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35 results on '"Freidank, Sebastian"'

1. Comprehensive analysis of spherical bubble oscillations and shock wave emission in laser-induced cavitation

Author

Liang, Xiao-Xuan, Linz, Norbert, Freidank, Sebastian, Paltauf, Guenther, and Vogel, Alfred

Subjects
Physics - Fluid Dynamics, Physics - Plasma Physics
Abstract

The dynamics of spherical laser-induced cavitation bubbles in water is investigated by plasma photography, time-resolved shadowgraphs, and single-shot probe beam scattering enabling to portray the transition from initial nonlinear to late linear oscillations. The frequency of late oscillations yields the bubble's gas content. Simulations with the Gilmore model using plasma size as input and oscillation times as fit parameter provide insights into experimentally not accessible bubble parameters and shock wave emission. The model is extended by a term covering the initial shock-driven acceleration of the bubble wall, an automated method determining shock front position and pressure decay, and an energy balance for the partitioning of absorbed laser energy into vaporization, bubble and shock wave energy, and dissipation through viscosity and condensation. These tools are used for analysing a scattering signal covering 102 oscillation cycles. The bubble was produced by a plasma with 1550 K average temperature and had 36 $\mu$m maximum radius. Predicted bubble wall velocities during expansion agree well with experimental data. Upon first collapse, most energy was stored in the compressed liquid around the bubble and then radiated away acoustically. The collapsed bubble contained more vapour than gas, and its pressure was 13.5 GPa. The pressure of the rebound shock wave initially decayed $\propto r^{-1.8}$, and energy dissipation at the shock front heated liquid near the bubble wall above the superheat limit. The shock-induced temperature rise reduces damping during late bubble oscillations. Bubble dynamics changes significantly for small bubbles with less than 10 $\mu$m radius., Comment: 75 pages, 20 figures

Published
2021
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2. Laser Micro- and Nanostructuring for Refractive Eye Surgery

Author

Linz, Norbert, Freidank, Sebastian, Liang, Xiao-Xuan, Vogel, Alfred, Lotsch, H.K.V., Founding Editor, Rhodes, William T., Editor-in-Chief, Adibi, Ali, Series Editor, Asakura, Toshimitsu, Series Editor, Hänsch, Theodor W., Series Editor, Krausz, Ferenc, Series Editor, Masters, Barry R., Series Editor, Midorikawa, Katsumi, Series Editor, Venghaus, Herbert, Series Editor, Weber, Horst, Series Editor, Weinfurter, Harald, Series Editor, Kobayashi, Kazuya, Series Editor, Markel, Vadim, Series Editor, Stoian, Razvan, editor, and Bonse, Jörn, editor

Published
2023
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8. Comprehensive analysis of spherical bubble oscillations and shock wave emission in laser-induced cavitation.

Author

Xiao-Xuan Liang, Linz, Norbert, Freidank, Sebastian, Paltauf, Günther, and Vogel, Alfred

Subjects
CAVITATION, SHOCK waves, OSCILLATIONS, FREQUENCIES of oscillating systems, WAVE energy, ENERGY dissipation, ACOUSTIC emission, PARTICLE acceleration
Abstract

The dynamics of spherical laser-induced cavitation bubbles in water is investigated by plasma photography, time-resolved shadowgraphs and sensitive single-shot probe beam scattering that portrays the transition from initial nonlinear to late linear oscillations. The frequency of late oscillations yields the bubble’s gas content. Numerical simulations with an extended Gilmore model using plasma size as input and oscillation times as fit parameter provide insights into experimentally not accessible bubble parameters and shock wave emission. Model extensions include a term covering the initial shock-driven acceleration of the bubble wall, an automated method determining shock front position and pressure decay and a complete energy balance for the partitioning of absorbed laser energy into vaporization, bubble and shock wave energy and dissipation through viscosity and condensation. These tools are used for analysing a scattering signal covering 102 oscillation cycles from a bubble with 36 μm maximum radius produced by a plasma with 1550 K average temperature. Predicted bubble wall velocities during expansion agree well with experimental data. Upon first collapse, most energy was stored in the compressed liquid around the bubble and radiated away acoustically. The collapsed bubble contained more vapour than gas and had a pressure of 13.5 GPa. The decay of the rebound shock wave pressure with radius r was initially ∝r−1.8, and energy dissipation at the shock front heated the liquid near the bubble wall to temperatures above the superheat limit. The shock-induced temperature rise reduces damping during late bubble oscillations. Damping in first collapse increases significantly for small bubbles with less than 10 μm radius. [ABSTRACT FROM AUTHOR]

