We present a novel, cost-efficient process chain for fast tooling and small-lot replication of high-quality, multi-scale microfluidic polymer chips within less than 5 days. The fabrication chain starts with a primary master which is made by well-established cleanroom processes such as DRIE or negative SU-8 resist based surface micromachining. The formation of undercuts in the master which would complicate demolding is carefully avoided. Secondary PDMS masters or epoxy-based masters which are more suitable for common polymer replication schemes such as soft-embossing, hot-embossing or injection molding are subsequently cast from the primary masters. The polymer replica are mainly made of COC and show excellent fidelity with the conventionally micromachined master while displaying no degeneration, even after more than 200 cycles. The use of other polymers such as PMMA is also possible. The process chain further includes surface modification techniques for overall, long-term stable hydrophilic coatings and for local hydrophobic patches as well as a durable sealing based on thermal bonding.

In this paper, we present a novel and fully integrated centrifugal microfluidic "lab-on-a-disk" for rapid colorimetric assays in human whole blood. All essential steps comprising blood sampling, metering, plasma extraction and the final optical detection are conducted within t=150 s in passive, globally hydrophilized structures which obviate the need for intricate local hydrophobic surface patterning. Our technology features a plasma extraction structure (V=500 nL, CV<5%) where the purified plasma (cRBC<0.11%) is centrifugally separated, metered by an overflow and subsequently extracted by a siphon-based principle through a hydrophilic extraction channel into the detection chamber.

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%.

This paper reports on the design, fabrication and characterization of silicon-based microprobes for simultaneous neural recording and drug delivery. The fabrication technology is based on two-stage deep reactive ion etching combined with silicon wafer bonding and grinding to realize channel structures integrated in needle-like probe shafts. Liquids can be supplied to microfluidic devices via in-plane and out-of-plane ports. The liquid is dispensed at circular out-of-plane ports with a diameter of 25 μm and rectangular in-plane ports with dimensions of 50 × 50 μm 2. Two-shaft probes with a pitch between shafts of 1.0 and 1.5 mm were realized. The probe shafts have a length of 8 mm and rectangular cross-sections of w × h (w = 250 μm and h = 200 or 250 μm). Each shaft contains one or two fluidic channels with a cross-section of 50 × 50 μm 2. In addition, each probe shaft comprises four recording sites with diameters of 20 μm close to the outlet ports. Mechanical and fluidic characterization demonstrated the functionality of the probes. Typical infusion rates of 1.5 μL min −1 are achieved at a differential pressure of 1 kPa. The Pt-gray electrodes have an average electrode impedance of 260 ± 59 k at 1 kHz.

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.

W e extend the toolbox of lab procedures in life sciences by development of centrifugal microfluidics for high-level process integration. This is accomplished by implementing novel functional principles for sedimentation, batch-mode mixing, frequencydependent online flow control, and optical read-out, which can be integrated into a process chain. The modular centrifugal setup comprises a microstructured disposable polymer disk as well as a reusable spinning and detection unit. We successfully developed centrifugal microfluidic technologies, which are suitable for sample preparation, process engineering, personalized diagnostics, and hematology, on this platform. (JALA 2005;10:331-41)

Based on a centrifugally-controlled ballpen-mechanism, the LabTube enables cost-efficient assay automation at even low sample throughput using standard centrifuges.

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