At a microscopic scale, surfactants, molecules attached to the interface between two fluids, can suffer the same fate, immobilizing the interface upstream of an obstacle. Therefore, SAW-induced EOF may be useful as a method for pumping liquids through small scale channels. We have studied the transport of gas mixtures along a Knudsen pump and observed differences in flow of the individual components of the mixture. With this in mind, we investigated the impact that surfactants have on this mechanism and found that parts of the gas-water interface become ‘solidified’ by surfactant pile-up. Reference: M. Shojaeian and S. Hardt, Mass transfer via femtoliter droplets in ping-pong mode, Physical Review Applied 13 (2020), 014015. 6 — June 2019. Formation of small droplets inside larger droplets, Microfluidic chip with two-phase flow for DNA or protein separation in an electric field, Wetting transition on a superhydrophobic surface, Electroosmotic flow along a superhydrophobic surface induced by a gate electrode. Anal. S. Dehe, B. Rofman, M. Bercovici, and S. Hardt, Electro-osmotic flow enhancement over superhydrophobic surfaces, Physical Review Fluids 5 (2020), 053701. You are here: TU Darmstadt; Maschinenbau; Nano- and Microfluidics; Home; Institute for Nano- and Microfluidics. “Tears of wine” is a phenomenon that can be observed in wine glasses: Driven by Marangoni stresses, a liquid film crawls up along the glass wall. Our research extends over a broad thematic spectrum and combines experimental, theoretical and numerical approaches. S. Dehe, B. Rofman, M. Bercovici, and S. Hardt, Electro-osmotic flow enhancement over superhydrophobic surfaces, Physical Review Fluids 5 (2020), 053701. Tobias Baier Center of Smart Interfaces, TU Darmstadt Verified email at nmf.tu-darmstadt.de. Human resources department, International office: neumann@nmf.tu-... +49 6151 16-24277. A summary of the main results can be found here. Nano- and Microfluidics You are here: TU Darmstadt; Maschinenbau; Nano- and Microfluidics; Sitemap. hardt@nmf.tu-... +49 6151 16-24274. Via the charges created at the gas-liquid interfaces, the flow velocity can be increased by more than a factor of 10 compared to unstructured surfaces. Latest supplement. SIAM J. Numer. Working area(s) Emeritus. For a small particle inside a gas, the fluid dynamics of such problems becomes very involved, since the Navier-Stokes equation is no longer applicable. Cited by. Your browser does not support the video element. Fachgebiet Nano- und Mikrofluidik – Herzlich willkommen am Fachgebiet Nano- und Mikrofluidik. Baier, T., Hardt, S. Gas separation in a Knudsen pump inspired by a Crookes radiometer. B. Rofman, S. Dehe, V. Frumkin, S. Hardt, and M. Bercovici, Intermediate states of wetting on hierarchical superhydrophobic surfaces, Langmuir 36 (2020), 5517−5523. Welcome to the Institute for Nano- und Microfluidics. Klingenberg, Dario ; Oberlack, Martin ; Pluemacher, Dominik (2020): Symmetries and turbulence modeling. 26 (1), 45 – 65. We have theoretically studied the EOF induced by SAWs and found that in small-scale channels, the EOF velocity may significantly exceed the velocity due to the acoustic field. A sphere moving in the vicinity of a wall experiences an increased fluid-dynamic drag force compared to motion far from solid boundaries, influencing the adsorption of particles at surfaces. Transferring chemical species or nanoparticles in a controlled way becomes challenging when very small species amounts are considered. We have computed the corresponding drag force on a particle and find that it is much lower than the one predicted by the Navier-Stokes equation. In: Physics of Fluids, (2), 32. 5, Iss. Stability and collapse of holes in liquid layers - Volume 855 - Cunjing Lv, Michael Eigenbrod, Steffen Hardt As a stream encounters an obstacle, floating debris sometimes piles up in front of the obstacle, forming a dense layer on the water surface. We have computed the corresponding drag force on a particle and find that it is much lower than the one predicted by the Navier-Stokes equation. The course language will be English. Weian Sheng Airbnb, Intel, University of Florida Verified email at airbnb.com. The droplet reciprocates between two aqueous reservoirs under the influence of a DC electric field. Principal institution: Darmstadt University of Technology (TU Darmstadt) Region: Global Subject/journal group: All The table to the right includes counts of all research outputs for Institute for Nano- and Microfluidics (NMF), TU Darmstadt published between 1 June 2019 - 31 May 2020 which are tracked by the Nature Index. SAWs are acoustic waves travelling along the interface between a solid and a fluid. Therefore, such a pump may be used for gas separation. This kind of separation of gas species by mass or size plays an important role for many applications in chemical engineering. SAWs are acoustic waves travelling along the interface between a solid and a fluid. Electronic address: hardt@nmf.tu-darmstadt.de. https://www.fdy.tu-darmstadt.de/fdy/fdystaff/details_17472.de.jsp Issue . 