Abstract
A method to actively controlling crystallization is one of promising technique for cryopreservation. The object of this paper is to study the effects of ultrasonic irradiation on ice formation during freezing of biological materials. In the experiments, agar gel was frozen under irradiation of ultrasound at frequency of 28kHz. It was found that ultrasound released the supercooling states, and reduced ice crystal size in the tissue. However, the fattning of ice crystal was observed by irradiation of higher ultrasonic power, since the cooling rate was reduced due to absorption of the ultrasonic wave. The mechanism of sonocrystallization in biological tissue was discussed in relation to ultrasonic power and tissue size.
