| 1. |
- Berglund, Martin, 1985-, et al.
(författare)
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Extreme-temperature lab on a chip for optogalvanic spectroscopy of ultra small samples – key components and a first integration attempt
- 2016
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Ingår i: 27th Micromechanics And Microsystems Europe Workshop (MME 2016). - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- This is a short summary of the authors’ recent R&D on valves, combustors, plasma sources, and pressure and temperature sensors, realized in high-temperature co-fired ceramics, and an account for the first attempt to monolithically integrate them to form a lab on a chip for sample administration, preparation and analysis, as a stage in optogalvanic spectroscopy.
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| 2. |
- Khaji, Zahra, et al.
(författare)
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Alumina-based monopropellant microthruster with integrated heater, catalytic bed and temperature sensors
- 2016
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Ingår i: 27th Micromechanics And Microsystems Europe Workshop (Mme 2016). - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- A liquid propellant alumina microthruster with an integrated heater, catalytic bed and two temperature sensors has been developed and tested using 30 wt. % hydrogen peroxide. The temperature sensors and the catalytic bed were screen-printed using platinum paste on tapes of alumina that was stacked and laminated before sintering. In order to increase the surface of the catalytic bed, the platinum paste was mixed with a sacrificial paste that disappeared during sintering, leaving behind a porous and rough layer. Complete evaporation and combustion, resulting in only gas coming from the outlet, was achieved with powers above 3.7 W for a propellant flow of 50 μl/min. At this power, the catalytic bed reached a maximum temperature of 147°C. The component was successfully operated up to a temperature of 307°C, where it cracked.
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| 3. |
- Khaji, Zahra, et al.
(författare)
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Catalytic Effect of Platinum and Silver in a Hydrogen Peroxide Monopropellant Ceramic Microthruster
- 2020
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Ingår i: Propulsion and power research. - : Elsevier. - 2212-540X. ; 9:3, s. 216-224
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Tidskriftsartikel (refereegranskat)abstract
- Ceramic microthrusters with an embedded Pt resistive heater, two temperature sensors, and a Pt or Ag catalytic bed were made of high-temperature co-fired alumina ceramics. To increase the surface area by a factor of 1.21, and so the catalytic effect, the Pt catalytic bed was made porous by mixing the Pt paste with 15–20vol.% graphite sacrificial paste before screen printing it. Ag was in-situ electroplated on the porous Pt surface after sintering. Decomposition of 50wt.% hydrogen peroxide as a monopropellant was studied both qualitatively and quantitatively by changing the catalyst (between Ag and Pt), flow rate (15–55 μl/min), and operating temperature (115–300 °C). A reference device without catalyst exhibited an unstable behavior as a result of no, or very little, decomposition, whereas the Ag catalyst was more stable, and the Pt one even more stable. Also, Pt was found to be slightly more effective. Quantitatively, there were small differences between Pt and Ag in the power needed to maintain the temperature. The inventive methods to make the Pt bed porous as well as in-situ electroplating Ag were successfully demonstrated.
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| 4. |
- Khaji, Zahra, et al.
