Makoto Ishida

Fabrication of the thermopile using SOI structure

In this paper, a thermopile which is applied to wide uses of temperature measuring was fabricated and its characteristic was improved by appling SOI structure to the fabrication. We improved characteristic of the thermopile by using single crystal silicon strips that has high seebeck coefficient and dielectric isolating the silicon strips from substrate with silicon dioxide film which dramatically decrease thermal conductivity between hot and cold junction compared to a silicon strip which was fabricated by ion implantation. The thermopile consists of 17 p-type single crystal silicon strips and 17 n-types by serial connection. The result of electromotive force measuring showed very good characteristic as 130mV/K when temperature difference between the two ends of the thermopile occurs by applying light on the thermopile fabricated with silicon strips of length, width, thickness.

Fabrication of a silicon pressure sensor for measuring low pressure using ICP-RIE

In this paper, we fabricated piezoresistive pressure sensor with dry etching technology which used ICP-RIE (inductively coupled plasma reactive ion etching) and etching delay technology which used SOI (silicon-on-insulator). Structure of the fabricated pressure sensor shows a square diaphragm connected to a frame which was vertically fabricated by dry etching process and a single-element four-terminal gauge arranged at diaphragm edge. Sensitivity of the fabricated sensor was about 3.5 mV/V kPa at 1 kPa full-scale. Measurable resolution of the sensor was not exceeding 20 Pa. The nonlinearity of the fabricated pressure sensor was less than 0.5 %F.S.O. at 1 kPa full-scale.

Three-Dimensional Silicon Smart Tactile Imager Using Large Deformation of Swollen Diaphragm with Integrated Piezoresistor Pixel Circuits

Recently, various kinds of tactile sensors have been investigated and reported for tactile applications with robot fingertips. Typical specifications of human fingertips are known as follows; spatial resolution of human fingertip is around 1 mm, time resolution is below 1 msec (1 kHz), and the minimum force resolution is around 1-10 mN. Also, human fingertip can recognize the three-dimensional (3-D) shape of touching object using flexible deformation in the convex shape of fingertip skin. However, it is very difficult to realize all the above requirements/performances in conventional tactile sensors at the same time. Tactile imager is a spatial distribution type of sensor, which can detect the object contact force and its distribution with an array of force or pressure sensors. In addition, detection ability of 3-D surface shape will be required for object handling. Tactile imagers can be applied to robot applications such as in robots for the assistance of visually handicapped and so on. There are two major trends in the previously reported tactile imagers. One is the polymer-based tactile imager realized by the substrate with organic materials, and the other one is silicon-MEMS type sensors. In polymer-based tactile imagers (Brussel & Belien, 1986; Engel et al., 2003; Shimojo et al., 2004; Someya et al., 2004, Engel et al., 2005), pressuresensitive conducting rubber has generally been used as a major force sensing element (Brussel & Belien, 1986; Shimojo et al., 2004; Engel et al., 2005). Polymer-based sensors are suitable for wide area tactile sensors since the fabrication cost per unit area is considered to be much lower than that of silicon sensors. Artificial skin mounted on large areas of robot surface is one of the major applications (Someya et al., 2004; Engel et al., 2005). Essential disadvantages of polymer-based sensors are relatively low spatial resolution and upper limitation on the number of pixels due to electronic signal wires. Typical spatial resolution of polymer-based tactile imagers is around 2 ~ 4 mm range, which is not high enough for fingertip tactile sensing applications as mentioned below. Although a tactile imager with a large number of pixels has been reported using organic-FET switching matrix (Someya et al., 2004), it still utilizes conducting rubber sensor elements. Also, the integration density of organic-FET is much lower than the present silicon technology, and its long term reliability in force sensor applications has not yet been demonstrated. Silicon-MEMS tactile imagers, integrating micro pressure sensor array (Sugiyama et al., 1990) or micro force-sensor array, have been reported earlier (Suzuki et al., 1990(a); (b); O pe n A cc es s D at ab as e w w w .in te ch w eb .o rg

A Durable Sensor for Blood Cell Counter Using MEMS Technology

In this study, a durable sensor device for blood cell counter has been developed using MEMS technology. The number of blood cells in human blood can be counted and checked with 10 mm × 5 mm silicon MEMS device. Aperture-impedance method was used to detect blood cells as voltage signals. As a result of investigations, suitable materials for the electrode of the device have been found. First, latex particles were used to confirm the operation of the blood cell counter instead of blood and finaly actual blood was measured. The size difference of latex particles and concentration of latex particles were successfully recognized from the height of voltage pulse and the number of pulses, respectively.