A two-ply polymer-based flexible tactile sensor sheet using electric capacitance.

Traditional capacitive tactile sensor sheets usually have a three-layered structure, with a dielectric layer sandwiched by two electrode layers. Each electrode layer has a number of parallel ribbon-like electrodes. The electrodes on the two electrode layers are oriented orthogonally and each crossing point of the two perpendicular electrode arrays makes up a capacitive sensor cell on the sheet. It is well known that compatibility between measuring precision and resolution is difficult, since decreasing the width of the electrodes is required to obtain a high resolution, however, this may lead to reduction of the area of the sensor cells, and as a result, lead to a low Signal/Noise (S/N) ratio. To overcome this problem, a new multilayered structure and related calculation procedure are proposed. This new structure stacks two or more sensor sheets with shifts in position. Both a high precision and a high resolution can be obtained by combining the signals of the stacked sensor sheets. Trial production was made and the effect was confirmed.

Determination of locations on a tactile sensor suitable for respiration and heartbeat measurement of a person on a bed.

Sleep monitoring systems that can be used in daily life for the assessment of personal health and early detection of diseases are needed. To this end, we are developing a system for unconstrained measurement of the lying posture, respiration and heartbeat of a person on a soft rubber-based tactile sensor sheet. The respiration and heartbeat signals can be detected from only particular locations on the tactile sensor, and the locations depend on the lying location and posture of the measured person. In this paper, we describe how to determine the measurement locations on the sensor. We also report a realtime program that detects the respiration rate and the heart rate by using this method.

Study on mental stress using near-infrared spectroscopy, electroencephalography, and peripheral arterial tonometry.

In this research, we used near-infrared spectroscopy (NIRS) as an alternative technique for mental state analysis, and compared its performance with other conventional techniques such as electroencephalography (EEG) and peripheral arterial tonometry (PAT) during stress and healing tasks. We measured biological signals simultaneously in our experiments using these techniques for comparison. NIRS results showed that the level of total hemoglobin in the frontal cortex increased during a stress task and decreased during a healing task for all subjects whose blood volume change was properly recorded. EEG, however, showed inconsistent results due to task variation. Only PAT gave consistent results in many of the subjects. Taken together, the results suggest that NIRS might be suitable for mental state evaluation, with PAT as an alternative.

A study on the frontal cortex in cognitive tasks using near-infrared spectroscopy.

The frontal cortex is the part of the brain that relates to higher brain functions, such as logical thinking and emotion. As part of the development of a brain-computer interface, we tested whether the frontal cortex reacts differently in people as they performed three different cognitive tasks. The reaction of the cortex was tested using near-infrared spectroscopy. Our preliminary research results showed a difference in blood flow volume occurred before and after two assigned tasks: a math task and a word task. However, after a naming task there was no particular reaction. We believe that mental stress might be the cause of the difference in frontal cortex activity.