TY - GEN A1 - Varlamova, Olga A1 - Reif, Jürgen A1 - Stolz, Michael A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Bestehorn, Michael T1 - Wetting properties of LIPSS structured silicon surfaces T2 - The European Physical Journal B N2 - The controlled dynamics of liquid drops via generation of specific wetting states on a solid surface is of great interests both in the fundamental and applied sciences. Considering that the wettability is strongly dependent on the surface topography and surface roughness, we investigate – through experiments and theory – the effect of laser-induced periodic surface structures (LIPSS) generated on silicon (100) targets as a control parameter of wetting properties. To obtain structured silicon surfaces with different morphological features, we patterned the surface by irradiation with femtosecond pulses from an amplified Ti:Sapphire laser system (790 nm/100 fs/1 kHz) at a fluence in the range of 0.4–1.2 J/cm2 on a spot with a diameter about of 100 μm. Variation of the applied irradiation dose results in surface modifications with the roughness about of a few tens of nanometers are ranging from regular LIPSS patterns with the lateral period of about 500–700 nm to complex agglomerations of 3-D microstructures with several-μm feature size. The theoretical study on the correlation of wetting properties with the surface topography has been performed within a phase field model. We found an excellent agreement of numerical results with experiments. Y1 - 2019 U6 - https://doi.org/10.1140/epjb/e2019-90672-2 SN - 1434-6036 SN - 1434-6028 VL - 92 IS - 5 ER - TY - GEN A1 - Ehrig, Lutz A1 - Schenk, Hermann A1 - Wall, Franziska A1 - Melnikov, Anton A1 - Stolz, Michael A1 - Langa, Sergiu A1 - Kaiser, Bert A1 - Conrad, Holger T1 - Electrostatic all-silicon MEMS audio transducer for in-ear audio applications – acoustic measurements and modelling approach T2 - 23rd International Congress on Acoustics, Aachen, Germany, 2019 Y1 - 2019 U6 - https://doi.org/10.18154/RWTH-CONV-239893 ER - TY - GEN A1 - Spitz, Barbara A1 - Wall, Franziska A1 - Schenk, Hermann A1 - Melnikov, Anton A1 - Ehrig, Lutz A1 - Langa, Sergiu A1 - Stolz, Michael A1 - Kaiser, Bert A1 - Conrad, Holger A1 - Schenk, Harald A1 - Pufe, Wolfram T1 - Audio-Transducer für In-Ear-Anwendungen auf der Basis CMOS-kompatibler, elektrostatischer Biegeaktoren T2 - MikroSystemTechnik-Kongress, Berlin, Germany, 2019 N2 - Recently an innovative mSpeaker technology, based on a novel kind of CMOS compatible small gap electrostatic actuators for large deflection, has been introduced [1]. In this paper, we devise methods to model such speakers in terms of lumped parameters using the deflection of the beam centre as sole dynamic variable. Optical, acoustical and finite element methods (FEM) are used to validate the non-linear lumped parameter model (LPM). The experimental evaluation and LPM simulations of the total harmonic distortion reveal deeper insights into the mechanisms governing linearity. Y1 - 2019 SP - 54 EP - 57 PB - VDE-Verlag ER - TY - GEN A1 - Melnikov, Anton A1 - Schenk, Hermann A1 - Wall, Franziska A1 - Spitz, Barbara A1 - Ehrig, Lutz A1 - Langa, Sergiu A1 - Kaiser, Bert A1 - Conrad, Holger A1 - Schenk, Harald A1 - Stolz, Michael T1 - Minimization of nonlinearities in nano electrostatic drive actuators using validated coupled-field simulation T2 - SPIE Conference: MOEMS and Miniaturized Systems XIX, San Francisco, USA, 2020, Proc. SPIE 11293 Y1 - 2020 U6 - https://doi.org/10.1117/12.2551271 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 - GEN A1 - Conrad, Holger A1 - Schenk, Harald A1 - Kaiser, Bert A1 - Langa, Sergiu A1 - Gaudet, Matthieu A1 - Schimmanz, Klaus A1 - Stolz, Michael A1 - Lenz, Miriam T1 - A small-gap electrostatic micro-actuator for large deflections T2 - Nature Communications Y1 - 2015 U6 - https://doi.org/10.1038/ncomms10078 SN - 2041-1723 IS - 6 SP - 10078 