TY - GEN A1 - Reif, Jürgen A1 - Varlamova, Olga A1 - Ratzke, Markus A1 - Uhlig, Sebastian T1 - Laser-Induced Periodic Surface Structures of Thin Complex Multi-Component Films T2 - Applied Physics / A Y1 - 2016 U6 - https://doi.org/10.1007/s00339-016-9936-7 SN - 1432-0630 N1 - Art. 338 VL - 122 IS - 4 SP - 1 EP - 6 ER - TY - GEN A1 - Reif, Jürgen A1 - Martens, Christian A1 - Uhlig, Sebastian A1 - Ratzke, Markus A1 - Varlamova, Olga A1 - Valette, Stephane A1 - Benayoun, Stephane T1 - On large area LIPSS coverage by multiple pulses T2 - Applied Surface Science Y1 - 2015 U6 - https://doi.org/doi:10.1016/j.apsusc.2014.11.153 SN - 0169-4332 VL - 336 SP - 249 EP - 254 ER - TY - GEN A1 - Reif, Jürgen A1 - Varlamova, Olga A1 - Uhlig, Sebastian A1 - Varlamov, Sergej A1 - Bestehorn, Michael T1 - On the physics of self-organized nanostructure formation upon femtosecond laser ablation T2 - Applied Physics A N2 - We present new results on femtosecond LIPSS on silicon, fostering the dynamic model of self-organized structure formation. The first set of experiments demonstrates LIPSS formation by irradiation with a femtosecond white light continuum. The ripples are, as usual, perpendicular to the light polarization with a fluence-dependent wavelength between 500 and 700 nm. At higher dose (fluence × number of shots), the LIPSS turn to much coarser structures. The second set of experiments displays the dose dependence of pattern evolution at about threshold fluence. In contrast to the general case of multi-pulse LIPSS, where a strong dependence of the structures on the laser polarization is observed, single-shot exposition of silicon at about the ablation threshold results in a concentric pattern of very regular sub-wavelength ripples following the oval shape of the irradiated spot, without any reference to the laser polarization. When increasing the number of pulses, the usual, typical ripples develop and then coalesce into broader perpendicular structures, interlaced with remnants of the first, finer ripples. Y1 - 2014 UR - http://link.springer.com/article/10.1007/s00339-014-8339-x U6 - https://doi.org/10.1007/s00339-014-8339-x SN - 0947-8396 SN - 1432-0630 VL - 117 IS - 1 SP - 179 EP - 184 ER - TY - GEN A1 - Uhlig, Sebastian A1 - Alkhasli, Ilkin A1 - Schubert, Frank A1 - Tschöpe, Constanze A1 - Wolff, Matthias T1 - A Review of Synthetic and Augmented Training Data for Machine Learning in Ultrasonic Non-Destructive Evaluation T2 - Ultrasonics N2 - Ultrasonic Testing (UT) has seen increasing application of machine learning (ML) in recent years, promoting higher-level automation and decision-making in flaw detection and classification. Building a generalized training dataset to apply ML in non-destructive evaluation (NDE), and thus UT, is exceptionally difficult since data on pristine and representative flawed specimens are needed. Yet, in most UT test cases flawed specimen data is inherently rare making data coverage the leading problem when applying ML. Common data augmentation (DA) strategies offer limited solutions as they don’t increase the dataset variance, which can lead to overfitting of the training data. The virtual defect method and the recent application of generative adversarial neural networks (GANs) in UT are sophisticated DA methods targeting to solve this problem. On the other hand, well-established research in modeling ultrasonic wave propagations allows for the generation of synthetic UT training data. In this context, we present a first thematic review to summarize the progress of the last decades on synthetic and augmented UT training data in NDE. Additionally, an overview of methods for synthetic UT data generation and augmentation is presented. Among numerical methods such as finite element, finite difference, and elastodynamic finite integration