| 1. |
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- 2019
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Journal article (peer-reviewed)
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| 2. |
- Berglund, Martin, 1985-, et al.
(author)
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Dynamic characterization and modelling of a dual-axis beam steering device for performance understanding, optimization, and control design
- 2013
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In: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 23:4, s. 045020-
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Journal article (peer-reviewed)abstract
- This paper presents a lumped thermal model of a dual-axis laser micromirror device for beam steering in a free-space optical (FSO) communication system, designed for fractionated spacecraft. An FSO communication system provides several advantages, such as larger bandwidth, smaller size and weight of the communication payload and less power consumption. A dual-axis mirror device is designed and realized using microelectromechanical systems technology. The fabrication is based on a double-sided, bulk micromachining process, where the mirror actuates thermally by joints consisting of v-grooves filled with the SU-8 polymer. The size of the device, consisting of a mirror, which is deflectable versus its frame in one direction, and through deflection of the frame in the other, is 15.4 × 10.4 × 0.3 mm3. In order to further characterize and understand the micromirror device, a Simulink state-space model of the actuator is set up using thermal and mechanical properties from a realized actuator. A deviation of less than 2% between the modelled and measured devices was obtained in an actuating temperature range of 20–200 °C. The model of the physical device was examined by evaluating its performance in vacuum, and by changing physical parameters, such as thickness and material composition. By this, design parameters were evaluated for performance gain and usability. For example, the crosstalk between the two actuators deflecting the mirror along its two axes in atmospheric pressure is projected to go down from 97% to 6% when changing the frame material from silicon to silicon dioxide. A feedback control system was also designed around the model in order to examine the possibility to make a robust control system for the physical device. In conclusion, the model of the actuator presented in this paper can be used for further understanding and development of the actuator system.
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| 3. |
- Berglund, Martin, 1985-, et al.
(author)
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Microfluidics integrable plasma source powered by a silicon through-substrate split-ring resonator
- 2013
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In: Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS EUROSENSORS XXVII). ; , s. 2608-2611
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Conference paper (other academic/artistic)abstract
- A novel microplasma source, based on a microstrip split-ring resonator design with electrodes integrated in its silicon substrate, was designed, manufactured and evaluated. This device should offer straightforward integration with other MEMS components, and has a plasma discharge gap with a controlled volume and geometry, with potential for microfluidics. Two realized devices were resonant at around 2.9 GHz with quality factors of 26.6 and 18.7. Two different plasma ignition modes were observed, where the plasma at low pressures was not confined to the gap but rather appeared between the ends of the electrodes on the backside.
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| 4. |
- Bruhn, Fredrik, et al.
(author)
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A Preliminary Design for a Spherical Inflatable Microrover for Planetary Exploration
- 2008
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In: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 63:5-6, s. 618-631
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Journal article (peer-reviewed)abstract
- The Spherical Mobile Investigator for Planetary Surface (SMIPS) concept aims at making use of the latest developments within extreme miniaturization of space systems. The introduction of Microelectromechanical Systems (MEMSs) and higher level Multifunctional Microsystems (MMSs) design solutions gives the robot high performance per weight unit. The untraditional spherical shape makes it easily maneuverable and thus provides a platform for scientific investigations of interplanetary bodies. Preliminary investigations of the SMIPS concept show several advantages over conventional robots and rovers in maneuverability, coverage, size, and mass. A locomotion proof-of-concept has been Studied together with a new distributed on-board data system configuration. This paper discusses theoretical robot analysis, an overall concept, possible science, enabling technologies, and how to perform scientific investigations. A preliminary design of an inflatable multifunctional shell is proposed.
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| 5. |
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| 6. |
- Böhnke, Tobias, et al.
(author)
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Surfaces with high solar reflectance and high thermal emittance on structured silicon for spacecraft thermal control
- 2008
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In: Optical materials (Amsterdam). - : Elsevier BV. - 0925-3467 .- 1873-1252. ; 30:9, s. 1410-1421
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Journal article (peer-reviewed)abstract
- Presented here is an examination of unstructured and structured (by anisotropic etching), monocrystalline silicon wafers coated with sputter deposited aluminum and chemical vapor deposited silicon dioxide for high solar reflectance and high thermal emittance, respectively. The topography of the samples was characterized with optical and scanning electron microscopy. Optical properties were examined with reflectance and transmittance spectroscopy, partly by usage of an integrating sphere. The measurement results were used to estimate the equilibrium temperature of the surfaces in space. The suitability of the surfaces with high solar reflectance and high thermal emittance to aid in the thermal control of miniaturized, highly integrated components for space applications is discussed. A silicon dioxide layer on a metal layer results in a slightly lower reflectance when compared to surfaces with only a metal layer, but might be beneficial for miniaturized space components and modules that have to dissipate internally generated heat into open space. Additionally, it is an advantage to microstructure the emitting surface for enhanced radiation of excess heat.
