Dennis Hohlfeld

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A recently introduced set up of capacitive micromachined ultrasonic transducers (cMUT) combines a conductive membrane above a structured sacrificial layer. All previous approaches either require an additional metallic electrode or do not possess a structured sacrificial layer and, consequently, may make exact adjustment of the membrane dimensions difficult.(More)
This work presents an optimization strategy towards extending the operational frequency range of piezoelectric MEMS energy harvesting devices. We propose to use coupled micromechanical resonators to enable efficient energy harvesting at multiple frequencies with a single device. The proposed design, obtained by optimization algorithms, exhibits closely(More)
In this work, we present a computationally efficient model order reduction technique for a large-scale multiport model of piezoelectric energy harvester. This novel technique generates stable reduced order models. The method combines model reduction based on Krylov subspaces and a Schur complement transformation of the resulting system. We demonstrate an(More)
In this paper we present a new possibility to determine unknown material thermal properties based on experimental measurements. We use a parametrized finite element (FE) model and fit it to a measured transient curve. Using brute force, this process requires an extensive computational time. However, it is possible to speed it up significantly by using model(More)
In this contribution we present system-level modeling and simulation results for an electrostatic energy harvester with electrically adjustable operation frequency. The device is able to convert mechanical energy present in ambient vibrations into electrical energy. The energy is stored by charging a capacitor and available at constant voltage. The lumped(More)
This work presents a general simulation approach for all relevant physical effects in electro-optical circuit boards. Such printed circuit boards integrate electrical components and connections together with optical wave-guides as signal lines for applications in data transmission and sensing. The proposed modelling approach includes a calculation of heat(More)
This paper proposes a novel modeling methodology for MEMS-based piezoelectric vibration energy harvesting systems. The approach is based on coupling of the reduced order model and the power circuitry. A numerically accurate reduced order model of the harvester was connected to a synchronized switch harvesting on inductor scheme and optimized subsequently.(More)
In this paper we present a novel highly efficient approach to determine material properties from measurement results. We apply our method to thermal properties of thin-film multilayers with three different materials, amorphous silicon, silicon-nitride and silicon-oxide. The individual material properties are identified by solving an optimization problem.(More)