Residence time distribution studies in microfluidic mixing structures. - In: Chemical engineering & technology, ISSN 1521-4125, Bd. 34 (2011), 3, S. 361-370
The residence time distribution (RTD) characteristics of three microreactors containing different passive mixing structures, namely, a three dimensional serpentine structure, a split-and-recombine structure and a staggered herringbone structure, were investigated and compared. An experimental input-response technique was applied which required deconvolution of the measured data by modeling of the RTD. The proposed technique provides useful information on optimized application and operation of microfluidic devices. The serpentine reactor and the split-and-recombine reactor show improvement in RTD behaviour, i.e., narrowing of RTD curves, at Re-numbers > 30 due to effective transversal mixing and therefore reduced axial dispersion. In the case of the staggered herringbone structure, dead volumes could be observed which considerably affect the RTD.
http://dx.doi.org/10.1002/ceat.201000352
Microtechnology in chemical engineering. - In: Chemical engineering & technology, ISSN 1521-4125, Bd. 34 (2011), 3, S. 330
http://dx.doi.org/10.1002/ceat.201190011
Cultivation of Chlorella vulgaris in microfluid segments and microtoxicological determination of their sensitivity against CuCl2 in the nanoliter range. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 11 (2011), 6, S. 580-587
The cultivation of the monocellular green alga Chlorella vulgaris was implemented into microfluid segments to demonstrate the possibility of an automated screening of toxic effects of the common algaecide CuCl2. Therefore, the nutritional as well as light and carbon dioxide requirements of the algae had to be adapted to the microfluidic device. Generally, sequences of about 350 fluid segments with single volumes of about 500 nL were applied for the dose-response experiments. The growth of algae cultures inside microfluidic segments was noninvasively measured by microflow through techniques using two different optical channels. A multi-endpoint detection was realized by the photometric characterization of cell density by transmission measurements and the measurement of density of autofluorescent cells. The different methods revealed comparable half maximal effective concentrations (EC50) in the range between 34.6 and 39.9 mg/mL for the toxicity of CuCl2 to the green algae C. vulgaris. By reference experiments in microtiter plates lower EC50 were achieved presumably caused by increased alkalinity of the growth medium due to higher photosynthesis. The results show that the microsegmented flow technique is well suited for the automated determination of dose/response functions for microorganisms like C. vulgaris and for the application of multi-endpoint procedures at the nanoliter scale.
http://dx.doi.org/10.1002/elsc.201100023
Editorial: microtechnology for life science applications. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 11 (2011), 2, S. 116-117
http://dx.doi.org/10.1002/elsc.201190011
Synergistic effects of metal nanoparticles and a phenolic uncoupler using microdroplet-based two-dimensional approach. - In: Journal of environmental monitoring, ISSN 1464-0333, Bd. 2 (2011), 13, S. 410-415
A droplet-based microfluidic technique for testing multiple reagent concentrations is presented. We used this experimental approach to study combined effects of gold (AuNP) and silver nanoparticles (AgNP) with the phenolic uncoupler 2,4-dinitrophenol (DNP) with respect to the growth of Escherichia coli. In order to evaluate the toxicity of binary mixtures, we first encapsulated the E. coli cells and particle mixtures inside the microdroplets using PEEK (polyetherketone) modules. Two-dimensional concentration spaces with about 500 well separated droplets were addressed. We subsequently analyzed the cell growth, the viability and the autofluorescence intensity (metabolic activity) of the bacteria with a micro-flow-through fluorometer and photometer. Dose-dependent synergistic effects were found for the binary mixture of AgNPs and DNP, which indicated a stronger interaction in the mixture than it was expected from effect summation. For the binary mixture of DNP and AuNPs in non-toxic concentrations, we found only weak synergistic effects at low DNP concentrations. Furthermore, the non-toxic tested AuNPs causes effect summation in the binary mixture with the phenolic uncoupler. In general, we demonstrated the efficiency of a droplet-based microfluidic system for fast high-throughput screenings of binary and multiple mixtures. This work also confirmed the relevance of highly resolved droplet-based assays for the miniaturization of ecotoxicological aquatic test systems.
http://dx.doi.org/10.1039/C0EM00162G
Convenient method for synthesis of thiazolo[3,2-a]pyrimidine derivatives in a one-pot procedure. - In: Tetrahedron letters, ISSN 1873-3581, Bd. 52 (2011), 29, S. 3814-3817
http://dx.doi.org/10.1016/j.tetlet.2011.05.067
Au/Ag/Au double shell nanoparticles with narrow size distribution obtained by continuous micro segmented flow synthesis. - In: The chemical engineering journal, ISSN 1873-3212, Bd. 166 (2011), 3, S. 1164-1169
http://dx.doi.org/10.1016/j.cej.2010.12.028
Metal nanoparticle synthesis in microreactors. - In: Applications, (2010), S. 361-393
Residence time distribution and nanoparticle formation in microreactors. - In: Fundamental concepts, (2010), S. 317-340
Ethyl 2-[(Z)-2-(4-cyanophenyl)-2-hydroxyvinyl]-4-(4-methoxyphenyl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate. - In: Molbank, ISSN 1422-8599, Bd. 2010 (2010), 1, M655, S. 1-4
A one-pot, two-step method has been developed for the synthesis of ethyl 2-[(Z)-2-(4-cyanophenyl)-2-hydroxyvinyl]-4-(4-methoxyphenyl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate, including a sulfide contraction step utilizing solution and solid phase synthesis.
https://doi.org/10.3390/M655