We demonstrated coloring elements with high ratio change of the coloring area by using bending deformation of electroactive hydrogel. By using the nondimensional deflection α of a gel, we showed that the response time for the color change and the thickness of the coloring element can be designed. We fabricated a 3 × 3 dot-matrix display with α of 0.56 and evaluated the performance of the coloring element. As a result, the coloring area ratios in blank state and colored state were 7.6±4.6% and 92.1±4.6%, respectively. The response times were 12 seconds from blank state to colored state, and 13 seconds from colored state to blank state.

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Ultrasonic sensors using cantilever beam and free-free beam resonators are designed and fabricated for acoustic emission (AE) sensing. The sensors are operated under the resonant conditions and the generated oscillation is detected by silicon piezoresistors. In order to investigate the air friction of the resonators, the quality factors are measured as a function of pressure. The sensitivities of the two resonators are compared. The cantilever beam resonator is vacuum-packaged by glass-silicon anodic bonding and the AE sensing test is carried out by the method of breaking pencil lead. The response time of the vacuum packaged sensor is also measured.

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This paper reports the Rayleigh wave sensor using a longitudinal wave radiation into a liquid phase. The sensor using a longitudinal wave radiation of dozens MHz band had been reported, but we have enabled to measure at a high frequency of 197 MHz by confining the sample solution of a few µL in glass groove holder. We have compared the already known longitudinal wave radiation model that varies with the sound velocity in the solution to the measured value of a SAW device that we have developed, reports on the results that led the model of new SAW sensor from the phenomenon that the phase shift caused by the groove opening shape.

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This paper describes the oscillation for a novel silicon microelectromechanical systems (MEMS) resonator which utilizes the torsional-to-transverse vibration conversion with quarter-wavelength torsional support beams. A fabricated 0.1-µm-gap resonator was measured with a laser-Doppler (LD) vibrometer to have a resonant frequency of 78.518 MHz and the Q-factor of 8.5 × 10³ in vacuum. The electrical characteristic evaluated with a network analyzer for the resonator showed the electrical transmission (S₂₁) and the phase shift of -42.7 dB and 12 degrees, respectively. Such a large insertion loss and small phase shift shows the need of compensation circuit to achieve the oscillation. We fabricate oscillation circuits and evaluate each component: i) In order to increase the phase shift, a C₀ compensation technique is used to cancel feedthrough current in the resonator. This compensation technique has provided the increase of the phase shift, 70 degrees; ii) A voltage follower circuit is adapted to convert the resonator impedance, alleviating mismatch loss and thus providing the increase in the transmission of the signal up to -17.4 dB; iii) An inverter amplifier is used to amplify this signal. With a loop of these circuits with the resonator, the oscillation utilizing the torsional-to-transverse vibration conversion has successfully been achieved for the first time. The measured phase noise of the oscillator at 1 kHz offset from the carrier has been -101 dBc/Hz.

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A silicon microelectromechanical systems (MEMS) resonator array utilizing torsional-to-transverse vibration conversion is designed, fabricated and evaluated. The fabricated resonator array, consisting of two resonators, was measured with an impedance analyzer and compared with the performance in a unit resonator. By compensating for the quality factor decrease in the array, the reduction ratio of the motional resistance in the array was shown to be 1/1.95, which agrees well with the estimated one (1/2). A close set of two resonant frequencies for anti-symmetric and symmetric vibration mode of 78.080 MHz of 78.536 MHz, respectively, were also measured. These resonant frequencies could be successfully switched by changing the polarity of DC bias voltage. This is useful for switching the resonant frequency in resonators for timing and filtering applications.

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