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Biomedical subjects

M Esashi

Publications and source records attributed to M Esashi.

10 recordsLinked to original sources
PubMed1990

Micro-pressure sensor for continuous monitoring of a ventricular assist device.

We have been involved in the development of a clinical ventricular assist device (VAD) system. Here, we report our investigation of in vitro and in vivo stability and sensibility of pressure microsensors. The sensors were mounted in the in-flow and out-flow cannulae wall to measure the left atrial and aortic pressures during VAD pumping. The pressure sensitive surface of the piezoresistive effect absolute pressure sensor was coated with a thrombo-resistant polymer, as was the inner surface of the cannulae of the VAD. In the in vitro and chronic animal experiments which were of more than a month duration, reliable stability and sensitivity, without any thrombus formation on the blood contacting surface of the sensors, and high sensitivity were observed. After chronic experiments, the sensitivity of sensors was reevaluated in the mock circulatory system as compared to reference values. The relationship between the output of the micro-sensors and the reference value was linear and correlated well.

Animals↗
PubMed1989

Manufacture of custom CMOS LSI for an implantable multipurpose biotelemetry system.

Implantable biotelemetry systems are indispensable tools not only in animal research but also in clinical medicine as such systems enable the acquisition of otherwise unavailable physiological data. This paper describes the manufacture of custom CMOS LSI to implement an implantable biotelemetry system. The internal circuits of this system are fabricated on a single silicon chip with a size of 4 x 5 mm. This IC is designed and manufactured not only to achieve as small size and low power dissipation as possible, but also to have multiple functions. Its main functions are to select one of implanted sensors and to accomplish On-Off power switching of an implanted battery by receiving appropriate control signals and command signals from an external circuit. This system, used together with appropriate sensors, is expected to be capable of measuring and transmitting such significant parameters as pressure, pH and temperature.

Electronics↗
PubMed1987

Solid-state micro sensors.

Recent research activities on solid state micro sensors in Japan are reviewed. Many kinds of micro sensors for chemical and physical quantitative analysis have been developed for biomedical instrumentation. Many of these sensors are fabricated with the advanced art of semiconductor technology, which is called micromachining. This technology enables fabrication of sensors so small that they can be used in catheter tubes etc. Moreover, it has brought out integrated sensing systems or multi sensors. In the field of chemical sensors, the development of ISFETs, i.e. ion sensitive field effect transistors, has been much advanced. These have been applied not only as ion sensors but also as biosensors or dissolved gas sensors. On the other hand, the major research activities on micro sensors for physical quantities have been on pressure sensors for measurements in blood vessels etc.

Biotechnology↗
PubMed1986

Characterization of human dental plaque formed on hydrogen-ion-sensitive field-effect transistor electrodes.

The purpose of this study was to evaluate (with scanning electron microscopy and microbiological characterization) the bacterial deposits which accumulate on hydrogen-ion-sensitive field-effect transistor electrodes (pH-ISFET) under conditions normally employed for telemetric monitoring of changes in human dental plaque pH. Electrodes were mounted in a carrier appliance which was worn for two, four, and six days. The plaque pH response to a sucrose solution increased with the age of the plaque, as expected from previous studies. After two days, the electrode was shown to be almost completely covered with cocci. At days 4 and 6 there was a dramatic increase in the number of rods present in the plaque. Adjacent enamel surfaces showed similar accumulations of bacteria. The total number of bacteria which had accumulated per unit area by day 4 was very similar for the electrode and enamel surfaces. On both surfaces the plaque contained approximately 25% streptococci, and the dominant species was Streptococcus sanguis (approximately 75%). The plaque which accumulated on pH-ISFET electrodes could not be distinguished visually or microbiologically from that which formed on control enamel surfaces.

Bacteria↗