Electrowetting features a change in the wettability of a metal surface or a dielectric on an electrode accompanying the application of a voltage. This technique has been used in various devices including microactuators, microlenses, displays, and microfluidic devices. The increasing number of papers relating to this topic and citations demonstrate that the expectation of this technique is rapidly growing. In this article, recent development of electrowetting-based devices will briefly be reviewed.

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The FeGa/PZT stacked-layer magnetic sensor was studied. The prototype sensor is 15mm long and 6mm wide with two 880μm-thick FeGa layers and a 590μm-thick PZT layer. The theoretical sensitivity using a simple model was calculated to be 69.6mV/Oe. The resonant modes were analyzed using a FEM simulator, resulting in the fundamental resonant frequency of 5.38kHz. A magnetic field was applied to the longitudinal direction of the sensor to cause a longitudinal stress magnetostrictively, which produces a piezoelectric output voltage in the PZT layer. The dependences of the magnetic sensitivity on the DC bias magnetic field were evaluated, together with the frequency characteristics and the temperature dependences. The measured sensitivity agreed roughly with the calculated one. A prototype with a single magnetostrictive layer was also fabricated and evaluated for investigating the possibility of the resonant sensor.

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The thin and long bimorph cantilever is mechanically responded in motion depending on the position of the heating laser which is focused from the side. The bimorph cantilever was designed in order to detect the heat from a bio cell in liquid. In the calibration process of the cantilever using a focused laser in vacuum and air, we found the quick and interesting responses of bimorph cantilever, which is vibrated and statically deflected due to the position of the local heat source on the cantilever. The deflections of cantilever have been investigated with a developed model. The responses are expressed by the modeled system with heat loss condition into ambient. To define the temperature distributions on the cantilever using a model, the temperature increments at the end of cantilever are successfully estimated to be +20 K in air and +110 K in vacuum with a laser power of 0.17 mW.

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An odor recorder is a system to record the odors as well as reproduce them. In order to record a wide range of odors, a number of available odor components are required in the odor recorder. Moreover, the sufficient pattern separation among all odor components is also required to avoid a collinearity problem caused by the lack of the pattern separation among odor components. In this study, we proposed an odor recorder based on real-time mass spectrometry with variable ionization energy in order to improve odor recording capability. In this system, the higher-order sensing capability due to the different ionization energies can be achieved. It was found that the enriched data obtained from this system could be used to improve the pattern separation among odor components. Moreover, the recipe of the target odor was more accurately estimated based on combination of m/z's obtained from different ionization energies. Thus, this proposed system could be useful to improve the odor recording capability so that the recordable range of odor could be extended.

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Bioelectric potential is generated by ions in a plant cell and the potential changes with physiological activities of the plant. Therefore, measurement of the potential is a promising method for evaluation of the plant activities. In this study, we investigated mechanism of the potential response generation due to photosynthesis reaction of plant. For this purpose, we measured bioelectric potential with replacing air by N₂ gas in order to suppress carbon-fixation reaction. In the result, the potential response was different from ambient gas, and we clarified that several behaviors of the potential response strongly related to activities of photochemical reaction and carbon-fixation reaction. Next, we measured the potential when illuminating condition was changed for accelerating or decelerating photosynthesis. At that time, shape of the potential response correlated with increase or decrease of photosynthetic rate. We considered that the measurement of the bioelectric potential can be applied to evaluation of photosynthetic activity and it can support for effective cultivation.

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