News Release

NPL unveils quantitative means of monitoring ultrasonic cleaning systems

Business Announcement

National Physical Laboratory

The CaviMeter in action

image: This is the CaviMeter in use. view more 

Credit: NPL

Ultrasonic Cleaning Systems are widely used in healthcare applications during the sterilization of surgical instruments, and in many manufacturing and process industries. They work by passing a high frequency sound wave through a liquid detergent to create thousands of small bubbles. The sound waves then makes the bubbles implode with such force, that the impacts remove contaminant particles from submerged materials.

The current NHS-recommended technique to measure the performance of ultrasonic cleaning systems uses aluminium foil, which is eroded and punctured by the imploding bubbles. This is an unreliable process to apply and can contaminate the vessel cleaning fluid, adding unnecessary costs.

The new NPL CaviMeter™ provides a quick and simple to use measurement solution for cleaning systems, and so is a new and improved method of quality assurance. It consists of a sensor connected by a thin flexible cable to a portable monitor and display unit. The sensor is shielded in a special rubber material designed to protect it, and crucially, providing it with spatial resolution of a few millimeters.

By monitoring the acoustic signals generated when the clouds of bubbles implode, the CaviMeter™ identifies how much cavitation is taking place at a given location, allowing 'hot-spots' and 'cold-spots' in cleaning systems to be identified. Manufacturers can use this information for fine-tuning equipment to produce the ideal quantity and distribution of cleaning action. This approach helps ensure that only the required energy is used, reducing costs and environmental impact.

Mark Hodnett, a Senior Research Scientist at NPL, said: "Until now, there have been no quantitative methods for identifying how much cavitation takes place at different locations in a cleaning system, and therefore no way to ensure that the cleaning process is totally effective. NPL's CaviMeter™ and sensor can now provide this capability, for both users and manufacturers of cleaning systems. It is the first of its kind for acoustically mapping cavitation produced by ultrasonic cleaning and processing systems used in healthcare and manufacturing industries."

The CaviMeter™ supports the manufacture and development of ultrasonic baths, and also allows healthcare organisations to make informed and cost-effective purchasing decisions for cleaning systems. Once a system is chosen, the CaviMeter™ can be used regularly to test the efficacy of its cleaning performance, even when using different detergents and surfactants (wetting agents that lower the surface tension of a liquid).

The CaviMeter™ was designed in response to a longstanding user need. The novel spatially-sensitive cavitation sensor it uses was conceived and developed under Strategic Research at NPL, with the accompanying electronics supported by the Measurement for Innovators programme. It is a great example of how products delivering real impact to end-users can be developed through the National Measurement System (NMS).

A further £2.5 million is now being invested by the NMS and NPL into ultrasound, which includes carrying out research into microbubbles – whereby the bubbles themselves can be used as sensors.

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Notes to Editors

The National Physical Laboratory (NPL) is one of the UK's leading science facilities and research centres. It is a world-leading centre of excellence in developing and applying the most accurate standards, science and technology available.

NPL occupies a unique position as the UK's National Measurement Institute and sits at the intersection between scientific discovery and real world application. Its expertise and original research have underpinned quality of life, innovation and competitiveness for UK citizens and business for more than a century:

  • NPL provides companies with access to world leading support and technical expertise, inspiring the absolute confidence required to realise competitive advantage from new materials, techniques and technologies
  • NPL expertise and services are crucial in a wide range of social applications - helping to save lives, protect the environment and enable citizens to feel safe and secure. Support in areas such as the development of advanced medical treatments and environmental monitoring helps secure a better quality of life for all
  • NPL develops and maintains the nation's primary measurement standards, supporting an infrastructure of traceable measurement throughout the UK and the world, to ensure accuracy and consistency.
  • NPL's Measurement Network provides comprehensive access to the latest measurement science. It brings together nineteen existing NPL knowledge transfer clubs and networks into a central hub – making it easier for a wide range of stakeholders to engage with NPL and for new groups to develop as technologies change. Organisations and individuals who want to become members should sign up at www.npl.co.uk/measurement-network


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