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Sterilising Medical Instruments with Sound
© Georgia Institute of Technology,
Research by scientists at the Georgia Institute of Technology and Georgia State University showed the technique killed more than 90 percent of bacteria in a test vial that also contained a mild solution of isopropyl alcohol. "Complex and extremely expensive endoscopes and related surgical equipment are very vulnerable to heat, and they are challenging to clean," explained Dr Stephen Carter, a dentist who is working with Georgia Tech Professor Kenneth Cunefare to develop the technique. "We believe that our methods will sterilise in shorter periods of time, which would be a substantial advantage for expensive medical equipment."
The patented technique uses a form of cavitation, a phenomenon in which acoustic energy applied to a liquid induces the creation of voids that release energy when they collapse. By pressurising their test chamber while inducing cavitation, Cunefare and Carter create a form of transient cavitation that causes violent collapse of the bubbles. The enhanced cavitation takes advantage of the anomalous depth effect, in which the impact of bubble collapse increases dramatically when subjected to roughly twice normal atmospheric pressure.
When applied to a solution of 66 percent isopropyl alcohol containing two forms of marker bacterial spores – Bacillus stearothermophilus and Bacillus subtilis – the enhanced cavitation reduced the bacterial count by more than 90 percent, Cunefare said. Research indicates that both the alcohol solution and increased pressure are necessary for killing the spores with cavitation.
Because acoustic disinfection could be carried out more quickly than existing heat and chemical techniques, Carter believes it could offer significant cost advantages by reducing the amount of time that expensive equipment is out of service. And it would also have the potential for minimising the risk of cross transmission of infection caused by contaminated instruments, he added.
MEDICA.de, Source: Georgia Institute of Technology