Published
2022
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13. Bus-based, miniaturized multi-sensory catheter system

Author

Wagner David, Petrova Hanna, Bachmann Philipp, Detert Markus, Schmidt Bertram, Freidank Sebastian, Schumann Ulrich, and Brinkhues Sven

Subjects
Catheter, Multi sensory, Computer science, business.industry, visual_art, Electronic component, visual_art.visual_art_medium, Miniaturization, Signal lines, business, Actuator, Computer hardware
Abstract

One trend in medical technology is the continuous miniaturization of components, assemblies and complete systems. Such complete systems are functionalized catheters with different sensor and actuator components [1–8]. If even the smallest bottlenecks, for example in blood vessels, are to be reached in the human body, the catheter diameter must be further reduced with the same functionalization. A new approach is chosen, which does not apply the supply and signal lines to the catheter surface or insert them into the existing lumen, but becomes a direct and inseparable part of the catheter. Contacting these conducting tracks with the electronic components is one of the key processes in the manufacture of this type of catheter. A final demonstrator is used for functional testing.

Published
2018
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16. Hot bar joining method for medical applications

Author

Markus Detert, Ulrich Schumann, David W. Wagner, Freidank Sebastian, Bertram Schmidt, and Kai Pitschmann

Subjects
chemistry.chemical_compound, Materials science, chemistry, Bar (music), Interposer, chemistry.chemical_element, Extrusion, Polyethylene, Composite material, Signal, Copper, Electrical conductor, Layer (electronics)
Abstract

The goal is to use the hot bar method to join the conductive lines of a flexible interposer with copper wires, which are located inside of the catheter wall. These copper wires with a diameter of 150 μm were integrated during the extrusion process of a polyethylene catheter with a diameter of 3 mm and a wall thickness of 1 mm. The wires will be used as signal and power lines. Because the copper wires located inside the catheter wall, the polyethylene material above the copper wires must be removed for joining the interposer copper lines. The material ablation was done by a femtosecond laser. Detailed knowledge about the heat sensitive handling with the polyethylene catheter must obtained before start the joining procedures. For the setup of the final joining procedure, there were used different types of test vehicles. With the help of the test vehicles the joining method is evaluated. Therefore, a hot bar stamp is placed at the back of the polyimide layer. The investigated parameters of the hot bar are stamp temperature, stamp force and time. After the setup analysis of the sensor test vehicle, the optimal joining parameters will be discovered and the flexible interposer and the copper wires inside of the catheter wall could be joined in future steps. Finally, non-destructive (ultrasound, x-ray) and destructive methods (tweezer pull test, microsection) will be investigated to evaluate the joining quality and quantity of the test vehicle and the final sensor catheter.

Published
2017
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26. A New Nanosecond UV Laser at 355 nm: Early Results of Corneal Flap Cutting in a Rabbit Model

Author

Trost, Andrea, primary, Schrödl, Falk, additional, Strohmaier, Clemens, additional, Bogner, Barbara, additional, Runge, Christian, additional, Kaser-Eichberger, Alexandra, additional, Krefft, Karolina, additional, Vogel, Alfred, additional, Linz, Norbert, additional, Freidank, Sebastian, additional, Hilpert, Andrea, additional, Zimmermann, Inge, additional, Grabner, Günther, additional, and Reitsamer, Herbert A., additional

Published
2013
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