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| 7. |
- Cheng, Shi, et al.
(author)
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79 GHz Slot Antennas Based on Substrate Integrated Waveguides (SIW) in a Flexible Printed Circuit Board
- 2009
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In: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 57:1, s. 64-71
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Journal article (peer-reviewed)abstract
- The design, fabrication and characterization of 79 GHz slot antennas based on substrate integrated waveguides (SIW) are presented in this paper. All the prototypes are fabricated in a polyimide flex foil using printed circuit board (PCB) fabrication processes. A novel concept is used to minimize the leakage losses of the SlWs at millimeter wave frequencies. Different losses in the SlWs are analyzed. SIW-based single slot antenna, longitudinal and four-by-four slot array antennas are numerically and experimentally studied. Measurements of the antennas show approximately 4.7%, 5.4% and 10.7% impedance bandwidth (S-11 = -10 dB) with 2.8 dBi, 6.0 dBi and 11.0 dBi maximum antenna gain around 79 GHz, respectively. The measured results are in good agreement with the numerical simulations.
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| 8. |
- Hansen, C. J., et al.
(author)
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Silver and palladium help unveil the nature of a second r-process
- 2012
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In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 545
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Journal article (peer-reviewed)abstract
- Context. The rapid neutron-capture process, which created about half of the heaviest elements in the solar system, is believed to have been unique. Many recent studies have shown that this uniqueness is not true for the formation of lighter elements, in particular those in the atomic number range 38 < Z < 48. Among these, palladium (Pd) and especially silver (Ag) are expected to be key indicators of a possible second r-process, but until recently they have been studied only in a few stars. We therefore target Pd and Ag in a large sample of stars and compare these abundances to those of Sr, Y, Zr, Ba, and Eu produced by the slow (s-) and rapid (r-) neutron-capture processes. Hereby we investigate the nature of the formation process of Ag and Pd. Aims. We study the abundances of seven elements (Sr, Y, Zr, Pd, Ag, Ba, and Eu) to gain insight into the formation process of the elements and explore in depth the nature of the second r-process. Methods. By adopting a homogeneous one-dimensional local thermodynamic equilibrium (1D LTE) analysis of 71 stars, we derive stellar abundances using the spectral synthesis code MOOG, and the MARCS model atmospheres. We calculate abundance ratio trends and compare the derived abundances to site-dependent yield predictions (low-mass O-Ne-Mg core-collapse supernovae and parametrised high-entropy winds), to extract characteristics of the second r-process. Results. The seven elements are tracers of different (neutron-capture) processes, which in turn allows us to constrain the formation process(es) of Pd and Ag. The abundance ratios of the heavy elements are found to be correlated and anti-correlated. These trends lead to clear indications that a second/weak r-process, is responsible for the formation of Pd and Ag. On the basis of the comparison to the model predictions, we find that the conditions under which this process takes place differ from those for the main r-process in needing lower neutron number densities, lower neutron-to-seed ratios, and lower entropies, and/or higher electron abundances. Conclusions. Our analysis confirms that Pd and Ag form via a rapid neutron-capture process that differs from the main r-process, the main and weak s- processes, and charged particle freeze-outs. We find that this process is efficiently working down to the lowest metallicity sampled by our analysis ([Fe/H] = -3.3). Our results may indicate that a combination of these explosive sites is needed to explain the variety in the observationally derived abundance patterns.
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| 9. |
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| 10. |
- Janhunen, Pekka, et al.
(author)
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Electric Solar Wind Sail in tailwind
- 2011
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In: EPSC-DPS Joint Meeting 2011.
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Conference paper (peer-reviewed)abstract
- The Electric Solar Wind Sail (E-sail) is a novelpropulsion concept that enables faster space travel tomany solar system targets. E-sail uses charged solarwind particles as the source of its propulsion. This isachieved by deploying long, conducting and chargedtethers, which get pushed by the solar wind byCoulomb drag [1].E-sail technology is being developed to technicalreadiness level (TRL) 4-5 by the European Union’sSeventh Framework Programme for Research andTechnological Development, EU FP7, in a projectnamed ESAIL (http://www.electric-sailing.fi/fp7).Prototypes of the key parts are to be produced. Thedesign will be scalable so that a real solar winddemonstration mission could be scaled up from them.We review here the latest results of the constantlyevolving E-sail project.
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| 11. |
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| 12. |
- Janhunen, P., et al.
(author)
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Invited Article: Electric solar wind sail : Toward test missions
- 2010
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 81:11, s. 111301-
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Journal article (peer-reviewed)abstract
- The electric solar wind sail (E-sail) is a space propulsion concept that uses the natural solar wind dynamic pressure for producing spacecraft thrust. In its baseline form, the E-sail consists of a number of long, thin, conducting, and centrifugally stretched tethers, which are kept in a high positive potential by an onboard electron gun. The concept gains its efficiency from the fact that the effective sail area, i.e., the potential structure of the tethers, can be millions of times larger than the physical area of the thin tethers wires, which offsets the fact that the dynamic pressure of the solar wind is very weak. Indeed, according to the most recent published estimates, an E-sail of 1 N thrust and 100 kg mass could be built in the rather near future, providing a revolutionary level of propulsive performance (specific acceleration) for travel in the solar system. Here we give a review of the ongoing technical development work of the E-sail, covering tether construction, overall mechanical design alternatives, guidance and navigation strategies, and dynamical and orbital simulations.
