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This paper describes some aspects of micro sensors developed as part of the micromachine project in Japan. This national R&D project, industrial science and technology frontier program “Micromachine technology”, was inaugurated in 1991 as a ten‐year project. The R&D goal is to establish technologies to realize micromachines for the following practical applications; maintenance and repair of power plant facilities; miniaturization of manufacturing facilities; medical diagnosis and treatment. As a result, various types of micro sensors have been successfully developed.

This article reports on the 4th International Micromachine Symposium and Exhibition Micromachine (1998) which were held in Tokyo, 28‐30 October 1998 and also serves as a supplementary information to the article “Micro sensor developments in Japan” in this special “Micro sensors” issue of the journal. The symposium and exhibition are the annual showcase of the current status of the “Micromachine technology” project which is sponsored by the Japanese Government. Unlike efforts in other countries the Japanese approach is unique in trying to achieve real workable micromachines by establishing micro mechatronics technology. It differs from, for instance, the American MEMS where research is heavily dependent on silicon processing technology to fabricate micro devices on chips. Various kinds of micro sensors are now under development. These initiatives are well worth watching.

The purpose of this paper is to describe the fabrication of a miniaturized membrane type double cavity vacuum‐sealed micro sensor for absolute pressure using front‐side lateral etching technology.

Potassium hydroxide‐based anisotropic etching of single crystal silicon is used to realize the cavities under the membrane type diaphragms through channels on the sides. The diaphragms consist of composite layers of plasma‐enhanced chemical vapour deposition (PECVD) of silicon nitride and silicon dioxide. PECVD of silicon dioxide is done for sealing the channels and the cavity in vacuum. Boron thermal diffusion in low‐pressure chemical vapour deposition of polysilicon layer over the membrane is done for realizing resistors. The fabricated device uses Wheatstone half bridge circuit to read the variation of resistance with respect to an applied pressure.

A double cavity vacuum‐sealed absolute pressure micro sensor has been fabricated successfully using front‐side lateral etching technology and has been measured for pressure range of 0‐0.45 MPa. The measured pressure sensitivity of two pressure sensors is 9.28 and 10.44 mV/MPa.

The paper shows that front‐side lateral etching technology is feasible in the fabrication of small vacuum‐sealed cavities and absolute pressure sensors.

To fabricate submicrometer thin membrane of silicon nitride and silicon dioxide over an anisotropically etched cavity in (100) silicon.

PECVD of silicon dioxide and Silcion nitride layers of compatible thicknesses followed by thermal annealing in nitrogen ambients at 1,000°C for 30 min, leads to stable membrane formation. Anisotropic etching of (100) silicon below the membrane through channels on the sides has been used with controlled cavity dimensions.

Lateral front side etching through channels slows down etching rate drastically. The etching mechanism has been discussed with experimental details.

Vacuum sealed cavity membranes can be realised for micro sensor applications.

The process is new and feasible for micro sensor technologies.

The present paper aims to propose a basic current mirror-sensing circuit as an alternative to the traditional Wheatstone bridge circuit for the design and development of high-sensitivity complementary metal oxide semiconductor (CMOS)–microelectromechanical systems (MEMS)-integrated pressure sensors.

