We have been studying a new type of biosensor that uses and mimics sensory functions of insects. The biosensor can be characterized in combination with immobilized signal transduction biomolecules, i.e., receptor proteins, and a semiconductor device as a transducer. We have developed a lipid bilayer membrane for receptor immobilization and combined it with an insulated-gate field-effect transistor (IGFET). By using this bilayer-IGFET device, we have measured changes in the bilayer membrane potential after introducing α-hemolysin, which acts as a model of receptors. This indicates that the developed device could be used for the biosensor using receptor proteins.
This paper describes a high-speed CMOS image sensor with a new type of global electronic shutter pixel. A global electronic shutter is necessary for imaging fast-moving objects without motion blur or distortion. The proposed pixel has two potential wells with pinned diode structure for two-stage charge transfer that enables a global electronic shuttering and reset noise canceling. A prototype high-speed image sensor fabricated in 0.18μm standard CMOS image sensor process consists of the proposed pixel array, 12-bit column-parallel cyclic ADC arrays and 192-channel digital outputs. The sensor achieves a good linearity at low-light intensity, demonstrating the perfect charge transfer between two pinned diodes. The input referred noise of the proposed pixel is measured to be 6.3 e-.
This paper reports on a new type of a tilt sensor fabricated using silicon MEMS processing technologies. The sensor consists of a ring shaped movable electrode, an extremely thin (15 μm) spiral spring connected with the movable electrode and eight surrounding lower electrodes. When a gravitational acceleration 1 G (9.80 m/s2) is applied to the movable electrode, it moves and makes a short circuit between itself and a pair of the lower electrodes. The movable electrode comes in contact with different surrounding electrodes depending on the tilt angle of the chip. Therefore, it is possible to detect the tilt. The tilt sensor was fabricated utilizing the following MEMS processes including anodic bonding of an extremely thin 60 μm-thick silicon wafer on a glass substrate, photolithography on the silicon film and dry etching the silicon film using an inductively coupled plasma (ICP) dry etcher. Then, the underneath glass was selectively etched off using a hydrofluoric (HF) solution to release the movable parts. Since the device layers were fabricated on a single-crystal silicon, it enables to fabricate stress free silicon spring. The sensor successfully detected the tilt of the chip.
A taste sensor consisting of a back-gate type field effect transistor(FET) chip based on carbon nanotube compound materials[poly(ethylene glycol)(PEG)-grafted single-walled carbon nanotubes(PEG-SWNTs)] was developed. The results of impedance measurements for five tastes (sourness, saltiness, bitterness, sweetness, and umami), are shown much difference for specific tastes which are difficult to identify by using Langmuir-Blodgett(LB)film. Moreover, the sensor is able to distinguish most of the experimental taste materials with a short response time. Characteristics of the sensor involve in taste material concentration , initial impedance and frequency characteristics. A clear difference is observed over five basic taste materials.
In this paper, sensor responses with only metal electrode as Au, Cr, Ti and more with LB film were described. LB film material was the Dioctadecyldimethylammonium bromide combined by PVSK as an underlayer. To detect five basic taste substances, sensor parameters were defined as maximum voltage change and response time. Response time for sourness and umami with Ti and Cr evaporated metal electrode was larger than that of usual Au electrode. LB film effect was finally found to increase response time for five basic taste materials.
Ethylene sensors are developed using semiconducting thin-film and Pd-deposited porous alumina. The semiconducting thin-film is used as a sensing element, while porous alumina is used as a gas filtering element. The sensing film is double layered; SnO2+V2O5(5mol%) or WO3+TiO2(10mol%) film is deposited as an upper layer on Fe2O3+TiO2(5mol%)+MgO(4mol%) film as a lower layer. Pt+W(8wt.%) film is used as electrodes. All films are deposited on an alumina substrate by r.f. sputtering. Palladium film is also deposited on both sides of a porous alumina by r.f. sputtering, and it is used as catalyst that is effective for ethylene gas. The highest sensitivity to ethylene gas occurs at 275°C for the SnO2-based sensor and at 250°C for the WO3-based sensor. The SnO2-based and WO3-based sensors are selective to ethylene gas in temperature ranges from 240°C to 290°C and from 170°C to 350°C, respectively. Both sensors are sensitive to ethylene gas even at lower concentrations from 10ppm to 100ppm.
We deal with the problem of direction and distance estimate of emission sources in 3-D space. We first introduce a partial differential equation (PDE) what we call the location constraint PDE (LC-PDE), which provides a necessary and sufficient description of wavefield generated by a source at direction n and distance R. To remove differentials, we integrate the LC-PDE in a finite rectangular area with complex sinusoidal weight functions. By using a well-known class of window function to eliminate the integral boundary terms, we show an exact finite set of algebraic equations can be obtained including n, R as the unknown variables and small number of 2-D discrete Fourier transform (DFT) components of wavefield as the measurements.
The resonance frequencies of various diaphragms in glass-based guided-wave optical pressure sensors were examined experimentally. In this study, acoustic sound pressure was applied to six fabricated sensors with square diaphragms of different dimensions to evaluate frequency characteristics as well as resonance frequency. The measured resonance frequencies were proportional to the diaphragm thicknesses, and inversely proportional to the square of the side-length of diaphragms, as theoretically predicted.
High curvature micro lens array of 240-570 μm diameters and 110-270 μm heights has been fabricated by using UV-LED lithography and imprinting technique. Curved SU-8 structures were fabricated by backside exposure through thin glass substrate because UV-LED array light source has wide directivity characteristics of UV dose. The structure was transferred to Polydimethylsiloxsane (PDMS) mold. Micro lens array of photosensitive acrylic resin was fabricated by using the mold.