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| 13. |
- Jonsson, Jonas, 1979-, et al.
(author)
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A compact projection system enabling topographical measurements for a miniaturized submersible explorer
- 2011
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In: Proceedings of the 16th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS), 2011. - : IEEE conference proceedings. - 9781457701573 ; , s. 2518-2521
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Conference paper (peer-reviewed)abstract
- To enable photogrammetry of underwater images using a miniaturized submersible explorer, a compact projection system has been developed. By registering the deformation of a known projected pattern, using a laser and a diffractive optical element (DOE), the distance to, shape and size of an object can be calculated. The DOE has been designed, using in-house developed software, and manufactured using microstructure technology. Distances to objects 45 to 30 cm away were determined to within 0.5 cm, and the developed GUI was able to recreate the shape from the measurements for easier examination of the object.
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| 14. |
- Jonsson, Jonas, et al.
(author)
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A compact system to extract topography information from scenes viewed by a miniaturized submersible explorer
- 2012
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In: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 188:SI, s. 401-410
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Journal article (peer-reviewed)abstract
- In images taken underwater, it is generally difficult to correctly extract distances and geometric informationof objects. Different techniques, collectively referred to as photogrammetry, exist to measurefeatures in images. One of these is to project a reference pattern onto an object in a scene viewed by acamera, and register the distortion of this pattern, to calculate the shape of, and distance to, that object.This method is implemented here on a miniaturized submersible explorer equipped with, among manyother instruments, a camera. Diffractive optical elements (DOEs) have been designed and manufacturedusing microsystems technology, to, together with a laser diode, camera, and in-house developed software,provide a compact system for projecting reference patterns and analyzing their deformations. Thesystem has been characterized by measuring the distances and angles of objects in a water tank, andattempting to reproduce their shapes. The range of operation of the system, verified to be at least onemeter, is limited by the compact mounting in the small submersible and the cameras’ performance.The system was found to work well under turbid conditions as well as in water containing larger particles.Together with a vehicle-mounted camera, the compact and low-power DOE laser projection systemenables topographical measurement.
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| 15. |
- Jonsson, Jonas, et al.
(author)
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Enclosure-Induced Interference Effects in a Miniaturized Sidescan Sonar
- 2012
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In: IEEE Journal of Oceanic Engineering. - 0364-9059 .- 1558-1691. ; 37:2, s. 236-243
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Journal article (peer-reviewed)abstract
- On, for instance, the miniaturized submersible explorer, Deeper Access, Deeper Understanding (DADU), only 20 cm in length and 5 cm in diameter, the sidescan sonar needs to be tightly mounted in the hull. Finite element analysis (FEA) as well as physical measurements were used to investigate the effects of beam interaction with acoustically nearby rigid boundaries. Computer simulations showed the first major dip in the beam shape to vary in strength, size, and position with the enclosure wall height, from a position of 47° at 0.0-mm wall height to 32° at 3.0-mm wall height. Hydrophonic measurements on the manufactured test device confirmed these values to within 9%, varying between 47° and 29°. In addition, Schlieren imaging was proposed and used as a noninvasive means of qualitative beam shape characterization. A field test was performed with the enclosure height set to 0 and 3 mm. With the latter height, a dark band, corresponding to a sonar sensitivity dip at about 30° in the beam, appeared in the sonar image. It was found that the beam shape is sensitive to small mounting errors, in this case where the wavelength of the sonar is on the same size scale as the enclosure. Furthermore, it was found that FEA models can be used to accurately predict enclosure effects on sonar beam shapes, and Schlieren imaging can be used to visually detect the shape deformations in mounted sonar devices.
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| 16. |
- Jonsson, Jonas, et al.
