Hardt S. – TechConnect Briefs

Iron-oxide nanoparticle synthesis from liquid spray flames under variable pressure conditions

Hardt S., Wiggers H., Wlokas I., Kempf A., Schulz C., University of Duisburg-Essen, DE

Iron-oxide nanoparticles have been synthesized via liquid-fed flame spray pyrolysis (FSP) under variable pressure conditions. The work focuses on the effect of pressure, precursor flow rate, and flame stoichiometry on particle size, composition, and morphology. [...]

Methods of energizing micro flows by acoustic and electric fields

Schönfeld F., Dadic D., Hardt S., Püschl R., Schmitz F., Institut für Mikrotechnik Mainz –(IMM), DE

We present two different concepts for energizing (e.g. mixing, pumping) of micro flows, which rely on the coupling of acoustic and electromagnetic energy into a liquid. Both concepts are analyzed using computational fluid dynamics (CFD) [...]

Design Paradigms and Methodologies for Microfluidics

Hardt S., Darmstadt University of Technology, DE

This paper reviews and compares different strategies for designing and building up microfluidic systems, with a special emphasis on the system aspect as opposed to single components capable of performing only special operations. An overwhelming [...]

Optimized Distributive u-Mixing by Chaotic Multilamination

Schönfeld F., Drese K.S., Hardt S., Hessel V., Hofmann C., Institut für Mikrotechnik Mainz –(IMM), DE

We present a new type of micro mixer relying on a multi-step split-and-recombine (SAR) approach. Using computational fluid dynamics (CFD), a favourable mixer design is identified which allows for an almost ideal multilamination. The numerical [...]

Development of a Slug-Flow PCR Chip with Minimum Heating Cycle Times

Hardt S., Dadic D., Doffing F., Drese K.S., Münchow G., Sörensen O., Institute of Microtechnology Mainz, DE

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 [...]

CFD-based Optimization of Gas/Liquid Microreactors with Droplet and Bubble Transport

Hardt S., Pennemann H., Jiang F., Institute of Microtechnology Mainz, DE

Microreactors offer unique opportunities for the control of process parameters unparalleled by macroscopic equipment. A new gas/liquid microreactor is proposed allowing for fast mass transfer and small concentration gradients as well as a very narrow [...]

Simulation of Hydrodynamic Dispersion in Gas/Liquid Microreactors

Hardt S., Doffing F., Pennemann H., Institut für Mikrotechnik Mainz GmbH, DE

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. [...]

Simulation of Droplet Formation in Micromixers

Hardt S., Schönfeld F., Weise F., Hofmann C., Ehrfeld W., Institut für Mikrotechnik, DE

Droplet formation in micromixers developed by the Institute of Microtechnology Mainz (IMM) is investigated by methods of computational fluid dynamics (CFD). The CFD results are compared to experimental data obtained with transparent micromixers made from [...]

Simulation of Heat-Transfer Enhancement Effects in Microreactors

Hardt S., Ehrfeld W., Hessel V., Vanden Bussche K.M., Institut für Mikrotechnik Mainz GmbH, DE

Sate-of-the-art microstructuring techniques allow to model the interface for heat and mass transfer in miniaturized reactions systems on a micrometer scale. In this context, two different approaches for heat transfer enhancement are presented. The ideas [...]