Abstract
It has been known that ultrasonically induced cavitation is effective for sterilization of liquids contaminated by microorganisms. We have devised a system to induce cavitation utilizing the squeeze film effects and fabricated a prototype sterilizer with the system. In the sterilizer, sterilization is performed in an area formed by a cylindrical shell and two short columns vibrating at the fundamental coupling vibrational mode in the axial and radial directions. We evaluated the sterillizer by using water contaminated with E. coli in a flow system and obtained very promising results. We found that sterilization could be achieved more efficiently and steadily than a conventional ultrasonic sterilizer which uses a standing wave field. The steadiness is a very important factor in ultrasonic sterilization.