(author)
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Miniaturized submersible for exploration of aqueous environments on Earth and beyond
- 2011
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Conference paper (peer-reviewed)abstract
- Some of the most likely environments to support extraterrestrial life in our solar system are the ice-covered moons, suchas Europa, thought to harbor a liquid ocean underneath its frozen crust. Exploration, however, necessitates an ice-penetratingcryobot, or a long and narrow borehole, and the subsequent deployment of a small submersible, a hydrobot, with severe sizerestrictions imposed on its scientific payload. As a stepping stone for exploration of such environments, a small instrumentladenedsubmersible vehicle is currently under development.Employment of a large set of instruments capable of characterizing the aqueous environment, imaging the surroundingsand collecting microorganisms is essential for the determination of habitability. Despite the submersible being only 20 cm inlength and 5 cm in diameter, a high degree of functionality is facilitated here through the use of miniaturization technologies. Forinstance, a compact laser-illuminated diffractive optical element, paired with a high-resolution camera, enable photogrammetryand the reconstruction of objects’ shapes in 3-D space. Also for imaging, the world’s smallest side-scanning sonar has beendeveloped to acoustically image, either where water is too turbid for the camera, or where longer range is necessary. Currently,the sonar exhibits centimeter resolution and ranges over 30 meters. On the sensor side, a most vital oceanographic instrument, theCTD, used to measure the conductivity, temperature, and depth of water, has been heavily miniaturized and preliminaryevaluated. Additionally, a water sampler combining integrated selection and enriching capabilities to filter out and accommodate,e.g., microbes in the size range of 1-10 μm, is under development. Among other parts, its high-pressure valves and microfluidicacoustic traps have already been realized.For remote operation and upload of measurement data or images, or even live streaming of video, the submersible will betethered with a bi-directionally transmitting fiber optic cable, also capable of charging the onboard batteries for long missions.The one kilometer long fiber will be fitted within the hull, and by reeling out the fiber from the submersible, drag will be reduced.Herein, test results and images of the vehicle and its complete, and continuously developed, subsystems are presented.The vehicle, and its subsystems as stand-alone instruments, will enable the exploration of previously unreachable analogenvironments on Earth, vital to the field of astrobiology, and act as a forerunner to a submersible hydrobot that can explore icecoveredoceans elsewhere in our solar system.
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| 17. |
- Jonsson, Jonas, et al.
(author)
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Miniaturized submersible for exploration of small aqueous environments
- 2011
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In: Oceans’11 MTS/IEEE Kona, Hilton Waikoloa Village, Kona, Hawai‘i September 19-22, 2011.
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Conference paper (peer-reviewed)abstract
- Remotely operated vehicles (ROVs) are commonlyused for sub-surface exploration. However, multi-functionalROVs tend to be fairly large, while preferred small and compactROVs suffer from limited functionality. The Deeper Access,Deeper Understanding (DADU) project aims to develop a smallsubmersible concept using miniaturization technologies to enablea high functionality. An operator is able to maneuver the vehiclewith five degrees of freedom using eight small thrusters, while aset of accelerometers and gyros monitor the orientation of thesubmersible. A single fiber optic cable will connect thesubmersible to a control station and enable simultaneous dataand command transfers. Rechargeable battery packs providepower to the submersibles subsystems during operation. Thesewill be rechargeable through the fiber connection. A forwardlooking camera is aided by a laser topography measurementsystem, where distances, sizes and shapes of objects in view canbe determined to within 0.5 cm. For murkier environments, orwhen a more extensive mapping of the surroundings is needed,the small high-frequency side-scanning sonar can be used.Salinity calculations of the water will be available throughmeasurements of the conductivity, temperature and depth.Samples of water and particles within it will be enabled through awater sampler with an enriching capability. Flow sensors will beable to measure the water movement around the submersible’shull. The submersible and its subsystems are under continuousdevelopment. The vehicle itself, and its subsystems as stand-aloneinstruments, will enable the exploration of previouslyunreachable submerged environments, such as the sub-glaciallakes found in Iceland and Antarctica, or other submerged smallenvironments, such as pipe and cave systems.
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| 18. |
- Jonsson, Jonas, et al.
(author)
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Simulation and Evaluation of Small High-Frequency Side Scan Sonars Using COMSOL
- 2009
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In: COMSOL Conference 2009 Milan.
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Conference paper (other academic/artistic)abstract
- High frequency side-scan sonar, to be fitted on a miniaturized submersible explorer, have been simulated and built. The purpose of this study is to see if COMSOL Multiphysics can be used to predict the performance of the sonar, especially the beam width, setting the resolution of the system. Four models were created, from simple 2-D geometries to more complex 3-D models. The simulated beam widths were compared with measurements to see which of the models agreed best. It was found that all models agree with the experimental results to varying degrees, and mostly with a difference of less than 6%. . It was found that the simplest model agreed best with the measurements, closely followed by the most complex model. Also taking the computational load into consideration the simpler model might then be a better choice to use.
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| 19. |
- Jonsson, Jonas, 1979-, et al.
(author)
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Simulation, manufacturing, and evaluation of a sonar for a miniaturized submersible explorer
- 2010
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In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 57:2, s. 490-495
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Journal article (peer-reviewed)abstract
- Single-beam side-scan sonar elements, to be fitted on a miniaturized submersible, are here simulated, manufactured, and evaluated. Finite element analysis simulations are compared with measurements, and an overall observation is that the agreement between simulations and measurements deviates from the measured values of 1.5 to 2°, for the narrow lobe angle, by less than 10% for most models. An overall finding is that the lobe width along the track direction can be accurately simulated and, hence, the resolution of the sonars can be predicted. This paper presents, to the authors’ knowledge, the world’s smallest side-scan sonars.
