A chip-based PCR device is presented that is capable of rapid temperature ramping and handling sample volumes in the microliter range. The PCR chip comprises a microchannel thermally connected to three temperature zones. Inside this microchannel, the PCR sample plug is driven and precisely positioned by a ferrofluidic actuator for more than 40 cycles within 5 min. Computer simulations predict that the sample plugs are thermally equilibrated on a time scale of some 10 ms when transported to a different temperature zone. Hence, the thermal limitations on the cycle speed of the system are considerably reduced compared with conventional cyclers. The system was developed on a modular platform suitable for handling further microfluidic tasks such as DNA extraction and preparation of the PCR mix. Thus, the aspired chip-based platform represents not only a PCR system but a complete analysis system, from the injection of a patient's blood sample to its final appraisal.

A chip based PCR device is presented capable of rapid temperature ramping and handling of sample volumes in the microliter and nanoliter range. The PCR chip, existing of PMMA or COC, comprises of a microchannel that is positioned above three temperature zones. Inside this microchannel the PCR sample plug is driven precisely by a ferrofluidic actuator for over 40 cycles. Computer simulations suggest that the sample plugs are heated or cold on a time scale of some ten milliseconds when transported to a different temperature zone. Hence the thermal limitations on the speed of the system are minimized. The system was developed on a modular platform that can also handle other microfluidic tasks like extraction and preparation of the master mix.

A microfluidic PCR device is presented capable of rapid temperature ramping and handling of sample volumes in the microliter and submicroliter range. The PCR chip comprises a straight micro channel in which a sample slug is periodically moved over three temperature zones. As part of the sample preparation a method for metering of the sample volume was developed. The PCR chip and the chips for sample preparation and fluidic actuation were fabricated by ultra-precision milling in polymer substrates. Computer simulations suggest that the sample slugs are heated or cooled on a time scale of some ten milliseconds when transported to a different temperature zone. The fluidic actuation based on a ferrofluid transducer is capable of positioning the sample volumes with a high accuracy after a large number of cycles. The design developed should be ideally suited for fast PCR of small sample amounts in a highly parallel manner.

Dispersion and spreading of concentration signals in gas/liquid microreactors is studied with methods of computational fluid dynamics (CFD). It is shown that conventional reactor designs exhibit a broad residence-time distribution due to convective signal dispersion. This result is supported by experiments monitoring the transport of a liquid plug introduced into the microreactor by a microdispenser. A new reactor design is proposed which exhibits a more favorable velocity profile by guiding the liquid stream over alternating platelets. With simulations based on the volume-of-fluid (VOF) method it is shown that a thin, continuous liquid film forms inside the reactor. Subsequently, the transport of concentration fields described by a convection-diffusion equation is studied. It is found that, due to the approximate plug-flow character of fluid motion within this film, concentration signals experience significantly lower dispersion than in the conventional design. The new reactor design will provide the basis of a new class of gas/liquid microreactors to be developed at the Institute of Microtechnology Mainz.