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Fabrication of a paraffin actuator using hot embossing of polycarbonate
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
2003 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 103, no 3, 307-316 p.Article 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.

Place, publisher, year, edition, pages
2003. Vol. 103, no 3, 307-316 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-89917DOI: 10.1016/S0924-4247(02)00403-XOAI: oai:DiVA.org:uu-89917DiVA: diva2:161777
Available from: 2002-05-16 Created: 2002-05-16 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Miniature Phase-Transistion Actuators
Open this publication in new window or tab >>Miniature Phase-Transistion Actuators
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. 28 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 728
Keyword
Materials science, Materialvetenskap
National Category
Materials Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-2138 (URN)91-554-5345-7 (ISBN)
Public defence
2002-06-06, Ångströmslaboratoriet 2002, Uppsala, 09:30
Opponent
Available from: 2002-05-16 Created: 2002-05-16Bibliographically approved
2. Microstructures for Chemical Analysis: Design, Fabrication and Characterisation
Open this publication in new window or tab >>Microstructures for Chemical Analysis: Design, Fabrication and Characterisation
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The interest for miniaturisation in chemical and biological analysis has increased in recent years. In this work, the design, fabrication and characterisation of tools for microanalysis have been studied. The focus is set on polymer microchips for applications in chemical analysis. The work consists of three parts: design and fabrication of paraffin microactuators, design and fabrication of polymer microchips as interfaces in electrospray ionisation mass spectrometry (ESI-MS), and characterisation of conducting films for fused silica capillaries as interfaces in ESI-MS.

The principle of the paraffin actuators is based on the volume increase resulting from paraffin melting. Paraffin expansion is utilised to cause membrane deflection. The first plastic microactuator using paraffin as the actuator material was successfully demonstrated.

The microchips as interfaces in ESI-MS have been designed with the objective that the interface should be as much a part of the microchip as possible, and as to as large extent as possible, be fabricated in the same step as the microchannels. Sheathless electrospray from microchips was demonstrated for the first time. In addition a simplified fabrication process for ESI-MS interfaces in poly(dimethyl siloxane) (PDMS) was developed.

The degradation of conductive coatings for sheathless ESI-MS on fused silica capillaries was studied. It was shown that electrochemical experiments could successfully be used to simulate the electrospray conditions and predict the failure of different gold coatings.

It was concluded that a common issue in the fabrication of thermoplastic microchips is the crucial sealing of microchannels and cavities. From this point of view, PDMS is a more advantageous material in microfluidics.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 64 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 15
Keyword
Materials science, electrospray ionisation mass spectrometry, polymer microfabrication, paraffin actuators, hot embossing, Materialvetenskap
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-4792 (URN)91-554-6151-4 (ISBN)
Public defence
2005-03-18, Siegbahnsalen, Ångströmlaboratoriet, Uppsala, 09:30
Opponent
Supervisors
Available from: 2005-02-24 Created: 2005-02-24 Last updated: 2013-05-30Bibliographically approved

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Klintberg, LenaNikolajeff, FredrikThornell, Greger

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