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Adaptive-optical 3D microscopy for microfluidic multiphase flows

Light(Advanced Manufacturing) 2024年第3期5卷 105-119页

作者： Clemens Bilsing Erik Nützenadel Sebastian Burgmann Jürgen Czarske Lars Büttner Laboratory of Measurement and Sensor System Techniques TUD Dresden University of Technology01069 DresdenGermany Chair of Fluid Mechanics Bergische Universitát Wuppertal42119 WuppertalGermany BIOLAS Laboratory of Measurement and Sensor System Techniques01069 DresdenGermany

measurements based on optical microscopy can be severely impaired if the access exhibits variations of the refractive *** the case of fluctuating liquid-gas boundaries,refraction introduces dynamical aberrations that increase the measurement *** is prevalent at multiphase flows(***,film flows)that occur in many technical applications as for example in coating and cleaning processes and the water management in fuel *** this paper,we present a novel approach based on adaptive optics for correcting the dynamical aberrations in real time and thus reducing the measurement *** shape of the fluctuating water-air interface is sampled with a reflecting light beam(Fresnel Guide Star)and a Hartmann-Shack sensor which makes it possible to correct its influence with a deformable mirror in a closed ***-dimensional flow measurements are achieved by using a double-helix point spread *** measure the flow inside a sessile,oscillating 50-μl droplet on an opaque gas diffusion layer for fuel cells and show that the temporally varying refraction at the droplet surface causes a systematic underestimation of the flow field magnitude corresponding to the first droplet eigenmode which plays a major role in their detachment *** demonstrate that the adaptive optics correction is able to reduce this systematic ***,the adaptive optics system can pave the way to a deeper understanding of water droplet formation and detachment which can help to improve the efficiency of fuels cells.

关键词： Double-Helix point spread function Adaptive optics Particle tracking velocimetry Aberration correction Depth-resolving microscopy Closed-loop control

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Ultrasound flow mapping of 3D turbulent liquid metal flows

Ultrasound flow mapping of 3D turbulent liquid metal flows

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2017 IEEE International Ultrasonics Symposium, IUS 2017

作者： Thieme, Norman Buchner, Karl Nauber, Richard Buttner, Lars Patzold, Olf Czarske, Jurgen Laboratory for Measurement and Sensor System Techniques TU Dresden Germany TU Freiberg Germany

ISBN: (纸本)9781538633830

Conductive fluids, e.g. metallic melts, can be driven by magnetic fields, which is a branch of magnetohydrodynamics (MHD). MHD can be used for driving a melt flow during the crystal growth of photovoltaic silicon in order to improve the mass and heat transfer in the melt for better structural and electrical properties of the silicon crystals. However, the optimal application of MHD requires a good understanding of the flow, which is generally complex and unsteady during crystal growth. Substantial knowledge about the flow is usually gained through numerical simulations and MHD model experiments at room temperature. For model experiments, a comprehensive flow mapping of complex and unsteady flow phenomena is required. © 2017 IEEE.

关键词： Magnetic field measurement Ultrasonic variables measurement Magnetohydrodynamics Metals Fluid flow measurement Ultrasonic imaging Magnetic fields

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Transmission of multiple independent signals through a multimode fiber using optical wavefront shaping

Transmission of multiple independent signals through a multi...

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Adaptive Optics: Analysis, Methods and systems, AO 2016

作者： Haufe, Daniel Koukourakis, Nektarios Büttner, Lars Czarske, Jürgen W. TU Dresden Laboratory of Measurement and Sensor System Techniques Helmholtzstr. 18 Dresden01162 Germany

The transmission of multiple independent signals through a multimode fiber using individually shaped wavefronts for each signal by a segmented spatial light modulator is proposed, having perspectives due to scalabilit... 详细信息

ISBN: (纸本)9781943580156

关键词： Multimode fibers

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Transmission of individual optical signals through a multimode fiber using digital optical phase conjugation

Transmission of individual optical signals through a multimo...

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Frontiers in Optics, FiO 2016

作者： Büttner, Lars Haufe, Daniel Koukourakis, Nektarios Czarske, Jürgen W. Technische Universität Dresden Laboratory of Measurement and Sensor System Techniques Helmholtzstraße 18 Dresden01062 Germany

Transmission through a multimode fiber is demonstrated using phase conjugation. Using multiple windows of a spatial light modulator allows asynchronous imaging through the fiber. Potential for optogenetics and communi... 详细信息

ISBN: (纸本)9781943580194

关键词： Multimode fibers

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Transmission of structured light through a multimode fiber using digital optical phase conjugation

Transmission of structured light through a multimode fiber u...

