Showing papers by "Takashi Tokuda published in 2013"

Efficient approach for the design of effective chiral quaternary phosphonium salts in asymmetric conjugate additions

Abstract: An efficient approach for the design of chiral quaternary phosphonium bromides as chiral phase-transfer catalysts was demonstrated. A catalyst library of phosphonium salts with various structures was readily constructed using commercially available chiral phosphines as catalyst precursors, and an optimized catalyst was successfully applied to highly enantioselective conjugate additions under base-free phase-transfer conditions with low catalyst loading.

Image sensor pixel with on-chip high extinction ratio polarizer based on 65-nm standard CMOS technology

Abstract: In this study, we demonstrate a polarization sensitive pixel for a complementary metal-oxide-semiconductor (CMOS) image sensor based on 65-nm standard CMOS technology. Using such a deep-submicron CMOS technology, it is possible to design fine metal patterns smaller than the wavelengths of visible light by using a metal wire layer. We designed and fabricated a metal wire grid polarizer on a 20 × 20 μm(2) pixel for image sensor. An extinction ratio of 19.7 dB was observed at a wavelength 750 nm.

Sputtering condition optimization of sputtered IrOx and TiN stimulus electrodes for retinal prosthesis

Abstract: We have optimized the sputtering conditions for sputtered IrOx and TiN electrodes for retinal prosthesis. The basic electrochemical characteristics were evaluated by cyclic voltammetry, and the surface morphology was inspected by atomic force microscopy. To measure the charge delivery capacity (CDC), a 300-µm diameter electrode was formed, a balanced biphasic current pulse was applied, and the voltage response was measured. From the experimental results, the CDCs of IrOx and TiN in the best sputtering conditions were improved by more than 8 and 4 times compared to that of Pt, respectively. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Polarisation analysing complementary metal-oxide semiconductor image sensor in 65-nm standard CMOS technology

Abstract: In the present study, the authors demonstrate a complementary metal-oxide semiconductor (CMOS) image sensor implemented with on-chip polarisers using 65-nm standard CMOS technology. The polariser is composed of metal wire grids made of metal wires fabricated by the CMOS process. An extinction ratio of 18.8 dB was obtained for a single pixel with an on-chip polariser, where the line/space widths have the finest pitch obtainable by 65-nm technology. Electrical crosstalk between pixels is reduced by over 25% using a guard ring structure. Polarisation imaging by the sensor was also performed.

A CMOS microchip-based retinal prosthetic device for large numbers of stimulation in wide area

Abstract: We have developed a retinal prosthetic device based on CMOS technology for STS, suprachoroidal transretinal stimulation method Introducing CMOS technology makes it easy to realize large numbers of stimulus electrodes without increasing numbers of lead wires We designed a micro CMOS chip integrating with stimulus current generation, decoding and controlling circuits on the chip area size of about 400 μm square The microchip has two inputs and one stimulus output In order to stimulate a wide area in the retina, we fabricated a fork-type stimulus device, where two sets of a stimulus array device based on the micro chip architecture are connected into one flexible substrate Each stimulus device was implanted in different place of the rabbit's retina, so that we can stimulate separated places of the retina By increasing the number of the stimulus array device, we can stimulate a wide area of the retina without increasing the number of wiring by virtue of our microchip architecture

Implantable image sensor based on intra-brain image transmission

Abstract: We developed and fabricated a micro-imager based on wireless intra-brain communication using conductive property of living tissues. An pixel array, analog-to-digital converter and transmitter are integrated on a single chip. The dimensions of the chip are 1 mm × 1mm × 0.15 mm. We demonstrate wireless image transmission through phosphate buffer saline as a brain phantom.

An in vitro demonstration of CMOS-based optoelectronic neural interface device for optogenetics

Abstract: A CMOS-based neural interface device equipped with an integrated micro light source array for optogenetics was fabricated and demonstrated. A GaInN LED array formed on sapphire substrate was successfully assembled with a multifunctional CMOS image sensor that is capable of on-chip current injection. We demonstrated a functionality of light stimulation onto ChR2-expressed cells in an in vitro experiment. A ChR2-expressed cell were successfully stimulated with the light emitted from the fabricated device.

CMOS sensor-based miniaturised in-line dual-functional optical analyser for high-speed, in situ chirality monitoring

Abstract: A miniaturised in-line dual-functional optical analyser equipped with a polarisation-analysing CMOS image sensor was proposed and demonstrated. A single-wavelength optical absorption measurement function was also implemented in this device. The feasibility of the proposed device was demonstrated by evaluating two functions. Quasi-simultaneous optical rotation and absorption measurements were also performed. The results suggest that the present device is feasible as an in-line, in situ monitoring device for microchemical systems.

