Karin D. Bauer

• Fraunhofer Research Institution for Microsystems and Solid State Technologies

Aluminum Nitride (AlN) is a well-known compound piezoelectric material with high Complementary Metal-Oxide Semiconductor process compatibility. Previous results show that the piezoelectric coefficient correlates with the c-axis orientation of AlN. In this work, the optical properties of reactively sputtered AlN thin-films have been investigated to...

Diese Arbeit untersucht das druckabhängige Dämpfungsverhalten auf mikromechanische Oszillatoren im Bereich der molekularen Strömung. Im Besonderen wird im Rahmen der Arbeit die abstandsabhängige Dämpfung für Edelgase und mehratomige Gase erforscht. Hierbei wird in der Nähe des Oszillators eine Platte parallel im Abstand von 150 - 3500 μm platziert...

This poster presents the pressure dependent damping behavior of micro-oscillators in the molecular flow regime for noble and polyatomic gases. In addition, a plate was positioned in the vicinity of the oscillator with an adjustable gap width, ranging from 150 – 3500 μm. As a novelty, it can be shown from these results that rotational and vibrationa...

Multiphysics and multiscale problems are encountered when the behaviour and/or underlying structure of a material or device is affected by several physical phenomena and depends on the geometry, scales and properties of the composing substructure. Interactions of the physical phenomena and geometric scales can lead to a completely different behavio...

The invention relates to an actuator assembly (10) for manipulating a fluid flowing around a flow body (12), said fluid being received or able to be received in a volume of at least one cavity (14) arranged in said flow body, and said fluid passing through at least one opening (16) in the at least one cavity (14) during manipulation of said fluid....

A fluidic oscillator device, in particular for a or in a flow control system for an aircraft or spacecraft, has a first and a second fluidic actuator, wherein each of the actuators has an inlet for supplying pressure and a first and a second outlet, from which an actuator flow can be discharged. The device further has a fluidic control for controll...

We present a new design of a miniaturized Synthetic Jet Actuator (SJA) for separation control applications. Its performance was optimized by multiphysics modelling and simulation. The resulting miniaturized SJA exhibits high peak velocities both in suction and blowing (>100m/s), despite working in a non-resonant mode at low frequencies (<200Hz). In...

An array of microstructured hot film sensors has been validated in a wind tunnel experiment on a natural laminar flow (NLF) airfoil model. The tests were conducted with freestream velocities up to cruise flight conditions and local Mach numbers in the supersonic range. The Tollmien-Schlichting (TS) dominated boundary layer transition could be ident...

With respect to the ability to reduce and remove organic contamination, including insects, on a laminar airfoil, biocatalytically active agents were here investigated, in solution or immobilized on airfoil materials surfaces. The feasibility and working principle of those structures were demonstrated within this study, and results of experiments re...

Purpose The purpose of this paper is to investigate the accuracy of different force calculation methods and their impact on mechanical deformations. For this purpose, a micrometer scaled actuator is considered, which consists of a micro‐coil and of a permanent magnet (PM) embedded in a deformable elastomeric layer. Design/methodology/approach For...

In this paper, a capacitive pressure sensor for aeronautical applications is presented. The sensor mainly consists of a thin structured layer of Polydimethylsiloxane (PDMS) that is embedded between two metal films. In this application the structured PDMS layer is used as dielectric and as spring element. The optimal design of the sensor was determi...

In this work, amplification units made of robust metallic nickel titanium (NiTi) and single crystal silicon are compared and evaluated for the application in miniaturized piezoelectric actuators for flow control purposes. The amplification mechanism with a sliced membrane structure is based on a mechanical lever in order to amplify the low piezoele...

One of the so-called Aero-MEMS applications is the drag reduction on airfoils by using an array of dedicated microactuators. When applying active wave cancellation principles in thin transitional boundary layers, these actuators need to exhibit relatively large stroke at relatively high operational frequencies. For this purpose, a novel micromachin...

Drag reduction on airfoils using arrays of micro-actuators is one application of so-called Aero-MEMS. These microactuators interact with TS instabilities (Tollmien-Schlichting waves) inside a transitional boundary layer by superimposing artificially generated counterwaves in order to delay the transition process. These actuators need to exhibit a r...

A hybrid numerical model of a micro mechanical actuator, which consists of a micrometer scaled coil and a permanent magnet, is presented. Furthermore, a comparison between different force calculation methods is given, which are opposed to laboratory measurements. Depending on these results, the impact on the mechanical deformation of the elastomeri...

In this work, a robust metallic amplification unit for piezoelectric microactuators is presented. The mechanism which is implemented with a sliced membrane structure made from a superelastic nickel titanium alloy is based on a mechanical lever in order to amplify the small piezoelectrically induced deformation. Therefore, increased stroke can be pr...

The present invention is directed to an object having an aero-or hydrodynamically active surface, wherein one or more biocatalytic and/or anti-icing proteins are immobilized on its surface. The present invention is further directed a method of providing a self-cleaning and/or anti-freeze coating to an aero-or hydrodynamically active surface of an o...

The amplitudes of miniaturized electromagnetic actuators are clearly enhanced if the eigenfrequencies of the membrane are used for actuation. However, the bandwidth for such operation is very limited. This can be overcome to some extent by the employment of membranes with electrically tunable stiffness. In this context we investigated membranes of...

