The large variety of applications of ultrasound means that producing an exhaustive list is not possible. Ultrasound should be considered a particular form of energy with multiple properties depending on the way in which it is used.

The energy transmitted by power ultrasound is able to alter the properties of the media that it comes into contact with.

The table below shows the main effects induced and some applications:

Interaction media, phenomenon and application examples:

Liquid :

Cavitation

  • Cleaning
  • Decontamination
  • Formulation and processing of liquids
  • Sonochemistry
  • Treating and reducing waste

Atomization

  • Humidification, vaporization of liquids
  • Production of powders

Solid:

Heating

  • Thermoplastic welding,
  • Textile welding
  • Metal welding,

Vibration

  • Slicing, Cutting,
  • Processing,

Powder: 

Vibration

  • Dedusting of mechanical parts,
  • Deagglomeration,
  • Sieving,
  • Dosing of powder,
  • Conveying powders,

Gas :

Acoustic pression

  • Dedusting,
  • Defoaming,
  • Agglomeration of partcles,

Ultrasound in Fluids: Cavitation

The action of ultrasound in liquids relies on cavitation: the creation, growth, and collapse of bubbles formed when a liquid is subjected to a pressure wave. This results in a shockwave near the bubble and the formation of a thermochemical microreactor inside it.

To trigger acoustic cavitation, a power threshold must be reached—around 0.5 W/cm² at 20 kHz for water at atmospheric pressure, and a few W/cm² for organic solvents. The required depression amplitude depends on various factors; the higher the viscosity (i.e., the internal cohesion of the liquid), the harder it is to achieve cavitation due to the difficulty in separating particles.ultrasonic cavitation

In liquids, acoustic cavitation is the primary source of power ultrasound effects.

🔹 Ultrasonic Cleaning

When cavitation bubbles collapse near a solid surface, they create violent microjets (up to 100 m/s) that blast the surface clean.

To achieve optimal cleaning while meeting application requirements, the following must be considered:

  • Ultrasonic power: around 5 to 20 W per liter of bath

  • Frequency:

    • 25 kHz – strong cleaning for hard, heavily soiled surfaces

    • 40 kHz – gentle cleaning for delicate surfaces

    • Up to 1–2 MHz – for cleaning silicon wafers

  • Detergent: neutral, acidic, or alkaline to dissolve contaminants without damaging parts

  • Bath temperature: generally 40–60 °C

  • Cleaning time: a few seconds for degreasing to several hours for stripping

The advantages of ultrasonic cleaning are:

  • Eco-friendly and cost-effective: both ecological and economical

  • An alternative to solvents using biodegradable detergents

  • Reduced cleaning time

  • High-performance, effortless precision cleaning

🔹Ultrasonic Liquid Treatment and Formulation

At high power levels (50 W to 1 kW/L), cavitation’s mechanical effects are used for:

  • Degassing

  • Catalyzing chemical reactionsultrasound chimiluminescence | SinapTec

  • Homogenization

  • Emulsification

  • Intensive mixing (even for viscous products up to 400 Pas

  • Enzyme/DNA extraction

  • Cell lysis

  • Bacterial destruction

  • Formulation

  • Electrochemistry

  • Deagglomeration

  • Extraction

🔹 Sonochemistry

Cavitation also drives chemical reactions such as:

  • Catalysis and radical formation

  • Electrochemistry

  • Crystallization of alkaloids, glycosides, fragrances, fruit juices, essential oils

  • Operating under less severe temperature and pressure

  • Improving yields and purity

Ultrasonic Aerosol Generators

Ultrasonic aerosol generators are used, among other things, for:

  • Efficiency testing and ventilationultrasound base | SinapTec

  • Thin-layer deposition

  • Air contaminant measurement

  • Environment scenting

  • Humidification

  • Odor treatment and room disinfection

  • Filter characterization and monitoring

  • Medicinal aerosols

The advantages of this technology are:

  • no noise pollution
  • precise droplet size controlled by the ultrasonic frequency
  • directional flow

The production of aerosols is based on the behavior of a thin layer of liquid in contact with a vibrating surface. When the vibrational amplitude exceeds a certain threshold, droplets are ejected from the liquid’s surface. The diameter of these droplets is determined by the ultrasonic frequency and the properties of the fluid, such as its density, viscosity, and surface tension.

The change in droplet size as a function of frequency is illustrated below for water:

  • At 20 kHz, the average droplet diameter is about 80 µm. At 2 MHz, the diameter is around 3 µm.
  • In the frequency range between 20 kHz and 80 kHz, the liquid is atomized as soon as it comes into contact with the vibrating surface.
  • In the high-frequency range (>250 kHz), the ultrasonic transducer is placed at the bottom of a liquid volume. The acoustic field generates a fountain at the surface, from which the aerosol forms.

Compared to pneumatic nebulization, ultrasonic aerosol generation offers several advantages:

  • The droplet size is very precisely defined. It depends on the resonance frequency of the piezoelectric system and the properties of the fluid solution to be nebulized.

  • The droplet size distribution is narrow, with a standard deviation of approximately 1.4.

  • The aerosol flow rate can be easily adjusted over a wide range by modifying the excitation of the power signal, without altering the particle size distribution. Solid particles with a defined grain size can also be obtained by drying the aerosol from a given solution.

