We demonstrated microfabrication of polytetrafluoethylene (PTFE) using X-ray-induced pyrochemical anisotropic etching process. We found the scission of PTFE main polymer chain was induced by X-ray irradiation. The decrease of fragment length enabled pyrochemical etching because of decreasing the desorption temperature of scission fragment. Here, we can diminish the distortion of fabricated PTFE fine pattern in a large area using the pyrochemical anisotropic etching process. We also found the thermal exchange process and vapor pressure through a He gas can provide a clue to achieve the higher precision fabrication of PTFE.

Oxygen gas sensor based on oxygen intercalation in the layered semiconductor CuFeTe₂ has been developed. In this study, fine powder was obtained by pulverizing CuFeTe₂ single crystal. Three groups with the range of grain size: 0 - 20 µm, 20 - 40 µm and 40 - 63 µm, was divided by sieves from the powder. CuFeTe₂ ceramics was synthesized with each group. We measured the response to oxygen gas of these ceramics. Sensitivity is defined as a saturation value of resistance change rate when oxygen intercalation occurs. It has been shown from experimental results that the sensitivity improved by 7.0 times with making grain size smaller from 40 - 63 µm to 0 - 20 µm.

Dry electrodes of a smart shirt for measuring biological signals were prepared by the additive printing method using a stretchable conductive paste with Ag fillers loading. Interfacial impedance between the electrode and skin depended on the contact pressure of electrode and the moisture of stratum corneum. When moisture of stratum corneum was more than 30%, ECG could be measured using the stretchable electrodes printed on a compression shirt. However, noise signal in the ECG signal increased when the moisture of stratum corneum was less than 30%. To solve this problem, we propose to use additional electrodes made of an electrically conductive kneaded rubber.

This paper reports low temperature hermetic wafer bonding using Al/Sn/Al/Sn/Al as a bonding layer. The Al surface of the bonding layer was oxidized in air, but hermetic sealing was demonstrated without surface treatment at 370∼390ºC, which was lower than the maximum temperature of CMOS backend process (400ºC). For the successfully sealed samples, the bonding layer was considerably compressed and squeezed, and the remaining thickness was only <16% of the initial one, i.e. the reduction rate was >84%. On the other hand, the samples without Sn layers inserted, i.e. using a pure Al bonding layer, were not hermetically sealed at similar temperatures, showing the reduction rate smaller than 70%. A clear correlation between the reduction rate and the yield of hermetic sealing was observed. Taking account of analytical results and Al-Sn phase diagram, it is suggested that Al-Sn liquid phase in Al grain boundaries enhances the grain slip deformation of the bonding layer and fractionates the surface Al oxide layer during the bonding process. The function of Sn for Al-Al bonding suggested in this paper is useful for wafer-level hermetic MEMS packaging at low temperature.

In this paper, we present a novel flexible sensor array manufacturing process that involves transfer printing methods using a chip mounter with a vacuum collet. We successfully transfer-printed continuously very fragile microelectromechanical systems (MEMS)-based 5-mm-long, 1-mm-wide, 5-µm-thick high-aspect-ratio ultra-thin PZT(1.9µm)/Si(3µm) strain sensors onto a polyimide based flexible printed-circuit (FPC) substrate with etched Cu wiring. Then, we connected the sensors to the Cu wiring by printing insulating and conductive pastes using a screen printer. The output voltage based on the deformation behavior of the test plate was generated from the flexible piezoelectric strain sensor array attached to the plate. Therefore, the developed piezoelectric sensor array is capable of easily performing the distribution measurement of the strain leading to damage such as cracks.

The purpose of this study was to develop a new system for measuring leg motions using a portable three-dimensional accelerometer applied to five positons of a lumber vertebra, and left and right lower limbs. The measuring system was composed of acceleration sensors, harnesses of which resin material for a subject was removed, a portable data logger with a Bluetooth module mounted, a personal computer, a software for both monitoring and evaluating signals from the acceleration sensors, and a Web camera. The portable data logger had the ability to simultaneously sample the data of maximal 24 signals. The average acceleration measured during the walk was related to the score of Tokyo Metropolitan Institute of Gerontology Index of Competence and that of fall risk assessment score sheet. Thus, the new system for measuring leg motions using a portable three-dimensional accelerometer seems to be a useful tool to estimate the fall risk during the walk.

A microfluidic system using electrochemical biosensor for continuous lactic acid (LA) monitoring at the skin's surface was fabricated and tested. The system consists of a micro flow-cell for sampling LA at the skin's surface and a microfluidic LA biosensor based on a redox reaction of osmium wired horseradish peroxidase (Os-HRP). Our system measures excreted LA by dissolving whole secretion in phosphate buffered saline (PBS), which was supplied into the micro channel as carrier flow. The measurement system was utilized in the real-time monitoring of LA secretion during stationary bike exercises. Exercise intensities were regulated by heartrates (HR) and the sampling device was attached on the right upper arm of the volunteer. During the exercise, PBS was circulated into the measurement system. As a result, change of LA levels correlated with the volunteer's physiological status was confirmed. Secretion of LA was estimated to be 4.50 µg/cm²/min when the intensity of exercise was high (HR: 160 bpm) and the signal decreased to the initial level after the exercise. This indicates that our system is suitable for not only the assessment of exercise intensity, but also useful in evaluation of metabolic activity.

One problem with the plethora of electronic instruments in the music world today is all the wires and cables that need to be transported, plugged in, and managed. For an electronic drum set, the wires make setup complicated and look messy, and the difficulty of assembly and disassembly limits its use to one fixed place. A wireless system, on the other hand, would provide portability and greatly expand the range of venues where electronic drums could be used in place of acoustic ones. A batteryless self-powered wireless transmitter that sends a signal from a pad to a synthesizer has been developed. A piezoelectric generator functions both as the “Play” signal for the synthesizer and as the power source. The system employs analog FM modulation so that zero latency is theoretically supported in the radio transmission process. The same numbers of receivers are required to receive FM signals from multiple sensors/transmitters. A multi-channel receiver with FFT process is proposed, which can handle all of signals by single hardware. Experimental results for an electronic drum without any connecting wires fully demonstrated the feasibility of a self-powered wireless transmission system with a latency of 700 µs.