5 — May 2020. Steffen Hardt. Philippe Bourrianne Princeton Verified email at princeton.edu. Electroosmotic flow (EOF) induced by surface acoustic waves. Nanoscale gas kinetics, electrokinetics, interfacial flows, wetting phenomena and biomolecular separation belong to our areas of work. Duval CNRS Research Director - LIEC Laboratory (Nancy, France) Verified email at univ-lorraine.fr. M. Eigenbrod and S. Hardt, The effective shear and dilatational viscosities of a particle-laden interface in the dilute limit, Journal of Fluid Mechanics 903 (2020), A26. Principal institution: Technical University of Darmstadt (TU Darmstadt) Region: Global Subject/journal group: All The table to the right includes counts of all research outputs for Institute for Nano- and Microfluidics (NMF), TU Darmstadt published between 1 October 2019 - 30 September 2020 which are tracked by the Nature Index. Ehsan Ro “Tears of wine” is a phenomenon that can be observed in wine glasses: Driven by Marangoni stresses, a liquid film crawls up along the glass wall. Administrative Staff Corinna Neumann. We find a multitude of intermediate states between the classical Cassie and Wenzel states. We have studied the transfer of chemical species between the two reservoirs mediated by the droplet. Song Jinlong The School of Mechanical Engineering, Dalian University of Technology Verified email at dlut.edu.cn. Apart from its relevance in applications, this process goes along with the formation of characteristic DNA concentration patterns, visible in the figure at the left. Steffen Hardt Professor, TU Darmstadt Verified email at nmf.tu-darmstadt.de. In that case, the viscosity coefficients represent the dissipation due to the presence of particles or surfactants in an average manner. Steffen Hardt Professor, TU Darmstadt Verified email at nmf.tu-darmstadt.de. At a microscopic scale, surfactants, molecules attached to the interface between two fluids, can suffer the same fate, immobilizing the interface upstream of an obstacle. Transferring chemical species or nanoparticles in a controlled way becomes challenging when very small species amounts are considered. Surface acoustic waves (SAW) are widely used in microfluidics for transporting and mixing liquids. In that case, ring-like structures are formed from the film. M. Dietzel and S. Hardt, Electroosmotic flow in small-scale channels induced by surface-acoustic waves, Physical Review Fluids 5 (2020), 123702. The theoretical predictions based on linear stability analysis compare favorably with the experimental results. Together with cooperation partners from the Technion/Israel, we have studied the electroosmotic flow along superhydrophobic surfaces, augmented by gate electrodes. Reference: S. Hardt, J. Hartmann, S. Zhao, and A. Bandopadhyay, Electric-field-induced pattern formation in layers of DNA molecules at the interface between two immiscible liquids, Physical Review Letters 124 (2020), 064501. We have experimentally studied the concentration patterns and formulated a theory describing the pattern formation. Reference: C. Lv, S. N. Varanakkottu, and S. Hardt, Liquid plug formation from heated binary mixtures in capillary tubes, Journal of Fluid Mechanics 889 (2020), A15. Dr. Dharmendra Tripathi Associate Professor, Mathematics, National Institute of Technology Uttarakhand Verified email at nituk.ac.in. Mikrosystemtechnik Kongress 2011, Darmstadt, Germany, [Conference or Workshop Item] Hahn, T. (2011): Interfacial electrokinetic transport phenomena and their impact on DNA electrophoresis in microfluidics. Surfactants can immobilize fluid–liquid interfaces under shear stress. 