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 - GEN A1 - Stolz, Michael A1 - Mrosk, Andreas A1 - Kaiser, Bert A1 - Langa, Sergiu A1 - Ehrig, Lutz A1 - Conrad, Holger A1 - Gaudet, Matthieu A1 - Schenk, Harald T1 - Optische Charakterisierungsmethoden von siliziumbasierten MEMS mit verdeckten Strukturen T2 - MikroSystemTechnik-Kongress, Berlin, Germany, 2019 N2 - In der Arbeitsgruppe integrierte Siliziumsysteme des Fraunhofer IPMS werden am Standort Cottbus innovative Anwen-dungen eines neuartigen nanoskopischen elektrostatischen Antriebs (nanoskopic electrostatic drive – NED) untersucht. Eine der vielversprechendsten Anwendungen sind Lautsprecher. Vollständig aus Silizium gefertigte MEMS-Lautsprecher auf Basis von NED-Biegeaktoren werden vor den akustischen Messungen mechanisch und elektrisch cha-rakterisiert. Beidseitig eingespannte elektrostatisch betriebene in-plane NED-Aktoren werden dabei über einen Fre-quenzbereich von 20 Hz bis 20 kHz angeregt. Dabei sind die Strukturen oft verdeckt, was ihre Charakterisierung er-schwert. Es werden zerstörungsfreie optische Methoden präsentiert, mit deren Hilfe die Bestimmung der mechanischen Schwingungseigenschaften einzelner Aktoren ermöglicht wird sowie die Beweglichkeit im verdeckten Zustand nach-gewiesen werden kann. Y1 - 2019 UR - https://www.ipms.fraunhofer.de/de/events/2019/mst-kongress.html SP - 366 EP - 369 PB - VDE-Verlag ER - TY - GEN A1 - Melnikov, Anton A1 - Schenk, Hermann A. G. A1 - Monsalve, Jorge Mario A1 - Wall, Franziska A1 - Stolz, Michael A1 - Mrosk, Andreas A1 - Langa, Sergiu A1 - Kaiser, Bert T1 - Coulomb-actuated microbeams revisited: experimental and numerical modal decomposition of the saddle-node bifurcation T2 - Microsystems & Nanoengineering N2 - Electrostatic micromechanical actuators have numerous applications in science and technology. In many applications, they are operated in a narrow frequency range close to resonance and at a drive voltage of low variation. Recently, new applications, such as microelectromechanical systems (MEMS) microspeakers (µSpeakers), have emerged that require operation over a wide frequency and dynamic range. Simulating the dynamic performance under such circumstances is still highly cumbersome. State-of-the-art finite element analysis struggles with pull-in instability and does not deliver the necessary information about unstable equilibrium states accordingly. Convincing lumped-parameter models amenable to direct physical interpretation are missing. This inhibits the indispensable in-depth analysis of the dynamic stability of such systems. In this paper, we take a major step towards mending the situation. By combining the finite element method (FEM) with an arc-length solver, we obtain the full bifurcation diagram for electrostatic actuators based on prismatic Euler-Bernoulli beams. A subsequent modal analysis then shows that within very narrow error margins, it is exclusively the lowest Euler-Bernoulli eigenmode that dominates the beam physics over the entire relevant drive voltage range. An experiment directly recording the deflection profile of a MEMS microbeam is performed and confirms the numerical findings with astonishing precision. This enables modeling the system using a single spatial degree of freedom. KW - Engineering KW - NEMS KW - Sensors Y1 - 2021 U6 - https://doi.org/10.1038/s41378-021-00265-y SN - 2055-7434 VL - 7 IS - 1 ER - TY - GEN A1 - Monsalve, Jorge Mario A1 - Melnikov, Anton A1 - Stolz, Michael A1 - Mrosk, Andreas A1 - Jongmanns, Marcel A1 - Wall, Franziska A1 - Langa, Sergiu A1 - Marica-Bercu, Ioana A1 - Brändel, Tim A1 - Kircher, Marco A1 - Schenk, Hermann A. G. A1 - Kaiser, Bert A1 - Schenk, Harald T1 - Proof of concept of an air-coupled electrostatic ultrasonic transducer based on lateral motion T2 - Sensors and Actuators A: Physical N2 - An alternative implementation of an electrostatic MUT (Micromachined Ultrasonic