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| 20. |
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| 21. |
- Kratz, Henrik, 1974-, et al.
(author)
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Analysis of Thermal Transients in an Asymmetric Silicon-Based Heat Dissipation Stage
- 2007
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In: 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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Journal article (peer-reviewed)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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| 22. |
- Kratz, Henrik, et al.
(author)
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Design and Modeling of a thermally regulated communications module for nanospacecraft
- 2006
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In: Journal of Spacecraft and Rockets. - : American Institute of Aeronautics and Astronautics (AIAA). - 0022-4650 .- 1533-6794. ; 43:6, s. 1377-1386
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Journal article (peer-reviewed)abstract
- A silicon-based integrated communications and thermal management microsystem qualifying for use on Nanospace-1, a modularized microsystem-based advanced integrated nanospacecraft, is presented. The transmitter and receiver share the same module framework with essential differences only in the electronics implementation. A data rate of 1 Mbps for the transmitter and 114 kbps for the receiver is accomplished with a transmitter power for the spacecraft and ground station of 2 and 10 W, respectively. Concurrent triple usage of paraffin as low loss antenna substrate, actuator material, and heat sink is designed and analyzed for the first time. On low-power or short-time high-power dissipation of heat from the electronics, energy is stored as latent heat in this phase-change material acting as a heat sink. Thermal transport through the module is initiated,by actuation of thermal switches when 75% of the paraffin's latent heat is consumed. A static thermal analysis reveals a thermal modulation factor of 5.6 between the on and off states of the thermal switches. The size of the module is 6.6 x 68 x 68 mm, and its weight is 43 g.
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| 23. |
- Kratz, Henrik, 1974-
(author)
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Integrated Communications and Thermal Management Systems for Microsystem-based Spacecraft : A Multifunctional Microsystem Approach
- 2006
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Doctoral thesis (other academic/artistic)abstract
- This thesis explores the potential of multifunctional silicon-based microsystems for advanced integrated nanospacecraft (AIN). Especially, multifunctional microsystems with the coexistant functions of communications and thermal management implemented in multilayer silicon stacks are approached with systems study. Host vehicles, composed of microsystems, including micro/nano-spacecraft and spherical rovers are contemplated with respect to future performance and implications, system level design, and breadboard realizations. A module of great importance, named the "integrated communications and thermal management system for advanced integrated spacecraft" or ICTM, symbolizes the achievements within the field of self-contained microsystems and is a prioritized entity throughout the thesis. The ICTM is natively placable onboard all types of highly miniaturized craft.The single AIN spacecraft and future clusters of these are investigated with respect to future full scale implementation of space systems designed and implemented with the distributed reconfigurable nanospacecraft cluster (DRNC) concept. Here, a true entanglement of microsystems technology (MST) and miniaturized spacecraft technology can revolutionize the applications, cost, and span of conceivable space missions.An intended communications scenario supporting a data rate of 1 Mbps, for the transmitter, is achieved during 6 minutes with a maximum continuous power dissipation of 10 W. Thermal simulations support the expectation, of a thermally biased ICTM, that the module is capable of supporting this energy burst, by using the mechanisms of heat storage and heat switches, and still fulfilling the requirements imposed by AIN type of spacecraft. In addition, multiple functional surfaces for the ICTM are evaluated with respect to equilibrium temperature and process compatibility. The tailored surfaces provide temperature control using micromachining methods.A design of a micromachined Ka-band front end with several MST enabled features is presented including e.g. vias, phase-shifters, and antennas. Similar antennas have been manufactured resulting in an evaluation of ring- and slot-antennas on silicon substrate. Based on a primitive version of the ICTM, a S-band patch antenna has been successfully implemented and characterized. Included in the thesis is a microthruster, an enabling technology for DRNC.
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| 24. |
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| 25. |
- Kratz, Henrik, et al.
(author)
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Micromachined S-band Patch Antenna with Reduced Dielectric Constant
- 2006
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In: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 130-131, s. 478-484
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Journal article (peer-reviewed)abstract
- A generic dielectric constant reduction method for silicon substrates is presented in detail along with a process description to produce variable dielectric layers for planar antennas. Virtually any dielectric constant below the value for solid silicon 11.9 can be produced down to the limit of structural durability. A first-order volumetric average yields a dielectric constant of 3.8 for the following bonded micromachined silicon substrates; small honeycomb cells with wall thickness of 16 μm and inner wall length of 87 μm are etched using deep reactive ion etch (DRIE) to 475 μm depth in each of two 525 μm 4 in. high ohmic wafers. These two wafers are bonded together with the etched side of both wafers facing each other. A manufactured coaxial-fed disk-patch S-band antenna illustrates the method to reduce the dielectric constant for a circular zone with a diameter of 50 mm. The antenna is designed for a center frequency of 2.5 GHz based on a lossless substrate with a dielectric constant of 3.8. Adjusting the simulation model to fit the measured values of the antenna indicates a dielectric constant of 2.2, a dielectric loss tangent of 0.002, a bulk conductivity loss of 0.006 S/m, and a resonance frequency of 3.2 GHz. A low frequency analysis in the interval 200–500 MHz with a lumped element model and a low frequency formula for the capacitance between the patch and ground plane indicates a dielectric constant in the order of 2.7–2.8. Based on measurements in an SEM, a corrected average dielectric constant is found to be 2.9. This correction is due to thinner walls than expected in the manufactured honeycomb structure. Antenna lobe characteristics have been measured with a half-power beamwidth of ∼76° in both the E-plane and H-plane at 3.2 GHz.
