Ultrasonic Cavitation in Liquids
Ultrasonic cavitation is the driving force behind high-intensity ultrasonic liquid processing. When powerful ultrasound is coupled into a liquid, microscopic vapor bubbles form, grow and collapse violently. This acoustic cavitation creates intense local shear forces, microjets, shock waves, pressure changes and micro-mixing effects that can accelerate homogenization, dispersing, emulsification, extraction, degassing, cell disruption and sonochemical reactions.
Hielscher probe-type sonicators use controlled acoustic cavitation to transfer ultrasonic energy directly into liquids, suspensions and slurries. From small laboratory samples to continuous industrial flow-through production, Hielscher systems allow you to adjust amplitude, sonotrode geometry, pressure, temperature, flow rate and residence time for reproducible cavitation results.
- For laboratories: develop and optimize sonication parameters in small volumes.
- For pilot plants: validate cavitation-driven processes under realistic processing conditions.
- For production: scale ultrasonic cavitation into batch, recirculation or continuous inline processes.
Tell us your liquid, batch volume or flow rate, viscosity, solids content, temperature limits and target process result. We will recommend the optimal sonicator, sonotrode and flow-cell configuration for your cavitation application.
Probe-type sonicators such as the UP400St use the working principle of acoustic cavitation.
The Working Principle of Ultrasonic Cavitation
When sonicating liquids at high intensities, the sound waves that propagate into the liquid media result in alternating high-pressure (compression) and low-pressure (rarefaction) cycles, with rates depending on the frequency. During the low-pressure cycle, high-intensity ultrasonic waves create small vacuum bubbles or voids in the liquid. When the bubbles attain a volume at which they can no longer absorb energy, they collapse violently during a high-pressure cycle. This phenomenon is termed cavitation. During the implosion very high temperatures (approx. 5,000K) and pressures (approx. 2,000atm) are reached locally. The implosion of the cavitation bubble also results in liquid jets of up to 280m/s velocity.
Acoustic cavitation (generated by power ultrasound) creates locally extreme conditions, so-called sonomechanical and sonochemical effects. Due to these effects, sonication promotes chemical reactions leading to higher yields, faster reaction speed, new pathways, and improved overall efficiency.
Probe Sonicator or Ultrasonic Bath: Which Cavitation Method Is Right?
Probe sonicators and ultrasonic baths both generate acoustic cavitation, but they differ significantly in intensity, control and process reliability. While ultrasonic baths are useful for cleaning, probe-type sonicators couple ultrasonic energy directly into the liquid and create a much stronger, focused cavitation zone. This makes probe sonicators the preferred choice for reproducible liquid processing applications such as homogenization, emulsification, extraction, cell disruption, nanoparticle dispersion and sonochemical reactions.
| Comparison Criteria | Probe Sonicator | Ultrasonic Bath |
|---|---|---|
| Cavitation intensity | Produces high-intensity acoustic cavitation directly at the sonotrode tip. | Produces weaker cavitation distributed across the bath volume. |
| Energy transfer | Transfers ultrasonic energy directly into the liquid, suspension or slurry. | Transfers energy indirectly through the bath liquid and vessel wall. |
| Process control | Allows precise adjustment of amplitude, power input, pulse mode, temperature and processing time. | Offers limited control over the actual ultrasonic energy reaching the sample. |
| Reproducibility | Provides reproducible sonication results when process parameters are defined and monitored. | Results can vary due to uneven cavitation distribution, vessel position, vessel material, fill level, and bath loading. |
| Processing efficiency | Highly efficient for homogenizing, dispersing, emulsifying, extraction, cell disruption and sonochemistry. | Suitable mainly for cleaning. |
| Sample volume | Available for small laboratory samples as well as pilot and industrial volumes. | Typically used for small vessels or multiple containers placed inside the bath. |
| Scale-up | Can be scaled from lab tests to pilot trials and continuous industrial inline processing. | Difficult to scale reliably because energy distribution and cavitation intensity are not easily transferable. |
| Suitable media | Effective for liquids, emulsions, suspensions, slurries and high-solids formulations. | Best suited for low-viscosity liquids and simple cleaning or degassing tasks. |
| Typical applications | Nanoparticle dispersion, nanoemulsions, extraction, cell lysis, homogenization, deagglomeration, wet milling and sonochemical reactions. | Cleaning glassware, degassing liquids, dissolving powders and mild sample agitation. |
| Best choice for | Controlled, powerful and reproducible ultrasonic liquid processing. | Simple cleaning or low-intensity ultrasonic treatment. |
Key Applications of Sonicators and Acoustic Cavitation
Probe-type ultrasonicators, also known as ultrasonic probes, efficiently generate intense acoustic cavitation in liquids. Therefore, they are widely used in various applications across different industries. Some of the most important applications of acoustic cavitation generated by probe-type ultrasonicators include:
- Homogenization: Ultrasonic probes can generate intense cavitation, which is characterised as an energy-dense field of vibration and shear forces. These forces provide excellent mixing, blending and particle size reduction. Ultrasonic homogenization produces uniformly mixed suspensions. Therefore, sonication is used to produce homogeneous colloidal suspension with narrow distribution curves.
