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Characteristics of a hot-wire microsensor for time-dependent wall shear stress measurements
Thermo and Fluid Dynamics, Chalmers University of Technology.
Thermo and Fluid Dynamics Department, Chalmers University of Technology.
KTH, Superseded Departments, Signals, Sensors and Systems.ORCID iD: 0000-0002-9327-2544
KTH, Superseded Departments, Signals, Sensors and Systems.ORCID iD: 0000-0001-9552-4234
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2003 (English)In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 35, no 3, 240-251 p.Article in journal (Refereed) Published
Abstract [en]

Hot-wire microsensors for the purpose of measuring the instantaneous velocity gradient close to a wall were designed and their characteristics were evaluated. The sensors were made using MEMS (microelectromechanical systems) technology, which permits the fabrication of various microgeometrical configurations with high precision and good repeatability. The design is based on estimates of the heat rates from the sensor wire to the air, through the supports, and to the wall. Several hot-wire configurations were fabricated with wires positioned in the range 50-250 mum from the wall. Requirements for the design and details of the fabrication methodology are outlined. The hot-wire microsensors were calibrated and tested in a flat-plate boundary layer with and without pressure gradients and were found to have good steady-state characteristics. In addition, the developed sensors were used for preliminary studies of transitional phenomena and turbulence, and the sensors were found to have a good time-dependent response as well.

Place, publisher, year, edition, pages
2003. Vol. 35, no 3, 240-251 p.
Keyword [en]
dynamic-response, viscous sublayer, skin-friction, voltage-perturbation, spatial-resolution, film probes, anemometer, flow, velocity, turbulence
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-22831DOI: 10.1007/s00348-003-0624-yISI: 000185458500003OAI: diva2:341529
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2010-10-19Bibliographically approved
In thesis
1. Assembly of microsystems for optical and fluidic applications
Open this publication in new window or tab >>Assembly of microsystems for optical and fluidic applications
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis addresses assembly issues encountered in optical and fluidic microsystem applications.

In optics, the first subject concerns the active alignment of components in optical fibersystems. A solution for reducing the cost of optical component assembly while retaining submicron accuracy is to integrate the alignment mechanism onto the optical substrate. A polymer V-shaped actuator is presented that can carry the weight of the large components - on a micromechanical scale - and that can generate movement with six degrees of freedom.

The second subject in optics is the CMOS-compatible fabrication of monocrystalline silicon micromirror arrays that are intended to serve as CMOS-controlled high-quality spatial light modulators in maskless microlithography systems. A wafer-level assembly method is presented that is based on adhesive wafer bonding whereby a monocrystalline layer is transferred onto a substrate wafer in a CMOS-compatible process without needing bond alignment.

In fluidics, a hybrid assembly method is introduced that combines two separately micromachined structures to create hotwire anemometers that protrude from a surface with minimum interference with the air flow. The assembled sensor enables one to make accurate time-resolved measurements of the wall shear stress, a quantity that has previously been hard to measure with high time resolution. Also in the field of hotwire anemometers, a method using a hotwire anemometer array is presented for measuring the mass flow, temperature and composition of a gas in a duct.

In biochemistry, a bio-analysis chip is presented. Single nucleotide polymorphism scoring is performed using dynamic allele-specific hybridization (DASH). Using monolayers of beads, multiplexing based on single-bead analysis is achieved at heating rates more than 20 times faster than conventional DASH provides.

Space and material e±ciency in packaging are the focus of the other two projects in fluidics. The first introduces an assembly based on layering conductive adhesives for the fabrication of miniature polymer electrolyte membrane fuel cells. The fuel cells made with this low-cost approach perform among the best of their type to date. The second project concerns a new cross-flow microvalve concept. Intended as a step towards the mass production of large-flow I/P converters, the silicon footprint area is minimized by an out-of-plane moving gate and in-plane, half-open pneumatic channels.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xiv, 70 p.
Trita-ILA, ISSN 0281-2878 ; 0501
Applied mechanics, microsystem technology, micromachining, assembly, active alignment, BCB, Teknisk mekanik
National Category
Mechanical Engineering
urn:nbn:se:kth:diva-120 (URN)91-7283-958-9 (ISBN)
Public defence
2005-02-11, Kollegiesalen, Valhallavägen 79, Stockholm, 14:00
QC 20101019Available from: 2005-02-09 Created: 2005-02-09 Last updated: 2010-10-19Bibliographically approved

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