methods, semi-analytical methods such as general point source synthesis, superposition of Gaussian beams, and the pencil method as well as other UT modeling software are presented and discussed. Likewise, existing DA methods for one- and multidimensional UT data, feature space augmentation, and GANs for augmentation are presented and discussed. The paper closes with an in-detail discussion of the advantages and limitations of existing methods for both synthetic UT training data generation and DA of UT data to aid the decision-making of the reader for the application to specific test cases. KW - Non-destructive testing KW - NDT KW - Non-destructive evaluation KW - NDE KW - Ultrasonic testing KW - Ultrasonics KW - Flaw detection KW - Machine learning KW - Artificial intelligence KW - Deep learning KW - Synthetic training data KW - Data augmentation Y1 - 2023 UR - https://www.sciencedirect.com/science/article/pii/S0041624X23001178 U6 - https://doi.org/10.1016/j.ultras.2023.107041 SN - 1874-9968 IS - 134 ER - TY - CHAP A1 - Uhlig, Sebastian A1 - Gaudet, Matthieu A1 - Langa, Sergiu A1 - Schimmanz, Klaus A1 - Conrad, Holger A1 - Kaiser, Bert A1 - Schenk, Harald T1 - Electrostatically in-plane driven silicon micropump for modular configuration T2 - Conference proceedings, The 3rd Conference on MicroFluidic Handling Systems (MFHS 2017), 4 - 6 October 2017, Enschede, The Netherlands Y1 - 2017 UR - http://publica.fraunhofer.de/dokumente/N-477736.html SP - 57 EP - 60 PB - University of Twente CY - Enschede ER - TY - PAT A1 - Conrad, Holger A1 - Gaudet, Matthieu A1 - Schenk, Harald A1 - Uhlig, Sebastian T1 - Mikromechanical devices with mechanical actuators T1 - Mikromechanische Bauelemente mit mechanischen Aktuatoren Y1 - 2018 ER - TY - CHAP A1 - Gaudet, Matthieu A1 - Uhlig, Sebastian A1 - Stolz, Michael A1 - Arscott, S. A1 - Conrad, Holger A1 - Langa, Sergiu A1 - Kaiser, Bert A1 - Schenk, Harald T1 - Electrostatic bending actuators with liquid filled nanometer scale gap T2 - MEMS 2017, the 30th IEEE International Conference on Micro Electro Mechanical Systems, Las Vegas, Nevada, USA, January 22-26 2017 Y1 - 2017 UR - http://ieeexplore.ieee.org/document/7863369/ SN - 978-1-5090-5078-9 SN - 978-1-5090-5079-6 SP - 175 EP - 178 PB - IEEE CY - Piscataway, NJ ER - TY - GEN A1 - Langa, Sergiu A1 - Conrad, Holger A1 - Kaiser, Bert A1 - Stolz, Michael A1 - Gaudet, Matthieu A1 - Uhlig, Sebastian A1 - Schimmanz, Klaus A1 - Schenk, Harald T1 - Technological aspects of a new micro-electro-mechanical actuation principle: nano e-drive T2 - Microsystem Technologies Y1 - 2017 U6 - https://doi.org/10.1007/s00542-017-3360-6 SN - 1432-1858 VL - 23 IS - 1 SP - 5697 EP - 5708 ER - TY - CHAP A1 - Schenk, Harald A1 - Conrad, Holger A1 - Gaudet, Matthieu A1 - Uhlig, Sebastian A1 - Kaiser, Bert A1 - Langa, Sergiu A1 - Stolz, Michael A1 - Schimmanz, Klaus T1 - A novel electrostatic micro-actuator class and its application potential for optical MEMS T2 - 2016 International Conference on Optical MEMS and Nanophotonics,31 July-04 August 2016, Singapore, proceedings Y1 - 2016 SN - 978-1-5090-1036-3 U6 - https://doi.org/10.1109/OMN.2016.7565867 SP - Tu 3.11-1 EP - Tu 3.11-2 PB - IEEE CY - Piscataway, NJ ER - TY - PAT A1 - Conrad, Holger A1 - Gaudet, Matthieu A1 - Schenk, Harald A1 - Uhlig, Sebastian T1 - Micromechanical devices with mechanical actuators Y1 - 2023 UR - https://www.freepatentsonline.com/11639718.html ER - TY - GEN A1 - Conrad, Holger A1 - Kaiser, Bert A1 - Gaudet, Matthieu A1 - Langa, Sergiu A1 - Stolz, Michael A1 - Uhlig, Sebastian A1 - Schimmanz, Klaus A1 - Schenk, Harald T1 - A novel electrostatic actuator class T2 - Procedia Engineering Y1 - 2016 U6 - https://doi.org/10.1016/j.proeng.2016.11.454 SN - 1877-7058 VL - 168 SP - 1533 EP - 1536 ER - TY - GEN A1 - Uhlig, Sebastian