Search for novel odor-sensing materials is vital for the general field of artificial olfaction using acoustic-wave based sensors such as QCMs. Here we present recent result of our ongoing study on application of pegylated lipids as sensing film supports for QCM odor-sensors. The method presented herein is based on chemisorption of lipopolymer- or lipid-lipopolymer cushion and subsequent physisorption of selected, amphiphilic gas chromatography (GC) materials. The GC materials physisorb onto the supports owing to hydrophobic interaction of their tails with lipid moieties of the lipopolymeric supports. The method allows for fabrication of hybrid QCM odor-sensors with high sensitivity to odorants without much acoustic loss, despite the liquid or semi liquid state of the GC materials used. The sensors are also capable of very good discrimination among odorant samples at various concentrations.

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An integrated sensor chip combining a heater for temperature control and a diode for temperature monitoring was fabricated and its characteristics evaluated. Furthermore, a new packaging structure with a gas permeable film and sensor chip attached to the glass to improve the heat efficiency were developed. Using this packaging structure, the optimum working conditions and protection for the sensor chip were realized. The features of the diode were sufficient to verify the sensor temperature. In terms of the value of heat efficiency per power consumption, we succeeded in advancing its values by about 15% compared to the glassless type. Furthermore, the time response curves for the sensor temperature and power consumption of the heater were measured. The thermal control system consists of a heater and the diode was successfully utilized to maintain the intended temperature. The heat efficiency was improved by attaching a glass and this system was found to be useful for the PPG-FET type hydrogen sensor.

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Capacitive inclination sensors have the advantage that they can easily provide a linear analog output with respect to inclination. Although inclination sensors featuring this advantages are already commercially available, they are generally too large. We fabricated a Micro-capacitive inclination sensor by a combination of a resin forming method and a mold. Since the dimensions of the sensing region are 5 × 5 × 3 mm³ this inclination sensor is expected to be widely used in fields where efficient and reliable position control is a primary factor to be considered. The use of resins is also expected to contribute to a reduction in the costs of materials. We successfully fabricated a micro inclination sensor as a molded product. In future, we will wire up the device to complete this inclination sensor, and will then conduct performance evaluations. If techniques using resin-molded parts are introduced to the low-cost mass-production of MEMS devices, the range of applications will further expand to new areas of technology and industry.

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A silicon beam resonator has been fabricated by using the bulk surface micromachining, and mechanical beam vibrations have been directly evaluated with the laser-Doppler technique. The in-plane vibration, caused by the electrostatic force exerted on a gap between the beam and the drive electrode, and the out-of-plane vibration, caused by the asymmetrical electric field around the beam, have been compared with each other. The measured resonant frequencies have well agreed with those calculated by a simulator. The air damping effect has been measured under various vacuum conditions. The result suggests the fabricated resonators should be packaged under 500 Pa for the air-damping-free vibration. The electrical characterization using an impedance analyzer has shown that the impedance and capacitance have depended on the operating bias voltage, while the resonant frequency has been slightly varied by the bias voltage. These electrical characteristics have been compared with the mechanical vibration behaviors. It has indicated that the qualitative similarity between them has been shown, although the 4 to 5% resonant frequency increase has been observed.

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The concept of MEMS sensors directly fabricated on a ceramic substrate, which can be used for a package of end product, was proposed. As one of such sensors, a micro accelerometer utilizing a fringe capacitance formed in a ferroelectric material was focused on. For this sensor, in stead of a previously used bulk PZT plate, a screen-printed BaTiO₃ (BTO) film on a ceramic alumina substrate was herein employed. A screen-printing method can save the amount of raw material of the film, because a comparatively thick film can be deposited only on a specified area. Moreover, BTO does not contain harmful lead material. The optimal condition for fabricating a BTO film on an alumina substrate with minimum unwanted surface defects was experimentally searched. The number of defects was decreased by employing a metal barrier of Pt layer underneath BTO, and by setting the annealing temperature for crystallization to a higher value of 1,400°C. A comparatively high relative dielectric constant of ε_r =926 was achieved. An accelerometer using a BTO film was practically fabricated. The sensitivity of it was estimated as 0.1 pF/g, which is degraded a little compare with the previously developed accelerometer using a PZT plate; however, the order is same.

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A new concept of inertial force sensor, which uses a Mach-Zehnder Interferometer (MZI) type optical waveguide made of crystal silicon, is proposed in this paper. In this sensor, one waveguide of branched two waveguides in the MZI has floating beam structure (air-bridge type). Additionally, the cantilever supporting a proof mass intersects with the floating optical waveguide. When inertial force is applied to the proof mass, the floating waveguide is expanded and the output of the MZI is modulated.
An optical optimization of the inertial force sensor is carried out by using a simulation, of which a solver is 2-dimentional beam-propagation method (2D BPM). As a result, optical loss at the intersection of the floating waveguide and the cantilever is improved by using multi-mode interference (MMI) waveguide as an intersected waveguide.
Structure of the sensor is also optimized by a simulation which uses 3-dimentical finite element method (3D FEM). Especially, deflection at the intersection of the sensor is focused on. As results of the simulation, it is found that the sensitivity of the sensor can be controlled by changing in the width and length of the cantilever. Additionally, it is also found that the using of MMI waveguide as interconnecting waveguide dose not decay the sensitivity of sensor. As the results of above simulation, it is expected that an inertial force sensor, which have both high sensitivity and good mechanical strength properties, can be fabricated by using the structure in which multiple cantilevers crosses with the MMI waveguide.

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Layers of ZnO micro-nano structures were deposited on quartz substrates and subsequently plasma treated in O₂ and N₂. It was found that exposure to O₂ plasma enhanced gas response to ethanol vapor of the ZnO layers by a factor eight, while exposure to N₂ plasma deteriorated the gas response. The gas response enhancement upon O₂ plasma treatment could be correlated to an increase in the layer resistance combined with surface roughening of the original ZnO tetrapod structure, suggesting the formation of a ZnO surface with a high density of active sites for ambient oxygen adsorption and subsequent reaction with reducing gases such as ethanol vapor.

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