Based on new developments on flat solenoid microcoils we aim to build microactuators and microsensors for aeronautic applications. Various device concepts based on flat microcoils are compared in terms of actuation and sensing capabilities using static finite element calculations. First the coenergy of the system is determined from which the force...

In microsystems technology, passivation layers are generally required to protect micro devices and functional elements against environmental impact, particularly against corrosion, thus increasing reliability and lifetime to acceptable values. In this work, the use of sputter-deposited aluminium oxide and aluminium nitride thin films on flexible po...

To ensure an enhanced life-time of micromachined devices, passivation layers are commonly applied to protect functionalized components against environmental stress. For flow sensitive elements on a flexible polyimide foil the use of reactively sputter-deposited aluminium oxide is investigated. Due to a high defect density located at the interface b...

Ein Drehratensensor besitzt einen stimmgabelförmigen Anregungsoszillator (11a, 11b, 12), der mit einem Ausleseoszillator (21a, 21b, 22) über eine Torsionsübertragungseinrichtung (23, 25a, 25b) verbunden ist, welche ihrerseits über eine Fixierung (4) zwischen dem Anregungsoszillator und dem Ausleseoszillator mit einem Substrat (1) verbunden ist. Die...

Aerospace applications of MEMS products, originally developed for automotive mass markets, are discussed. Various sensor examples with a high dual use potential are presented: inertial sensing, flow and gas sensing, robust micro sensors including SiC- and GaN-based devices, as well as first approaches towards flexible and distributed microsystems....

A new resonant accelerometer is presented consisting of a doubly clamped beam coupled to a seismic mass. The beam is thermally excited by an implanted resistor and its vibration is sensed piezoresistively. An acceleration which deflects the seismic mass leads to characteristic strains inside the resonator, shifting its resonance frequency. We studi...

The measurement of angular rate and linear acceleration are widely used in automotive systems [1,2]. In all present applications and even more in future „x-by-wire” steering systems sensor errors or undetected sensor failures may have serious consequences. In order to achieve a higher degree of sensor safety we developed a new self-test concept for...

This paper reports on a silicon angular rate sensor designed for automotive applications like overroll protection and electronic skidding protection. The sensor is based on a tuning fork principle with the tines being piezoelectrically excitated perpendicular to the wafer surface. Due to the Coriolis effect, an angular rate parallel to the axis of...

This paper reports on an enhanced anodic bonding technology of thin e-beam evaporated glass layers (d≤5 μm) for micromachined silicon sensors and actuators. This MOS-compatible technology has been developed for bonding between a silicon wafer with electrical structures and a bulk micromachined silicon wafer. A bonding frame structure can be realize...

Advanced automobile electronic systems like overroll protection , electronic skidding protection and x-by-wire systems require at least one robust and reliable angular rate sensor. Therefore a silicon micromachined gyroscope based on a tuning fork structure was developed with all resonant frequencies being above 10kHz and the primary and secondary...

In this work a silicon angular rate sensor for automotive applications with a new architecture is presented. It is based on the vibrating tuning fork principle with excitation direction of the tines perpendicular to the wafer surface. This arrangement allows the design of tines with significant inertial masses which lead to substantial signal. The...

We present an analysis of the attractors of a deterministic dynamics in formal neural networks characterized by binary threshold units and a nonsymmetric connectivity. It is shown that in these networks a stored pattern or a pattern sequence is represented by a cloud of attractors rather than by a single attractor. Dilution, which we describe by a...

We present an analysis of the attractors of a deterministic dynamics in formal neural networks characterized by binary threshold units and a nonsymmetric connectivity. It is shown that in these networks a stored pattern or a pattern sequence is represented by a cloud of attractors rather than by a single attractor. Dilution, which we describe by a...

We study the optimal learning capacity for neural networks withQ-state clock neurons, i.e. the states arecomplex numbers with magnitude 1 and azimuthal anglesn·2π/Q, withn=0, 1, ...,Q−1. Performing a phase space analysis, the learning capacity αc for given stability κ can be expressed by means of a double-integral with a simple geometrical interpre...

We study the storage capacity for temporal sequences of random patterns in networks with arbitrary delays, evolving under parallel dynamics. For sequences with a common period T, made up of patterns which remain constant for DELTA-time steps, couplings with delays tau = DELTA.k - 1, where k is integer, are particularly important since they are tune...

Starting from prescriptions for the learning and retrieval of correlated time-independent patterns in spin glass models we present a class of learning rules for the implementation of temporal sequences of patterns into spin models with randomly delayed interactions. From biological motivation a learning process is devised in such a way that, while...

The aim of this work is to discuss some similarities and differences between the Penrose model and certain random connections of pentagons as models for quasicrystalline alloys. A special growth process (by local rules) and geometric properties (like fractal dimensions, packing density, correlation functions) of the pentagon patterns are analysed a...

Extended x-ray absorption fine structure measurements show that in icosahedral (1) (MnAlSi) and (MnAl) there is a structural unit consisting of a cage of Mn atoms on the vertices of an icosahedron with an average distance between Mn atoms of 5 Å. The icosahedra are connected with an average of 3.4 ± 1.0 neighbouring icosahedra. It is suggested that...

A study on miniaturized actuators is presented in view of high speed flow control applications. Different actuation technologies are investigated in order to meet the challenging requirements for successful application. These are relatively high operational frequencies, high amplitudes, low overall power consumption and robustness to be ensured con...