Toyosaka Moriizumi

Study of autonomous mobile sensing system for localization of odor source using gas sensors and anemometric sensors

Abstract A new method for localization of an odor source is proposed. A probe with four anemometric sensors and four gas sensors has been developed so that the direction of an odor source can be determined. The anemometric sensors are used for measuring the direction of the air flow carrying odor molecules, and the gas sensors are used for detecting the gas-concentration gradient. Moreover, mounting the probe on a mobile stage with the probe under the control of a personal computer makes it possible to realize an autonomous mobile sensing system. An odor source has been successfully localized using this system in a wind tunnel.

Langmuir-Blodgett films as chemical sensors☆

Abstract This review covers the fundamental scheme of chemical sensors, fields of major interest in chemical sensors with Langmuir-Blodgett (LB) films, and new and future trends in LB sensor studies. The topics discussed are the relation between sensor characteristics and LB film structure, the biomimetic approach to sensor developments, proposals for transducer improvements, and the possibility of fabricating molecular filters by LB techniques.

Plume-Tracking Robots: A New Application of Chemical Sensors

Many animals have the ability to search for odor sources by tracking their plumes. Some of the key features of this search behavior have been successfully transferred to robot platforms, although the capabilities of animals are still beyond the current level of sensor technologies. The examples described in this paper are (1) incorporating into a wheeled robot the upwind surges and casting used by moths in tracking pheromone plumes, (2) extracting useful information from the response patterns of a chemical sensor array patterned after the spatially distributed chemoreceptors of some animals, and (3) mimicking the fanning behavior of silkworm moths to enhance the reception of chemical signals by drawing molecules from one direction. The achievements so far and current efforts are reviewed to illustrate the steps to be taken toward future development of this technology.

Odor-source localization in the clean room by an autonomous mobile sensing system

Abstract Experiments on odor-source localization using an autonomous mobile system were performed in a clean room. A new exploratory algorithm was developed since the algorithm of upwind searching previously developed by our group was found to be applicable only on a limited situation. The switchover of two strategies, moving upwind and along the gas-concentration gradient, was introduced to extend the applicable area. A threshold value of the gas sensor output used for exchanging two strategies was automatically adjusted during localization movements. As the flexibility of the system was enhanced, an ethanol source was successfully localized from almost anywhere in the prepared measurement space.

Perfume and flavour identification by odour-sensing system using quartz-resonator sensor array and neural-network pattern recognition

Abstract Perfume and flavour identification by an odour-sensing system using a quartz-resonator sensor array and neural-network pattern recognition has been performed. Good separations among the samples are obtained. Furthermore, orange flavours with a small amount of foreign substances have been examined. When the ratio of the foreign substances to orange flavour is more than 0.5%, the sample could be separated from an ordinary orange sample by the present system, with a detection limit near those of normal people.

Integrated enzyme fets for simultaneous detections of urea and glucose

The fabrication process and characteristics of monolithically integrated urea and glucose FETs are described. First, ISFETs were fabricated on a SOS substrate and a photosensitive dry film was coated on to it to form micropools over the ISFET gates. Then mixtures of photosensitive PVA and enzyme solutions were injected into these pools using microsyringes. After exposure to UV light, an insoluble membrane with enzyme entrapped in it was formed. The proposed fabrication process was considered to be compatible with IC technology. Urea and glucose concentrations in the range 1 × 10−4 to 1 × 10−2 g/ml could be detected by the urea and glucose FETs, respectively. The integrated enzyme FETs described here will be useful for measuring several kinds of substrates simultaneously. The present fabrication process can be used for the preparation of multifunctional and one-chip biosensors with various other pairs of immobilized enzymes.

Odour-sensing system using a quartz-resonator sensor array and neural-network pattern recognition

Abstract It is difficult to realize an odour or gas sensor with a high selectivity. From a biomimetic viewpoint, it is promising to make a sensor array and analyse the output pattern to recognize the various sorts of gases. We use six quartz resonators, with different coating materials, whose oscillation frequencies decrease when gas molecules are adsorbed on the sensing membranes over them. The pattern analysis method used in the present study is neural network pattern recognition. This network has been trained to identify the types of odours using the back-propagation algorithm. The system is trained to identify 11 kinds of liquors on the market and its recognition probability is 73% when the liquor signals used in the training are input. In order to enhance the odour recognition ability, the data vectors for the liquors are input to the network after subtracting those for aqueous ethanol solutions that have the same ethanol concentrations as the liquors. The recognition probability is then improved to 88%.

New Sensor in Liquid Using Leaky SAW

Utilizing a shear horizontal displacement of a leaky SAW mode, SAW sensors to be used in liquid can be realized. Theoretical and experimental works showed that 36O-rotated Y-cut X-propagation LiTaOj is a promising substrate for a biosensor and a viscosity sensor.

Identification capability of odor sensor using quartz-resonator array and neural-network pattern recognition

Abstract Although the identification of various kinds of odors in our daily life is important, few artificial odor sensing systems have been reported. From the biomimetic point of view, the use of plural sensors to recognize the output pattern of a sensor array for such identification is very promising. An odor sensor using a quartz-resonator array and neural-network pattern recognition has been previously reported. In the present study, optimization of the sensor-array components has been made and the recognition probability has been improved.

A theory of a quartz crystal microbalance based upon a Mason equivalent circuit

The authors analyzed the behavior of a quartz crystal microbalance (QCM) in the experimental environments of air and liquid using a Mason equivalent circuit. It was found that the mass loading effect of QCM could be regarded as an inductance increase, and the analytical equation of the frequency shift, which is valid over the wide range of the thickness of a loading film, was derived. Utilizing this equation, the frequency shift can be predicted without solving the transcendental equation. Furthermore, it was found that various kinds of QCM problems, such as liquid loading and mass loading in liquid, could be solved using the same method because the acoustic load was expressed as a circuit component. Finally, the method to enhance mass loading sensitivity by depositing a thick film with low acoustic impedance over the quartz plate, was suggested.