Transducer), relying on multiple beams that displace along the chip’s surface instead of a single membrane displacing perpendicular to it, is presented in this work. With this approach, a design requiring a low bias voltage (24 V) and occupying a small area (3.3×3.3 mm², 2D/λ≈0.77) was shown to generate a sound pressure level of 82 dB (re. 20 µPa-rms) at 40 kHz and a distance of 8.9 cm. The high level of damping allows this transducer to operate in a wide frequency range (35-63 kHz). The operation of this device as an ultrasonic receiver was also proven. An implementation of this transducer as a rangefinder requires a strong reduction in the noise level, particularly coming from radio-frequency interference, in order to increase its detection range. Y1 - 2022 U6 - https://doi.org/10.1016/j.sna.2022.113813 SN - 1873-3069 SN - 0924-4247 VL - Vol. 345 ER - TY - GEN A1 - Ehrig, Lutz A1 - Kaiser, Bert A1 - Conrad, Holger A1 - Schenk, Hermann A1 - Schuffenhauer, David A1 - Stolz, Michael A1 - Gaudet, Matthieu A1 - Schenk, Harald A1 - Kolkovsky, Vladimir T1 - MEMS-Loudspeaker - A Novel Class of Electroacoustic Transducers for Mobile Audio Applications T2 - Tonmeistertagung - VDT International Convention, Cologne, Germany, 2018, Proc. TMT 30 N2 - Wireless earphones require a tremendous degree of integration: In addition to the electroacoustic transducer at least the power supply and a radio module have to be accommodated, supplemented by several microphones for hands-free applications or for noise reduction, as well as position and bio sensors, memory and CPU. With increasing integration, the pressure on the individual components increases in terms of size, energy efficiency and costs. In the field of microphones, MEMS technology has enjoyed great popularity for almost 10 years, and due to their benefits (size, cost, integration) MEMS microphones have almost completely supersede other microphone technologies in mobile audio devices and opened up new fields of applications. Y1 - 2018 VL - TMT 30 SP - 189 EP - 192 ER - TY - CHAP A1 - Conrad, Holger A1 - Ehrig, Lutz A1 - Kaiser, Bert A1 - Schenk, Hermann A1 - Schuffenhauer, David A1 - Stolz, Michael A1 - Gaudet, Matthieu A1 - Schenk, Harald T1 - CMOS-kompatibler MEMS-Lautsprecher für Im-Ohr-Anwendungen T2 - Tagungsband, DAGA 2018, 44. Deutsche Jahrestagung für Akustik, 19.-22. März 2018, München Y1 - 2018 SN - 978-3-939296-13-3 SP - 892 EP - 894 PB - Deutsche Gesellschaft für Akustik e.V. (DEGA) CY - Berlin ER - TY - GEN A1 - Kaiser, Bert A1 - Schenk, Hermann A. G. A1 - Ehrig, Lutz A1 - Wall, Franziska A1 - Monsalve, Jorge Mario A1 - Langa, Sergiu A1 - Stolz, Michael A1 - Melnikov, Anton A1 - Conrad, Holger A1 - Schuffenhauer, David A1 - Schenk, Harald T1 - The push-pull principle: an electrostatic actuator concept for low distortion acoustic transducers T2 - Microsystems & Nanoengineering N2 - Electrostatic actuators are of particular interest for microsystems (MEMS), and in particular for MEMS audio transducers for use in advanced true wireless applications. They are attractive because of their typically low electrical capacitance and because they can be fabricated from materials that are compatible with standard complementary metal-oxide semiconductor (CMOS) technology. For high audio performance and in particular low harmonic distortion (THD) the implementation of the push-pull principle provides strong benefits. With an arrangement of three electrodes in a conjunct moving configuration on a beam, we demonstrate here for the first time a balanced bending actuator incarnating the push-pull principle operating at low voltages. Our first design already exhibits a harmonic distortion as low as 1.2% at 79 dB using a signal voltage of only 6 Vp and a constant voltage of only ±10 Vdc in a standard acoustic measurement setup. Thus, exceeding our previously reported approach in all three key performance indications at the same