Energy scavenging is a technology that derives required microwatt level power to drive electronics from ambient heat,
light, radio, or vibration, that is otherwise wasted. In this study, we have investigated the circuit optimization strategy for
vibration-based piezoelectric energy scavenging systems that supply the electric power to wireless sensors and
electronics for ubiquitous sensor networks. In this paper, we assert that not only the mechanical to electrical energy
conversion efficiency, but also the speed of energy storage is important in designing and evaluation of energy
scavenging system, since the energy scavenging system with higher speed of energy storage has faster start up response
to the mechanical input and can supply required power more frequently. Particularly in case of piezoelectric micropower
generator, we show that the low reverse leakage current characteristic rather than the low forward voltage drop of the
rectifying diodes is much more beneficial to improve conversion efficiency and that the storage capacitor should be as
small as possible to reduce the time to store required amount of energy. Experimental and PSPICE results show that,
when ultra-low leakage current diodes are adopted for a bridge rectifier, the mechanical-to-electrical energy conversion
efficiency is doubled or more in some cases, and the charging speed is increased by 20%, compared to the circuit that
adopts Schottky diodes. It is also found that, compared to the circuit with larger storage capacitor, the circuit with
smaller storage capacitor requires shorter time to store the same amount of energy and can drive voltage regulator more
frequently. This study suggests that low reverse leakage diode and small storage capacitor should be used to build
efficient high performance piezoelectric energy scavenging systems for ubiquitous sensor networks.
Latching optical switches and optical logic gates with AND or OR, plus the INVERT functionality are demonstrated for
the first time by the monolithic integration of a single and differential typed vertical cavity lasers with depleted optical
thyristor (VCL-DOT) structure with a low threshold current of 0.65 mA, a high on/off contrast ratio of more than 50 dB,
a high slope efficiency of 0.38 mW/mA, and high sensitivity to input optical light. By simply changing a reference
switching voltage, this single-typed device operates as two logic functions, optical logic AND and OR. The differential-typed
VCL-DOTs operate also as all logic gates, AND/NAND, OR/NOR, and INVERT function by simple change of a
reference input light power. The thyristor laser fabricated by using the oxidation process shows a high optical output
power efficiency and a high sensitivity to the optical input light.
This paper describes thermal denaturation and trypsin digestion of protein on a microchip as an alternative application of a temperature controllable microchip. Analysis of the protein of small volume and low concentration, which is impossible in macro scale, could be possible with the fairly reduced process time using the proposed temperature controllable microchip. We optimized the parameters concerning thermal denaturation on a microchip such as thermal denaturation temperature, thermal denaturation time, digestion time and concentration of protein using BSA(bovine serum albumin) as a reference sample. Then we applied the optimized parameters to the other proteins (ovalbumin, myoglobin, hemoglobin, cytochrome C, Ubiquitin). The proposed method on a microchip in this paper needed an even shorter reaction time, smaller volume of sample and smaller concentration of sample compared to the previously presented marco scale thermal denaturation and trypsin digestion method. We could successfully acquire the thermally denatured protein in 1 minute at 85°C and the digested peptides in 10 minutes at 37°C with 3 μl/0.2 μM protein. The acquired average sequence coverages are range from 24 to 57% for the test proteins, which are sufficient for the protein identification in practical use.
In this study, a new method is described for integrating an electrospray ionization interface to a mass spectrometer with a capillary electrophoresis channel. We have fabricated the ESI-MS device composed of the metal emitter tip, allowing the generation of an efficient nanospray for protein detection, and CE separation channel monolithically in a glass microchip. A triangular-shaped gold emitter tip was formed by electroplating at the end of the separation channel. As an ESI source, this emitter structure aided the formation of a stable Taylor cone. It is easily fabricated by MEMS technology and more robust than that of silica or polymer recently reported. Moreover, this approach is less involved than applying a conductive coating to the exit end to establish electrical contact. As such, the interface is less dependent upon the longevity or durability of such coating, factors that have been consideration in the sheathless interfaces. The spraying stability was evaluated and the ESI-MS experiment was performed by spraying standard peptides for mass spectrometric analysis. The spraying was stable, with a relative standard deviation of 2.9%. The CE/ESI-MS analysis was performed by separating and spraying standard peptide mixture of Bradykinin 1-5, Bradykinin 1-8, and Angiotensin I. Each peptide was separated successfully and singly-charged peaks and doubly-charged peaks of each peptide were detected, respectively. Direct comparisons with conventional ESI-MS system using glass or fused silica emitters showed very similar performance with respect to signal intensity and stability.
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.
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 μm2 in an upper plane and it has a slanted trapezoidal mirror reflective surface, which size is about 2000 x 1600 μm2, considering the micro prism dimension. The maximum deflection angle of the scanning mirror was 7° when 16 Vpp square type voltage is applied to the comb electrodes at resonant frequency.
KEYWORDS: Laser Doppler velocimetry, Digital signal processing, Signal processing, Doppler effect, Filtering (signal processing), Digital filtering, Beam splitters, Electronic filtering, Signal detection, Sensors
A novel technique that can measure the angle of a vertical microstructure with an accuracy of 0.05 degree(s) has been developed. The microstructure has a movable micromirror that is the main component of Micro-Optical Cross Connect (MOXC) that switches and couples optical signals in the optical communication networks. Since the performance of MOXC strongly depends on the angle between the vertical micromirror and the substrate, it is very important to measure the angle with high resolution better than 0.05 degree(s). In order to get the side view of the microstructure, a microscope imaging system that employs a long working distance objective lens and CCD camera has been built.
Micromirrors supported by S-shape girders were fabricated and their angular deflections were measured using a laser- based system. A micromirror consists of a 50 micrometers X 50 micrometers aluminum plate, posts and an S-shape girder. Two electrodes were deposited on two corners of the substrate beneath the mirror plate. 50 X 50 micromirror array were fabricated using the Al-MEMS process. The electrostatic force caused by the voltage difference between the mirror plate and one of the electrodes causes the plate to tilt under the girder touches substrate. Bias voltage of the mirror plate is between 25 approximately 35 V and signal pulse voltage on the electrodes is 5 V. A laser-based system capable of real-time two-dimensional measurements of the angular deflection of the micromirror was developed. The operation of the system is based on measuring the displacement of a HeNe laser beam reflecting off the micromirror. The resonance frequency of the micromirror is 50 kHz when the girder touches the substrate and it is 25 kHz when the micromirror goes back to flat position, since the moving mass is about twice of the former case. The measurement results also revealed that the micromirror slants to the other direction even after the girder touches the substrate.
Test equipment for the development and mass production of micromirror array have been devised. Test equipment for the static and dynamic response of a single micromirror consists of HeNe laser, lenses, XY stage, CCD camera, position- sensitive photodiode and PC. It can be used to measure reflectance, tilt angle--input voltage relation, response time and resonant frequency, in the developing stage. It can also check the lifetime and uniformity of mirror quality over the wafer. Test equipment for the evaluation of micromirror array consists of CCD camera, lenses, XY stage, video signal processor and PC. It can classify the error- state of micromirror, generate statistical data and map of the position of abnormal micromirrors. The test results are shown on the monitor as a map that shows the error state, position and statistical data. It takes about 90 seconds to evaluate 50 X 50 micromirror array.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.