The overall objective this work is the development of a miniaturized fluorescence spectroscopy analyzer realized via microfabrication technology. Previously, we reported a MEMS micro grating actuated by a piezoelectric cantilever. For such device to be used in a spectroscopic system, optical characterization of the grating's efficiency and the system's stray light are required. We report here the characterization of the grating cantilever with a MEMS micro lens with the intention of fitting into a packaged micro spectroscopic system. This packaging is accomplished by multi-wafer (silicon) bonding of strategically aligned crystalline planes in order to form the basic geometry of a miniaturized spectroscopy setup. One of these crystalline planes, <111> of silicon, is used as a mirror for folding and compacting the optics at the specific angle of 54.74° (with wafer plane normal). The packaging, microlens, and grating cantilever are position in the designed geometry to accept a self-aligned fiber input from a flash lamp source. The microlens component is presented with beam profilometry of its focusing at a focal length of 7.7 mm. The diffraction is interrogated by a monochromator for quantifying the above said characteristics. The relative efficiency of the grating was 40-70% in the 400-600 nm range. Together these characterized components define the geometry and performance of our micro fluorescence spectroscopy system.
Fluorescence spectroscopy plays a key role in a broad area of biological and medical applications. Development of fluorescence spectroscopy micro-devices will enable construction of fully integrated platforms for clinical diagnostics. We report the design, microfabrication and testing of a piezoelectric MEMS micro-grating as a part of the development of a combined spectral/time-resolved fluorescence biosensor for tissue characterization. For the design of the device, we simulated its theoretical performance using a piezoelectric multi-morph model with appropriate diffraction geometry. The microfabrication process was based on a SiN diaphragm (formed via KOH bulk-micromachining) on which the supporting layer of the micro-cantilevers was patterned. Piezoelectric ZnO was then magnetron sputtered and patterned on the cantilever as the physical source for linear actuation with low voltage (>32V). E-beam evaporation of aluminum formed the final reflective diffraction pattern as well as the electrode connections to the device units. The device actuation and displacement were characterized using LDDM (Laser Doppler Displacement Meter). Current cantilevers designed with 500 μm wide gratings (20 μm spacing) produced a maximum 38 μm bi-polar deflection at 3.5 kHz, with scanning from 350-650 nm at 26 nm resolution (10 nm with new 10 μm period prototype). The MEMS device was designed to be integrated with a fast response photomultiplier, and thus can be used with time-resolved fluorescence detection. Because in the case of time-resolved measurements, spectral resolution is not a crucial element, this configuration allows for the compensation of the geometric limitations (linear dispersion) of a micro-scale device that require wavelength differentiation and selection.
Conference Committee Involvement (3)
Smart Sensors, Actuators, and MEMS II
9 May 2005 | Sevilla, Spain
Device and Process Technologies for Microelectronics, MEMS, and Photonics
10 December 2003 | Perth, Australia
Smart Sensors, Actuators, and MEMS
19 May 2003 | Maspalomas, Gran Canaria, Canary Islands, Spain
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