P21 スターチ粒子に対する超音波ピッティング効果の周波数依存性

抄録

Micro samples (bacteria, algae, microcapsules, etc.) are required as probes for checking abilities of ultrasonic cavitation. Ultrasonic waves are one of the mechanisms by which microscopic specimens are destroyed, and it has been reported that microscopic specimens in the vicinity of cavitation bubbles that experience repeated expansion and contraction synchronously with the excitation frequency are destroyed as a result of resonance with the vibration. Past reports have observed that samples subjected to ultrasonic irradiation were most often ruptured or broken by the resonance and destroyed. Further, small holes (pits) were observed on the surfaces of small-diameter samples. It is well known that relatively minute air bubbles in a sample can sense asymmetry and generate a micro jet shock wave.
The purpose of this study was to investigate ultrasonic pitting effects on fine samples. A starch sample was irradiated with ultrasonic waves in a broadband frequency range of 26 kHz to 3.6 MHz. We then measured the number of pits on the surface of the sample at various frequencies and observed the surface using a scanning electron microscope. We further investigated the stress imparted by cavitation bubbles, which were destroyed near the sample, to the sample.