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| 26. |
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| 27. |
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| 28. |
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| 29. |
- Köhler, Johan, et al.
(author)
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A hybrid cold gas microthruster system for spacecraft
- 2001
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In: Digest of Papers for the 11th Int Conf on Solid-State Sensors and Actuators - Transducers '01 and Eurosensors XV, Munich, Germany, June 10-14. ; , s. 886-889
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Conference paper (peer-reviewed)
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| 30. |
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| 31. |
- Köhler, Johan, et al.
(author)
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A Hybrid Cold Gas Microthruster System for Spacecraft
- 2002
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In: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 97-98, s. 587-98
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Journal article (peer-reviewed)abstract
- A hybrid cold gas microthruster system suitable for low Δv applications on spacecraft have been developed. Microelectromechanical system (MEMS) components together with fine-mechanics form the microthruster units, intergrating four independent thrusters. These are designed to deliver maximum thrusts in the range of 0.1–10 mN.The system includes three different micromachined subsystems: a nozzle unit comprising four nozzles generating supersonic gas velocity, i.e. 455 m/s, four independent piezoelectric proportional valves with leak rates at 10−6 scc/s He, and two particle filters. The performances of all these MEMS subsystems have been evaluated.The total system performance has been estimated in two parameters, the system-specific impulse and the mass ratio of the propulsion system to the spacecraft mass. These figures provide input for spacecraft design and manufacture.
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| 32. |
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| 33. |
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| 34. |
- Lotfi, Sara, 1985-, et al.
(author)
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Hybrid microtransmitter for free-space optical spacecraft communication : design, manufacturing, and characterization
- 2009
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In: Proc. SPIEPhotonics West, MOEMS and Miniaturized Systems VIII, Jan 24-29, San Jose, CA. - : SPIE. ; , s. 72080N-12-
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Conference paper (other academic/artistic)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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| 35. |
- Nguyen, Hugo, 1955-, et al.
(author)
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A heavily miniaturized submersible : a terrestrial kickoff
- 2008
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In: Proceedings of ASTRA 2008. ; , s. 1-9
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Conference paper (peer-reviewed)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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| 36. |
- Nguyen, Hugo, 1955-, et al.
(author)
-
Heavily Miniaturized Submersible – A Terrestrial Kickoff
- 2008
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In: Heavily Miniaturized Submersible – A Terrestrial Kickoff. ; , s. S14-01
-
Conference paper (peer-reviewed)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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| 37. |
- Nguyen, Hugo, et al.
(author)
-
Micropropulsion systems research and manufacture in Sweden
- 2003
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In: Proceedings of the 4th Round Table on Micro/Nano Technology for Space, ESTEC, Noordwijk, The Netherlands. - : ESTEC/ESA. ; , s. 476-485
-
Conference paper (peer-reviewed)abstract
- Micropropulsion for spacecraft is an enabling technology for many future missions, and may increase the performance and drastically reduce the mass required for advanced propulsion systems. The Swedish activities in micropropulsion at The Angstrom Space Technology Centre (ASTC) are outlined. The research targets two major issues: the development of system parts, and the research into integration techniques and strategies. This paper collects a multitude of devices relevant to the micropropulsion system design, together with representative functional demonstrations. The items are mainly intended for chemical micropropulsion systems or fuel-feed systems for electric propulsion. In particular, gas handling devices, sensors, and actuators are presented. These include silicon nozzles, thin film heaters, suspended microcoil heaters, proportional piezoelectric valves, proportional and isolation valves using phase-change material, thermal throttle flow-regulators, high-pressure regulators, 3D-particle filters, and sensors for strain, pressure, flow, and thrust. Moreover, integration techniques and interface structures are presented, for example low-temperature plasma-assisted silicon wafer bonding, multiwafer bonding, thin film soldering, hermetic electric through-wafer via connections, and multiconnector through-wafer vias. Emphasis is on how these items are designed to allow for system integration in a multiwafer silicon stack, comprising a complete micropropulsion system. In this manner, all items form a parts collection available to the system design. This strategy is exemplified by three micropropulsion systems researched at the ASTC. First, the cold/hot gas micropropulsion system is suitable for small spacecraft or when the demands on stability and pointing precision are extreme. The system performance depends strongly on the use of gas flow control. The complete gas handling system of four independent thrusters is integrated in the assembly of four structured silicon wafers. Each independent thruster contains a proportional valve, sensors for pressure, temperature, and thrust feedback, a converging-diverging micronozzle, and a suspended microcoil heater. The mass of the system is below 60 g. In total, this will provide the spacecraft with a safe, clean, low-powered, redundant, and flexible system for three-axis stabilization and attitude control. Second, a Xenon feed system for ion propulsion is heavily miniaturized using microsystems technology. Basically, a micromachined high-pressure regulator receives the gas from the storage, and the flow is further modulated by a thermally controlled flow restrictor. The flow restrictor microsystem comprises narrow ducts, thin film heaters, suspended parts for heat management, and flow sensors. Hereby, the amount of xenon required by the electric propulsion systems can be promptly delivered. The complete system mass is estimated to 150g. Third, within the EU IST program, the ASTC participates in the development of a micro-pyrotechnic actuator system (Micropyros), suitable for short-duration space propulsion. The Micropyros integrate a full matrix of minute solid combustion rocket engines into panels situated on the spacecraft hull. The thrusters can be individually ignited, and each deliver thrust in the millinewton range. The ASTC focuses on the integration of the propulsion part by low-temperature bonding, and the characterization of the complete system.