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Digital Holography and Three-Dimensional Imaging, DH 2019

作者： Büttner, Lars Thümmler, Martin Koukourakis, Nektarios Czarske, Jürgen Technische Universität Dresden Faculty of Electrical and Computer Engineering Laboratory of Measurement and Sensor System Techniques Helmholtzstraße 18 Dresden01069 Germany

The generation of a localized fringe system through a multimode fiber at a certain distance to the distal fiber end without additional relay optics is reported. Perspectives for application in measurement are given. &... 详细信息

ISBN: (纸本)9781943580590

关键词： Multimode fibers

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Dynamic adaptive optical image correction for velocimetry

Dynamic adaptive optical image correction for velocimetry

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Adaptive Optics: Analysis, Methods & systems, AOMS 2018

作者： Büttner, Lars Teich, Martin Radner, Hannes Czarske, Jürgen Technische Universität Dresden Faculty of Electrical and Computer Engineering Laboratory of Measurement and Sensor System Techniques Helmholtzstraße 18 Dresden01069 Germany

Imaging, correlation-based velocity measurements through time-varying optical distortions are presented for application in microfluidics. Using a deformable membrane mirror and an iterative FPGA-based optimization pro... 详细信息

ISBN: (纸本)9781943580446

关键词： Geometrical optics

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Modular ultrasound velocimeter for adaptive flow mapping in liquid metals

Modular ultrasound velocimeter for adaptive flow mapping in ...

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IEEE International Ultrasonics Symposium

作者： Richard Nauber Hannes Beyer Kevin Mader Christian Kupsch Norman Thieme Lars Buttner Jurgen Czarske Laboratory of Measurement and Sensor System Techniques (MST) TU Dresden 01062 Germany

ISBN: (纸本)9781467398985

Understanding the complex interaction of conductive fluids and time-varying magnetic fields is the main goal of research in magnetohydrodynamics (MHD). Customized magnetic fields can be used to optimize flows in technical and industrial processes involving liquid metals. For example the performance of batteries with replaceable liquid electrolytes, such as zinc slurry energy storage systems, can be improved by magnetically influencing the flow of the electrolyte. However, necessary experimental studies are often limited by the performance of flow instrumentation for opaque liquids. We present a modular research platform for flow mapping in liquid metals, the phased array ultrasound Doppler velocimeter (PAUDV). It is based on the pulsed-wave ultrasound Doppler principle in combination with the phased array technique to provide an electrically steerable sound field, enabling novel applications in MHD research. The ability to dynamically focus the ultrasound beam allows to resolve smaller flow structures in planar measurements compared to fixed-beam sensors. The PAUDV can be applied to flows in narrow channels and two velocity components can be measured with only one acoustical access via the cross beam technique. Fast electrical traversing of the measurement volume allows to obtain and visualize turbulence statistics. A two-point correlation function can be retrieved by interleaving velocity measurements at two focal points of varying distance. The PAUDV consists of a modular electronics unit with up to eight beamformer cards, capable of driving a total of 256 channels. Each channel can be individually configured regarding the excitation pattern (three-level quantization, 64 samples) and the delay (1.6 ns resolution). Data acquisition and processing is implemented on multiple FPGAs, control and data visualization are performed on a PC. The capabilities of the modular research platform PAUDV are demonstrated on measurements in the alloy gallium-indium-tin at room tempe

关键词： liquid metals Flowcharts Volume measurement velocity component velocimeters Modularity magnetohydrodynamics PHASED ARRAY techniques narrow passage Flow Doppler Ultrasonography Data visualisation data acquisition and processing magnetic field

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Miniaturized interferometric 3-D sensor for shape measurement inside of cutting lathes

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Procedia CIRP 2018年 77卷 46-49页

作者： Hao Zhang Robert Kuschmierz Jürgen Czarske Laboratory of Measurement and Sensor System Techniques Faculty of Electrical and Computer Engineering Technische Universität Dresden Dresden 01062 Germany

We propose an in-situ coordinate measurement machine based on a Mach-Zehnder interferometer. The sensor system enables the simultaneous measurement of axial distance and lateral velocity at rough and fast rotating objects. This allows to guarantee ever-decreasing tolerances, measurements of surface profile, roundness and absolute diameter of workpieces inside of lathes. With a camera based detection, measurement uncertainties below 100 nm can be achieved. Furthermore, cameras allow an in-situ calibration of the measurement system. By employing coherent fiber bundles, a robust probe without active parts in the lathe was realized. An extended measurement volume was achieved for a 3-D shape measurement without scanning.

