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Novel SMA composite for microapplication

Donato Clausi 1Dominiek Reynaerts 1Jan Peirs 1Jan Van Humbeeck 2

1. Katholieke Universiteit Leuven-Mechanical Engineering Department (MECH-KUL), Celestijnenlaan 300B, Leuven 3001, Belgium
2. K. U. Leuven, Department of Materials Science and Engineering (KUL, MTM), Kasteelpark Arenberg 44, Leuven 3001, Belgium


A crucial topic for advancing of microsystem technology is the development of an integrated microactuation mechanism compatible with microfabrication and able to provide a large displacement and a large actuation energy density. Shape memory alloys allow the development of microactuators with a resulting work density unequaled by other actuator types. However, the implementation of these materials into actual devices is quite complex and mostly limited to deposition of thin film shape memory materials onto fabricated MEMS structures. Potential drawbacks to this technology are the necessity of expensive sputtering equipment, the accurate control of deposition parameters and the stability of the shape-memory effect in thin-film NiTi over the millions of cycles required for these devices. The current alternative, one-by-one assembly of discrete SMA elements (wire, spring or beam), is a time consuming and expensive process, not in accordance with the philosophy of batch fabrication, generally used for the production of the microstructures to be actuated.

Shape Memory Alloy composites could offer a cheap alternative, based on commercially available SMA wires embedded into a polymeric matrix. Integration of SMA fibres in large surfaces is already being investigated, e.g. by the aerospace industry for wing control. However, exploitation of these methods for wafer-scale integration is still in its infancy.

This paper is aimed at introducing a novel technique for producing SMA composites at microsystem level that overcomes the above mentioned limitations.

A fixture jig is used to position the fibres with the correct pitch. They are eventually annealed in order to set the memorized shape and obtain the same stress level amid the wires. The fibres treated as such are then embedded into the polymeric matrix, which had previously been deposited onto the target substrate. Curing of the polymer and patterning of the structures provide the last step to obtaining microactuators.

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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium E, by Donato Clausi
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 18:49
Revised:   2009-06-07 00:44