@inproceedings{ConradEhrigKaiseretal., author = {Conrad, Holger and Ehrig, Lutz and Kaiser, Bert and Schenk, Hermann and Schuffenhauer, David and Stolz, Michael and Gaudet, Matthieu and Schenk, Harald}, title = {CMOS-kompatibler MEMS-Lautsprecher f{\"u}r Im-Ohr-Anwendungen}, series = {Tagungsband, DAGA 2018, 44. Deutsche Jahrestagung f{\"u}r Akustik, 19.-22. M{\"a}rz 2018, M{\"u}nchen}, booktitle = {Tagungsband, DAGA 2018, 44. Deutsche Jahrestagung f{\"u}r Akustik, 19.-22. M{\"a}rz 2018, M{\"u}nchen}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V. (DEGA)}, address = {Berlin}, isbn = {978-3-939296-13-3}, pages = {892 -- 894}, language = {de} } @misc{EhrigKaiserConradetal., author = {Ehrig, Lutz and Kaiser, Bert and Conrad, Holger and Schenk, Hermann and Schuffenhauer, David and Stolz, Michael and Gaudet, Matthieu and Schenk, Harald and Kolkovsky, Vladimir}, title = {MEMS-Loudspeaker - A Novel Class of Electroacoustic Transducers for Mobile Audio Applications}, series = {Tonmeistertagung - VDT International Convention, Cologne, Germany, 2018, Proc. TMT 30}, volume = {TMT 30}, journal = {Tonmeistertagung - VDT International Convention, Cologne, Germany, 2018, Proc. TMT 30}, pages = {189 -- 192}, abstract = {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.}, language = {en} } @misc{SpitzWallSchenketal., author = {Spitz, Barbara and Wall, Franziska and Schenk, Hermann and Melnikov, Anton and Ehrig, Lutz and Langa, Sergiu and Stolz, Michael and Kaiser, Bert and Conrad, Holger and Schenk, Harald and Pufe, Wolfram}, title = {Audio-Transducer f{\"u}r In-Ear-Anwendungen auf der Basis CMOS-kompatibler, elektrostatischer Biegeaktoren}, series = {MikroSystemTechnik-Kongress, Berlin, Germany, 2019}, journal = {MikroSystemTechnik-Kongress, Berlin, Germany, 2019}, publisher = {VDE-Verlag}, pages = {54 -- 57}, abstract = {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.}, language = {de} } @misc{KaiserLangaEhrigetal., author = {Kaiser, Bert and Langa, Sergiu and Ehrig, Lutz and Stolz, Michael and Schenk, Hermann and Conrad, Holger and Schenk, Harald and Schimmanz, Klaus and Schuffenhauer, David}, title = {Concept and proof for an all-silicon MEMS micro speaker utilizing air chambers}, series = {Microsystems and Nanoengineering}, journal = {Microsystems and Nanoengineering}, number = {5}, issn = {2055-7434}, doi = {10.1038/s41378-019-0095-9}, pages = {11}, abstract = {MEMS-based micro speakers are attractive candidates as sound transducers for smart devices, particularly wearables and hearables. For such devices, high sound pressure levels, low harmonic distortion and low power consumption are required for industrial, consumer and medical applications. The ability to integrate with microelectronic circuitry, as well as scalable batch production to enable low unit costs, are the key factors benchmarking a technology. The Nanoscopic Electrostatic Drive based, novel micro speaker concept presented in this work essentially comprises in-plane, electrostatic bending actuators, and uses the chip volume rather than the its surface for sound generation. We describe the principle, design, fabrication, and first characterization results. Various design options and governing equations are given and discussed. In a standard acoustical test setup (ear simulator), a MEMS micro speaker generated a sound pressure level of 69 dB at 500 Hz with a total harmonic distortion of 4.4\%, thus proving the concept. Further potential on sound pressure as well as linearity improvement is outlined. We expect that the described methods can be used to enhance and design other MEMS devices and foster modeling and simulation approaches.}, language = {en} } @misc{EhrigKaiserSchenketal., author = {Ehrig, Lutz and Kaiser, Bert and Schenk, Hermann and Stolz, Michael and Langa, Sergiu and Conrad, Holger and Schenk, Harald and M{\"a}nnchen, Andreas and Brocks, Tobias}, title = {Acoustic validation of electrostatic all-silicon MEMS-speakers}, series = {AES International Conference on Headphone Technology, San Francisco, New York, USA, 2019}, journal = {AES International Conference on Headphone Technology, San Francisco, New York, USA, 2019}, doi = {10.17743/aesconf.2019.978-1-942220-29-9}, language = {en} } @misc{EhrigSchenkWalletal., author = {Ehrig, Lutz and Schenk, Hermann and Wall, Franziska and Melnikov, Anton and Stolz, Michael and Langa, Sergiu and Kaiser, Bert and Conrad, Holger and Schenk, Harald}, title = {Electrostatic all silicon MEMS speakers for in-ear audio applications - acoustic measurements and modelling approach}, series = {23rd International Congress on Acoustics, Aachen, Germany, 2019}, journal = {23rd International Congress on Acoustics, Aachen, Germany, 2019}, doi = {10.18154/RWTH-CONV-239893}, pages = {6}, language = {en} } @misc{MelnikovSchenkWalletal., author = {Melnikov, Anton and Schenk, Hermann and Wall, Franziska and Spitz, Barbara and Ehrig, Lutz and Langa, Sergiu and Kaiser, Bert and Conrad, Holger and Schenk, Harald and Stolz, Michael}, title = {Minimization of nonlinearities in nano electrostatic drive actuators using validated coupled-field simulation}, series = {SPIE Conference: MOEMS and Miniaturized Systems XIX, San Francisco, USA, 2020, Proc. SPIE 11293}, journal = {SPIE Conference: MOEMS and Miniaturized Systems XIX, San Francisco, USA, 2020, Proc. SPIE 11293}, doi = {10.1117/12.2551271}, language = {en} } @misc{SchenkMelnikovStolzetal., author = {Schenk, Harald and Melnikov, Anton and Stolz, Michael and Wall, Franziska and Kaiser, Bert and Mrosk, Andreas and Schuffenhauer, David and Monsalve Guaracao, Jorge Mario and Langa, Sergiu and Schenk, Hermann and Ehrig, Lutz and Conrad, Holger and Ahnert, Maik}, title = {Nonlinearity of balanced MEMS loudspeakers: optical experiments and numerical modeling using time-harmonic signals}, series = {27th International Congress on Sound and Vibration, Annual Congress of International Institute of Acoustics and Vibration (IIAV)}, journal = {27th International Congress on Sound and Vibration, Annual Congress of International Institute of Acoustics and Vibration (IIAV)}, pages = {7}, abstract = {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.}, language = {en} } @misc{MonsalveGuaracaoMelnikovKaiseretal., author = {Monsalve Guaracao, Jorge Mario and Melnikov, Anton and Kaiser, Bert and Schuffenhauer, David and Stolz, Michael and Ehrig, Lutz and Schenk, Hermann and Conrad, Holger and Schenk, Harald}, title = {Large-Signal Equivalent-Circuit Model of Asymmetric Electrostatic Transducers}, series = {IEEE/ASME Transactions on Mechatronics}, volume = {7}, journal = {IEEE/ASME Transactions on Mechatronics}, number = {5}, issn = {1083-4435}, doi = {10.1109/TMECH.2021.3112267}, pages = {2612 -- 2622}, abstract = {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.}, language = {en} } @misc{KaiserSchenkEhrigetal., author = {Kaiser, Bert and Schenk, Hermann A. G. and Ehrig, Lutz and Wall, Franziska and Monsalve Guaracao, Jorge Mario and Langa, Sergiu and Stolz, Michael and Melnikov, Anton and Conrad, Holger and Schuffenhauer, David and Schenk, Harald}, title = {The push-pull principle: an electrostatic actuator concept for low distortion acoustic transducers}, series = {Microsystems \& Nanoengineering}, volume = {Vol. 8}, journal = {Microsystems \& Nanoengineering}, issn = {2055-7434}, doi = {10.1038/s41378-022-00458-z}, abstract = {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.}, language = {en} } @misc{MonsalveGuaracaoMelnikovStolzetal., author = {Monsalve Guaracao, Jorge Mario and Melnikov, Anton and Stolz, Michael and Mrosk, Andreas and Jongmanns, Marcel and Wall, Franziska and Langa, Sergiu and Marica-Bercu, Ioana and Br{\"a}ndel, Tim and Kircher, Marco and Schenk, Hermann A. G. and Kaiser, Bert and Schenk, Harald}, title = {Proof of concept of an air-coupled electrostatic ultrasonic transducer based on lateral motion}, series = {Sensors and Actuators A: Physical}, volume = {Vol. 345}, journal = {Sensors and Actuators A: Physical}, issn = {1873-3069}, doi = {10.1016/j.sna.2022.113813}, abstract = {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.}, language = {en} } @misc{WallSchenkMelnikovetal., author = {Wall, Franziska and Schenk, Hermann A. G. and Melnikov, Anton and Kaiser, Bert and Schenk, Harald}, title = {A non-destructive electro-acoustic method to characterize the pull-in voltage of electrostatic actuators}, series = {Nonlinear Dynamics}, volume = {111}, journal = {Nonlinear Dynamics}, number = {19}, issn = {1573-269X}, doi = {10.1007/s11071-023-08811-1}, pages = {17809 -- 17818}, abstract = {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.