Ultrasonic cavitation

NPL has developed a sensor capable of measuring localised ultrasonic cavitation - the implosion of bubbles in a liquid when a high-frequency sound wave is applied.

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. But 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 measurable way to ensure the cleaning process is effective.

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.