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 - 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 - 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 - Wall, Franziska A1 - Schenk, Hermann A. G. A1 - Melnikov, Anton A1 - Kaiser, Bert A1 - Schenk, Harald T1 - A non-destructive electro-acoustic method to characterize the pull-in voltage of electrostatic actuators T2 - Nonlinear Dynamics N2 - For electrostatic actuators, the pull-in marks an upper limit for the operation range. Once reached, the electrodes come into contact and are shorted without further protection. A non-destructive measurement technique to predict this failure mode is of high interest to allow, e.g. fabrication monitoring or reliability studies. To this end, we develop a surprisingly simple nonlinear lumped parameter model (LPM) for a rather complex electrostatic actuator, designed for an in-ear loudspeaker application. It turns out that a single degree-of-freedom model with only one parameter is sufficient. Our key approach is to experimentally determine this free model parameter by analysing harmonic distortions at low frequencies. Harmonic distortions are a very sensitive tool for nonlinearities. Our method is suggested by simulations with a 2D stationary finite element method (FEM), demonstrating how the analysis of harmonic distortions for voltages far below the pull-in can predict not only the DC pull-in but also the quasi-static AC pull-in voltages at different working points. The distortion analysis of electrostatic actuator ensembles therefore seems a viable route for their non-destructive characterization in the nonlinear domain. KW - Pull-in KW - Electrostatic actuator KW - Microspeaker KW - Harmonic distortions Y1 - 2023 UR - https://link.springer.com/article/10.1007/s11071-023-08811-1 U6 - https://doi.org/10.1007/s11071-023-08811-1 SN - 1573-269X SN - 0924-090X VL - 111 IS - 19 SP - 17809 EP - 17818 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 -