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| 2. |
- Bejhed, Johan, et al.
(författare)
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Numerical modeling and verification of gas flow through a network of crossed narrow v-grooves
- 2006
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 16:10, s. 2006-2013
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Tidskriftsartikel (refereegranskat)abstract
- The gas flow through a network of crossing thin micro-machined channels has been successfully modeled and simulated. The crossings are formed by two sets of v-grooves that intersect as two silicon wafers are bonded together. The gas is distributed from inlets via a manifold of channels to the narrow v-grooves. The narrow v-grooves could work as a particle filter. The fluidic model is derived from the Navier–Stokes equation and assumes laminar isothermal flow and incorporates small Knudsen number corrections and Poiseuille number calculations. The simulations use the finite element method. Several elements of the full crossing network model are treated separately before lumping them together: the straight v-grooves, a single crossing in an infinite set and a set of exactly four crossings along the flow path. The introduction of a crossing effectively corresponds to a virtual reduction of the length of the flow path, thereby defining a new effective length. The first and last crossings of each flow path together contribute to a pressure drop equal to that from three ordinary crossings. The derived full network model has been compared to previous experimental results on several differently shaped crossed v-groove networks. Within the experimental errors, the model corresponds to the mass flow and pressure drop measurements. The main error source is the uncertainty in v-groove width which has a profound impact on the fluidic behavior.
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| 3. |
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| 4. |
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| 5. |
- Nguyen, Hugo, 1955-, et al.
(författare)
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A heavily miniaturized submersible : a terrestrial kickoff
- 2008
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Ingår i: Proceedings of ASTRA 2008. ; , s. 1-9
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Konferensbidrag (refereegranskat)abstract
- The vision of exploring extraterrestrial water findings employing a remotely operated submersible, as proposed by JPL/NASA for the investigation of the possible ocean underneath the frozen crust of Jupiter’s moon Europa, is now taking a step further into fulfilment. The Ångström Space Technology Centre has developed a sophisticated vehicle concept based on microtechnology for most of the navigational systems and payload systems. This enables a high function density, and a compact vehicle with a diameter of 50 mm and length of 200 mm, i.e. an overall size allowing the vehicle to be deployed through a borehole like that typical for arctic drilling.Here, the system architecture of the vehicle complying with the requirements on manoeuvrability, operational functions, and mission objectives is presented. In short, the vehicle in the first version will operate in deep and narrow waters, and will be equipped with a camera, sonar imaging system, an electronic tongue for chemical sampling, and a Conductivity-Temperature-Depth (CTD) sensor. Although the vehicle will be given certain autonomy in later versions, the first edition will rely on remote manual guidance. Commands for this, as well as power download, and data upload will be communicated through an optic fibre.The objective of this contribution is to present, for the first time, the status of the project including, briefly, the first results from miniaturized sonar, the vehicle bus design, and the design, realization and testing of the propulsion and attitude control systems differing in manoeuvrability, weight/volume, redundancy and efficiency.
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| 6. |
- Nguyen, Hugo, et al.
(författare)
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A solder sealing method for paraffin-filled microcavities
- 2006
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 16:11, s. 2369-2374
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Tidskriftsartikel (refereegranskat)abstract
- Demonstrated and investigated here is a method to seal microfluidic systems by soldering. As a particularly difficult case of growing importance, the sealing of openings contaminated with paraffin wax was studied. Solder paste, screen printed on a metallized silicon, substrate was melted locally through application of 6.5 to 10 V to a 5 Ω copper film resistor for a few seconds and found able to drive an intermediate layer of paraffin away and seal a 0.2 mm diameter circular via by wetting to a surrounding copper pad. Although verified to be robust, the process did result in failing seals on excessive heating because of consumption of the pads. Correctly performed, the technique provided a seal at least withstanding a pressure of 8 bar for 8 h at 85ºC.
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| 7. |
- Nguyen, Hugo, 1955-, et al.
(författare)
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Heavily Miniaturized Submersible – A Terrestrial Kickoff
- 2008
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Ingår i: Heavily Miniaturized Submersible – A Terrestrial Kickoff. ; , s. S14-01
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Konferensbidrag (refereegranskat)abstract
- The vision of exploring extraterrestrial water findings employing a remotely operated submersible, as proposed by JPL/NASA for the investigation of the possible ocean underneath the frozen crust of Jupiter’s moon Europa, is now taking a step further into fulfilment. The Ångström Space Technology Centre has developed a sophisticated vehicle concept based on microtechnology for most of the navigational systems and payload systems. This enables a high function density, and a compact vehicle with a diameter of 50 mm and length of 200 mm, i.e. an overall size allowing the vehicle to be deployed through a borehole like that typical for arctic drilling.Here, the system architecture of the vehicle complying with the requirements on manoeuvrability, operational functions, and mission objectives is presented. In short, the vehicle in the first version will operate in deep and narrow waters, and will be equipped with a camera, sonar imaging system, an electronic tongue for chemical sampling, and a Conductivity-Temperature-Depth (CTD) sensor. Although the vehicle will be given certain autonomy in later versions, the first edition will rely on remote manual guidance. Commands for this, as well as power download, and data upload will be communicated through an optic fibre.The objective of this contribution is to present, for the first time, the status of the project including, briefly, the first results from miniaturized sonar, the vehicle bus design, and the design, realization and testing of the propulsion and attitude control systems differing in manoeuvrability, weight/volume, redundancy and efficiency.
