Search

In this research, we developed wireless, inductive, pressure sensors with high sensitivity and investigated the effects of the inner materials (copper or ferrite) on the performance of the sensors. The proposed sensor is comprised of two parts, i.e., the top and the bottom parts. The top part includes a micro coil and a capacitor for the wireless transfer of data, and the bottom part includes the inner materials and a thick or thin flexible membrane to induce changes in the inductance. An anchor is used to assemble the top and bottom parts. The behavior of the sensor with copper was based on the eddy current effect, and, as the pressure increased, its resonance frequency increased, while its phase depth decreased exponentially. The principle of the sensor with ferrite was related to the effective permeability between a ferrite and a coil, and its response was the opposite of that with copper, i.e., as the pressure increased, the resonance frequency decreased linearly, and the phase depth increased linearly. These different operational mechanisms can be explained by the changes in the equations of inductance presented in this paper. After characterizing four different types of inductive pressure sensors in ambient air, one type of inductive pressure sensor was used to monitor the intraocular pressure (IOP) of a rabbit's eye as a biomedical application. The results showed that, in the animal tests, the measured responsivity and sensitivity were 16.7 kHz/mmHg and 1340 ppm/mmHg, respectively. These data indicate that the proposed sensor is a good candidate for monitoring IOP. [ABSTRACT FROM AUTHOR]

In this paper, we propose an energy-harvesting device that uses snap-through buckling for mechanical frequency-up conversion. The proposed device consists of buckled slender bridges with a proof mass and cantilever beams attached on them. When subjected to a low-frequency vibration above the threshold acceleration value, the buckled bridges snap through between two equilibrium states, providing high acceleration to the attached piezoelectric cantilever beams and thus causing them to resonate at a high frequency. A maximum power of 131 μW was generated at an excitation frequency of 30 Hz and a peak acceleration of 30 m/s2 by using a proposed device. [ABSTRACT FROM AUTHOR]