A1 - Gaudet, Matthieu A1 - Langa, Sergiu A1 - Schimmanz, Klaus A1 - Conrad, Holger A1 - Kaiser, Bert A1 - Schenk, Harald T1 - Electrostatically driven in-plane silicon micropump for modular configuration T2 - Micromachines N2 - In this paper, an in-plane reciprocating displacement micropump for liquids and gases which is actuated by a new class of electrostatic bending actuators is reported. The so-called “Nano Electrostatic Drive” is capable of deflecting beyond the electrode gap distance, enabling large generated forces and deflections. Depending on the requirements of the targeted system, the micropump can be modularly designed to meet the specified differential pressures and flow rates by a serial and parallel arrangement of equally working pumping base units. Two selected, medium specific micropump test structure devices for pumping air and isopropanol were designed and investigated. An analytical approach of the driving unit is presented and two-way Fluid-Structure Interaction (FSI) simulations of the micropump were carried out to determine the dynamic behavior. The simulation showed that the test structure device designed for air expected to overcome a total differential pressure of 130 kPa and deliver a flow rate of 0.11 sccm at a 265 Hz driving frequency. The isopropanol design is expected to generate 210 kPa and pump 0.01 sccm at 21 Hz. The device is monolithically fabricated by CMOS-compatible bulk micromachining processes under the use of standard materials only, such as crystalline silicon, silicon dioxide and alumina. KW - micropump; electrostatic actuation; nano e-drive; in-plane reciprocating displacement micropump; MEMS Y1 - 2018 U6 - https://doi.org/10.3390/mi9040190 SN - 2072-666X VL - 9 IS - 4 ER - TY - CHAP A1 - Schenk, Harald A1 - Conrad, Holger A1 - Gaudet, Matthieu A1 - Uhlig, Sebastian A1 - Kaiser, Bert A1 - Langa, Sergiu A1 - Stolz, Michael A1 - Schimmanz, Klaus T1 - A contribution to the expansion of the applicability of electrostatic forces in micro transducers T2 - MOEMS and Miniaturized Systems XVI, 30 January-1 February 2017, San Francisco, California, United States Y1 - 2017 SN - 978-1-5106-0674-6 SN - 978-1-5106-0673-9 U6 - https://doi.org/10.1117/12.2249575 PB - SPIE CY - Bellingham, Washington, USA ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael A1 - Uhlig, Sebastian A1 - Gaudet, Matthieu A1 - Schenk, Harald T1 - Liquid pumping induced by transverse forced vibrations of an elastic beam: A lubrication approach T2 - Physical Review Fluids N2 - Two liquid pumps are investigated theoretically and numerically: a single thin liquid layer actuated by a periodic force at an elastic beam and a two-layer geometry actuated by an elastic beam. For the second geometry, the beam actuates the liquid from both sides. For both pumps, the liquid film thickness is small compared to the lateral characteristic length of the system. A lubrication theory is developed. The Euler-Bernoulli equation for transverse deformations of an elastic beam is coupled to the fundamental hydrodynamic equations: the Navier-Stokes equation and a continuity equation in the long-wave approximation. In this way, one connects the transverse displacement of the beam with the hydrodynamic quantities (pressure, velocity fields, and flow rates). Appropriate boundary conditions incorporate the function of the valves. The derivation of the theoretical model is followed by numerical simulations. We estimate flow rates (in two and three spatial dimensions) for different system parameters and we compute the efficiency of a well-designed liquid pump. KW - Microfluidic devices KW - Thin fluid films Y1 - 2018 UR - https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.3.084202 U6 - https://doi.org/10.1103/PhysRevFluids.3.084202 SN - 2469-990X VL - 3 IS - 8 ER -