This study presents a novel polyimide-based self-assembly three dimensional micro blade using surface micromachining technology for the development of micro-fan chip. The high surface-tension-force of reflowed polyimide has can be used to lift the free-standing micro blade. In addition, the thesis introduces a micro hinge structure to effectively limit the maximum lifting angle of the micro blade and to accurately lock hinge-pin into the vertical position. Many parameters have been investigated its influence on the surface-tension- force of polyimide, including the thickness of polyimide and the temperature/time in reflow processing. Based on the experimental results, 18 £gm-thick polyimide can lift the micro blade at 70¢X angle under 380 ¢J/10 hrs reflow condition. On the other hand, 25 £gm-thick polyimide has demonstrated its maximum lifting angle can be achieved to 130¢X utilizing the very high surface-tension-force induced by over contraction and deformation when it was reflowed at higher temperature (400 ¢J). Finally, this dissertation has studied the relation between the position of polyimide elastic-joint and the deflection angle (£r). Furthermore, this thesis has successfully demonstrated a novel multi-joint and asymmetrical microstructure for the development of the spiral and out-of-plane 3D micro blade.

ABSTRACT Fabrication and Characterization of Torsional Micro-Hinge Structures Mike Marrujo There are many electronic devices that operate on the micrometer-scale such as Digital Micro-Mirror Devices (DMD). Micro actuators are a common type of DMD that employ a diaphragm supported by torsional hinges, which deform during actuation and are critical for the devices to have high stability and reliability. The stress developed within the hinge during actuation controls how the actuator will respond to the actuating force. Electrostatically driven micro actuators observe to have a fully recoverable non-linear viscoelastic response. The device consists of a micro-hinge which is suspended by two hinges that sits inside a micro machined well. To achieve a specific angle of rotation when actuated, the mechanical forces need to be characterized with a range of different forces applied to the edge of the micro-hinge. This research investigates the mechanical properties and the amount of force needed to rotate to specific angles by comparing theoretical performance to experimentally measured values. Characterizing the mechanical forces on the micro-hinge will further the understanding of how the device operates under a specific applied force. The material response to the amount of stress within the hinges will control the amount of actuation that is achieved by that force. The test devices were fabricated using common semiconductor fabrication techniques. The micro-hinge device was created on a 500µm, double-sided polished, single crystal (100) silicon wafer. In order to create this device, both wet etching and dry etching techniques were employed to produce an 8µm thick plate structure. The bulk etching of 480µm was achieved by wet etching down into the silicon (Si) to create the wells. Dry etching was used for its high precision to release the micro-hinge structure. Once fabricated, the micro-hinge actuators were tested using a Technics turntable arm with a built in micrometer that applied a constant force while measuring the displacement of the actuator. The rotation of the hinge was measured by reflecting a Helium-Neon (HeNe) laser beam off a mirror, which is attached to the pivot of the arm that’s applying the force, and any type of displacement was recorded with a Photo Sensitive Device (PSD). The test stand applied a small force which replicated the amount of electrostatic forces needed to achieve a specific degree of rotation. Results indicate that the micro-hinge achieved a repeatable amount of rotation when forces were applied to it. The micro-hinge would endure deformation when too much force would be applied and yield a maximum amount of force allowed.