Hirokazu Nakazawa

Progressive-Type Fused pH and Optical Image Sensor

A fused pH and optical image sensor is proposed and fabricated using a complimentary metal–oxide–semiconductor (CMOS) integrated circuit technology. In the proposed image sensor, a pH sensor and an optical sensor are fused in the same pixel, enabling the pH and the optical signal to be detected simultaneously in the same sensing area. Moreover, the proposed image sensor enables us to measure each piece of information without any signal cross-talk. Therefore, the relationship between pH and light distributions can be clarified by using the proposed image sensor. The proposed image sensor is expected to have applications in various fields, such as biochemical, environmental, and medical fields.

A Fused pH and Fluorescence Sensor Using the Same Sensing Area

A fused pH and fluorescence sensor is proposed, and a prototype has been fabricated using CMOS silicon integrated circuit technology. Fluorescence intensity and pH can be detected at the same pixel for the first time. In the proposed device, a pH sensor which uses CCD image sensor technology and a filter-less fluorescence detection sensor are fused in the same pixel, enabling fluorescence and pH signals to be detected simultaneously in the same sensing area.

High-Sensitivity Charge-Transfer-Type pH Sensor With Quasi-Signal Removal Structure

Charge-transfer-type pH sensors can be used to improve pH sensitivity with enhanced signal-to-noise ratio by applying the charge-accumulation technique. Theoretically, the pH sensitivity improves directly with the accumulated count. However, in a conventional sensor structure, a quasi-signal resulting from low charge transfer efficiency limits the accumulated count. In this paper, an effective solution to the problem of the quasi-signal and the novel sensor structure are investigated.

A fused pH and fluorescence sensor using the same sensing area

A fused pH and fluorescence sensor is proposed, and a prototype has been fabricated using CMOS silicon integrated circuit technology. Fluorescence intensity and pH can be detected at the same pixel for the first time. In the proposed device, a pH sensor which uses CCD image sensor technology and a filter-less fluorescence detection sensor are fused in the same pixel, enabling fluorescence and pH signals to be detected simultaneously in the same sensing area.

Reduction of Interference Between pH and Optical Output Signals in a Multimodal Bio-Image Sensor

We have developed a low interference multimodal sensor for pH (power of Hydrogen) and optical imaging. The signal interference between pH and optical outputs is shown to be caused during pH sensing by the photogenerated electrons. We suppressed this interference by adding another charge accumulation region to the conventional multimodal sensor structure for measuring only the amount of photogenerated electrons and thereby discriminating between pH and optical signals.

Reduction of interference between pH and optical output signals in a multimodal bio-image sensor

A low-interference multimodal sensor for pH and optical imaging has been developed. The interference signal that occurs between pH and the optical outputs is found to be caused by photogenerated electrons during pH sensing. This interference could be suppressed by adding another charge-accumulation region to a conventional multimodal sensor structure in order to measure only photogenerated electrons. Conventional pH sensing devices combine accumulation regions for photo generated electrons, thereby discriminating between pH and optical signals.

Multicolor fluorescence detection for single nucleotide polymorphism genotyping using a filter-less fluorescence detector

Single nucleotide polymorphism (SNP) analysis that is commonly performed using fluorescence is important in drug development and pathology research. In this study, to facilitate the analysis, multicolor fluorescence detection for SNP genotyping using a filter-less fluorescence detector (FFD) was investigated. FFDs do not require any optical filters for multicolor fluorescence detection. From the experimental results, FFD could identify 0 μM, 1 μM, and 10 μM solutions of Texas Red and fluorescein isothiocyanate. Moreover, a mixture of Texas Red and 6-FAM could be detected in the SNP genotyping simulation. Therefore, a small and low-cost SNP genotyping system is feasible.

Improvement of the Detection Accuracy and Detection Limit of a Filter-less Fluorescence Detector

Filter-less fluorescence detectors (FFDs) do not require any optical filters for multicolor fluorescence detection. Therefore, a small and low-cost fluorescence detector is realizable, and applications to pathological examination and drug development are expected. In order to apply such devices to biochemical and medical diagnosis, it is important to detect weak fluorescence with high accuracy. However, in some situations, the fluorescence intensity may be less than 10-5 of the excitation light intensity. In this study, we experimentally demonstrate an FFD with improved detection accuracy and detection limit. By this approach, the detectable fluorescence intensity decreased to the dark-current level.

Multimodal bio - image sensor for real - time proton and fluorescence imaging

A multimodal bio-image sensor for proton (pH, power of Hydrogen) and filter-less fluorescence imaging is developed, and its prototype has been fabricated using CMOS silicon integrated circuit technology. Both pH and fluorescence images were successfully obtained without optical filters or gratings and simultaneously in the same area in real time using the developed image sensor for the first time. In the developed device, a pH sensor which uses CCD image sensor technology and a filter-less fluorescence detection sensor are fused in the same pixel.

Proposal of a high accuracy filter-less fluorescence detector for bio-applications

Filter-less fluorescence detectors (FFDs) do not require any optical filters for multicolor fluorescence detection. In this study, we experimentally demonstrate an FFD with improved detection accuracy for bio-applications, such as single nucleotide polymorphism (SNP) genotyping.