time. We expect that our novel electrode configurations will stimulate innovative electrostatic actuator developments for a broad range of applications. In this paper we report the basic theory, the fabrication and the performance of our novel actuator design acting as an audio transducer. Y1 - 2022 U6 - https://doi.org/10.1038/s41378-022-00458-z SN - 2055-7434 VL - Vol. 8 ER - TY - GEN A1 - Schenk, Harald A1 - Melnikov, Anton A1 - Stolz, Michael A1 - Wall, Franziska A1 - Kaiser, Bert A1 - Mrosk, Andreas A1 - Schuffenhauer, David A1 - Monsalve, Jorge Mario A1 - Langa, Sergiu A1 - Schenk, Hermann A1 - Ehrig, Lutz A1 - Conrad, Holger A1 - Ahnert, Maik T1 - Nonlinearity of balanced MEMS loudspeakers: optical experiments and numerical modeling using time-harmonic signals T2 - 27th International Congress on Sound and Vibration, Annual Congress of International Institute of Acoustics and Vibration (IIAV) N2 - A recently introduced novel actuator class, called the nano electrostatic drive (NED), uses the elec-trostatic actuation to generate large deflections of elastic structures. The NED principle was recently successfully applied to create an all silicon loudspeaker based on micro-electro-mechanical systems (MEMS) technology. Such MEMS audio transducers cover the full frequency range required for high fidelity audio applications. High fidelity audio reproduction also demands minimizing harmonic distortions substantially below 1 %. A major advance in this direction is combining the NED principle with a push-pull driving scheme in a balanced design (BNED), eliminating even harmonics. The practical implementation of a BNED design is however demanding. The nature of the Coulomb force, the impact of stress stiffening and the large deformations required for generating high sound pressures, to name a few aspects, potentially contribute to the harmonic distortion and therefore need advanced experimental methods and simulation models to allow for an apt design. In this paper, we report first results of an experimental technique, combining an optical microscope with a high-speed camera, capable of analyzing the local details of the actuator movement at frame rates of 50,000 frames per second. Dynamic features, such as the excitation of harmonics and intermodulations become clearly visible. These experimental results are then used to scrutinize and refine our multi physics FEM simulations. Y1 - 2021 UR - https://www.researchgate.net/publication/354465569_Nonlinearity_of_balanced_MEMS_loudspeakers_optical_experiments_and_numerical_modeling_using_time-harmonic_signals ER - TY - GEN A1 - Monsalve, Jorge Mario A1 - Melnikov, Anton A1 - Kaiser, Bert A1 - Schuffenhauer, David A1 - Stolz, Michael A1 - Ehrig, Lutz A1 - Schenk, Hermann A1 - Conrad, Holger A1 - Schenk, Harald T1 - Large-Signal Equivalent-Circuit Model of Asymmetric Electrostatic Transducers T2 - IEEE/ASME Transactions on Mechatronics N2 - This article presents a circuit model that is able to capture the full nonlinear behavior of an asymmetric electrostatic transducer whose dynamics are governed by a single degree of freedom. Effects such as stress-stiffening and pull-in are accounted for. The simulation of a displacement-dependent capacitor and a nonlinear spring is accomplished with arbitrary behavioral sources, which are a standard component of circuit simulators. As an application example, the parameters of the model were fitted to emulate the behavior of an electrostatic MEMS loudspeaker whose finite-element (FEM) simulations and acoustic characterisation where already reported in the literature. The obtained waveforms show good agreement with the amplitude and distortion that was reported both in the transient FEM simulations and in the experimental measurements. This model is also used to predict the performance of this device as a microphone, coupling it to a two-stage charge amplifier. Additional complex