关键词： in-situ on-line shape diameter metrology interferometry control of machining operations

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Ultrasound Imaging in Hot Melts with Time Reversal Virtual Arrays

Ultrasound Imaging in Hot Melts with Time Reversal Virtual A...

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IEEE International Ultrasonics Symposium

作者： Richard Nauber Lars Buttner Jurgen Czarske Laboratory of Measurement and Sensor System Techniques Faculty of Electrical and Computer Engineering TU Dresden Dresden Germany

Industrial processes, such as silicon crystal growth for the photovoltaics industry, continuous steel casting, plastics and aluminum extrusion, involve hot, opaque liquids. Noninvasive inline monitoring is desirable to improve the quality of the products and the resource efficiency of the process. However, ultrasound-based imaging methods are severely limited by the transducer's resistance to high *** propose a method for imaging hot liquids using an ultrasound phased-array probe attached to a multi-mode waveguide (MMWG) for thermal decoupling. The complex wave propagation through the MMWG leads to a strongly distorted image, which is addressed with a time reversal virtual array (TRVA). The TRVA method performs a system identification and compensates the distortions based on the time-reversal invariance of sound propagation. We demonstrate planar imaging with this method in liquid tin at ≈ 300℃, well above the destruction limit of the transducers. The characterization of the imaging properties of the system showed a spatial resolution better than 1.6 mm. The proposed method for imaging through MMWG may open a new window into a variety of technical and industrial processes involving hot, opaque liquids in harsh environments.

关键词： Imaging Ultrasonic imaging Liquids Acoustics Tin Temperature measurement Ultrasonic variables measurement

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Electrolyte droplet spraying in H₂ bubbles during water electrolysis under normal and microgravity conditions

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Nature Communications 2025年第1期16卷 1-10页

作者： Bashkatov, Aleksandr Bürkle, Florian Demirkır, Çayan Ding, Wei Sanjay, Vatsal Babich, Alexander Yang, Xuegeng Mutschke, Gerd Czarske, Jürgen Lohse, Detlef Krug, Dominik Büttner, Lars Eckert, Kerstin Institute of Fluid Dynamics Helmholtz-Zentrum Dresden-Rossendorf Bautzner Landstrasse 400 Dresden 01328 Germany Physics of Fluids Group Max Planck Center for Complex Fluid Dynamics and J. M. Burgers Centre for Fluid Dynamics University of Twente P.O. Box 217 Enschede 7500AE Netherlands Institute of Aerodynamics RWTH Aachen University Wüllnerstraße 5a Aachen 52062 Germany Laboratory for Measurement and Sensor System Techniques Faculty of Electrical and Computer Engineering Technische Universität Dresden Helmholtzstr. 18 Dresden 01069 Germany Max Planck Institute for Dynamics and Self-Organization Am Fassberg 17 Göttingen 37077 Germany Institute of Process Engineering and Environmental Technology Technische Universität Dresden Dresden 01062 Germany

Electrolytically generated gas bubbles can significantly hamper the overall electrolysis efficiency. Therefore it is crucial to understand their dynamics in order to optimise water electrolyzer systems. Herein, we elucidate a distinct transport mechanism whereby electrolyte droplets are sprayed into H₂ bubbles. These droplets arise from the fragmentation of the Worthington jet, which is engendered by the coalescence with microbubbles. The robustness of this phenomenon is corroborated under both normal and microgravity conditions. Reminiscent of bursting bubbles on a liquid-gas interface, electrolyte spraying results in a flow inside the bubble. This flow couples, in an intriguing way, with the thermocapillary convection at the bubble’s surface, clearly underlining the high interfacial mobility. In the case of electrode-attached bubbles, the sprayed droplets form electrolyte puddles affecting the dynamics near the three-phase contact line and favoring bubble detachment from the electrode. The results of this work unravel important insights into the physico-chemical aspects of electrolytic gas bubbles, integral for optimizing gas-evolving electrochemical systems. © The Author(s) 2025.

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