| Fluorescence spectroscopy plays a key role in a broad area of biological and medical applications. Development of miniaturized fluorescence detection devices will enable the construction of fully integrated platforms for clinical diagnostics. This dissertation reports the conceptual design, fabrication implementation, and experimental application of a piezoelectrically tunable Microoptoelectromechanical System (MOEMS) device as the central system for a combined spectral/time-resolved fluorescence biosensor for tissue characterization. From design point of view, this dissertation examined the theoretical characteristics using a piezoelectric multimorph model with the appropriate diffraction geometry and evaluated the ray tracing geometries to estimate the system spectroscopic performance. To realize the MOEMS device, the fabrication was divided into three main parts: (1) Piezoelectrically actuated grating, (2) microoptics for light coupling, and (3) a three-dimensional aligned packaging. The micrograting actuator was fabricated via bulk-micromachining process with a ZnO thin-film sandwich to provide linear actuation with input voltage. Its performance is characterized by measured frequency response and linearity of actuation as well as the optical efficiency of its lithographically patterned grating. As the center of the microoptics, the microlens diaphragm is built via a polymer molding technique and is characterized with a novel setup based on Gaussian beam propagation technique. The integrated microoptics geometry is constructed from multiple layers of silicon cavity that includes microstructures such as the folding mirror, the diaphragm suspended microlens, and a v-groove aligned fiber input port. After encapsulation in the silicon cavity package, the system efficiency, resolution, and stray light quality are measured. To demonstrate the device utility, a set of fluorescence experiments was done on FITC, rhodamine B, and type II collagen as biologically inspired applications. The spectral resolution of 25 nm was sufficient for the fluorescence spectroscopy as the experiments included lifetime components to help improve selectivity. Demonstrated here is a completely packaged, microoptics and MEMS fabricated, piezoelectrically tunable fluorescence detector capable of looking at biological fluorescence. |
