Mikrofluidik

In mikrofluidischen Reaktoren und Wärmeübertragern ist es oftmals notwendig gleichzeitig das drei-dimensionale Strömungs- und Temperaturfeld mit Zeitauflösung zu vermessen, um Rückschlüsse auf die grundlegenden physikalischen Phänomene ziehen zu können. Beim Astigmatismus PTV beruht die Geschwindigkeitsbestimmung auf der dreidimensionalen Verfolgung von Partikeln im Messvolumen. Grundprinzip ist die Kodierung der Tiefenposition der Partikel über optische Verzerrungen durch eine zusätzliche Zylinderlinse in der Beobachtungsoptik. Wenn für die Messung Partikel verwendet werden, die mit einem temperatursensitiven Farbstoff beladen sind, kann das Fluoreszenzsignal zusätzlich genutzt werden, um die Temperatur zu bestimmen. Ziel in diesem Forschungsvorhaben ist es daher, das Signal-zu-Rauschverhältniss der Messtechnik zu verbessern und diese für mikrofluidische Wärmeübertrager mit Nanofluiden und andere komplexe mikrofluidische Bauteile zu verwenden.

Partner:

Universität der Bundeswehr München

Bearbeiter:

• Prof. Dr.-Ing. Christian Cierpka (Projektleiter)
• Dr. Jörg König (Projektleiter)
• Zhichao Deng (Bearbeiter)
   

Publikationen:

S. Sachs, Manuel Ratz, Patrick Mäder, J. König, C. Cierpka (2023) Particle detection and size recognition based on defocused particle images: a comparison of a deterministic algorithm and a deep neural network, Exp Fluids 64, 21

Z. Deng, J. König, C. Cierpka (2022) A combined velocity and temperature measurement with an LED and a low-speed camera, Measurement Science and Technology 33. 115301  

J. Massing, N. van der Schoot, C. J. Kähler, C. Cierpka (2019) A fast start up system for microfluidic direct methanol fuel cells, International Journal of Hydrogen Energy 44, 26517-26529, DOI: 10.1016/j.ijhydene.2019.08.107

J. Massing, C.J. Kähler, C. Cierpka (2018) A volumetric temperature and velocity measurement technique for microfluidics based on luminescence lifetime imaging, Experiments in Fluids 59, 163

X. Yang, D. Baczyzmalski, C. Cierpka, G. Mutschke, K. Eckert (2018) Marangoni convection at electrogenerated hydrogen bubbles, Physical Chemistry Chemical Physics 20, 11542

J. Massing, D. Kaden, C.J. Kähler, C. Cierpka (2016) Luminescent two-color tracer particles for simultaneous velocity and temperature measurements in microfluidics, Measurement Science and Technology 27, 1153014

R. Segura, M. Rossi, C. Cierpka, C.J. Kähler (2015) Simultaneous three-dimensional temperature and velocity field measurements using astigmatic imaging of non-encapsulated thermo-liquid crystal (TLC) particles. Lab on a Chip 15, 660-663

The magnetohydrodynamic conversion of kinetic energy of fluids into electric energy is well known and applied for power generation. A recent experiment shows a similarity between the magnetic field and the spin-orbit orientation in liquid metals, which opens a completely undiscovered path for energy conversion. This promising technique, known as spin hydrodynamic generation, relies on a coupling between the flow vorticity and electron spins to generate electricity with no needs of any external magnetic field. The spin hydrodynamic generation, however, is in its early infancy stage and many unresolved questions need to be addressed to enhance our understanding of how the macroscopic hydrodynamic world couples with the spin-orbitals on atomistic levels. In this regard, an experimental setup consisting of a large box to control the environmental conditions, a pressure vessel which is filled with the eutectic alloy Indium-Gallium-Tin (GaInSn), and connecting circular and non-circular capillary tubes was built. When a pressure (up to 10 bar) is applied the liquid metal is pushed through the capillary into another storage vessel placed on a high precision scale to determine the mass flow rate. The electrical potential is then measured between the electrodes at the beginning and at the end of the capillary. The primarily experimental results show a significant agreement with previous studies in the same range of the flow Reynolds number. For the extended range to lower and higher Reynolds numbers, measurements have provided compelling evidence for the validity of the proposed theories describing the generated electrical voltage via the spin-vorticity coupling.

Despite the first successful experiments, there is still a great need for a very good control of many parameters. Rigorous investigation of the concept could alter our perception of spintronics and our way of electric energy production completely.

Funding: Volkswagen Foundation                     

Partner:

• Prof. Dr. Jörg Schumacher

Project staff:

• Prof. Dr.-Ing. Christian Cierpka

• Dr. Hamid Tabaei Kazerooni

Publications:

H. Tabaei Kazerooni, A. Thieme, J. Schumacher, C. Cierpka (2020) Electron spin-vorticity coupling in low and high Reynolds number pipe flows, Physical Review Applied, accepted for publication (preprint on arxiv)