 

Assembly of Thermoplastic Materials

Ultrasonic welding is one of the most widely used processes in the thermoplastic parts industry. It is applied to:

  • Plastics (polyester, polyamide, polypropylene, acrylic, or blends containing at least 50% of these fibers with natural fibers like cotton or viscose)

  • Textiles made from synthetic fibers (woven and non-woven)

  • Textiles made from special fiber materials (carbon fiber, glass fiber, aramid fiber)

Principle

The key features of ultrasonic welding are the cleanliness of the result and the speed of the process. The welding time can be less than one second for spot welding.

The principle of ultrasonic assembly involves combining applied pressure with ultrasonic vibration. Depending on the material’s characteristics, the ultrasonic energy generates intense heat within the material, causing it to melt at the interface. No bonding agent is required. The pressure force can be applied manually or using a cylinder. The vibration amplitude required from the sonotrode depends on the material and the geometry of the sonotrode. Semi-crystalline materials generally require higher amplitudes (25–50 μm) than amorphous materials (10–30 μm).

The required amplitude is usually confirmed through successive trials and fine-tuning of the equipment.

Different Types of Assembly

The choice of sonotrode and anvil profiles allows for a wide range of effects.

Using a flat anvil results in a welding action. It provides enough cutting energy to slice without excessive force, avoiding delamination in materials such as carbon fiber. This type of welding is suitable for materials with a thickness of just a few millimeters.

With a shallow-angle anvil, the system performs cutting or punching only.

If the anvil angle is sharper, it enables cut-sealing, which prevents fraying along textile edges.

Ultrasonic assembly is also used for continuous welding using rotary ultrasonic tools, generally for thin materials. In this case, the welding speed can vary from a few meters to over 200 meters per minute. The ultrasonic system’s power is adjusted according to the material’s feed speed, density, and thickness.

Advantages of This Welding Technology

  • Clean, precise welds and cuts — no burning or fraying

  • Effortless cutting

  • Possibility of marking using specially shaped anvils

  • Fast execution

 

Clean and Effortless Cutting

Ultrasonic cutting is now well established in the food industry. This technique offers numerous advantages that make it competitive compared to other methods, such as water jet cutting, which can leave slight moisture on products and involves high installation and maintenance costs.

The ultrasonic cutting process involves vibrating a sharpened blade. These vibrations, typically at 20 kHz with an amplitude between 30 and 100 microns, make cutting easier because the blade penetrates the product without force or compression. Additionally, the blade is continuously self-cleaning, which simplifies tool maintenance and allows for the cutting of sticky products. The process produces no waste.

Advantages of Ultrasonic Cutting

  • Cutting without tearing material, resulting in better finish quality and reduced product loss

  • Reduced cutting force, improved efficiency, and less blade wear

  • Suitable for all types of food products—sheets, pieces, strips, rolls, rounds, blocks, loaves

  • No sticking or fouling of the blade

  • Low operating cost

  • Easy maintenance, low maintenance cost

Two Common Cutting Methods

Guillotine Cutting (or Mechanical Chopper)
A sonotrode blade with a triangular cross-section produces ultrasonic vibration at its tip. This blade is mechanically driven into the product. The system allows for continuous slicing of strips in a production line.

Rotary Cutting (SinapTec Patent)
This technique uses a driven circular blade. The cutting system operates with a standard ultrasonic generator, and an appropriate coupling mechanism at the center of the disk induces vibration in both the surface of the disk and its cutting edge.

Advantages of Rotary Cutting

  • Greater cutting thickness enabled by the use of circular blades with diameters up to 300 mm and blade thicknesses around 2 mm

  • High cutting speed, reaching several meters per minute across a wide range of materials

  • Unique vibration behavior of the blade allows for an exceptionally fine cutting edge compared to guillotine systems

  • Easier implementation from a mechanical point of view: only rotational drive is needed to achieve high-quality cutting

  • Additionally, it has been observed that precise tuning of the rotation speed is not critical in relation to the product’s feed rate.

Ultrasonic Sieving

Ultrasonic vibration helps reduce the friction coefficients between parts and improves powder flow.

Ultrasonic sieving is particularly effective for improving:

  • Sieving throughput

  • The breakdown of agglomerates

  • The proportion of oversize product

  • Continuous self-cleaning of the mesh

Ultrasonic Blowing

Ultrasonic technology generates an acoustic air stream in front of the probe without any actual gas displacement. The focused acoustic waves produced by the probe create a pressure field a few centimeters ahead of it. This field is strong enough to move particles suspended in the air or resting on a surface.

What makes this process unique is that the acoustic air stream is contactless. The propagation of ultrasonic waves in gases is limited due to the high absorption of the medium: the transmission of an ultrasonic wave from a solid medium into a gas is less than 0.1%.

Despite these limitations, producing high-intensity ultrasound in gas enables several applications:

  • Droplet levitation, achieved by generating a standing wave field between an ultrasonic emitter and a reflector.

  • Foam removal, successfully implemented on production lines and even in large volumes (such as tanks).

  • Ultrasonic agglomeration, which promotes the growth of fine particles (smaller than 2 microns) suspended in air. Larger particles are then easier to filter using conventional methods.

  • Contactless ultrasonic blowing is used for filter cleaning, dust removal, dry decontamination, and defoaming. This technique is especially valuable in confined environments such as cleanrooms, the food industry, or the nuclear sector, where the use of compressed air is not possible.

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