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Manufacturing Miniature Langmuir probes by Fusing Platinum Bond Wires
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. (Ångström Space Technology Centre (ÅSTC))ORCID iD: 0000-0003-0832-1848
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Swedish Defence University. (ÅSTC)ORCID iD: 0000-0002-0501-0887
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. (ÅSTC)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. (ÅSTC)
2015 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 10, article id 105012Article in journal (Refereed) Published
Abstract [en]

This paper reports on a novel method for manufacturing microscopic Langmuir probes with spherical tips from platinum bond wires for plasma characterization in microplasma sources by fusing. Here, the resulting endpoints, formed by droplets of a fused wire, are intended to act as a spherical Langmuir probe. For studying the fusing behavior, bond wires were wedge-bonded over a 2 mm wide slit, to emulate the final application, and fused at different currents and voltages. For electrical isolation, a set of wires were coated with a 4 µm thick layer of Parylene before they were fused. After fusing, the gap size, as well as the shape and area of the ends of the remaining stubs were measured. The yield of the process was also investigated, and the fusing event was studied using a high-speed camera for analyzing the dynamics of fusing. Four characteristic tip shapes were observed: spherical, semi-spherical, serpentine shaped and folded. The stub length leveled out at ~420µm. The fusing of the coated wires required a higher power for attaining a spherical shape. Finally, a Parylene coated bond wire was integrated into a stripline split-ring resonator (SSRR) microplasma source, and fused to form two Langmuir probes with spherical endpoints. These probes were used for measuring the I-V characteristics of a plasma generated by the SSRR. In a voltage range between -60 V and 60 V, the fused stubs exhibited the expected behavior of spherical Langmuir probes and will be considered for future integration.

Place, publisher, year, edition, pages
2015. Vol. 25, no 10, article id 105012
Keywords [en]
Langmuir probe; bond wire; fusing; microplasma source
National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
URN: urn:nbn:se:uu:diva-251306DOI: 10.1088/0960-1317/25/10/105012ISI: 000366827400028OAI: oai:DiVA.org:uu-251306DiVA, id: diva2:805315
Funder
Swedish National Space BoardKnut and Alice Wallenberg FoundationAvailable from: 2015-04-15 Created: 2015-04-15 Last updated: 2018-08-03Bibliographically approved
In thesis
1. Miniature Plasma Sources for High-Precision Molecular Spectroscopy in Planetary Exploration
Open this publication in new window or tab >>Miniature Plasma Sources for High-Precision Molecular Spectroscopy in Planetary Exploration
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The prospect of finding life outside Earth has fascinated mankind for ages, and new technology continuously pushes the boundary of how remote and how obscure evidence we can find. Employing smaller, or completely new, types of landers and robots, and equipping them with miniature instruments would indeed revolutionize exploration of other planets and moons.

In this thesis, microsystems technology is used to create a miniature high-precision isotope-resolving molecular spectrometer utilizing the optogalvanic effect. The heart of the instrument, as well as this thesis, is a microplasma source.

The plasma source is a split-ring resonator, chosen for its simplicity, pressure range and easily accessible plasma, and modified to fit the challenging application, e.g., by the adding of an additional ground plane for improved electromagnetic shielding, and the integration of microscopic plasma probes to extract the pristine optogalvanic signal.

Plasma sources of this kind have been manufactured in both printed circuit board and alumina, the latter for its chemical inertness and for compatibility with other devices in a total analysis system. From previous studies, classical optogalvanic spectroscopy (OGS), although being very sensitive, is known to suffer from stability and reproducibility issues. In this thesis several studies were conducted to investigate and improve these shortcomings, and to improve the signal-to-noise ratio. Moreover, extensive work was put into understanding the underlying physics of the technique.

The plasma sources developed here, are the first ever miniature devices to be used in OGS, and exhibits several benefits compared to traditional solutions. Furthermore, it has been confirmed that OGS scales well with miniaturization. For example, the signal strength does not decrease as the volume is reduced like in regular absorption spectroscopy. Moreover, the stability and reproducibility are greatly increased, in some cases as much as by two orders of magnitude, compared with recent studies made on a classical OGS setup. The signal-to-noise ratio has also been greatly improved, e.g., by enclosing the sample cell and by biasing the plasma. Another benefit of a miniature sample cell is the miniscule amount of sample it requires, which can be important in many applications where only small amounts of sample are available.

To conclude: With this work, an important step toward a miniature, yet highly performing, instrument for detection of extraterrestrial life, has been taken.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. p. 53
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1253
Keywords
MEMS, MST, Optogalvanic Spectroscopy, Molecular Spectroscopy, Split-Ring Resonator, Microplasma
National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-251315 (URN)978-91-554-9245-8 (ISBN)
Public defence
2015-06-05, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2015-05-11 Created: 2015-04-15 Last updated: 2015-07-07
2. Sense, Actuate and Survive: Ceramic Microsystems for High-Temperature Aerospace Applications
Open this publication in new window or tab >>Sense, Actuate and Survive: Ceramic Microsystems for High-Temperature Aerospace Applications
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In aerospace applications, but also in manufacturing, mining, energy industry and natural hazards, high temperature, corrosion, erosion and radiation, challenge the performance and being of hardware.

In this work, high-temperature co-fired ceramic (HTCC) alumina and platinum have been used for a range of devices intended for aerospace applications at up to 1000°C.

The thermomechanics of a pressure sensor was investigated, and the interfacing was attained by wireless powering and reading. However, read range was limited and sensitivity decreased with temperature. Silver, electroplated after sintering, was found to remedy this until it eventually alloyed with platinum.

Copper was electroplated and oxidized for oxygen storage in a microcombustor, intended for sample preparation for optogalvanic spectroscopy (OGS) to indicate extraterrestrial life. Despite delamination, caused by residual stresses, the device operated successfully.

Conversely, pre-firing metallization by integration of platinum wires was studied. Freely suspended, and despite heat-induced shape irregularities, these were found advantageous over screen printed elements for gas heating, and temperature and pressure sensing. By fusing off the wires, spherical tips, allowing for impedance monitoring of microplasma sources in, e.g., OGS, were formed.

Microplasma sources can also be used for gas heating. This, together with screen printed and suspended resistive heaters, was evaluated in a microthruster, showing that plasma heating is the most effective, implying fuel consumption reduction in satellite propulsion.

In conclusion, HTCC alumina microdevices are thermally stable and could benefit several aerospace applications, especially with the complementary metallization schemes devised here.

Future developments are expected to include both processing and design, all with the intention of sensing, actuating and surviving in high-temperature environments.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 44
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1696
Keywords
High temperature, ceramics, microsystems, aerospace, sensors, thrusters
National Category
Aerospace Engineering Materials Engineering
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-356692 (URN)978-91-513-0392-5 (ISBN)
Public defence
2018-09-21, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30 (Swedish)
Opponent
Supervisors
Available from: 2018-08-31 Created: 2018-08-03 Last updated: 2018-09-10

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Berglund, MartinSturesson, PeterThornell, GregerPersson, Anders

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