- Nanoparticle Dispersion: Ultrasonicators are employed for the dispersion, deagglomeration and wet-milling of nanoparticles. Low-frequency ultrasound waves can generate impactful cavitation, which breaks down agglomerates and reduces particle size. In particular the high shear of the liquid jets accelerates particles in the liquid, which collide with each other (interparticulate collision) so that the particles consequently break and erode. This results in uniform and stable distribution of particles preventing sedimentation. This is crucial in various fields, including nanotechnology, materials science, and pharmaceuticals.
- Emulsification and Mixing: Probe-type ultrasonicators are used to create emulsions and mix liquids. The ultrasonic energy causes cavitation, the formation and collapse of microscopic bubbles, which generates intense local shear forces. This process aids in emulsifying immiscible liquids, producing stable and finely dispersed emulsions.
- Extraction: Due to cavitational shear forces, ultrasonicators are highly efficient in disrupting cellular structures and to improve mass transfer between solid and liquid. Therefore, ultrasonic extraction is widely used to release intracellular material such as bioactive compounds for the production of high-quality botanical extracts.
- Degassing and Deaeration: Probe-type ultrasonicators are employed to remove gas bubbles or dissolved gases from liquids. The application of ultrasonic cavitation promotes the coalescence of gas bubbles so that they grow and float to the top of the liquid. Ultrasonic cavitation makes degasification a quick and efficient procedure. This is valuable in various industries, such as in paints, hydraulic fluids, or food and beverage processing, where the presence of gases can negatively impact product quality and stability.
- Sonocatalysis: Ultrasonic probes can be used for sonocatalysis, a process that combines acoustic cavitation with catalysts to enhance chemical reactions. The cavitation generated by ultrasonic waves improves mass transfer, increases reaction rates, and promotes the production of free radicals, leading to more efficient and selective chemical transformations.
- Sample Preparation: Probe-type ultrasonicators are commonly used in laboratories for sample preparation. They are used to homogenize, disaggregate, and extract biological samples, such as cells, tissues, and viruses. The ultrasonic energy generated by the probe disrupts the cell membranes, releasing cellular contents and facilitating further analysis.
- Disintegration and Cell Disruption: Probe-type ultrasonicators are utilized to disintegrate and disrupt cells and tissues for various purposes, such as extraction of intracellular components, microbial inactivation, or sample preparation for analysis. The high-intensity ultrasonic waves and the thereby generated cavitation cause mechanical stress and shear forces, resulting in the disintegration of cell structures. In biological research and medical diagnostics, probe-type ultrasonicators are used for cell lysis, the process of breaking open cells to release their intracellular components. Ultrasonic energy disrupts cell walls, membranes, and organelles, enabling the extraction of proteins, DNA, RNA, and other cellular constituents.
These are some of the key applications of probe-type ultrasonicators, but the technology has an even wider range of other uses, including sonochemistry, particle size reduction (wet-milling), bottom-up particle synthesis, and sono-synthesis of chemical substances and materials in various industries such as pharmaceuticals, food processing, biotechnology, and environmental sciences.
A high-speed sequence (from a to f) of frames illustrating sono-mechanical exfoliation of a graphite flake in water using the UP200S, a 200W ultrasonicator with 3-mm sonotrode. Arrows show the place of splitting particles with cavitation bubbles penetrating the split.
© Tyurnina et al. 2020
Take Advantage of Ultrasonic Cavitation!
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:
| Batch Volume | Flow Rate | Recommended Devices |
|---|---|---|
| 1 to 500mL | 10 to 200mL/min | UP100H |
| 10 to 2000mL | 20 to 400mL/min | UP200Ht, UP400St |
| 0.1 to 20L | 0.2 to 4L/min | UIP2000hdT |
| 10 to 100L | 2 to 10L/min | UIP4000hdT |
| n.a. | 10 to 100L/min | UIP16000 |
| n.a. | larger | cluster of UIP16000 |
Video of Acoustic Cavitation in Liquid
The following video demonstrates acoustic cavitation at the cascatrode of the ultrasonicator UIP1000hdT in a water-filled glass column. The glass column is illuminated from the bottom by red light in order to improve the visualization of the cavitation bubbles.