(författare)
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Endurance and Failure of an Alumina-based Monopropellant Microthruster with Integrated Heater, Catalytic Bed and Temperature Sensors
- 2017
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 27:5, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Monopropellant ceramic microthrusters with an integrated heater, catalytic bed and two temperature sensors, but of various designs, were manufactured by milling a fluidic channel and chamber, and a nozzle, and screen printing platinum patterns on green tapes of alumina that were stacked and laminated before sintering. In order to increase the surface area of the catalytic bed, the platinum paste was mixed with a sacrificial paste that disappeared during sintering, to leave behind a porous and rough layer. As an early development level in manufacturing robust and high-temperature tolerant microthrusters, the influence of design on the temperature gradients and dry temperature tolerance of the devices was studied. On average, the small reaction chambers showed a more than 1.5 times higher dry temperature tolerance (in centigrade) compared to devices with larger chambers, independent of the heater and device size. However, for a given temperature, big devices consumed on average 2.9 times more power than the small ones. It was also found that over the same area and under the same heating conditions, devices with small chambers were subjected to approximately 40% smaller temperature differences. A pressure test done on two small devices with small chambers revealed that pressures of at least 26.3 bar could be tolerated. Above this pressure, the interfaces failed but the devices were not damaged. To investigate the cooling effect of the micropropellant, the endurance of a full thruster was also studied under wet testing where it was fed with 31 wt.% hydrogen peroxide. The thruster demonstrated complete evaporation and/or full decomposition at a power above 3.7 W for a propellant flow of 50 mu l min(-1). At this power, the catalytic bed locally reached a temperature of 147 degrees C. The component was successfully heated to an operating temperature of 307 degrees C, where it cracked. Under these firing conditions, and assuming complete decomposition, calculations give a thrust and specific impulse of 0.96 mN and 106 s, respectively. In the case of evaporation, the corresponding values are calculated to be 0.84 mN and 92 s.
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| 5. |
- Khaji, Zahra, et al.
(författare)
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Manufacturing and characterization of a ceramic single-use microvalve
- 2016
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 26:9
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Tidskriftsartikel (refereegranskat)abstract
- We present the manufacturing and characterization of a ceramic single-use microvalve withthe potential to be integrated in lab-on-a-chip devices, and forsee its utilization in space andother demanding applications. A 3 mm diameter membrane was used as the flow barrier, andthe opening mechanism was based on cracking the membrane by inducing thermal stresses onit with fast and localized resistive heating.Four manufacturing schemes based on high-temperature co-fired ceramic technology werestudied. Three designs for the integrated heaters and two thicknesses of 40 and 120 μmfor the membranes were considered, and the heat distribution over their membranes, therequired heating energies, their opening mode, and the flows admitted through were compared.Furthermore, the effect of applying +1 and −1 bar pressure difference on the membraneduring cracking was investigated. Thick membranes demonstrated unpromising results forlow-pressure applications since the heating either resulted in microcracks or cracking of thewhole chip. Because of the higher pressure tolerance of the thick membranes, the designwith microcracks can be considered for high-pressure applications where flow is facilitatedanyway. Thin membranes, on the other hand, showed different opening sizes depending onheater design and, consequently, heat distribution over the membranes, from microcracks toholes with sizes of 3–100% of the membrane area. For all the designs, applying +1 bar overpressure contributed to bigger openings, whereas −1 bar pressure difference only did so forone of the designs, resulting in smaller openings for the other two. The energy required forbreaking these membranes was a few hundred mJ with no significant dependence on designand applied pressure. The maximum sustainable pressure of the valve for the current designand thin membranes was 7 bar.
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| 6. |
- Kratz, Henrik, 1974-, et al.
(författare)
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Analysis of Thermal Transients in an Asymmetric Silicon-Based Heat Dissipation Stage
- 2007
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Ingår i: IEEE transactions on components and packaging technologies (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1521-3331 .- 1557-9972. ; 30:3, s. 444-456
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Tidskriftsartikel (refereegranskat)abstract
- Thermal management is crucial for many microsystems and electronics applications (and that of miniaturized spacecraft is particularly demanding). This paper presents thermal modeling and scaling of a generic multiwafer silicon segment for placement in between two devices, or as a stage for a single one, in need of asymmetric thermal management. The unit is autonomous, i.e., it doesn't require any input signals or power. It comprises paraffin acting both as a heat sink, or thermal storage, and a material activating heat switches. The former mitigates heat bursts and accommodates power initially generated in, e.g., attached electronics, whereas the latter facilitates heat dissipation through heat guides during more intensive operation. Its function and physical properties are described in detail. A lumped thermal model has been constructed and implemented in the Simulink environment to investigate effects from: physical scaling of the unit, and change of its boundary temperature and coupling thereto, power generated, its emission and absorption properties and area fractions dedicated for passive devices, infrared (IR) emission, and heat guides on the unit's exterior, as well as fractional cross sections of paraffin, heat guides and other structural material in its interior. Conclusions, based on simulation results, are made and design rules based on the thermal modeling are presented. It was found that a 68 × 68 mm module could handle more than 10 W for 6 min in its heat sink mode alone. Subjected to 15 W for the same time, the module enters its active dissipation mode by closing its heat switches. A lateral increase and simultaneous vertical decrease of the unit's size resulted in overheating, whereas most scaling did not cause depletion of the heat sink. Changing the area fractions of various constituents also indicated operational stability with exception for excessive enlargement of passive heat guide material, exchanging structural material with paraffin, or severely limiting IR emission (by emitter area reduction or using low emission material), or using high absorbance material. Altering the boundary temperature and interface conductance proved to be means of biasing the system to various operating temperatures.
