Microfluidic Apps for off-the-shelf instruments

Within the last decade a huge increase in research activity in microfluidics could be observed. However, despite several commercial success stories, microfluidic chips are still not sold in high numbers in mass markets so far. Here we promote a new concept that could be an alternative approach to commercialization: designing microfluidic chips for existing off-the-shelf instruments. Such "Microfluidic Apps" could significantly lower market entry barriers and provide many advantages: developers of microfluidic chips make use of existing equipment or platforms and do not have to develop instruments from scratch; end-users can profit from microfluidics without the need to invest in new equipment; instrument manufacturers benefit from an expanded customer base due to the new applications that can be implemented in their instruments. Microfluidic Apps could be considered as low-cost disposables which can easily be distributed globally via web-shops. Therefore they could be a door-opener for high-volume mass markets.     

Fully vectorial eigenmode calculation of dielectric waveguides using a Rayleigh--Ritz method with rational basis functions

A fully vectorial Rayleigh--Ritz method for the eigenmode calculation of dielectric waveguides is presented. It uses the four transversal field components and takes rational functions as an orthonormal basis. This formalism is especially useful near the cutoff frequency and has been applied for the investigation of the polarization properties of the output waveguides in integrated spot-size transformers. This revised version was published online in November 2006 with corrections to the Cover Date.     

Essential oil composition of wild growing Apiaceae from Europe and the Mediterranean

In this overview, the essential oil composition of more than 150 species from about 50 genera of the Apiaceae is reviewed. Essential oil components encountered in Apiaceae proved to be very diverse; they include monoterpenes, sesquiterpenes, rarely diterpenes, phenylpropanoids, phthalides, octanol and octyl esters, trimethylbenzaldehydes and aliphatic aldehydes. In assessing the data one has to keep in mind that the essential oil amount and composition is influenced by many factors, including geographic and genetic variation, physiological aspects and environmental conditions. In some species the occurrence of chemotypes could be demonstrated, but in many cases the data available do not allow the evaluation of infraspecific variability.     

Fully integrated whole blood testing by real-time absorption measurement on a centrifugal platform

We present a novel microfluidic concept to enable a fast colorimetric alcohol assay from a single droplet of whole blood. The reduced turn-around time of 150 seconds is, on the one hand, achieved by a full process integration including metering, mixing with reagents, and sedimentation of cellular constituents. On the other hand, our novel total internal reflection (TIR) scheme allows to monitor the increase of the absorbance values in real-time. Thus, the saturation values can be predicted accurately based on an extrapolation of real-time measurements acquired during a 100 second initial period of rotation. Additionally, we present a metering structure to define nanolitre sample volumes at a coefficient of variation (CV) below 5%.     

Centrifugal extraction of plasma from whole blood on a rotating disk

We present a centrifugal process for the extraction of plasma from sediment by a decanting structure, terminating with metered plasma which is readily available for subsequent on-disk processing. Our technique supplies 2 microl plasma from 5 microl of whole blood at moderate spinning frequencies of 40 Hz within 20 s, only. The residual cell concentration in the purified plasma amounts to less than 0.11%, independent of the frequency of rotation. A capillary duct connects the extracted plasma to subsequent on-disk processing units.     

Ueber Kapillarsysteme,XIII. Der Einfluß der Gerüststruktur technischer Kapillarsysteme auf physikalisch-chemische Vorgänge, 2

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