic scale. However, in microchannels the flow lines almost run in parallel," explains Richard Stein from the IBMT. "The question, therefore, was, how is it possible for vortices to be formed from this which were sufficiently stable and effective for the concentration of nanoparticles?"

Experiments were not successful in determining the parameters by which the filter effect could be systematically controlled. This is because in the pump mechanism examined, high-frequency electrical traveling waves propel the fluid into the microchannels, superimposing a large number of effects on one another.

"In order to understand the complex procedures, there was a clear need for a theoretical description. My task was to describe the surprising phenomenon and to make it controllable," reflects Richard Stein. In his thesis "Mathematical modeling, analysis and numerical simulation of electr
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