This paper investigates a novel current mirror-sensing-based CMOS–MEMS-integrated pressure-sensing structure based on the piezoresistive effect in metal oxide field effect transistor (MOSFET). A resistive loaded n-channel MOSFET-based current mirror pressure-sensing circuitry has been designed using 5-μm CMOS technology. The pressure-sensing structure consists of three identical 10-μm-long and 50-μm-wide n-channel MOSFETs connected in current mirror configuration, with its input transistor as a reference MOSFET and output transistors are the pressure-sensing MOSFETs embedded at the centre and near the fixed edge of a silicon diaphragm measuring 100 × 100 × 2.5 μm. This arrangement of MOSFETs enables the sensor to sense tensile and compressive stresses, developed in the diaphragm under externally applied pressure, with respect to the input reference transistor of the mirror circuit. An analytical model describing the complete behaviour of the integrated pressure sensor has been described. The simulation results of the pressure sensor show high pressure sensitivity and a good agreement with the theoretical model has been observed. A five mask level process flow for the fabrication of the current mirror-sensing-based pressure sensor has also been described. An n-channel MOSFET with aluminium gate was fabricated to verify the fabrication process and obtain its electrical characteristics using process and device simulation software. In addition, an aluminium gate metal-oxide semiconductor (MOS) capacitor was fabricated on a two-inch p-type silicon wafer and its CV characteristic curve was also measured experimentally. Finally, the paper presents a comparative study between the current mirror pressure-sensing circuit with the traditional Wheatstone bridge.

The simulated sensitivities of the pressure-sensing MOSFETs of the current mirror-integrated pressure sensor have been found to be approximately 375 and 410 mV/MPa with respect to the reference transistor, and approximately 785 mV/MPa with respect to each other. The highest pressure sensitivities of a quarter, half and full Wheatstone bridge circuits were found to be approximately 183, 366 and 738 mV/MPa, respectively. These results clearly show that the current mirror pressure-sensing circuit is comparable and better than the traditional Wheatstone bridge circuits.

The concept of using a basic current mirror circuit for sensing tensile and compressive stresses developed in micro-mechanical structures is new, fully compatible to standard CMOS processes and has a promising application in the development of miniaturized integrated micro-sensors and sensor arrays for automobile, medical and industrial applications.

One of the key components of the micro-sensors is MEMS micro-hotplate. The purpose of this paper is to introduce a platinum micro-hotplate with the proper geometry using the analytical model based on the heat transfer analysis to improve both heating efficiency and time constant.

This analytical model exhibits that suitable design for the micro-hotplate can be obtained by the appropriate selection of square heater (LH) and tether width (WTe). Based on this model and requirements of routine sample loading, the size of LH and WTe are chosen 200 and 15 μm, respectively. In addition, a simple micro-fabrication process is adopted to form the suspended micro-heater using bulk micromachining technology.

The experimental results show that the heating efficiency and heating and cooling time constants are 21.27 K/mW and 2.5 ms and 2.1 ms, respectively, for the temperature variation from 300 to 400 K in the fabricated micro-hotplates which are in closed agreement with the results obtained from the analytical model with errors within 5 per cent.

Our design based on the analytical model achieves a combination of fast time constant and high heating efficiency that are comparable or superior to the previously published platinum micro-hotplate.

The purpose of this paper is to bridge the gap between human emotions and wearable technologies for interactive fashion innovation. To consider the reasons why smart clothing should satisfy the internet of things (IoT) technical functions and human emotional expression simultaneously, to investigate the manner in which artistic design perspectives and engineering methods combined effectively, to explore the R&D elements of future smart clothing based on the IoT technology.

This study combines artistic design perspectives with information-sensing engineering methods as well as kansei evaluation method. Micro-sensors and light-emitting diodes (LEDs) embedded in couples clothing prototype. The first experiment step in the design and production of prototype clothing, and do the initial emotional evaluation. The second experiment is the comparative evaluation of the prototype and other typical smart clothing.

The interactive clothing prototype was proven to correlate well with human emotional expressive patterns. The evaluation I indicated the prototype can stimulate the emotional response of the participants to achieve a higher score in the activate sensor state. Evaluation II revealed that in the process of interactive clothing design, the technical functionality should synchronize with the requirements of human emotional expression.

This study builds the research and development theoretical model of interactive clothing that can be integrated into daily smart clothing life design, and analyze the methods and means of blending IoT smart information-sensing technology with emotional design. By means of this experimental demonstration of human-centered interactive clothing design, the authors provide smart clothing 3.0 evolutionary roadmap and propose a new concept of internet of clothes (IoC) for further research reference.