behaviors can be introduced to this network model if it is required. KW - Acoustic transducers KW - Duffing oscillator KW - Acoustic electrostatic actuators KW - equivalent-circuit model KW - microactuators KW - Electrostatics KW - Transducers KW - Mathematical models KW - Integrated circuit modeling KW - Capacitors KW - Microphones KW - Force Y1 - 2021 U6 - https://doi.org/10.1109/TMECH.2021.3112267 SN - 1083-4435 SN - 1941-014X VL - 7 IS - 5 SP - 2612 EP - 2622 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 - CHAP A1 - Conrad, Holger A1 - Gaudet, Matthieu A1 - Kaiser, Bert A1 - Langa, Sergiu A1 - Stolz, Michael A1 - Schenk, Harald T1 - CMOS-kompatible elektrostatische Biegeaktoren (CMOS-compatible electrostatic actuators T2 - MikroSystemTechnik Kongress 2017, München, Germany, 23.-25. Oktober 2017 Y1 - 2017 SN - 978-3-8007-4491-6 SP - 219 EP - 222 PB - VDE-Verlag CY - Berlin [u.a.] ER - TY - GEN A1 - Ruffert, Christine A1 - Schenk, Hermann A. G. A1 - Kaiser, Bert A1 - Ehrig, Lutz A1 - Monsalve Guaracao, Jorge Mario A1 - Langa, Sergiu A1 - Wall, Franziska A1 - Melnikov, Anton A1 - Stolz, Michael A1 - Morsk, Andreas A1 - Schuffenhauer, David A1 - Conrad, Holger A1 - Schenk, Harald T1 - Elektrostatischer Gegentakt NED-Aktor für Im-Ohr-µLautsprecher Y1 - 2023 UR - https://publica.fraunhofer.de/entities/publication/af8b72ee-2b53-4478-a964-a9dfb17ac3ad/details U6 - https://doi.org/10.24406/publica-2553 N1 - Im Rahmen der Mittelstandskonferenz 2023 in Berlin präsentiert. ER - TY - GEN A1 - Schenk, Harald A1 - Stolz, Michael A1 - Langa, Sergiu A1 - Kaiser, Bert T1 - Reliability Aspects of in-plane NED Bending Actuators in Silicon-based MEMS T2 - MikroSystemTechnik Kongress 2021 : Mikroelektronik / Mikrosystemtechnik und ihre Anwendungen Innovative Produkte für zukunftsfähige Märkte 08. – 10. November 2021, Stuttgart-Ludwigsburg N2 - For several years, Fraunhofer IPMS has been developing a new type of an electrostatic MEMS actuator, called nanoscopic electrostatic drive - NED. Since the first publication in 2015, the project group at IPMS has succeeded in providing lateral actuators, which serve as innovative drives in applications such as micro-positioners or micro-speakers. These applications require a high long-term stability of the drive in order to ensure that the system operates as desired. For this purpose, the reliability of such novel lateral electrostatic actuators was evaluated. Long-term studies of NED actuators have shown that different degradation phenomena can occur during operation. The experiments indicate that high electric fields in the range of several MV/m are one of the most important triggers of the degradations observed. On the one hand, they lead to anodic oxidation occurring at the boundary layers between the NED electrodes and neighbored insulators, which results in corrosion of the silicon electrodes. On the other hand, geometry-based field enhancement far from the insulator interfaces lead to permanent field emission, which causes dark discharges in the electrode gap. This in turn leads to cold plasma oxidation and the growth of oxide b ulges on the electrode surfaces. In the course of the experiments, it was shown that corrosion does not take place in a vacuum and can be avoided with the help of passivation layers. Non silicon oxides, e.g. Al2O3, are well suited as passivation layers. Although they bring additional flexural rigidity to the overall structure, which changes the mechanical behavior of the actuators, they increase the effective relative permittivity in the electrode gap, which in turn makes the actuators more effective. Thanks to the passivation coating,the lifespan of the NED actuators was increased and they can become even more effective by choosing a layer with suitable properties. Y1 - 2021 UR - https://www.vde-verlag.de/proceedings-de/455656134.html SN - 978-3-8007-5656-8 SN - 978-3-8007-5657-5 PB - VDE-Verlag ER -