Biomedical subjects

R Zengerle

Publications and source records attributed to R Zengerle.

3 recordsLinked to original sources

PubMed2006

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%.

Blood Chemical Analysis↗

PubMed2006

Sensitivity enhancement for colorimetric glucose assays on whole blood by on-chip beam-guidance.

In this paper, we present a novel concept for optical beam-guidance to significantly enhance the sensitivity of colorimetric assays by extending the optical path length through the detection cell which linearly impacts the resulting attenuation of a probe beam according to the law of Beer-Lambert. In our setup, the incident probe beam is deflected by 90( composite function) into the chip plane at monolithically integrated V-grooves to pass a flat detection cell at its full width (i.e., with a path length of 10 mm) instead of its usually much smaller height. Afterwards, the attenuated beam is redirected by another V-groove towards an external detector. The general beam-guidance concept is demonstrated by a glucose assay on human whole blood on a centrifugal microfluidic "lab-on-a-disk" platform made of COC. We achieve an excellent linearity with a correlation coefficient (R (2)) of 0.997 paired with a lower limit of detection (200 microM) and a good reproducibility with a coefficient of variation (CV) of 4.0% over nearly three orders of magnitude. With an accelerated sedimentation of cellular constituents by centrifugal forces, the sample of whole blood can be analyzed in a fully integrated fashion within 210 s. This time-to-result can even be improved by the numerical extrapolation of the saturation value. Additionally, the direct assay on whole blood also shows a negligible correlation with the hematocrit of the blood sample.

Blood Chemical Analysis↗

PubMed2005

Batch-mode mixing on centrifugal microfluidic platforms.

We present two novel fluidic concepts to drastically accelerate the process of mixing in batch-mode (stopped-flow) on centrifugal microfluidic platforms. The core of our simple and robust setup exhibits a microstructured disk with a round mixing chamber rotating on a macroscopic drive unit. In the first approach, magnetic beads which are prefilled into the mixing chamber are periodically deflected by a set of permanent magnets equidistantly aligned at spatially fixed positions in the lab-frame. Their radial positions alternatingly deviate by a slight positive and negative offset from the mean orbit of the chamber to periodically deflect the beads inbound and outbound during rotation. Advection is induced by the relative motion of the beads with respect to the liquid which results from the magnetic and centrifugal forces, as well as inertia. In a second approach--without magnetic beads--the disk is spun upon periodic changes in the sense of rotation. This way, inertia effects induce stirring of the liquids. As a result, both strategies accelerate mixing from about 7 minutes for mere diffusion to less than five seconds. Combining both effects, an ultimate mixing time of less than one second could be achieved.

Centrifugation↗