@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} } @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{KaiserSchenkEhrigetal., author = {Kaiser, Bert and Schenk, Hermann A. G. and Ehrig, Lutz and Wall, Franziska and Monsalve, 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{SchenkMelnikovStolzetal., author = {Schenk, Harald and Melnikov, Anton and Stolz, Michael and Wall, Franziska and Kaiser, Bert and Mrosk, Andreas and Schuffenhauer, David and Monsalve, 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{MonsalveMelnikovKaiseretal., author = {Monsalve, 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{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{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} }