}, language = {en} } @misc{RuffertSchenkKaiseretal., author = {Ruffert, Christine and Schenk, Hermann A. G. and Kaiser, Bert and Ehrig, Lutz and Monsalve Guaracao, Jorge Mario and Langa, Sergiu and Wall, Franziska and Melnikov, Anton and Stolz, Michael and Morsk, Andreas and Schuffenhauer, David and Conrad, Holger and Schenk, Harald}, title = {Elektrostatischer Gegentakt NED-Aktor f{\"u}r Im-Ohr-µLautsprecher}, doi = {10.24406/publica-2553}, language = {de} } @misc{WallSchenkSchenketal., author = {Wall, F. and Schenk, Hermann and Schenk, Harald and Melnikov, A. and Ehrig, L. and Kaiser, B.}, title = {P31 - Optimization of Harmonic Distortions for Electrostatic MEMS Push-Pull NED-Microspeakers}, series = {iCCC2024 - iCampµs Cottbus Conference 2024-05-14 - 2024-05-16 Cottbus : Poster}, journal = {iCCC2024 - iCampµs Cottbus Conference 2024-05-14 - 2024-05-16 Cottbus : Poster}, publisher = {AMA Service GmbH, Von-M{\"u}nchhausen-Str. 49, 31515 Wunstorf, Germany}, isbn = {978-3-910600-00-3}, doi = {10.5162/iCCC2024/P31}, pages = {218 -- 221}, language = {en} } @inproceedings{SandnerGrashoffSchenketal., author = {Sandner, Thilo and Grashoff, Thomas and Schenk, Harald and Kenda, Andreas}, title = {Translatory MEMS actuator and their system integration for miniaturized Fourier transform spectrometers}, series = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, booktitle = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, edition = {1. Auflage}, publisher = {SPIE Press}, address = {Bellingham}, isbn = {978-0-8194-8930-2}, doi = {10.1117/12.909817}, pages = {82520C-1 -- 82520C-10}, language = {en} } @inproceedings{TortschanoffBaumgartFranketal., author = {Tortschanoff, Andreas and Baumgart, M. and Frank, A. and Wildenhain, Michael and Sandner, Thilo and Schenk, Harald and Kenda, Andreas}, title = {Optical position feedback for electrostatically driven MOEMS-scanners}, series = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, booktitle = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, edition = {1. Auflage}, publisher = {SPIE, The Society of Photo-Optical Instrumentation Engineers}, address = {Bellingham}, isbn = {978-0-8194-8930-2}, pages = {82520S-1 -- 82520S-8}, language = {en} } @inproceedings{JungSandnerKallweitetal., author = {Jung, Denis and Sandner, Thilo and Kallweit, David and Schenk, Harald}, title = {Vertical comb drive microscanners for beam steering, linear scanning and laser projection applications}, series = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, booktitle = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, edition = {1. Auflage}, publisher = {SPIE, The Society of Photo-Optical Instrumentation Engineers}, address = {Bellingham}, isbn = {978-0-8194-8930-2}, pages = {82520U-1 -- 82520U-10}, language = {en} } @inproceedings{PuegnerKnobbeGruegeretal., author = {P{\"u}gner, Tino and Knobbe, Jens and Gr{\"u}ger, Heinrich and Schenk, Harald}, title = {Realization of a hybrid-integrated MEMS scanning grating spectrometer}, series = {SPIE Conference Next-Generation Spectroscopic Technologies V, 23 - 24 April 2012, Baltimore, Maryland}, booktitle = {SPIE Conference Next-Generation Spectroscopic Technologies V, 23 - 24 April 2012, Baltimore, Maryland}, edition = {1. Auflage}, publisher = {SPIE, The Society of Photo-Optical Instrumentation Engineers}, address = {Bellingham}, pages = {83740W-1 -- 83740W-8}, language = {en} } @inproceedings{GrahmannWildenhainGrashoffetal., author = {Grahmann, Jan and Wildenhain, Michael and Grashoff, Thomas and Gerwig, Christian and Dallmann, Hans-Georg and Wolter, Alexander and Schenk, Harald}, title = {Laser projector solution based on two 1D resonant micro scanning mirrors assembled in a low vertical distortion scan head}, series = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, booktitle = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, number = {1. Auflage}, publisher = {SPIE, The Society of Photo-Optical Instrumentation Engineers}, address = {Bellingham}, isbn = {978-0-8194-8930-2}, pages = {825205-1 -- 825205-9}, language = {en} } @inproceedings{DrabeKallweitDreyhauptetal., author = {Drabe, Christian and Kallweit, David and Dreyhaupt, Andre and Grahmann, Jan and Schenk, Harald and Davis, Wyatt}, title = {Bi-resonant scanning mirror with Piezo-resistive position sensor for WVGA laser projection systems}, series = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, booktitle = {SPIE Conference MOEMS and Miniaturized Systems XI, San Francisco, 2012}, edition = {1. Auflage}, publisher = {SPIE Press}, address = {Bellingham}, isbn = {978-0-8194-8930-2}, doi = {10.1117/12.910203}, pages = {825209-1 -- 825209-10}, language = {en} }