Andreas Dietzel

Bio: Andreas Dietzel is an academic researcher from Braunschweig University of Technology. The author has contributed to research in topics: Materials science & Medicine. The author has an hindex of 21, co-authored 215 publications receiving 1887 citations. Previous affiliations of Andreas Dietzel include HGST & Eindhoven University of Technology.

Transient behaviour of magnetic micro-bead chains rotating in a fluid by external fields.

Abstract: Magnetic micro-beads can facilitate many functions in lab-on-a-chip systems, such as bio-chemical labeling, selective transport, magnetic sensing and mixing. In order to investigate potential applications of magnetic micro-beads for mixing in micro fluidic systems, we developed a pin-jointed mechanism model that allows analysing the behaviour of rotating superparamagnetic bead chains. Our numerical model revealed the response of the chains on a rotating magnetic field over time. We could demonstrate that the governing parameters are the Mason number and number of beads in the chain. The results are in agreement with the simplified analytical model, assuming a straight chain, but also allow prediction of the transient chain shape. The modelled chains develop an anti-symmetric S-shape that is stable, if the Mason number for a given chain length does not surpass a critical value. Above that value, rupture occurs in the vicinity of the chain centre. However, variations in bead susceptibility can shift the location of rupture. Moreover, we performed experiments with superparamagnetic micro-beads in a small fluid volume exposed to a uniform rotating magnetic field. Our simulation could successfully predict the observed transient chain form and the time for chain rupture. The developed model can be used to design optimised bead based mixers in micro fluidic systems.

Particle/cell separation on microfluidic platforms based on centrifugation effect: a review

Abstract: Particle/cell separation in heterogeneous mixtures including biological samples is a standard sample preparation step for various biomedical assays A wide range of microfluidic-based methods have been proposed for particle/cell sorting and isolation Two promising microfluidic platforms for this task are microfluidic chips and centrifugal microfluidic disks In this review, we focus on particle/cell isolation methods that are based on liquid centrifugation phenomena Under this category, we reviewed particle/cell sorting methods which have been performed on centrifugal microfluidic platforms, and inertial microfluidic platforms that contain spiral channels and multi-orifice channels All of these platforms implement a form of centrifuge-based particle/cell separation: either physical platform centrifugation in the case of centrifugal microfluidic platforms or liquid centrifugation due to Dean drag force in the case of inertial microfluidics Centrifugal microfluidic platforms are suitable for cases where the preparation step of a raw sample is required to be integrated on the same platform However, the limited available space on the platform is the main disadvantage, especially when high sample volume is required On the other hand, inertial microfluidics (spiral and multi-orifice) showed various advantages such as simple design and fabrication, the ability to process large sample volume, high throughput, high recovery rate, and the ability for multiplexing for improved performance However, the utilization of syringe pump can reduce the portability options of the platform In conclusion, the requirement of each application should be carefully considered prior to platform selection

Magnetic bead manipulation in a sub-microliter fluid volume applicable for biosensing

Abstract: Magnetic actuation principles using superparamagnetic beads suspended in a fluid are studied in this paper An experimental setup containing a sub-microliter fluid volume surrounded by four miniaturized electromagnets was designed and fabricated On the basis of optical velocity measurements, the induced behavior of single beads and ordered chains was analyzed and compared to a theoretical model This research can be used to develop new techniques for accelerated transportation in lab-on-a-chip bio-assays

Numerical Heat Transfer And Fluid Flow

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Structural (n,m) determination of isolated single wall carbon nanotubes by resonant Raman scattering

Abstract: We show that the Raman scattering technique can give complete structural information for one-dimensional systems, such as carbon nanotubes. Resonant confocal micro-Raman spectroscopy of an (n,m) individual single-wall nanotube makes it possible to assign its chirality uniquely by measuring one radial breathing mode frequency omega(RBM) and using the theory of resonant transitions. A unique chirality assignment can be made for both metallic and semiconducting nanotubes of diameter d(t), using the parameters gamma(0) = 2.9 eV and omega(RBM) = 248/d(t). For example, the strong RBM intensity observed at 156 cm(-1) for 785 nm laser excitation is assigned to the (13,10) metallic chiral nanotube on a Si/SiO2 surface.

Magnetic Helical Micromachines: Fabrication, Controlled Swimming, and Cargo Transport

Abstract: A simple and general fabrication method for helical swimming micromachines by direct laser writing and e-beam evaporation is demonstrated. The magnetic helical devices exhibit varying magnetic shape anisotropy, yet always generate corkscrew motion using a rotating magnetic field. They also exhibit good swimming performance and are capable of pick-and-place micromanipulation in 3D. Cytotoxicity of the devices was investigated using mouse myoblasts. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanofabricated and self-assembled magnetic structures as data storage media

Abstract: Nanofabrication of magnetic storage media, where servo marks, discrete tracks or individual islands are defined, offer the prospect for improved performance and increased areal density. However, this increase in performance will require that new and additional processes be introduced into disk manufacturing. We review here the fundamental patterning and fabrication processes that have been proposed, along with their respective strengths and weaknesses and the potential advantages they may offer for magnetic recording. The increase in data density afforded by nanofabrication may have added significance as more conventional approaches to ever increasing density will encounter physical limitations set by the thermal stability of the recorded bits.

White organic light-emitting diodes.

Abstract: White organic light-emitting diodes (WOLEDs) offer a range of attractive characteristics and are in several regards conceptually different from most currently used light sources. From an application perspective, their advantages include a high power efficiency that rivals the performance of fluorescent lamps and inorganic LEDs and the potential for a very low cost of manufacturing. As flat-panel light sources they are intrinsically glare-free and generate light over a large area. WOLEDs are constantly improving in terms of performance, durability, and manufacturability, but these improvements require joint research efforts in chemistry and the materials sciences to design better materials as well as in physics and engineering to invent new device concepts and design suitable fabrication schemes, a process that has generated many exciting scientific questions and answers. This article reviews current developments in the field of WOLEDs and puts a special focus on new device concepts and on approaches to reliable and cost-efficient WOLED manufacturing.