Kiyoshi Taninaka

Analysis of Ultrasound Radiation and Proposal of Design Criteria in Ultrasonic Haptic Display for Practical Applications

This paper describes a technology to reduce ultrasound radiation which is caused by normal mode vibration of an ultrasonic haptics display. Reduction and analysis of ultrasonic acoustic radiation from the display were implemented for safety use and coexistence with other devices. The focus on solving the problem of ultrasound radiation is based on the investigation of constructive interference conditions of acoustic waves on the top panel. We successfully demonstrated a practical sound pressure level on the prototype. To reduce radiation, it is necessary to reduce the thickness or the lower stiffness-to-density ratio E/ρ. A thickness of 0.3 mm has practical stiffness in the case of glass and the maximum pressure is 110 dB or less at 30 kHz for the usual size of smartphone. This means that raising the “coincident frequency” higher than the driving frequency by reducing the thickness and lowering the E/ρ, causes sound radiation to be sharply reduced.

Precise microinjection into living cells by summation of fluorescence intensity

It is difficult to introduce a specific amount of a substance into cells by existing injection methods because there is no appropriate method of directly measuring the quantity of the injected substance. Although radioisotopes can be used, there is currently no apparatus that can practically handle such radioisotopes. The measurement of the diameter of a liquid droplet in air or oil is affected by surface tension if the liquid droplet is very small; but this issue does not occur with microinjection, in which a water solution is discharged under pressure through a capillary and into a cell. It is also difficult to measure the density or mass of the injected substance because of the low discharge rate, unlike the case of inkjet printers. To solve these problems, we propose a method of precise microinjection by summation of fluorescence intensity. In addition, we developed a new pressure pulse injection device that generates pressure with a rectangular waveform and a precise amplitude and pulse width to improve controllability of the discharge amount. Lastly, when the above device and method are combined, the coefficient of correlation between the specified number of pressure pulses per unit of time and the actual discharge amount exceeded 0.999. This research paper describes in detail the measurement system, standalone performance, and quantities of substances introduced into living cells.