We have demonstrated a wide range of hydrogen gas detection from 200 ppm to 100% at room temperature by using optical cavity type of sensor elements with polarization interference. This explosion-proof type of sensor element provides a hydrogen monitoring system in flammable environments for gaseous fuels.

This paper addresses a mode I dynamic crack tip singular stress field based on an isolated moving edge dislocation elastic stress field for MEMS structural design. The crack tip singular stress field was derived by applying the Eshelbian eigenstrain and Fourier transform method. The large normal stress component of the crack tip singular stress appeared as the crack velocity increased up to the Rayleigh sonic speed. Therefore, the principal stress plane of the fast-moving crack tip deviates from the original mode I crack plane, which can initiate crack kink or bifurcation.

This paper addresses the optimization of AT-cut quartz crystal resonator shape on a support substrate. This resonator is capable of oscillating via a physical separator while reinforcing its mechanical strength by inserting the support substrate between the excitation electrode and the quartz substrate. The fabricated resonator was evaluated by changing the thickness of the support substrate, the crystal axis, and the distance between the electrodes of the excitation electrodes. Even when support substrates of different thicknesses were used, only the crystal plate on the support substrate was successfully excited. The data reproducibility was also obtained by bonding and fixing with PDMS. Furthermore, the electromechanical coupling coefficient increased, and the impedance decreased when the excitation electrode spacing was increased. The frequency response to mass loading showed excellent linearity, indicating that this quartz crystal resonator can be used as a QCM.

Nanoparticles have been used in various fields, such as electronic materials, pharmaceuticals, and cosmetics. Therefore, it is necessary to generate nanoparticles with a uniform particle size appropriate for each purpose. In previous studies, nanoparticles were generated by quenching microdroplets for recrystallization using microfluidic droplet generation devices and quenching devices. However, although the temperature of the solution is important for generating nanoparticles by recrystallization phenomenon, the liquid temperature was not maintained during droplet generation. In this study, the liquid temperature at the droplet generation process has been maintained and a nanoparticle generation system has been constructed. The structure of the quenching device is also modified to improve the cooling effect. As a result, nanoparticles with small diameters have been generated.

High sound pressure is always preferred in pMUT (piezoelectric micromachined ultrasonic transducer) applications, and large displacement becomes the key to achieving high SPL (sound pressure level). However, large displacement also leads to non-linearity, which will bring significant deviations from the design goals and is usually difficult to predict in simulation by finite element method. To investigate the non-linear characteristics, non-linear fitting was used to quantitatively analyze two different structures in this study. The frequency response and quality factor change experimentally observed in non-linear region were discussed. In addition, a structure with a central mass attached to promote piston-like vibration was investigated. Compared to the conventional structure, the proposed structure had a 30% smaller non-linear coefficient and an 81.3% larger non-linear damping. However, higher SPL was not obtained due to the lower natural frequency and amplitude of displacement.