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| 38. |
- Palmer, Kristoffer, et al.
(author)
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A highly integratable silicon thermal gas flow sensor
- 2012
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In: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 22:6, s. 065015-
-
Journal article (peer-reviewed)abstract
- Thermal flow sensors have been designed, fabricated, and characterized. All bulk material in these devices is silicon so that they are integratable in silicon-based microsystems. To mitigate heat losses and to allow for use of corrosive gases, the heating and sensing thin film titanium/platinum elements, injecting and extracting heat, respectively, from the flow, are placed outside the channel on top of a membrane consisting of alternating layers of stress-balancing silicon dioxide and silicon nitride. For the fabrication, an unconventional bond surface protection method using sputter-deposited aluminum instead of thermal silicon dioxide is used in the process steps prior to silicon fusion bonding. A method for performing lift-off on top of the transparent membrane was also developed. The sensors, measuring 9.5 x 9.5 mm(2), are characterized in calorimetric and time-of-flight modes with nitrogen flow rates between 0 sccm and 300 sccm. The maximum calorimetric sensor flow signal and sensitivity are 0.95 mV and 29 mu V sccm(-1), respectively, with power consumption less than 40 mW. The time-of-flight mode is found to have a wider detectable flow range compared with calorimetric mode, and the time of flight measured indicates a response time of the sensor in the millisecond range. The design and operation of a sensor with high sensitivity and large flow range are discussed. A key element of this discussion is the configuration of the array of heaters and gauges along the channel to obtain different sensitivities and extend the operational range. This means that the sensor can be tailored to different flow ranges.
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| 39. |
- Palmer, Kristoffer, 1983-, et al.
(author)
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A micromachined dual-axis actuator for Use in a miniaturized optical communication system
- 2008
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In: Proceeding of the International Astronautical Congress, Sep 29 - Oct 3, Glasgow, Scotland.
-
Conference paper (peer-reviewed)abstract
- A micromachined beam-steering device for use in a miniaturized free-space optical communication system is presented. This device is part of a communication system intended for microspacecraft flying in kilometer-sized formations. Central to it, is a laser-reflecting mirror tiltable in two orthogonal directions using electrothermal actuators based on heating of a polymer confined in silicon v-grooves. The device is fabricated using standard microstructure technology. Successful experiments show a maximum mechanical scan range of 19º in two orthogonal directions. The voltages applied are below 100 V, and the power consumption is less than 2.4 W. Thermal coupling between orthogonal joints has been investigated with infrared imaging. The overall results are very promising, and improvement in the design and fabrication can be suggested.
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| 40. |
- Palmer, Kristoffer, et al.
(author)
-
A micromachined dual-axis beam steering actuator for use in a miniaturized optical space communication system
- 2010
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In: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 20:10, s. 105007-
-
Journal article (peer-reviewed)abstract
- The design, fabrication and evaluation of an electrothermally actuated micromachined beam steering device for use in a free-space optical communication system intended for use on micro-and nanospacecraft in kilometer-sized formations are presented. SU-8 confined in v-grooves is heated to create bending movement in two orthogonal directions for two-axial steering with large static bending angles and low actuation voltages. Standard MEMS processing is used to fabricate the devices with square mirror side lengths of 1, 3.5 and 5 mm. In addition, a method to prevent thermal damage to SU-8 during deep reactive ion etching has been successfully developed. Characterization shows optical scan ranges larger than 40 degrees in both directions with the maximum driving voltage of 16 V corresponding to a total power consumption of 1.14 W. Infrared imaging is used to investigate thermal cross-talk between actuators for the two scanning directions. It is found that a silicon backbone on the joint backside is crucial for device performance. Differences from expected performance are believed to arise from the SU-8 curing process and excessive heating during fabrication. A finite element method simulation is used to find the eigenfrequencies of the structures, and these are in good agreement with the measured frequency response.