7 Physics of Surfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 16, 64287 Darmstadt, Germany. We find a multitude of intermediate states between the classical Cassie and Wenzel states. M. Eigenbrod and S. Hardt, The effective shear and dilatational viscosities of a particle-laden interface in the dilute limit, Journal of Fluid Mechanics 903 (2020), A26. Verified email at nmf.tu-darmstadt.de. These liquid rings finally collapse and form plugs that are propelled along the capillary tube by evaporation. Enhancement of electroosmotic flow on superhydrophobic surfaces. christophe clanet CNRS, LadHyX, Ecole … DNA molecules can be concentrated by electrophoretic accumulation at an interface between two immiscible polymer solutions. Tobias Baier Center of Smart Interfaces, TU Darmstadt Потвърден имейл адрес: nmf.tu-darmstadt.de. DOI: 10.1103/PhysRevLett.124.064501, Tutorium „CFD-based simulation and optimization of microfluidic components“, This tutorium will equip students with the basic methodology needed to design and optimize microfluidic components on the computer. Link: https://doi.org/10.1017/jfm.2019.921. Picture: NMF. Steffen Hardt Professor, TU Darmstadt Verified email at nmf.tu-darmstadt.de. Institute for Nano- and Microfluidics (NMF), TU Darmstadt . Herzlich willkommen am Fachgebiet Nano- und Mikrofluidik. DOI:10.1017/jfm.2019.921. The method is sketched in the schematic on the left. Up to now, the electrokinetic effects due to SAWs have remained largely unexplored. Please find below all contacts to board, project coordinators, researchers, administrative and technical staff of the CRC 1194. pp. Office. † Email address for correspondence: hardt@nmf.tu-darmstadt.de. The transition from the Cassie state to these intermediate states is partially reversible. 82-85, Proc. 6 Intitut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Schnittspahnstraße 9, 64287 Darmstadt, Germany. Unsere Forschung erstreckt sich über ein breites Themenspektrum und kombiniert experimentelle, theoretische und numerische Ansätze. References (Subscription Required) Click to Expand. DOI: 10.1103/PhysRevApplied.13.014015. Together with cooperation partners from the Technion/Israel, we have studied the electroosmotic flow along superhydrophobic surfaces, augmented by gate electrodes. Upon touching the reservoir, the droplet reverses its charge and its direction of motion. Formation of small droplets inside larger droplets, Microfluidic chip with two-phase flow for DNA or protein separation in an electric field, Wetting transition on a superhydrophobic surface, Electroosmotic flow along a superhydrophobic surface induced by a gate electrode. DOI: 10.1017/jfm.2020.80, Pattern formation in layers of DNA molecules. Cited by. Следене. We have experimentally studied the concentration patterns and formulated a theory describing the pattern formation. Nature Index 2020 Artificial Intelligence. Babovsky, H. & Illner, R. 1989 A convergence proof for Nanbu’s simulation method for the full Boltzmann equation. … Seyed Mahmood Mousavi High Performance Computing center (HPCC) Потвърден имейл адрес: shirazu.ac.ir. The transition from the Cassie state to these intermediate states is partially reversible. Supplemental Material (Subscription Required) Click to Expand. Apart from its relevance in applications, this process goes along with the formation of characteristic DNA concentration patterns, visible in the figure at the left. Bird, G. A. These liquid rings finally collapse and form plugs that are propelled along the capillary tube by evaporation. The droplet reciprocates between two aqueous reservoirs under the influence of a DC electric field. Usually, viscosity is a quantity associated with the bulk of a fluid. The course language will be English. Vol. With this in mind, we investigated the impact that surfactants have on this mechanism and found that parts of the gas-water interface become ‘solidified’ by surfactant pile-up. DOI: 10.1103/PhysRevApplied.13.014015. Jérôme F.L. TU Darmstadt incorporates diverse science cultures to create its characteristic profile. DNA molecules can be concentrated by electrophoretic accumulation at an interface between two immiscible polymer solutions. These results could significantly simplify simulations of two-phase flows with particle-laden interfaces. Articles Cited by Co-authors. Now imaging shrinking the diameter of the wine glass to one millimeter. The method is sketched in the schematic on the left. Dr. Naren Bag PhD, IIT Kharagpur Verified email at iitkgp.ac.in. L2|06 112. Intermediate wetting states on superhydrophobic surfaces. Steffen Hardt Professor, TU Darmstadt Verified email at nmf.tu-darmstadt.de. We have found a solution to this problem, where a droplet with a diameter of the order of 5 µm serves as carrier for the cargo. No articles found. In addition, the flow is entirely pH-independent. Issue. Up to now, the electrokinetic effects due to SAWs have remained largely unexplored.