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| 7. |
- Lotfi, Sara, 1985-, et al.
(författare)
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Hybrid microtransmitter for free-space optical spacecraft communication : design, manufacturing, and characterization
- 2009
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Ingår i: Proc. SPIEPhotonics West, MOEMS and Miniaturized Systems VIII, Jan 24-29, San Jose, CA. - : SPIE. ; , s. 72080N-12-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Opticalintra-communication links are investigated by several currently operational qualification missions.Compared with RF communication systems, the optical domain obtains awider bandwidth, enables miniaturized spacecraft and reduced power consumption. Inthis project, a microtransmitter is designed and manufactured for formationflying spacecraft with transmission rates of 1 Gbit/s. Simulations inMatlab and Simulink show that a BER of 10-9 canbe achieved with aperture sizes of 1 cm and atransmitter output peak power of 12 mW for a distanceof 10 km. The results show that the performance ofthe communication link decreases due to mechanical vibrations in thespacecraft together with a narrow laser beam. A dual-axis microactuatordesigned as a deflectable mirror has been developed for thelaser beam steering where the fabrication is based on adouble-sided, bulk micromachining process. The mirror actuates by joints consistingof v-grooves filled with SU-8 polymer. The deflection is controlledby integrated resistive heaters in the joints causing the polymerto expand thermally. Results show that the mirror actuates 20-30°in the temperature interval 25-250°C. Flat Fresnel lenses made ofPyrex 7740 are used to collimate the laser beam. Theselenses are simulated in the Comsol software and optimized fora 670 nm red VCSEL. The lenses are manufactured usinglithography and reactive ion etching. All tests are made ina normal laboratory environment, but the effect of the spaceenvironment is discussed
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| 8. |
- 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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| 9. |
- Nguyen, Hugo, et al.
(författare)
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Experimental Studies of Sealing Mechanism of a Dismountable Microsystem‑to‑Macropart Fluidic Connector for High Pressure and a Wide Range of Temperature
- 2010
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Ingår i: Advances in Mechanical Engineering. - : Hindawi. - 1687-8132 .- 1687-8140. ; 2010
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Tidskriftsartikel (refereegranskat)abstract
- As fluidic microelectromechanical devices are developing and often attached to, or embedded in, large, complex and expensive systems, the issues of modularity, maintenance and subsystem replacement arise. In this work, a robust silicon connector suitable for high-pressure applications – likely with harsh fluids – in the temperature range of +100 to –100°C is demonstrated and tested together with a stainless steel nipple representing a simple and typical macropart. With a micromachined circular membrane equipped with a 5 μm high ridge, this connector is able to maintain a leak rate below 2.0´10-8 scc/s of gaseous helium with a pressure of up to 9.7 bar. Degradation of the sealing performance on reassembly is associated with the indentation of the ridge. However, the ridge makes the sealing interface less sensitive to particles in comparison with a flat reference. Most evaluation is made through so called heat-until-leak tests conducted to determine the maximum working temperature and the sealing mechanism of the connector. A couple of these are followed by cryogenic testing. The effect of thermal mismatch of the components is discussed and utilized as an early warning mechanism.
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| 10. |
- 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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