Kimio Otsuka

Imaging of skin thermal properties with estimation of ambient radiation temperature

Our latest system for the imaging of temperature and other thermal properties of the skin provides not only precise temperature distribution of the skin but also high-speed measurement of emissivity and inertia distribution. The method enabled us to measure the emissivity and thermal inertia of the skin even when the temperature distribution of the inner surface of the hood was not uniform. Two-dimensional measurement with hood switching, and a single-hood measurement system were considered.

Remote monitoring of daily activities and behaviors at home

In maintaining the health of people, both elderly and younger, it can be useful to monitor their health status through their daily routines in their own home. This paper reports on the remote monitoring of the daily routine behaviors in an ordinary house. We attempted to monitor the daily behaviors of a subject, mainly in the kitchen and dining room. Several sensors were installed, including infrared sensors to detect human movement, magnetic switches to detect the opening and closing of doors, a carbon dioxide sensor to detect presence of the subject, and temperature sensors at the kitchen sink to detect cooking. A 31-year-old man who lived alone was monitored for about three months. The output of sensors was recorded on a personal computer and the data were transferred to another site by the Internet. Monitoring was performed fully automatically. As a result, daily habits could be clearly identified. Such monitoring can contribute to the maintenance of health.

Flexible Glucose Sensor Using Biocompatible Polymers

A flexible amperometric glucose sensor formed on biocompatible polymer was fabricated and tested. The sensor was fabricated by laminating biocompatible polymers and film electrodes. Functional and biocompatible polymers of polydimethyl siloxane (PDMS) and 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymerized with dodecyl methacrylate (DMA) were utilized as the sensor material. Particularly, poly (MPC-co-DMA) (PMD) was not only used as a gas-permeable layer by optimizing the thickness but also used as an enzyme immobilized layer by casting with glucose oxidase (GOD). The sensor measures the glucose concentration as a current change induced by enzyme reaction at the GOD immobilized PMD layer. The advantage of our sensor is its flexibility which enables the sensor to fit a rounded shape of measuring site. The basic characteristics of the biosensor were evaluated using batch measurement system. As a result, output current of the glucose sensor related to the glucose level over a range of 0.100 to 3.00 mmol/1 with a correlation coefficient of 0.998. The calibration range includes the reported concentration of tear glucose in normal human subject (0.14 mmol/1). Owing to flexibility and biocompatibility, which are both suitable characteristics for bioinstrumentation, the sensor might be useful for monitoring of glucose concentration in tear fluids.

Imaging of thermal inertia to visualize reactive hyperemia in the forearm skin after arterial occlusion

An imaging system has been developed to visualize the effect of reactive hyperemia by measuring skin thermal inertia after releasing arterial occlusion because it was known that thermal inertia depends on the blood flow. The method is based on the ability to calculate thermal inertia from thermographic measurements of the response to a known stepwise change in ambient radiation temperature. Measurements were made during reactive hyperemia after 1 min of complete occlusion. After immediate releasing the cuff pressure, the response of reactive hyperemia appeared in the image of thermal inertia, where many island-shaped nonuniform thermal inertia distributions were observed.

An Optical Halitosis (Bad Breath) Sensor with Mao-A

Methyl mercaptan (MM: CH3SH) is known as one of major chemicals of halitosis (bad breath). Monoamine oxidase type-A (MAO-A) has been reported to catalyze the oxidation of methyl mercaptan for a xenobiotic metabolism in human liver. In this research, an oxygen sensitive optical fiber was applied for developing a optical bio-sniffer for methyl mercaptan in halitosis. An optical bio-sniffer was constructed by applying an MAO-A immobilized membrane onto the fiber-tip with a tube-ring. The optical device was possible to detect the oxygen consumption induced by MAO-A enzymatic reaction with methyl mercaptan as an index of halitosis level. As the result of the physiological application, the bio-sniffer could be successfully used the halitosis monitoring.

A wearable humidity sensor with hydrophilic membrane by Soft-MEMS techniques

An electric conductimetric sensor (thickness: 80 mum) constructed in a sandwich configuration with a hydrophilic poly-tetrafluoroethylene membrane placed between two gold deposited layers was evaluated for use as a moisture sensor. The humidity level was measured by electrical conductivity of the device using the multifrequency LCR-meter at frequencies ranging from 100 Hz to 100 k Hz, the device was calibrated at 100 Hz against the moisture air over the range of 30 - 85 % RH, which includes normal humidity level in the atmosphere and physiologic air such as breath and sweating. The response sensitivity of the conductimetric device was extremely high (i.e. less than 1 sec. for conductivity shift between humid air of 80 % RH and dried air of -60 degC dew point) even for recovery to dried air. The sensor performance was reproducible over multiple measurements, showing the highly reproducibility with a coefficient of variation of 1.77 % (n = 5).

