When you beat a carpet in the yard – if you still do this! – you are basically using soundwaves to dislodge dirt. In the 1950s, with the advent of better electronic components, it became possible to improve on this using high-frequency vibrations. Dry acoustic cleaning is often used to shake grain or other raw materials from hoppers, but the real breakthrough came with the development of ultrasound tanks.
In a large ultrasonic cleaner, the item is immersed in water or a more suitable fluid such as dry-cleaning solvents. High-frequency sound waves then convert the fluid into microscopic bubbles. Each bubble is a vacuum, or cavity, and collapses with a tremendous release of energy; in fact, brief local pressures of 135 MPa can be generated in this way and temperatures of up to 5,000 degrees Kelvin. The energy of these implosions creates microscopic pressure waves that reach into every crevice, dislodging all the loose particles and surface contaminants.
The scale of cavitation is so small that it causes no harm to the material being cleaned. The higher the frequency, the smaller the bubble and the smaller the holes and cavities they penetrate and clean.
What materials are suitable?
Almost any material or item can be ultrasonically cleaned with a suitable fluid and a big enough tank, including metals, plastics, ceramics and textiles. Small domestic cleaners have been available since the 1970s and are so safe that they are often used by jewellers and antique restorers. There are also many applications in commercial kitchens, electronics, laboratories and medicine.
Hospitals often use a large ultrasonic cleaner to sanitise items as large as wheelchairs before they are passed on to another user. A large ultrasonic cleaner can also accommodate soft items, such as draperies or museum taxidermy exhibits.
Ultrasonics are enormously labour saving. This is good news for everyone; in industry, it means lower overheads and better results. Ultrasonic cleaning penetrates places that are manually inaccessible, such as bolt holes or around surface-mounted electronics, providing a consistent and uniform outcome. A few minutes are usually enough, so it is also time-saving.
Using an ultrasonic cleaner enables you to minimise or completely abolish the use of harsh or polluting chemicals. This is better for your item, your cleaner, and the environment in general. It is also another significant cost saving