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Topic Name: New Sensor Ensures Hospitals Are Hygienic By Listening To Collapsing Bubbles
Category: Integrated Systems
Research persons: Research Scientist at NPL
Location: London, United Kingdom
Details
The National Physical Laboratory (NPL) has developed the first sensor capable
of measuring localized ultrasonic cavitation – the implosion of bubbles in a
liquid when a high frequency sound wave is applied. The sensor will help
hospitals ensure that their instruments are properly disinfected before they are
used on patients.
The device recently won the annual Outstanding Ultrasonics Product award from
the Ultrasonic Industry Association.
Cavitation is used throughout the NHS by doctors and dentists to clean and
disinfect surgical instruments. A high frequency sound wave is passed through a
disinfecting liquid to create bubbles that implode. The force of each implosion
removes contaminate particles from surrounding materials. Cavitation is one of
the most effective cleaning processes. There are more than 200 000 places in a
teaspoon of tap water where a bubble can emerge and implode, and the process is
self-stimulating because the implosion of one bubble creates new sites for
further bubbles to emerge.
Until now there has been no accurate method of identifying how much cavitation
takes place at different locations in a cleaning system, and therefore no
measureable way to ensure the cleaning process is effective. The new sensor also
means that technicians can fine-tune and optimise equipment so that only the
energy required is used, reducing costs and environmental impact.
Previously the only way to measure cavitation rates has been to lower a piece of
aluminium foil into the liquid and count the number of 'dents' caused by bubble
implosion. NPL's new sensor takes a different approach by monitoring the
acoustic signals generated when the bubbles implode. It listens to the bubbles
as they collapse and uses the sound to identify how much cavitation is taking
place at a given location.
"To spark cavitation we use ultrasonics to 'shout' at a liquid. Our sensor then
listens to the response and tells us how much cavitation is taking place as a
result of using that particular stimulus," explains Mark Hodnett, a Senior
Research Scientist at NPL. "Cavitation is a powerful process but until now users
have had no way to measure exactly how loud to shout in order to get a useful
amount of bubbles, nor been able to quantify how energetic those bubbles are.
They've previously had to rely on trial and error. This is dangerous when you
are dealing with cleanliness in medical environments, and a waste of energy. The
NPL sensor provides a new tool for improving cleaning systems and aiding
instrument hygiene."
Sonic Systems has purchased one of NPL's sensors and say that it fills an
important gap in the market. "There is nothing else like the NPL sensor
available to sonic equipment manufacturers. We use it as part of our product
development process. It has enabled us to verify the cavitation fields inside
some of our more complex systems. This has given us the confidence to confirm to
customers that our equipment is truly optimised."
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