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Miniature Phase-Transistion Actuators
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science.
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Clearly, there is a need for simple, strong actuators capable of large strokes in miniaturized systems such as valves and optical shutters.

The basis for this work is the microstructure technology with processing techniques adopted from the integrated circuit industry. In many cases alternative techniques have been developed to obtain features not achievable with conventional silicon technology. Techniques to fabricate thermally activated phase transition actuators capable of large strokes, as well as strong, piezoceramic actuators, have been investigated

Multilayered piezoceramic actuators have been fabricated and used in a miniature linear motor. A technique to build freestanding, three-dimensional structures drop by drop using a micromachined ink jet head and a slurry of piezoceramic particles has been developed. Ion track technology was used to create narrow pores in polyimide. To make bimorph-like structures capable of large strokes, these pores were impregnated with paraffin- a material with a large volume expansion associated with its solid-to-liquid phase transition. Paraffin was used in a silicon thermal switch intended for a passive thermal control system, and in a device to be used as a valve in a gas regulation system. Finally, paraffin actuators for integration in thermoplastic microfluidic systems have been developed.

During the course of this work not only the importance of identifying the best materials for a given application has been addressed and acknowledged, but also that of finding a processing route on occasion far from the conventional one, and perhaps most important, that of anticipating the often surprising effects following from miniaturization.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2002. , p. 28
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 728
Keywords [en]
Materials science
Keywords [sv]
Materialvetenskap
National Category
Materials Engineering
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-2138ISBN: 91-554-5345-7 (print)OAI: oai:DiVA.org:uu-2138DiVA, id: diva2:161778
Public defence
2002-06-06, Ångströmslaboratoriet 2002, Uppsala, 09:30
Opponent
Available from: 2002-05-16 Created: 2002-05-16Bibliographically approved
List of papers
1. Characterisation of a linear piezoelectric miniature motor
Open this publication in new window or tab >>Characterisation of a linear piezoelectric miniature motor
1998 In: Proc. of World Ceramic Congress & Forum on New Materials, CIMTEC´98, Florence, ItalyArticle in journal (Refereed) Accepted
Identifiers
urn:nbn:se:uu:diva-89910 (URN)
Available from: 2002-05-16 Created: 2002-05-16Bibliographically approved
2. Desktop microfabrication: initial experiments with a piezoceramic
Open this publication in new window or tab >>Desktop microfabrication: initial experiments with a piezoceramic
Show others...
1999 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 9, no 4, p. 434-437Article in journal (Refereed) Published
Abstract [en]

A method for building microstructures from a suspension of micrometre-sized piezoelectric particles by depositing droplets on top of droplets and promoting drying is devised. A micromachined dispensing unit similar to a drop-on-demand inkjet-printer head is used. The relation of the vertical building rate to the ejection frequency and the substrate temperature is established, and a mechanism explaining the tubular structures built is proposed.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-89911 (URN)10.1088/0960-1317/9/4/322 (DOI)
Available from: 2002-05-16 Created: 2002-05-16 Last updated: 2017-12-14Bibliographically approved
3. Drop-by-drop deposition of ceramic slurry for fabrication of PZT microstructures
Open this publication in new window or tab >>Drop-by-drop deposition of ceramic slurry for fabrication of PZT microstructures
1999 In: Proc. of SPIE´s In. Symp. on Microelectronics and Micro Electro Mechanical Syst. Royal Pine Resort, Australia, p. 158-165Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-89912 (URN)
Available from: 2002-05-16 Created: 2002-05-16Bibliographically approved
4. Sodium hypochlorite as a developer for heavy ion tracks in polyimide
Open this publication in new window or tab >>Sodium hypochlorite as a developer for heavy ion tracks in polyimide
2001 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 184, no 4, p. 536-543Article in journal (Refereed) Published
Abstract [en]

he developing and etching of heavy ion tracks in polyimide with sodium hypochlorite have been studied to gain control over the parameters that affect the etch result. The shape of the resulting pores is a function of both alkalinity and hypochlorite content of the solution. Sodium hypochlorite decomposes during etching, and the rate constant has been determined as a function of the alkalinity at 62 °C. Polished cross-sections have been examined to determine the pore shape, and this method has shown to be a straightforward way to characterise the pores. Decreasing the alkalinity gives more cylindrical pores, but increases the decomposition rate of the hypochlorite solution and decreases the etch rate.

