Quality factor (Q factor) is one of the important parameters for mechanical resonant sensors. The higher Q factor contributes to higher sensitivity for physical sensors, while lower responsiveness, and vice versa, which means the appropriate values of Q factor depend on its application. Therefore, Q factor controlling is a primitive technique for physical sensors using mechanical resonators. In the past, many researches for Q factor controlling have been conducted. Electrical feedback methods and external pumping methods are representative. These well-established methods need to add external equipment to the resonators systems. In this paper, novel Q factor control methods are introduced; one is non-linear vibration damping, another is a variable phononic bandgap. Non-linear vibration damping occurs in especially nano-mechanical resonator and can control the Q factor by just changing the vibration amplitude of the resonator. Also, the phononic bandgap generally does not propagate actuation vibrations. The introducing phononic device can change the bandgap as to include and exclude the resonant frequency of the resonator, which works to control the Q factor. These introduced methods achieve simple systems and good compatibility with conventional MEMS, which are expected as interesting Q factor control methods.

In leguminous plants, rhizobium symbiotically forms nodules, which are responsible for nitrogen fixation and obtaining nutrients necessary for growth. Plant roots are thought to secrete chemicals that signal the formation of nodules. In this study, we attempted to visualize the concentration distribution of the exudates from pea roots by using the phenomenon that the fluorescence intensity decreases due to the interaction of bovine serum albumin (BSA) with phenolic compounds. BSA was immobilized on a glass microfiber filter (sheets with immobilized BSA), and the quenched fluorescence of BSA due to the interaction with root exudates was visualized. The correlation coefficient between the quenched fluorescence intensity per sheet and the amount of kaempferol in hydrolyzed sample recovered from six sheets with immobilized BSA was 0.8 (p < 0.05), indicating a high correlation.

We have developed a sensor for damage detection and abnormality notification using a MEMS vibrational energy harvester as an event-driven sensor picking up a specific frequency signature. Owing to a substantial power-saving performance, the monitoring system becomes almost maintenance-free for more than 10 years, thereby enabling efficient and reliable inspections of social infrastructure.

Due to the optical fiber have a small diameter and it can propagate light efficiently, it possible to realize ultra-compact remote sensors. We have invented to the fiber-optic pressure sensor utilizes magneto-optical effect with polarized light, ring-type interferometer and a magnetic material, in order to propose the pressure measurement system which can measure in vivo or in harsh environments. We have confirmed that the prototype sensor based on magneto-optical effect was possible to detect pressures in range of -4 to +40 kPa.

We propose a novel sensing film for nitric oxide (NO) gas detection using graphene ink and NNN'N'-tetramethyl-p-phenylenediamine (TMPD). This sensing film can be fabricated by a low-temperature annealing process at about 80°C, which is suitable for flexible gas sensors. The proposed sensing film was deposited on alumina and polyethylene terephthalate (PET) substrates, and resistive NO gas sensors were fabricated. These sensors were able to detect NO gas concentrations from 2 ppm to 10 ppm, and had sufficient NO gas selectivity, regardless of the substrate. The high-temperature annealing process of the sensing film increased the sensitivity to ammonia (NH₃) gas, and deteriorated NO gas selectivity.

In this study, we have developed a new pen-type pulse wave measurement system to evaluate heart failure treatment based on cardiovascular information. In order to acquire minute pathological changes in diseases such as heart failure, the pen-type pulse wave measurement system is equipped with a high-resolution MEMS tactile sensor that achieves a displacement resolution of 0.4µm and an input resolution of 50µN. This measurement system consists of a small sensor package, a pen-type measurement system, and a glass sensor package to enable physicians to measure the radial artery of men and women of all ages in a minimally invasive, rapid, and precise manner. Realizing this measurement system, simple and precise pulse wave measurement by direct measurement and measurement of pulse wave characteristics for individual differences has been possible.

Human-derived acetone vapor could be utilized in clinical practice. In this paper, we prepared and demonstrated secondary alcohol dehydrogenase (S-ADH) immobilized mesh toward acetone vapor imaging. Immobilized S-ADH activity was evaluated by autofluorescence of reduced nicotinamide adenine dinucleotide which is consumed in S-ADH catalytic reaction with acetone. As a result, a glutaraldehyde crosslink method showed higher S-ADH activity and allowed fluorometric imaging of acetone vapor without distortions.

Temperature sensor and humidity sensor, that are transparent, highly breathable and flexible, were fabricated using elastomer nanosheet and ionic liquid gels with different hydrophilicity. Both sensors showed light transmittance of more than 75% in the visible light range and moisture transmittance 2.8 times higher than transepidermal water loss of human skin. The temperature sensor showed a logarithmic response to temperature, with a sensitivity of 3.2∼2.0%/℃, while humidity sensor showed a linear response to humidity, with a sensitivity of 0.9%/percentage of relative humidity.