Hielscher Ultrasonics manufactures high-performance ultrasonic homogenizers for mixing applications, dispersion, emulsification and extraction on lab, pilot and industrial scale.
Frequently Asked Questions
What is ultrasonic cavitation?
Ultrasonic cavitation is the formation, growth and violent collapse of microscopic bubbles in a liquid exposed to high-intensity ultrasound. The collapse of these bubbles creates intense local shear, liquid microjets, shock waves, high pressure gradients and strong micro-mixing effects.
What is the difference between ultrasonic cavitation and acoustic cavitation?
Acoustic cavitation is the general term for cavitation caused by sound waves. Ultrasonic cavitation is acoustic cavitation generated by ultrasonic frequencies, typically above the audible range. In industrial liquid processing, both terms are often used for cavitation produced by high-power ultrasonicators.
How does ultrasonic cavitation improve liquid processing?
Ultrasonic cavitation improves liquid processing by creating intense mechanical and chemical effects inside the liquid. The mechanical effects support mixing, homogenization, emulsification, particle deagglomeration, wet milling, extraction and cell disruption. In reactive systems, cavitation can also promote sonochemical effects and improve mass transfer.
Which applications use ultrasonic cavitation?
Ultrasonic cavitation is used for homogenizing, dispersing, emulsifying, nanoemulsification, extraction, degassing, deagglomeration, particle size reduction, cell lysis, microbial disruption, sonochemistry, sonocatalysis and advanced liquid-phase reactions.
Why are probe-type ultrasonicators effective for cavitation?
Probe-type ultrasonicators transmit ultrasonic energy directly into the liquid through a sonotrode. This direct energy coupling creates an intense cavitation zone near the probe surface and allows precise adjustment of important process parameters such as amplitude, power input, temperature, pressure and processing time.
Is an ultrasonic bath suitable for strong cavitation?
Ultrasonic baths produce cavitation, but the energy density is usually much lower and less focused than with a probe-type sonicator. Baths are useful for cleaning and mild treatment, while probe-type ultrasonicators are preferred for reproducible homogenization, extraction, emulsification, dispersion, cell disruption and industrial liquid processing.
Read and watch how probe-type sonicators and ultrasonic baths differ!
Which parameters influence ultrasonic cavitation intensity?
Important parameters include amplitude, ultrasonic power, sonotrode surface area, liquid volume, viscosity, solids content, pressure, temperature, vessel geometry, flow-cell geometry, flow rate and residence time. Adjusting these parameters allows the cavitation intensity to be adapted to the process target.
Can ultrasonic cavitation be scaled from lab to production?
Yes. Ultrasonic cavitation processes can be developed in laboratory volumes and transferred to pilot or industrial scale by controlling amplitude, energy input, sonotrode geometry, flow rate and residence time. Hielscher offers ultrasonicators and reactors for laboratory testing, pilot trials and continuous industrial production.
Literature / References
- Suslick, K.S. (1998): Kirk-Othmer Encyclopedia of Chemical Technology; 4th Ed. J. Wiley & Sons: New York, 1998, vol. 26, 517-541.
- Aharon Gedanken (2003): Sonochemistry and its application to nanochemistry. Current Science Vol. 85, No. 12 (25 December 2003), pp. 1720-1722.
- Suslick, Kenneth S.; Hyeon, Taeghwan; Fang, Mingming; Cichowlas, Andrzej A. (1995): Sonochemical synthesis of nanostructured catalysts. Materials Science and Engineering: A. Proceedings of the Symposium on Engineering of Nanostructured Materials. ScienceDirect 204 (1–2): 186–192.
- Brad W. Zeiger; Kenneth S. Suslick (2011): Sonofragmentation of Molecular Crystals. J. Am. Chem. Soc. 2011, 133, 37, 14530–14533.
- Ali Gholami, Fathollah Pourfayaz, Akbar Maleki (2021): Techno-economic assessment of biodiesel production from canola oil through ultrasonic cavitation. Energy Reports, Volume 7, 2021. 266-277.
- Anastasia V. Tyurnina, Iakovos Tzanakis, Justin Morton, Jiawei Mi, Kyriakos Porfyrakis, Barbara M. Maciejewska, Nicole Grobert, Dmitry G. Eskin 2020): Ultrasonic exfoliation of graphene in water: A key parameter study. Carbon, Vol. 168, 2020.
Hielscher Ultrasonics manufactures high-performance ultrasonic homogenizers from lab to industrial size.