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Gas bubble fragmentation in an ultrasonic field |
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| Authors: | AD Walmsley WRE Laird AR Williams |
| Institution: | Departments of Medical Biophysics and Prosthetic Dentistry, University of Manchester, Oxford Road, Manchester M13 9PT UK;Department of Prosthetic Dentistry, Birmingham Dental School, University of Birmingham, St. Chad''s Way, Birmingham, B4 6NN UK;Department of Medical Biophysics, Stopford Building, Oxford Road, Manchester, M13 9PT, UK |
| Abstract: | A model system consisting of a thin layer of vacuum-deposited metallic aluminium on a glass microscope slide was developed to demonstrate the effectiveness of cavitational activity (occurring within the cooling water supply of a dental ultrasonic descaler operating at 25 kHz) in the removal of particulate matter from solid surfaces. The pattern of particulate matter removal using this model system demonstrated both the mechanism of bubble activity and the erosive nature of microbubbles.Non-resonant bubbles were formed by surface wave activity and adhered to the surface of the slide. There was some removal of the aluminium metal at the periphery of the bubble (probably by a microstreaming mechanism) giving a ‘ghost’ outline. The majority of aluminium removal was caused by numerous microbubbles of non-resonant sizes (typically 1 to 2 μm diameter) formed by surface wave induced fragmentation of the parent bubble.The damaging and erosive effects of transient cavitational activity appear to be the result of sub-resonant sized microbubble formation from larger parent bubbles. |
| Keywords: | ultrasonics cavitation bubble dynamics |
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