@inproceedings{ConradGaudetKaiseretal., author = {Conrad, Holger and Gaudet, Matthieu and Kaiser, Bert and Langa, Sergiu and Stolz, Michael and Schenk, Harald}, title = {CMOS-kompatible elektrostatische Biegeaktoren (CMOS-compatible electrostatic actuators}, series = {MikroSystemTechnik Kongress 2017, M{\"u}nchen, Germany, 23.-25. Oktober 2017}, booktitle = {MikroSystemTechnik Kongress 2017, M{\"u}nchen, Germany, 23.-25. Oktober 2017}, publisher = {VDE-Verlag}, address = {Berlin [u.a.]}, isbn = {978-3-8007-4491-6}, pages = {219 -- 222}, 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{MonsalveKaiserSchenk, author = {Monsalve, Jorge M. and Kaiser, Bert and Schenk, Harald}, title = {Design of Micromachined Ultrasonic Transducers for Variability with the Sample-Average Approximation Method}, series = {Tagungsband MikroSystemTechnik Kongress 2023, Dresden, 23. - 25. Oktober 2023}, journal = {Tagungsband MikroSystemTechnik Kongress 2023, Dresden, 23. - 25. Oktober 2023}, publisher = {VDE Verlag}, address = {Berlin}, isbn = {978-3-8007-6204-0}, pages = {S. 639}, language = {en} } @misc{SchenkStolzLangaetal., author = {Schenk, Harald and Stolz, Michael and Langa, Sergiu and Kaiser, Bert}, title = {Reliability Aspects of in-plane NED Bending Actuators in Silicon-based MEMS}, series = {MikroSystemTechnik Kongress 2021 : Mikroelektronik / Mikrosystemtechnik und ihre Anwendungen Innovative Produkte f{\"u}r zukunftsf{\"a}hige M{\"a}rkte 08. - 10. November 2021, Stuttgart-Ludwigsburg}, journal = {MikroSystemTechnik Kongress 2021 : Mikroelektronik / Mikrosystemtechnik und ihre Anwendungen Innovative Produkte f{\"u}r zukunftsf{\"a}hige M{\"a}rkte 08. - 10. November 2021, Stuttgart-Ludwigsburg}, publisher = {VDE-Verlag}, isbn = {978-3-8007-5656-8}, pages = {4}, abstract = {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.}, language = {en} } @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{UhligGaudetLangaetal., author = {Uhlig, Sebastian and Gaudet, Matthieu and Langa, Sergiu and Schimmanz, Klaus and Conrad, Holger and Kaiser, Bert and Schenk, Harald}, title = {Electrostatically driven in-plane silicon micropump for modular configuration}, series = {Micromachines}, volume = {9}, journal = {Micromachines}, number = {4}, issn = {2072-666X}, doi = {10.3390/mi9040190}, pages = {15}, abstract = {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.}, language = {en} } @inproceedings{SchenkConradGaudetetal., author = {Schenk, Harald and Conrad, Holger and Gaudet, Matthieu and Uhlig, Sebastian and Kaiser, Bert and Langa, Sergiu and Stolz, Michael and Schimmanz, Klaus}, title = {A contribution to the expansion of the applicability of electrostatic forces in micro transducers}, series = {MOEMS and Miniaturized Systems XVI, 30 January-1 February 2017, San Francisco, California, United States}, booktitle = {MOEMS and Miniaturized Systems XVI, 30 January-1 February 2017, San Francisco, California, United States}, publisher = {SPIE}, address = {Bellingham, Washington, USA}, isbn = {978-1-5106-0674-6}, doi = {10.1117/12.2249575}, language = {en} }