Quartz Resonator for Simultaneously Measuring Changes in the Mass and Electrical Resistance of a Polyaniline Film

Moisture-induced power generator fabricated on a lateral field-excited quartz resonator

We fabricated a moisture-induced power generator on a lateral field-excited quartz resonator to simultaneously measure changes in mass and voltage generation during water vapor adsorption. Circularly interdigitated gold electrodes were vacuum deposited on the top surface and used to measure changes in mass, and two symmetric semicircular gold electrodes were vacuum deposited on the bottom surface and used to measure changes in voltage generation. After coating a thin film of a mixture comprising sodium alginate, carbon black, and polyvinyl alcohol (SCP) on the top surface, an electric field was applied to create a concentration gradient of sodium ions between the interdigitated electrodes. The changes in the resonant frequency and voltage generation of the SCP-coated quartz resonator were measured simultaneously under various relative humidity conditions. The results revealed, for the first time, three distinct voltage-generation regions during moisture adsorption: (i) a region of negligible voltage generation, (ii) that of an increase in voltage generation, and (iii) that of a decrease in voltage generation.

Direct synthesis of Cu-BDC frameworks on a quartz crystal microresonator and their application to studies of n-hexane adsorption

Cu-BDC frameworks were synthesized from metallic copper and the adsorption of n-hexane vapor was investigated by using a quartz crystal microbalance.

Characterization of underwater stability of superhydrophobic surfaces using quartz crystal microresonators

We synthesized porous aluminum oxide nanostructures directly on a quartz crystal microresonator and investigated the properties of superhydrophobic surfaces, including the surface wettability, water permeation, and underwater superhydrophobic stability. After increasing the pore diameter to 80 nm (AAO80), a gold film was deposited onto the AAO80 membrane, and the pore entrance size was reduced to 30 nm (AAO30). The surfaces of the AAO80 and AAO30 were made to be hydrophobic through chemical modification by incubation with octadecanethiol (ODT) or octadecyltrichlorosilane (OTS), which produced three different types of superhydrophobic surfaces on quartz microresonators: OTS-modified AAO80 (OTS-AAO80), ODT-modified AAO30 (ODT-AAO30), and ODT-OTS-modified AAO30 (TS-AAO30). The loading of a water droplet onto a microresonator or the immersion of a resonator into water induced changes in the resonance frequency that corresponded to the water permeation into the nanopores. TS-AAO30 exhibited the best performance, with a low degree of water permeation, and a high stability. These features were attributed to the presence of sealed air pockets and the narrow pore entrance diameter.