An implantable CMOS device for functional brain imaging under freely moving experiments of rats

Abstract: Observation of brain activities under freely moving condition is very important to elucidate brain functions of an animal. In this study, we developed an ultra-small implantable CMOS imaging device and successfully measured blood flow velocity of the brain surface under freely moving condition.

Implantable micro CMOS imaging devices for biomedical applications

Abstract: This paper reviews recent advancement of micro CMOS imaging devices to measure brain neural activities in an un-tethered mouse. Three types of imaging devices have been developed: a fiber endoscope, a head-mountable imaging device, and a brain-implantable imaging device. Among them, a brain-implantable imaging device can realize to observe neural activity in deep brain regions of the brain, such as hippocampus. The detail device structure and characteristics are presented.

A CMOS image sensor with low fixed pattern noise suitable for lensless observation system of digital enzyme-linked immunosorbent assay (ELISA)

Abstract: Digital enzyme-linked immunosorbent assay (ELISA) systems can be miniaturized by applying on-chip CMOS image sensor detection instead of conventional fluorescence microscopy. We have developed a CMOS image sensor dedicated to digital ELISA, which is sensitive to small changes of fluorescent intensity.

Needle type CMOS imaging device for fluorescence imaging of deep brain activities with low invasiveness

Abstract: We propose a thin type CMOS image sensor for measuring neural activities. The sensor is designed very thin shape for low invasiveness to a mouse brain. We demonstrate fluorescence imaging with the sensor.

A CMOS Image Sensor Having Stacked Photodiodes for Lensless Observation System of Digital Enzyme-linked Immunosorbent Assay (ELISA)

Abstract: A CMOS image sensor having stacked photodiodes was fabricated using 0.18 μm mixed signal CMOS process. The stacked photodiodes consist of N / P-well / Deep-NW / P-sub. P-well and P-sub are shorted to ground. By monitoring the voltage of N and Deep-NW individually, we can observe two monoclonal colors simultaneously without any color filters. Therefore the sensor is suitable for fluorescent imaging especially contact imaging such as lensless observation system of digital enzyme-linked immunosorbent assay (ELISA).

Lensless imaging device for digital counting of fluorescent micro-droplet chambers

Abstract: We developed a miniaturized lensless fluorescence imaging device for digital counting of micro-droplet chamber array, which is used in single molecule detection. Fluorescent beads in a droplet array were imaged with the device and its resolution was improved by using deconvolution method.

A high-extinction-ratio optical polarizer based on advanced CMOS technology

Abstract: The development of image sensors that incorporate metal-wiregrid polarizers is being explored with CMOS technologies. Although this approach shows promise for on-chip polarization image sensing, the sensors have yet to match the performance of those that use off-chip polarizers. This is because conventional CMOS fabrication techniques do not allow a sufficiently fine grid design. The recently developed, deep-submicron forms of CMOS-integrated circuits could potentially address this problem, since the metal wire structures made from this advanced form of technology are smaller than the wavelengths of visible light. As such, it is possible to directly integrate a nanophotonic wire structure onto a CMOS image-sensing chip for the purpose of detecting light in the visible to near-IR regions. The production of image-sensing circuits with directly integrated imaging devices is achieved via established CMOS fabrication processes. A particular advantage of such mixed-signal circuits is that they enable real-time signal processing of polarized images: this a feature that off-chip polarizers cannot offer.1, 2 On-chip polarizers are also well suited to conducting large-scale optical measurements in parallel. Using a 65nm CMOS process, we designed and fabricated a image sensor that contained a polarizer composed of a grid of metal wire arranged in a parallel array. The metal grid was positioned on top of the image-sensing pixel (see Figure 1).3–5 With a pixel size of 20 20 m2 and a photodiode area of 13:2 13:2 m2, the fill factor corresponded to 43.6%. Others have reported that the extinction ratio of polarizers constructed from similar metal wire grids increases with decreasing grid pitch. The extinction ratio relates the transmission of the unwanted component to the wanted component. For the metal wire Figure 1. Conceptual diagram of image sensor pixel with a single-layer, on-chip polarizer.4 TE: Transverse-electric wave. TM: Transversemagnetic wave.

Optoelectronics devices for biomedical applications

Abstract: CMOS-based bio-implantable optoelectronic devices for biomedical applications are presented. Designs, functionalities of implantable on-chip brain imaging devices, optical stimulators for optogenetics and CMOS-based flexible neural stimulators for retinal prosthesis are described.

Efficient Approach for the Design of Effective Chiral Quaternary Phosphonium Salts in Asymmetric Conjugate Additions.

Abstract: Various phosphonium bromide catalysts are presented, one of them proves to be an efficient promoter for asymmetric conjugate additions under base-free phase transfer conditions with low catalyst loading.