A small form factor microsensor system with optical MEMS devices is discussed in this paper. The key components in
the microsensor system include a temperature and humidity sensor for environmental monitoring, a microprocessor for
signal processing, and an optical MEMS device (active corner cube retroreflector or CCR) for remote free space optical
communication. A flexible circuit design and a folded packaging scheme have been utilized to minimize the overall form
factor. Flat, flexible polymer batteries are incorporated to minimize the vertical profile to a few millimeters. The entire
fully packaged sensor system is about 30mmx30mmx6 mm. MEMS design of the CCR, fabrication, hermetic packaging
of CCR, flexible circuit design and fabrication, flip chip bonding of die form microprocessor, and a battery replacement
scheme for extended operation lifetime are crucial elements for the development of a real product for the microsensor
system. Optical MEMS CCR is a torsion mirror design and was fabricated using surface micromachining with Si3N4 as a
structural layer. A finite element analysis (FEA) model was developed to optimize design and performance of the
MEMS structures. The sensor system has a miniature mechanical switch for local actuation and an optical switch for
remote actuation. The applications of such a microsensor system include both tracking, tagging, locating (TTL) and
remote sensing.
Optical spectrometers are used in a variety of chemical and biological analytical instruments. Typically these employ a single input slit, a spectrograph, and a CCD or photodiode array for sensing. Only a few wavelengths may be of interest to the operator in many applications, due to absorption or fluorescence occurring within these specific optical regions. In the case of fluorescence, the excitation light intensity can be orders of magnitude greater than the fluorescence signal. In lieu of a detector array, a setup where a microelectromechanical system (MEMS) fabricated mirror array directs only the wavelengths of interest to a few detectors can be advantageous over sequential-readout arrayed detector systems. The MEMS mirrors and detector combination allows the desired wavelengths to be simultaneously and rapidly measured, with specialized detectors or electronics dedicated to each band. Integration time and electronic filtering may be adjusted independently, yielding better sensitivity and dynamic range. This combination is especially relevant in the infrared region, where arrayed detectors can be noisy or expensive, and arrays of dedicated amplifiers and filters are not cost effective. This paper reports on the design, fabrication, testing and control of MEMS-fabricated one-dimensional micromirror arrays for use in visible or infrared spectrometer applications. The micromirrors are fabricated using a surface micromachining process. A multiplexing method is introduced in the design to enable positioning a large number of mirrors from a few electrical inputs, which is necessary for practical applications when integrated control circuitry cannot be created on-chip with the MEMS devices. This approach also enables separate optimization of the actuation and control sections, and significantly reduces the number of drive signals required.
Miniaturization of laboratory sensors has been enabled by continued evolution of technology. Field portable systems are often desired, because they reduce sample handling, provide rapid feedback capability, and enhance convenience. Fieldable sensor systems should include a method for initiating the analysis, storing and displaying the results, while consuming minimal power and being compact and portable. Low cost will allow widespread usage of these systems. In
this paper, we discuss a reconfigurable Personal Data Assistant (PDA) based control and data collection system for use with miniature sensors. The system is based on the Handspring visor PDA and a custom designed motherboard, which connects directly to the PDA microprocessor. The PDA provides a convenient and low cost graphical user interface, moderate processing capability, and integrated battery power. The low power motherboard provides the voltage levels, data collection, and input/output (I/O) capabilities required by many MEMS and miniature sensors. These capabilities
are relayed to connectors, where an application specific daughterboard is attached. In this paper, two applications are
demonstrated. First, a handheld nucleic acid sequence-based amplification (NASBA) detection sensor consisting of a heated and optical fluorescence detection system is discussed. Second, an electrostatically actuated MEMS micro mirror controller is realized.
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