In this study, we report selective measurements of capacitive and resistive sensors via simultaneous position control of multiple liquid metal droplets (LMDs) in a flow channel. We evaluated the impedance of parts where LMDs pass between electrodes and selectively measured the sensor signals. Then, we succeeded in selectively measuring both the capacitive signals (0.5-5.0 pF) and the resistive signals (100-1000 Ω). The findings of this study will facilitate the integration of multiple sensors of different types in devices, thereby enhancing multifunctionality and efficiency.

In this study, we tested the application of a load to the elastomer hemisphere, the sensing part of the sensor, from all directions to measure the load vector using a micro-cantilever-type MEMS tactile sensor. The results show that the sensor sensitivity depends on the relative positional relationship between the cantilever and the hemispherical projection and the 3-D polar coordinate position of the load on the hemispherical projection. This indicates that the position and magnitude of the applied load to the sensor can be estimated with high accuracy by measuring the relationship between the applied load position and the sensor sensitivity in advance.

While the diaphragm of PMUTs (piezoelectric micromachined ultrasonic transducers) is driven with large displacement in nonlinear regime, they exhibit unstable vibration displacement due to hysteresis response. In this study, the nonlinear behavior of PMUTs related to initial deflections of the diaphragm is analyzed for stable driving with large displacement. The PMUT with initial deflection of 0.7 µm showed an increase in resonant frequency with displacement of the diaphragm, called the hard spring effect. In the case of 6.2 µm initial deflection, the PMUT has the soft spring effect, resulting in larger maximµm displacement than that of the hard spring effect. On the other hand, we have found that the PMUT having mediµm initial deflection of 4.0 µm exhibited mixed frequency response of hard spring and soft spring, which demonstrated the largest maximµm displacement. In addition, the frequency region without hysteresis become wider by increasing the drive voltage. From these results, we conclude that stable driving in large displacements is achieved with optimized initial diaphragm deflection and drive voltage.

In this research, we developed a complex capacitance sensor with a crystal oscillator circuit for measuring the water retention and permeability of concrete. Differences in water-tightness due to aggregate size, curing method, and admixture were successfully measured. This technology is expected to be applied to on-site watertightness evaluation of concrete, contributing to the diagnosis of durability and deterioration of concrete and extending its service life through appropriately timed maintenance.