Date on Master's Thesis/Doctoral Dissertation

12-2012

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Electrical and Computer Engineering

Committee Chair

Harnett, Cindy K.

Author's Keywords

MEMS; infrared absorption; nanoparticles; fabrication; polymer

Subject

Microelectromechanical systems; Nanostructured materials

Abstract

This dissertation demonstrates an elegant method, known as 'micro-origami' or strain architecture to design and fabricate three-dimensional MEMS structures which are assembled using actuation of a metal-oxide bilayer with conventional planar lithography. Folding allows creating complex, robust, three-dimensional shapes from two-dimensional material simply by choosing folds in the right order and orientation, small disturbances of the initial shape may also be used to produce different final shapes. These are referred to as "pop-up structures" in this work. The scope of this work presented the deposition of colloidal gold nanoparticles (GNPs) into conformal thin films using a microstenciling technique. Results illustrated that the gold nanoparticle deposition process can easily be integrated into current MEMS microfabrication processes. Thin films of GNPs deposited onto the surfaces of siliconbased bistable MEMS and test devices were shown to have a significant effect on the heating up of microstructures that cause them to fold. The dissertation consists of four chapters, covering details of fabrication methods, theoretical simulations, experimental work, and existing and potential applications. Chapter II illustrates how control of the folding order can generate complex three-dimensional objects from metal-oxide bilayers using this approach. By relying on the fact that narrower structures are released from the substrate first, it is possible to create multiaxis loops and interlinked objects with several sequential release steps, using a single photomask. The structures remain planar until released by dry silicon etching, making it possible to integrate them with other MEMS and microelectronic devices early in the process. Chapter III depicts the fabrication process of different types of bistable structures. It describes the principle of functioning of such structures, and simulations using CoventorWare are used to support the concept. We talk over about advantages and disadvantages of bistable structures, and discuss possible applications. Chapter IV describes fabrication procedure of nanoparticle-MEMS hybrid device. We introduce a convenient synthesis of GNPs with precisely controlled optical absorption in the NIR region by a single step reaction ofHAuCl4 and Na2S203. We take a look at different techniques to pattern gold nanoparticles on the surface of MEMS structures, and also provide a study of their thermal properties under near IR stimulation. We demonstrate the first approach of laser-driven bistable MEMS actuators for bioapplications. Finally, in Conclusion discuss the contributions of this dissertation, existent limitations and plans of the future work.

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