@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{MelnikovSchenkMonsalveGuaracaoetal., author = {Melnikov, Anton and Schenk, Hermann A. G. and Monsalve Guaracao, Jorge Mario and Wall, Franziska and Stolz, Michael and Mrosk, Andreas and Langa, Sergiu and Kaiser, Bert}, title = {Coulomb-actuated microbeams revisited: experimental and numerical modal decomposition of the saddle-node bifurcation}, series = {Microsystems \& Nanoengineering}, volume = {7}, journal = {Microsystems \& Nanoengineering}, number = {1}, issn = {2055-7434}, doi = {10.1038/s41378-021-00265-y}, abstract = {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.}, language = {en} }