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| 8. |
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| 9. |
- Nguyen, Hugo, 1955-
(författare)
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Microsystem Interfaces for Space
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microsystem interfaces to the macroscopic surroundings and within the microsystems themselves are formidable challenges that this thesis makes an effort to overcome, specifically for enabling a spacecraft based entirely on microsystems. The NanoSpace-1 nanospacecraft is a full-fledged satellite design with mass below 10 kg. The high performance with respect to mass is enabled by a massive implementation of microsystem technology – the entire spacecraft structure is built from square silicon panels that allow for efficient microsystem integration. The panels comprise bonded silicon wafers, fitted with silicone rubber gaskets into aluminium frames. Each module of the spacecraft is added in a way that strengthens and stiffens the overall spacecraft structure. The structural integrity of the silicon module as a generic building block has been successfully proven. The basic design (silicon, silicone, aluminium) survived considerable mechanical loads, where the silicon material contributed significantly to the strength of the structural element. Structural modeling of the silicon building blocks enables rapid iterative design of e.g. spacecraft structures by the use of pertinent model simplifications. Other microsystem interfaces treats fluidic, thermal, and mechanical functions. First, solder sealing of microsystem cavities was demonstrated, using screen-printed solder and localized resistive heating in the microsystem interface. Second, a dismountable fluidic microsystem connector, using a ridged silicon membrane, intended for monopropellant thruster systems, was developed. Third, a thermally regulated microvalve for minute flows, made by a silicon ridge imprint in a stainless steel nipple, was investigated. Finally, particle filters for gas interfaces to microsystems, or between parts of fluidic microsystems, were made from sets of crossed v-grooves in the interface of a bonded silicon wafer stack. Filter manufacture, mass flow and pressure drop characterization, together with numeric modeling for filter design, was performed. All in all this reduces the weight and volume when microsystems are interfaced in their applications.
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| 10. |
- Nguyen, Hugo, et al.
(författare)
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Structural Integrity of Flat Silicon Panels for Nanosatellites : Modeling and Testing
- 2006
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Ingår i: Journal of Spacecraft and Rockets. - : American Institute of Aeronautics and Astronautics (AIAA). - 0022-4650 .- 1533-6794. ; 43:6, s. 1319-1327
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Tidskriftsartikel (refereegranskat)abstract
- To utilize the high mass fraction of silicon material in a nanosatellite based on micro-electro-mechanical systems, part of the structural function has been assigned to the flat silicon stacks embracing these systems. Three modules for destructive testing in bending, warping and shearing cases were built with 68x68x1 mm silicon stacks bonded in aluminium frames by in-situ casting of silicone rubber. The rubber served as the deformation zone between the stiff and brittle silicon stacks and their weaker and ductile aluminium frames. A special test module of the same size was built with strain gauges of Nichrome (thin film deposited directly on the surface of the silicon stack). Elastic deformation tests on this as well as simulations using finite element analysis were performed for bending, warping and shearing loads of up to 80, 40 and 99 N, respectively. The test module was disassembled after the test series and examined. The actual thickness of the rubber was measured and entered into the model for simulation. The correlation between simulations and experimental measurements was good with deviation of about 30%. The results show that the rubber works well as a mechanical interface. Its thickness influences the stress in the silicon stack significantly. The silicon stack stiffens the module by a factor of 46 and lowers the stress in its frame 24 times in shearing mode, which is the most relevant loading case for the satellite framework. Thus, the concept of using flat silicon panels as structural elements is fully feasible.
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| 11. |
- Nguyen, Hugo, et al.
(författare)
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Thermally regulated valve for minute flows
- 2007
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 25:4, s. 686-691
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a gas valve using a microstructured silicon valve lid and a stainless steel valve seat clamped axially together in an aluminum cylinder is investigated. The difference in coefficient of thermal expansion of these components makes the valve open and close on a temperature change. A simple model accounting for elastic deformation of the system’s components is proposed to facilitate design of the valve. By means of a helium leak detector, a typical increase in flow rate from 1.0×10−8 to 1.0×10−4 sccs gaseous helium under a pressure of up to 10 bars was observed upon the increase of temperature from 12 to around 98 °C, after a single breaking-in. Plastic deformation of the valve seat as a consequence of an imprint of the microstructured valve lid and contaminating particles was studied. Microscopy confirmed a tolerance for particles of up to a few micrometers in diameter. Larger particles were found to be a possible cause of failure.
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| 12. |
- Persson, Anders, 1982-, et al.
(författare)
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Micro- and nanostructured magnetic field sensor for space applications
- 2009
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Ingår i: 15th International Conference on Solid-State SensorsTransducers 2009. ; , s. 1190-1193
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Konferensbidrag (refereegranskat)abstract
- Magnetometers are popular payloads on scientific space missions. Here, the design and fabrication process of a miniaturized magnetometer based on tunneling magnetoresistance is presented. The process is capable of making magnetic tunnel junctions in a wide size range, by employing both UV lithography and focused ion beam milling and deposition. Ga implantation in the ferromagnetic electrodes of the junction is studied in more detail. It was shown that Ga implantation may harm the magnetometer if the irradiation dose exceeds 1014 Ga+ cm-2.
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| 13. |
- Raanaei, Hossein, et al.
(författare)
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Imprinting layer specific magnetic anisotropies in amorphous multilayers
- 2009
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Ingår i: Journal of Applied Physics. - : AIP. - 0021-8979 .- 1089-7550. ; 106:2, s. 023918-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate how layer specific in-plane magnetic anisotropy can be imprinted in amorphous multilayers. The anisotropy is obtained by growing the magnetic layers in the presence of an external field and the anisotropy direction can thereby be arbitrarily chosen for each of the magnetic layers. We used Co68Fe24Zr8 and Al70Zr30 layers as building blocks for demonstrating this effect. The imprinting is expected to be obtainable for a wide range of amorphous materials when grown at temperatures below the magnetic ordering temperature.
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