A Fiber Optic Immunosensor for Rapid Bacteria Determination

Attention is currently focused on fiber optic immunosensor as sensitive and nearly real time protein detector. This kind of sensor is expected to detect bacteria in foods directly by dipping the thin optical fiber dominant area into foods. In the study, an antibody based fiber optic immunosensor to detect Escherichia coli O157:H7 (E.coli O157:H7) was constructed. The principle of the sensor was a sandwich immunoassay on the optical fiber surface. A goat polyclonal antibody was first immobilized on polystyrene optical fiber. E.coli O157:H7 and a cyanine 5 (Cy5) -labeled goat polyclonal antibody were used to generate a specific fluorescent signal. An excitation light (λ = 635 nm) was illuminated into the optical fiber, and the Cy5 florescent molecules near the optical fiber (approximately 100 nm) were excited by evanescent wave emitted from the optical fiber. The fluorescent light (λ = 670 nm) collected by the optical fiber was measured using a photodiode. The measurement range for E.coli O157:H7 diluted with phosphate buffer (PB) was from 1×102 to 1×107 cells/ml. This method could also detect E.coli O157:H7 in milk artificially inoculated with 1×102 to 1×107 cells/ml. This immunosensor was specific for E.coli O157:H7 and showed significantly higher signal strength than for nonpathogenic E.coli or other bacteria, including Listeria monocytogenes and Vibrio s.p., in pure or in mixed-culture setup. The results could be obtained within about 15 min of sampling.

Biochemical sniffer for odourless hydrogen peroxide vapour

A biochemical gas-sensor (bio-sniffer) was constructed for convenient measurement of odourless hydrogen peroxide (H2O2) vapour, which is harmful to skin and mucous membranes. An enzyme-immobilized membrane was fabricated by spreading the mixture of catalase and photo-crosslinkable polymer on a dialysis membrane. An H2O2 biosensor was constructed by attaching this catalase-immobilized membrane to the sensitive top of a Clark-type oxygen electrode, and the oxygen generation from the decomposition of H2O2 catalysed by catalase was measured amperometrically. This biosensor was first applied to the measurement of H2O2 solution and was able to quantify the concentrations of H2O2 solution from 0.02 to 10.0 mmol L−1. Then, this biosensor was applied to gaseous phase as a bio-sniffer and was able to detect the odourless H2O2 vapour with the calibration range from 0.5 to 30 ppm, where the threshold limit value assigned by the American Conference of Governmental Industrial Hygienists (1 ppm) is covered.

A model of cortical neural network structure

A model of cortical neural structure consisting of threshold elements is proposed in which the single-cell-representation hypothesis is introduced. A random coding scheme was assumed so that a cell representing the content of cognition can be specified by the coded output. It was shown that this structure can be extended to the scale of the human cerebral cortex, and that the relationship between the number of neurons in the entire cortex and the number of synapses on each neuron can be explained consistently. To explain memory, the recruitment of unused element, called virgin cell, was assumed. This model provides a consistent explanation of the structure and function of the cortical neural network, and may also be applied to explain mental processes such as cognition and consciousness.

Wearable humidity sensor with porous membrane by soft-MEMS techniques

An electric conductimetric sensor (thickness: 80 /spl mu/m) constructed in a sandwich configuration with a hydrophilic poly-tetrafluoroethylene membrane placed between two gold deposited layers was evaluated for use as a moisture sensor. The humidity level was measured by electrical conductivity of the device using the multifrequency LCR-meter at frequencies ranging from 100 Hz to 100 kHz, the device was calibrated at 100 Hz against the moisture air over the range of 30-85 % RH, which includes normal humidity level in the atmosphere and physiologic air such as breath and sweating. The response sensitivity of the conductimetric device was extremely high (i.e. less than 1 sec. for conductivity shift between humid air of 80 % RH and dried air of -60 /spl deg/C dew point) even for recovery to dried air. The sensor performance was reproducible over multiple measurements, showing the highly reproducibility with a coefficient of variation of 1.77 % (n = 5).