National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-89913 (URN)10.1016/S0168-583X(01)00794-7 (DOI)
Available from: 2002-05-16 Created: 2002-05-16 Last updated: 2017-12-14Bibliographically approved
5. A thermal microactuator made by partial impregnation of polyimide with paraffin
Open this publication in new window or tab >>A thermal microactuator made by partial impregnation of polyimide with paraffin
2002 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 12, no 6, p. 849-854Article in journal (Refereed) Published
Abstract [en]

We have fabricated and tested thermal, paraffin-impregnated polyimide actuators, utilizing the large volume increase associated with the solid-to-liquid phase transition of paraffin. In the bimorph-like device, the top layer was made porous by ion track technology. Stochastically distributed pores of various lengths (95, 70, 45 and 20 µm) and various lateral coverages (5–45%) were filled with paraffin by liquid substitution or from vacuum, and sealed with epoxy. Actuators, 125 µm thick, 35 mm long and 7 mm wide, have been characterized with respect to tip deflection and load-carrying capacity with one end rigidly clamped. Loaded with 0.6 g or about ten times their own weight at their free end, about 50% of the maximum stroke (17 mm) was still attained.

National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-89914 (URN)10.1088/0960-1317/12/6/316 (DOI)
Available from: 2002-05-16 Created: 2002-05-16 Last updated: 2017-12-14Bibliographically approved
6. A large stroke, high force paraffin phase transition actuator
Open this publication in new window or tab >>A large stroke, high force paraffin phase transition actuator
Show others...
2002 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 96, no 2-3, p. 189-195Article in journal (Refereed) Published
Abstract [en]

An actuator that uses the volume expansion related to the solid-to-liquid phase transition of paraffin wax has been fabricated and evaluated. The actuator consists of a ring-shaped paraffin cavity confined by two joint silicon diaphragms with rigid centers. When the paraffin is melted, the resulting hydrostatic pressure deflects the joined rigid centers in one direction only. The magnitude of the deflection is primarily a function of the geometrical relation between the two diaphragms, giving the opportunity to tailor the behavior of the actuator in a large range. Conventional IC-processing techniques have been used to fabricate a prototype with a width of 68 mm and a thickness of 825 μm. The prototype attained a maximum deflection of ca. 90 μm. Loaded with 3 N it still exhibits a deflection of ca. 75 μm. The device can be used as a thermal switch.

National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-89915 (URN)10.1016/S0924-4247(01)00785-3 (DOI)
Available from: 2002-05-16 Created: 2002-05-16 Last updated: 2017-12-14
7. A thermally activated paraffin-based actuator for gas-flow control in a satellite electrical propulsion system
Open this publication in new window or tab >>A thermally activated paraffin-based actuator for gas-flow control in a satellite electrical propulsion system
2003 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 105, no 3, p. 237-246Article in journal (Refereed) Published
Abstract [en]

Microstructured silicon devices consisting of three inflatable paraffin-filled, corrugated caddies suspended in springs to minimize thermal losses have been fabricated and evaluated with a valve application in mind. The large volume expansion associated with the thermally induced solid-to-liquid phase transition of paraffin is used to activate the caddies’ diaphragms. Theses components all with a thickness of 600 μm and a diameter of 39 mm, but with three different corrugations, have been fabricated with deep reactive etching (DRIE). Whereas the corrugated diaphragms could endure a deflection larger than 50 μm, only strokes of 15 μm on each side were attained when the components were activated. Together with the valve seats proposed, the investigated devices have a potential in electrical propulsion systems for satellites.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-89916 (URN)10.1016/S0924-4247(03)00203-6 (DOI)
Available from: 2002-05-16 Created: 2002-05-16 Last updated: 2017-12-14
8. Fabrication of a paraffin actuator using hot embossing of polycarbonate
Open this publication in new window or tab >>Fabrication of a paraffin actuator using hot embossing of polycarbonate
2003 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 103, no 3, p. 307-316Article in journal (Refereed) Published
Abstract [en]

In this paper a fabrication process for integrating paraffin-actuated structures in polycarbonate is outlined. A paraffin-actuated membrane with a diameter of 2.5 mm, where the volume expansion of 10–15% associated with the solid-to-liquid phase transition of paraffin is utilized, has been fabricated and evaluated. Microstructures fabricated in silicon have via an electroplated nickel mould been replicated in polycarbonate by hot embossing and the resulting structures have been sealed by thermal bonding. The bonding strength was measured by a pressurizing test, and the polycarbonate surfaces were characterized with electron spectroscopy for chemical analysis (ESCA). It was found that the bond strength increased when an oxygen plasma treatment was used prior to bonding. ESCA measurements showed a corresponding increase in oxygen content on the plasma treated surfaces. This procedure also improved the wetting properties. The contact angle between paraffin and polycarbonate decreased from 10° after embossing to about 5° after plasma treatment. The fabricated actuator had a total thickness of 1 mm and the membrane deflected about 140 μm when heating the actuator above the melting point of paraffin. Paraffin wax actuators are possible to integrate in plastic structures making them promising candidates in applications such as disposable microfluidic systems where inexpensive and robust valves and pumps are needed.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-89917 (URN)10.1016/S0924-4247(02)00403-X (DOI)
Available from: 2002-05-16 Created: 2002-05-16 Last updated: 2017-12-14Bibliographically approved

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