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| 41. |
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| 42. |
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| 43. |
- Palmer, Kristoffer, 1983-
(author)
-
Development of Microcomponents for Attitude and Communication Systems on Small Vehicles in Space and Extreme Environments
- 2013
-
Doctoral thesis (other academic/artistic)abstract
- In this thesis, components intended for vehicles in space and other extreme environments have been realized using microsystems technology to facilitate miniaturized, yet high-performing systems beneficial for small spacecraft and other vehicles with limited size and power.Cold gas thrusters commonly used on spacecraft basically accelerate a gaseous propellant stored under high pressure. When miniaturized, their performance is reduced because of viscous forces. Here, with a special masking and etching scheme, making silicon micronozzles close to rotationally symmetric, this shortcoming was mitigated as indicated by schlieren imaging of the rocket exhaust and a comparison with conventionally manufactured micronozzles with rectangular cross-sections. Schlieren imaging was also used to detect leakage, quantify thrust vector deviation, and measure shock cell periods in the exhaust. Correlation was made to operational conditions.Similarly operating zirconia thrusters with integrated heaters and flow sensors were developed to allow for higher operating temperature. Successful testing at 1000°C, suggests that the propellant efficiency could be increased by 7.5%, and also makes them candidates for chemical propulsion.A silicon thruster operating in rarefied gas regimes was also developed. Being suspended in a silicon dioxide frame reducing heat losses, a total efficiency of 17% was reached.Relating to the integrated micropropulsion systems, two types of flow sensors were developed. Through finite element modeling, the insertion of sensor fingers in the fluid was shown to be an interesting concept for high-pressure applications.Utilizing the same principle, a velocity sensor for a miniaturized submersible was developed. With a power consumption below 15 mW, it was able to measure directions with an accuracy of ±8º, and speed with an error less than 22%.To enable high-speed optical communication between spacecraft, a Free Space Optics communication system, and particularly its dual-axis beam-steering actuator, was developed. Through thermal actuation, optical angles larger than 40º were obtained. A lumped thermal model was used to study design changes, vacuum operation and feedback control.Understanding and mastering heat transfer in microsystems have been vital in many of the studies conducted. Throughout, advanced micromachining and modeling have been used as a step towards high-performance systems for space and other extreme environments.
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| 44. |
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| 45. |
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| 46. |
- Toss, Henrik, et al.
(author)
-
Ferroelectric surfaces for cell release
- 2017
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In: Synthetic metals. - : Elsevier Ltd. - 0379-6779 .- 1879-3290. ; 228, s. 99-104
-
Journal article (peer-reviewed)abstract
- Adherent cells cultured in vitro must usually, at some point, be detached from the culture substrate. Presently, the most common method of achieving detachment is through enzymatic treatment which breaks the adhesion points of the cells to the surface. This comes with the drawback of deteriorating the function and viability of the cells. Other methods that have previously been proposed include detachment of the cell substrate itself, which risks contaminating the cell sample, and changing the surface energy of the substrate through thermal changes, which yields low spatial resolution and risks damaging the cells if they are sensitive to temperature changes. Here cell culture substrates, based on thin films of the ferroelectric polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) co-polymer, are developed for electroactive control of cell adhesion and enzyme-free detachment of cells. Fibroblasts cultured on the substrates are detached through changing the direction of polarization of the ferroelectric substrate. The method does not affect subsequent adhesion and viability of reseeded cells.
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| 47. |
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| 48. |
- Yousef, Hanna, et al.
(author)
-
Substrate Integrated Waveguides (SIW) in a Flexible Printed Circuit Board for Millimeter Wave Applications
- 2009
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In: Journal of microelectromechanical systems. - 1057-7157 .- 1941-0158. ; 18:1, s. 154-162
-
Journal article (peer-reviewed)abstract
- Substrate integrated waveguides (SIWs) are presented and demonstrated in a flexible printed circuit board (flex PCB) for application in the 77-81 GHz range. The vertical walls of the SIWs presented in this paper consist of multiple electrodeposited metallic wires. The diameters of these wires and the spacing between them are on the order of hundreds of nanometers. Hence, the walls can be seen as continuous metallic walls, and the leakage losses through them become negligible. In turn, the SIWs presented in this paper can operate at higher frequencies compared with previously presented structures that are realized with PCB fabrication processes. The attenuation of the SIWs is comparable to that of microstrip lines on the same sample. The SIWs are successfully demonstrated in a SIW-based slot antenna. The antenna gain along the z-axis (normal-to-plane) was found to be around 2.8 dBi at 78 GHz which is in agreement with the simulated values. [2008-0047]
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| 49. |
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| 50. |
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