We report the development of miniature fluorescence detection systems that employ miniature prism, mirrors and low cost CCD camera to detect the fluorescence emitted from 40 fluorescently-labeled protein patterns without scanner. This kind of miniature fluorescence detection systems can be used in point of care. We introduce two systems, one uses prism + mirror block and the other uses prism and two mirrors. A large NA microscope eyepiece and low cost CCD camera are used. We fabricated protein chip containing multi-pattern BSA labeled with Cy5, using MEMS technology and modified the surface chemically to clean and to immobilize proteins. The measurements show that the combination of prism and mirrors can homogenize elliptical excitation light over the sample with higher optical efficiency, and increase the separation between excitation and fluorescence light at the CCD to give higher signal intensity and higher signal to noise ratio. The measurements also show that protein concentrations ranging from 10 ng/ml to 1000 ng/ml can be assayed with very small error. We believe that the proposed fluorescence detection system can be refined to build a commercially valuable hand-held or miniature detection device.
This paper presents the design, fabrication, and testing of a single crystalline silicon (SCS) micromirror array (MMA) for peptide synthesis applications. Also, preliminary peptide synthesis experiments are presented for the proof of MMA performance. The application specific MMA had a simple fabrication process (only 3 photomasks), large mirror size (210x210μm<sup>2</sup>) and proper separation (60um). In order to obtain reliable structure and characteristics, we incorporated silicon on insulator (SOI) wafer and stepper photolithography. To maximize the pull-in voltage uniformity, sequential designing steps were described considering design limitations. The proposed fabrication process showed that the fabrication yield was very high up to 91.3%. The total array size consisted of 16 x 16 mirrors and tilting angle was 8.5° for left side or right side operations. The surface roughness was very low and less than 4 nm. The switching time of 156 μsec was reasonable since the exposure time during peptide synthesis was a few seconds. The fabricated MMA had a little pull-in voltage non-uniformity because of dimensional non-uniformities or fabrication errors. We have implemented an automated pull-in voltage measurement setup for verifying the pull-in voltage variation among the array. The measured pull-in voltage among 256 mirrors had the average of 96.99 V and the standard deviation of 2.12 V. The fabricated and analyzed MMA was adapted to the automatic peptide synthesis system and the peptide synthesis experiments showed that the SCS MMA improved the synthesis performance.
We fabricated a scanning mirror and optical benches monolithically in a silicon substrate using DRIE process and trench passivation by capillary filling. The micro scanning mirror, actuated by comb electrodes and supported by torsional spring, was fabricated with the optical benches in single crystalline silicon for the integration of optical fibers and ball lenses. Micro prism was adopted for high sensitive fluorescence detection system with scanning mirror. The excitation beam needs to be focused mainly on the slanted area of the micro prism in order to increase optical power efficiency. Considering beam collimation for high power efficiency, beam steering on the micro prism, and simple integration with the micro prism, we proposed silicon scanning mirror having slanted reflective plane and optical benches monolithically fabricated in the same silicon substrate. Reflective surface of the proposed scanning mirror makes parallel incident laser to the substrate be normal downward to the plane of substrate so that optical alignments become simple just by the alignment of scanning mirror’s and micro prism’s substrate. In this research the slanted angle of mirror plane is (-) 54.74 degree inclined instead of 45 degree because the scanning mirror was fabricated in single crystalline silicon (100)-oriented wafer using KOH wet process for the easy fabrication and fast feasibility test. The scanning mirror scans the laser one dimensionally by the actuation so that laser spot can be line-shape on the prism plane. The mirror is a pyramidal structure actuated by comb electrodes and torsion spring. The designed scanning mirror is 2165 x 778 μm<sup>2</sup> in an upper plane and it has a slanted trapezoidal mirror reflective surface, which size is about 2000 x 1600 μm<sup>2</sup>, considering the micro prism dimension. The maximum deflection angle of the scanning mirror was 7° when 16 V<sub>pp</sub> square type voltage is applied to the comb electrodes at resonant frequency.
Two dimensional micromirror array(MMA) is designed and fabricated to be used as a spatial light modulator for biochip fabrication. The optical projection system is setup using the MMA for maskless photolithography process, which is applied to photochemical surface modification. The photoresist (AZ1512) pattern is fabricated by the MMA projection in the maskless photolithography system, which consists of MMA and other optical components like projection lens. The patterned PR on a chip substrate is analyzed to improve pattern edge definition. The parameters of the optical system, which are lens location, incident angle of the UV light and the MMA location, are adjusted to obtain fine pattern edge definition by the MMA deflection. To immobilize proteins on the specific surface regions of a chip substrate to make protein patterning, nitroveratryloxycarbonyl(NVOC) group is used as a photolabile protecting group. The surface which is protected by NVOC group, is selectively irradiated by UV illuminator using the MMA. After removing the NVOC group, FITC(fluorescein isothianade) is tagged to the NVOC-cleaved site to find out the photo-cleavage condition of NOVC group by UV irradiation in the maskless photolithography system. Using the photocleavage condition, biotin was coupled to the NVOC-cleaved site. Then, we could obtain streptavidin-patterned surface.