How Does an Ultrasonic Cleaner Work? Cavitation, Parts and Limits

An ultrasonic cleaner works by sending high-frequency sound through a liquid so that millions of tiny bubbles form and collapse against the surface of whatever is submerged. The CDC’s disinfection and sterilization guideline describes it this way: ultrasonic cleaning “removes soil by cavitation and implosion,” with acoustic energy propagated through an aqueous solution to break the bonds that hold particles to surfaces. This page explains the mechanism, the parts, how loading and frequency change the result, and one limit that matters in healthcare and laboratory reprocessing: ultrasound cleans, but it does not disinfect.

How does cavitation clean a surface?

Cavitation is, in one manufacturer’s words, “the rapid formation and violent collapse of minute bubbles or cavities in a cleaning liquid” (Sonics). Another maker, Safetykleen, describes the bubbles as collapsing and generating tiny shock waves. Those collapses happen at the surface of the submerged part and break the grip of soil on it. The cleaning liquid then carries the loosened particles away.

What are the main parts of an ultrasonic cleaner?

Per the Sonics primer, a unit has three working elements:

• Tank, which holds the cleaning solution and the load.
• Generator, which produces the high-frequency electrical signal.
• Transducer, which converts that electrical energy into mechanical vibration in the liquid. Sonics notes that magnetostrictive transducers use nickel or alloys, while electrostrictive types use ceramics such as lead zirconate titanate.

A probe-type instrument uses ultrasound too, but a cleaning tank treats the whole bath rather than a single sample. For the probe version used in sample preparation, see what is a sonicator.

What you need

• An ultrasonic cleaner with its manufacturer’s instructions for use (IFU).
• A cleaning solution compatible with the materials being cleaned. Sonics notes water-based solutions are the simple option and solvents are used for soils water cannot handle. Safetykleen advises avoiding flammable liquids.
• A basket or fixture that keeps parts off the tank bottom.
• For healthcare or laboratory reprocessing, your facility’s reprocessing procedure and the device maker’s IFU for the item being cleaned.

Steps

These are general steps. The equipment IFU and, in a healthcare setting, the facility’s infection-prevention procedure take priority.

1. Fill the tank with the solution the manufacturer specifies for the material being cleaned. Safetykleen suggests distilled or deionised water to reduce mineral buildup.
2. If the IFU calls for heating, set the temperature it gives. Sonics notes the most intense cavitation occurs considerably below the liquid’s boiling point; Safetykleen suggests heating solution to 40-60 C. These are vendor statements, not a universal setting.
3. Load parts in a basket so nothing rests on the tank bottom. Sonics advises that the combined cross-section of parts should not exceed 70% of the tank cross-section.
4. Run the cycle for the time the IFU specifies.
5. Remove the load and rinse it as the IFU directs. The CDC notes that enzymatic products are used per the manufacturer’s instructions and that “enzymes must be rinsed from the equipment.”
6. Dry and store the item as its own IFU directs.

How do loading and fixturing change the result?

Sound has to reach the surface to clean it, so what goes in the tank matters as much as the tank. The Sonics primer gives these limits:

Loading factor	What the manufacturer says
Position	Keep parts and baskets off the tank bottom.
Load size	Combined cross-section of parts should not exceed 70% of the tank cross-section.
Mesh baskets	Mesh finer than 50 mesh acts like a solid; openings over a quarter inch pass the waves.
Fixturing materials	“Elastomers and non-rigid plastics will absorb ultrasonic energy and should be used cautiously for fixturing.”

Does frequency matter?

Yes, and manufacturers describe the ranges differently, so treat the figures as vendor guidance rather than a standard.

Source	Lower frequency	Higher frequency
Sonics (manufacturer)	Roughly 20-30 kHz suits heavy soils on large, dense loads. Below 20 kHz, noise can exceed safety limits.	More, smaller cavities with less energy each and lower risk to parts; suits delicate work and tiny particles.
Safetykleen (manufacturer)	20-40 kHz gives larger, more forceful bubbles.	60-80 kHz gives smaller, gentler bubbles.

The common thread is direction: lower frequency is more forceful, higher frequency is gentler. Check the part maker’s IFU before choosing a unit or setting for delicate items.

What can go wrong?

• Ultrasound is not disinfection. The CDC states that “ultrasound alone does not significantly inactivate bacteria,” although sonication “can act synergistically to increase the cidal efficacy of a disinfectant.” A cleaned item has not been disinfected or sterilized by the bath.
• Used bath fluid can carry bacteria. The CDC notes bacterial contamination can be present in used ultrasonic cleaning solutions because these solutions “generally do not make antibacterial label claims.”
• Endotoxin. The CDC warns that the cleaning fluid could result in endotoxin contamination of surgical instruments, which can cause serious inflammatory reactions. Fluid change intervals come from the equipment and instrument IFU.
• Blocked or absorbed waves. Parts resting on the bottom, fine mesh baskets and soft fixturing can reduce the energy reaching the load (see the table above).
• Incompatible solution or part. Sonics says the solution must be compatible with the materials. Safetykleen advises against parts with loose coatings and fragile plastics that may warp.

When to get professional help

Ask the equipment manufacturer or your facility’s infection-prevention or sterile processing staff before cleaning any item whose IFU does not mention ultrasonic cleaning, before changing a reprocessing step, or if items come out of the bath still visibly soiled. The CDC lists ultrasonic cleaners alongside washer-decontaminators, washer-disinfectors and washer-sterilizers as the most common mechanical cleaners; which one applies to an item is set by that item’s maker. For where these washers sit in the department, see sterile processing department equipment. For the cleaning chemistry sometimes used in these baths, see enzymatic cleaner. For the step that follows cleaning, see what an autoclave does, and for a device-specific example of reprocessing, endoscope reprocessing.

FAQ

How does an ultrasonic cleaner work in simple terms?

A generator drives a transducer that vibrates the liquid in the tank. The vibration makes tiny bubbles that collapse against submerged surfaces, and that cavitation dislodges soil.

Does an ultrasonic cleaner disinfect instruments?

No. The CDC states that ultrasound alone does not significantly inactivate bacteria. Disinfection or sterilization is a separate step per the instrument’s IFU.

Can I use plain water?

Sonics describes water-based solutions as the simple option, with solvents reserved for soils water cannot handle. Use the solution the unit and item makers specify.

Why should parts not sit on the tank bottom?

Sonics advises keeping parts and baskets off the bottom of the tank so the waves can reach the load.

Sources

• CDC, Cleaning (Disinfection and Sterilization Guideline), checked 2026-10-29.
• Sonics, Ultrasonic Cleaning Primer (manufacturer), checked 2026-10-29.
• Safetykleen, Cavitation and ultrasonic cleaners (manufacturer), checked 2026-10-29.