Benecke, Wolfgang
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Benecke, Wolfgang
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Benecke, Wolfgang
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Benecke, W.
GND
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Item type:Publication, Capacitive Surface-Micromachined Pressure Sensors on Fused SilicaContributions to Micromachining on Fused Silica(2009-06-09); ; ; Capacitive absolute pressure sensors fabricated by means of surface-micromachining on fused silica are presented. The non-conductive substrate material eliminates all parasitic capacitances to the bulk. Fabricated prototypes are simulated with SPICE and a lumped components model is derived. Simulation data is compared to wafer and package level test results. Touch-mode hysteresis, sensitivity, and magnitude of capacitance are discussed. Processing on fused silica is covered in detail with a focus on surface micromachining. Substrate material related process challenges are addressed such as high film stress levels as well as viscose and elastic deformation. Analytic formulas for surface-micromachined circular plates are presented. Topography, stress, and a limited displacement magnitude are considered by means of normalization. The approach leads to a solution for plates in touch-mode. General characteristics of capacitive circular plate transducers in normal- and touch-mode are discussed.doctoral thesis308 402 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Development of the technological process for the production of the electrostatic curved beam actuator for pneumatic microvalves(2012-07-16); ; ; This work focuses on the development of an effective technological process for the production of the electrostatic curved beam actuator capable to be used as a driving element in different devices such as microswitches or microvalves. Main attention was drawn to the investigation of electroplating technique as a critical process in the microactuator fabrication as well as to the design of the actuator. In addition, usability of ceramic substrates for the microactuator and microvalve production was examined. The idea behind it was that ceramic substrates can be preprocessed and delivered already with necessary electrical connections on it. This would make the entire production process simpler and cheaper. Several types of polished alumina (Al2O3) substrates were used for this purpose. Electrostatic actuation principle was chosen for its good scaling properties to small dimensions, low power consumption, smaller size and higher switching speed. Curved shape of the actuator allows to reduce its pull-in voltage and thus to increase the amplitude of motion as compared to the parallel-plate structures. The material of the actuator is nickel. It was chosen for its good mechanical properties and relative simplicity of processing. Double layer nickel electroplating was used to produce the microactuator. The layers have different stress gradients controlled by current density during the electroplating process, making it possible to achieve the desired bending of the structure. Compared to bimetallic bending cantilever actuators, the curvature of the single-metal beam is less dependable on temperature and aging. Thus, more stable performance under changing working conditions was ensured. In order to avoid sticking of the microactuator to the isolation layer in the closed state, an array of stand-off bumps was added on the back-side of the beam. These bumps reduce the contact area and increase the distance between the actuator and the isolation layer. Fifteen design variants of the actuator differing in length and width were fabricated in order find the most effective solution for given system requirements. Based on the actuators technological process developed in this work, a simple electrostatic microvalve was designed and produced. Final variants of microvalve were fabricated on a standard 380 µm thick silicon wafer. Gas inlet channel as well as the electrodes and the actuator itself are all placed on the same substrate in order to reduce the size and cost of the system. During characterization, mechanical stability of the actuators and microvalves were studied by means of drop, temperature and shear tests in order to prove the reliability of the system. System performance tests proved stable pull-in voltages from 8,6 V to 11,6 V. Maximal gas flow through the valve was 110±5 ml/min at applied differential pressure of 2 bar.doctoral thesis283 150 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Entwicklung und Charakterisierung von siliziumbasierten mikrotechnischen Komponenten für miniaturisierte DNA-Analysen(2003-07-16); ; ; This thesis deals with the design, fabrication and characterization of microsystems for use as single components within a miniaturized multistage DNA analysis. Within the first part of this work the example of a new microreaction chamber is used to demonstrate the suitability of silicon-based microsystems for DNA amplification by the temperature- and enzymatically controlled polymerase chain reaction (PCR). Covering design and fabrication aspects, two alternative system concepts are presented and compared. By the selected microchamber with double-sided heaters and sensor elements for temperature-controlling a high temperature homogeneity as well as maximum heating and cooling rates are achieved. A main focus of the characterization is the analysis of binding reactions of single-stranded oligonucleotide primers, double-stranded template molecules and the polymerase on microchamber surfaces. The successful DNA amplification in microchambers with volumes of 6 µl are demonstrated, whereas for a complete PCR with 30 cycles less than 18 min are needed.The second part is focused on a novel measurement principle for real-time detection of hybridization reactions on planar sensor surfaces by an impedance analysis of metallicinterdigitated electrodes. By using functionalized polymer microparticles, so-called microbeads, for labeling of DNA to be analyzed an increasing of the signal intensity is achieved.For modeling the sensor behaviour a two-dimensional electrical equivalent circuit is developed and applied for deriving of design and measurement criterions. The fabricated single sensor element consists of a thin film interdigitated electrode based on a tungsten titanium alloy with a dielectric passivation layer. Monocrystalline silicon and amorphous quartz glass are used as substrate materials. By experiments in a stopped-flow hybridization buffer the proof of functionality of the sensor element is provided.doctoral thesis256 99