Pesch, Georg
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Pesch, Georg
Official Name
Pesch, Georg
Alternative Name
Pesch, Georg R.
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GND
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Item-typ:Veröffentlichung, Recovery of submicron particles using high-throughput dielectrophoretically switchable filtration(Elsevier, 2014-06-25); ; ; ; Conventional methods for separation of submicron particles, e.g., filtration or centrifugation, suffer from severe problems, such as loss of particles during resuspension and high energy demands due to fouling of separating membranes. Here we present the novel concept of dielectrophoretically switchable filtration using pore sizes that are two to three orders of magnitude larger than the particles. We used layer-by-layer (LbL) assembled nanocapsules of 340 nm diameter that were to be separated and recovered from polyelectrolyte solution. The filter being an insulating porous structure is placed in between two electrodes generating an electric field which is bend at the solid–liquid interface and is thus highly inhomogeneous. Dielectrophoresis (DEP) is used as a driving force to trap particles in the filter. The filtration is based on electric effects and could thus be easily turned off by switching off the electric field allowing safe and easy resuspension of the trapped nanocapsules. A parametric study has been conducted to investigate the influence of voltage, pore size, flux and membrane thickness on the separation efficiency. Maximum separation and recovery efficiencies in a semi-continuous run reached almost 65% when working with a specific flow rate of 4.12 mL s−1 m−2, a voltage of 200 V, frequency of 210 kHz and a filter with thickness of 1.5 mm and pore sizes in the range of 20–60 μm. The results demonstrate that electrically switchable retardation of nanoparticles is possible even in large flow systems. This finding paves the way for preparative DEP chromatography of nanoparticles. Its ease makes this switchable filtration attractive for nanoparticle separation and purification in general.Wissenschaftlicher ArtikelBand:132103 128 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Microparticle trajectories in a high-throughput channel for contact-free fractionation by dielectrophoresisContinuous, contact-free fractionation of sensitive microparticles at high throughput is a challenge. For this purpose, we developed a sheath flow assisted dielectrophoretic (DEP) field-flow separator with a tailored arrangement of cylindrical interdigitated electrodes (cIDE) and observed size-dependent trajectories of dispersed particles. Using a voltage input of 200 Veff at a frequency of 200 kHz, polystyrene particles (45, 25, and 11 µm in diameter) levitated to different heights along the channel length due to a negative DEP force. Experimental observations agree well with simulated particle trajectories that were obtained by a modified Lagrangian particle tracking model in combination with Laplace's and Navier–Stokes equations. By exploiting the size-dependent levitation height difference the desired particle size fraction can be collected at a specific channel length. The required channel length of the proposed cIDE separator increases with decreasing particle size to be separated. The quality of theoretical fractionation, which we quantify by resolution, improves strongly with reduced collector width, reduced volume flow rate and increased voltage input. The sensitivity of these dependencies increases with decreasing particle size. We calculated a theoretical throughput of up to 47 mL min−1 when trading-off design and operation parameters, allowing for contact-free fractionation of sensitive microparticles with negligible shear stress.Wissenschaftlicher ArtikelBand:153148 108 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Electrodeless dielectrophoresis: Impact of geometry and material on obstacle polarizationInsulator-based (electrodeless) dielectrophoresis (iDEP) is a promising particle manipulation technique, based on movement of matter in inhomogeneous fields. The inhomogeneity of the field arises because the excitatory field distorts at obstacles (posts). This effect is caused by accumulation of polarization charges at material interfaces. In this study, we utilize a multipole expansion method to investigate the influence of geometry and material on field distortion of posts with arbitrary cross-sections in homogeneous electric fields applied perpendicular to the longitudinal axis of the post. The post then develops a multipole parallel or anti parallel to the excitatory field. The multipoles intensity is defined by the post's structure and material properties and directly influences the DEP particle trapping potential. We analyzed posts with circular and rhombus-shaped cross-sections with different cross-sectional width-to-height ratios and permittivities for their polarization intensity, multipole position, and their particle trapping behavior. A trade-off between high maximum field gradient and high coverage range of the gradient is presented, which is determined by the sharpness of the post's edges. We contribute to the overall understanding of the post polarization mechanism and expect that the results presented will help optimizing the structure of microchannels with arrays of posts for electrodeless DEP application.Wissenschaftlicher ArtikelBand:37Heft:2100 119 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Implementation of parcel method for surface reactions in DSMC(Elsevier, 2019-05-06); ; ; ; The parcel concept in Direct Simulation Monte Carlo method has been added to the reaction algorithm to the DSMC solver in OpenFOAM to reduce computational demand. Parcel per cell is checked for different cell sizes and different parcel sizes to obtain the right cell size for a given system. At this cell size, diffusion of CO in O2 is simulated in a porous structure to ascertain the feasibility of this concept. After adding adsorption and reaction models, concentration profiles are obtained for different temperatures and different time steps. These profiles are compared with the single molecule algorithm written by Pesch et al. [14]. The local surface coverages and reaction rates are evaluated at a parcel size ranging from 10 to 100 to further validate the new approach. Computational time demand reduces by half at maximum parcel size to reach similar steady state results as that of the single molecule approach.Wissenschaftlicher ArtikelBand:187135 104 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, On the dielectrophoretic particle retention in porous media(2018-01-31); ; ; Dielectrophoresis (DEP) is a very suitable particle manipulation technique that is able to solve a range of separation problems because it is label-free, very sensitive and, if applied correctly, highly selective towards a specific target particle. DEP has mostly been researched and applied (bio-)analytical chemistry to solve separation problems on lab-on-a-chip devices at uL/min throughputs, which makes it incompatible for industrial scale processes. This thesis investigates a high-throughput method, DEP filtration, which is particle retention due to DEP in porous media. Particle retention dynamics in model porous media are scrutinized using simulative and experimental methods. Particle movement in transparent microchannels gives first-hand insight into DEP trapping dynamics. The results presented pave the way toward actual high-throughput DEP filtration that could tackle important separation problems, such as the separation of metal from scrap in recycling.Dissertation960 278 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Influence of geometry and material of insulating posts on particle trapping using positive dielectrophoresisInsulator-based dielectrophoresis (iDEP) is a powerful particle analysis technique based on electric field scattering at material boundaries which can be used, for example, for particle filtration or to achieve chromatographic separation. Typical devices consist of microchannels containing an array of posts but large scale application was also successfully tested. Distribution and magnitude of the generated field gradients and thus the possibility to trap particles depends apart from the applied field strength on the material combination between post and surrounding medium and on the boundary shape. In this study we simulate trajectories of singe particles under the influence of positive DEP that are flowing past one single post due to an external fluid flow. We analyze the influence of key parameters (excitatory field strength, fluid flow velocity, particle size, distance from the post, post size, and cross-sectional geometry) on two benchmark criteria, i.e., a critical initial distance from the post so that trapping still occurs (at fixed particle size) and a critical minimum particle size necessary for trapping (at fixed initial distance). Our approach is fundamental and not based on finding an optimal geometry of insulating structures but rather aims to understand the underlying phenomena of particle trapping. A sensitivity analysis reveals that electric field strength and particle size have the same impact, as have fluid flow velocity and post dimension. Compared to these parameters the geometry of the post's cross-section (i.e. rhomboidal or elliptical with varying width-to-height or aspect ratio) has a rather small influence but can be used to optimize the trapping efficiency at a specific distance. We hence found an ideal aspect ratio for trapping for each base geometry and initial distance to the tip which is independent of the other parameters. As a result we present design criteria which we believe to be a valuable addition to the existing literature.Wissenschaftlicher ArtikelBand:1483157 128