This paper reviews the centrifugal 'Bio-Disk' platform which is based on rotationally controlled, multi-scale liquid handling to fully integrate and automate complex analysis and synthesis protocols in the life sciences. The platform offers the crucial ingredients for a rapid development of applications: a coherent library of fluidic unit operations, a device technology for actuation, liquid interfacing and detection as well as a developer toolbox providing experimental testing, rapid prototyping and simulation capabilities. Various applications in the fields of life science, in vitro diagnostics and micro-process engineering are demonstrated.

For the first time we demonstrate a self-sufficient lab-on-a-foil system for the fully automated analysis of nucleic acids which is based on the recently available isothermal recombinase polymerase amplification (RPA). The system consists of a novel, foil-based centrifugal microfluidic cartridge including prestored liquid and dry reagents, and a commercially available centrifugal analyzer for incubation at 37 degrees C and real-time fluorescence detection. The system was characterized with an assay for the detection of the antibiotic resistance gene mecA of Staphylococcus aureus. The limit of detection was <10 copies and time-to-result was <20 min. Microfluidic unit operations comprise storage and release of liquid reagents, reconstitution of lyophilized reagents, aliquoting the sample into < or = 30 independent reaction cavities, and mixing of reagents with the DNA samples. The foil-based cartridge was produced by blow-molding and sealed with a self-adhesive tape. The demonstrated system excels existing PCR based lab-on-a-chip platforms in terms of energy efficiency and time-to-result. Applications are suggested in the field of mobile point-of-care analysis, B-detection, or in combination with continuous monitoring systems.

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 new method for aliquoting liquids on the centrifugal microfluidic platform. Aliquoting is an essential unit operation to perform multiple parallel assays (''geometric multiplexing'') from one individual sample, such as genotyping by real-time polymerase chain reactions (PCR), or homogeneous immunoassay panels. Our method is a two-stage process with an initial metering phase and a subsequent transport phase initiated by switching a centrifugo-pneumatic valve. The method enables aliquoting liquids into completely separated reaction cavities. It includes precise metering that is independent on the volume of prestored reagents in the receiving cavities. It further excludes any cross-contamination between the receiving cavities. We characterized the performance for prototypes fabricated by three different technologies: micro-milling, thermoforming of foils, and injection molding. An initial volume of *90 ll was split into 8 aliquots of 10 ll volume each plus a waste reservoir on a thermoformed foil disk resulting in a coefficient of variation (CV) of the metered volumes of 3.6%. A similar volume of *105 ll was split into 16 aliquots of 6 ll volume each on micro-milled and injection-molded disks and the corresponding CVs were 2.8 and 2.2%, respectively.Thus, the compatibility of the novel aliquoting structure to the aforementioned prototyping and production technologies is demonstrated. Additionally, the important question of achievable volume precision of the aliquoting structure with respect to the production tolerances inherent to each of these production technologies is addressed experimentally and theoretically. The new method is amenable to low cost mass production, since it does not require any post-replication surface modifications like hydrophobic patches.

We designed and experimentally validated a new type of passive valve for centrifugal microfluidic platforms. A liquid column entering an unvented receiving chamber is stopped by the counter-pressure of compressed air. This valve opens under defined conditions at high centrifugal frequencies at which the interface between liquid and air becomes unstable and enables a phase exchange, forwarding the liquid. Burst frequencies of the valve were determined for liquids typically used in biochemical assays: pure water, water with detergent concentrations between 0.01 and 10%, and pure ethanol. Burst frequencies between 8.5 +/- 0.6 and 27.9 +/- 2.0 Hz were measured for different surface tensions. The burst frequencies can be tuned by simple geometrical changes in the valving structure. The valve does not require ultra-precise structures or local surface modifications and is therefore ideal for low-cost microfluidic polymer disks. Potential applications are in the field of multiparameter and panel analysis, such as PCR-genotyping.

Self-containing, ready-to-use cartridges are essential for mobile Lab-on-a-Chip (LoaC) systems intended for Point-of-Care (POC) use. Up to now, a common weak point in many LoaC developments is the need to dispense liquid reagents into the test cartridge before or during processing of the assay. To address this issue we have developed an efficient method for fusing liquid reagents into glass ampoules, which are then sealed into a centrifugally operated cartridge. For on-demand reagent release, the ampoules are disrupted through the flexible lid of the cartridge. Upon centrifugation, 98.7 microL out of 100 microL (CV = 2.5%) of the pre-stored contents are released into the microfluidic system. No liquid loss is observed for ethanol and H(2)O stored for 300 days at room temperature. Frozen storage is possible without damage to the ampoules. Applicability of this concept is demonstrated by performing a LoaC integrated DNA extraction after 140 days of reagent pre-storage. DNA yield from 32 microL of whole blood was up to 199 ng, which is 77% of an off-chip reference extraction. The presented approach allows the improvement of existing LoaC cartridges where pre-storage of liquid reagents was not implemented yet.

We present a novel concept to process human blood on a spinning polymer disk for the determination of the hematocrit level by simple visual inspection. The microfluidic disk which is spun by a macroscopic drive unit features an upstream metering structure and a downstream blind channel where the centrifugally enforced sedimentation of the blood is performed. The bubble-free priming of the blind channel is governed by centrifugally assisted capillary filling along the sloped hydrophilic side-wall and the lid as well as the special shape of the dead end of the two-layer channel. The hematocrit is indicated at the sharp phase boundary between the plasma and the segregated cellular pellet on a disk-imprinted calibrated scale. This way, we conduct the hematocrit determination of human blood within 5 min at a high degree of linearity (R(2) = 0.999) and at a high accuracy (CV = 4.7%) spanning over the physiological to pathological working range. As all processing steps including the priming, the metering to a defined volume as well as the centrifugation are executed automatically during rotation, the concept is successfully demonstrated in a conventional PC-CDROM drive while delivering the same performance (R(2) = 0.999, CV = 4.3%).

We provide a method for the selective surface patterning of microfluidic chips with hydrophobic fluoropolymers which is demonstrated by the fabrication of hydrophobic valves via dispensing. It enables efficient optical quality control for the surface patterning thus permitting the low-cost production of highly reproducible hydrophobic valves. Specifically, different dyes for fluoropolymers enabling visual quality control (QC) are investigated, and two fluoropolymer-solvent-dye solutions based on fluorescent quantum dots (QD) and carbon black (CB) are presented in detail. The latter creates superhydrophobic surfaces on arbitrary substrates, e.g. chips made from cyclic olefin copolymer (COC, water contact angle = 157.9 •), provides good visibility for the visual QC in polymer labs-on-a-chip and increases the burst pressures of the hydrophobic valves. Finally, an application is presented which aims at the on-chip amplification of mRNA based on defined flow control by hydrophobic valves is presented. Here, the optimization based on QC in combination with the Teflon-CB coating improves the burst pressure reproducibility from 14.5% down to 6.1% compared to Teflon-coated valves.