Ultrasonication: Principle, Parts, and Applications

Ultrasonication, also known as sonication, is one of the homogenization techniques that uses high-frequency sound waves (i.e.,>20 KHz) to break large particles into smaller fragments or better uniform-sized particles in the base fluid. Due to its versatility and effectiveness, this technique is commonly used in various fields, including chemistry, biology, materials science, and food processing. This technique is applicable for multiple purposes, such as; cell disruption, denaturation of proteins, and cleaning solid surfaces.

Parts of Sonicator

The machine used to carry out ultrasonication is known as a sonicator. The significant parts of the sonicator are as follows;

Generator

It is one of the essential parts of the sonicator that helps to convert electrical power into an electrical signal to control the transducer. The generator consists of various keypads or nobs that allow it to adjust multiple parameters required during sonication. 

Converter

It is also known as a transducer. Because of the properties of the intrinsic piezoelectric crystals, the converter converts electrical signals into high-frequency mechanical vibration (i.e.,>20KHz). Furthermore, the generator and transducer are connected by high-voltage cable, and generated pulse is amplified and transmitted down the probe. 

Probe

It is also known as a horn or tip. The probe is attached to the transducer and amplifies the ultrasonic vibrations generated by the transducer into a longitudinal vibration resulting in a cavity in the sample.

Sonication vessel

The sonication vessel or container holds the sample that needs to be processed. It is typically made of glass or plastic and can vary in size and shape depending on the application. The vessel should be compatible with the sonicator’s probe or horn for effective sample processing. Furthermore, the vessel we use during sonication should be soundproof and high-energy to minimize noise and any potential hazards from the ultrasonic energy.

Principle

The main principle of ultrasonication is based on generating high-frequency ultrasonic sound that results in a cavitation phenomenon. 

During ultrasonication, high-frequency sound waves are applied to a solution, creating tiny bubbles in the liquid. These bubbles form and collapse during the cavitation process. When the bubbles collapse, they release a large amount of energy through shockwaves.

Thus, produced energy breaks the molecular connections between water molecules. As the bond weakens, the particles in the solution start to disperse, allowing the mixing process to begin. Therefore, this process, known as cavitation, generates intense forces that facilitate various applications such as cleaning, extraction, and chemical reactions. Furthermore, cooling methods like ice cubes prevent the solution from getting too hot.

Applications of Ultrasonication

Ultrasonication is a technique that has many applications that, are as follows;

1. It is used for homogenization and emulsification in food and beverage, pharmaceuticals, cosmetics, and paint manufacturing industries.
2. It is used to clean rust surfaces, jewelry, and delicate laboratory equipment.
3. It is used to reduce particles’ size and synthesize nanoparticles applicable in pharmaceuticals and nanotechnology.
4. It is also an energy source in chemical reactions such as organic synthesis, wastewater treatment, and environmental remediation.
5. It is used to break cells and release their contents in biological research, including DNA/RNA extraction, protein extraction, and extraction of bioactive compounds from microorganisms.
6. It removes dissolved gases or bubbles in a liquid, a process known as degassing.
7. It is also used in gene therapy, target therapy, and drug delivery.

Advantages of Ultrasonication

Ultrasonication has lots of benefits in various fields, which are as follows;

1. It is an efficient and rapid processing method.
2. It is simple to operate and requires minimal maintenance.
3. It is a versatile technique applicable to various samples and materials.
4. It requires a relatively low power consumption than other methods.
5. It effectively reduces the size of particles, leading to improved homogeneity and uniformity of materials.

Disadvantages of Ultrasonication

Ultrasonication also has some disadvantages, which are as follows;

1. This technique has limited penetration depth.
2. The intense mechanical forces generated during ultrasonication can cause sample degradation, particularly for delicate biological or sensitive compounds.
3. It can generate heat that leads to sample heating, which may affect the stability of heat-sensitive compounds or induce unwanted reactions.
4. High-quality ultrasonic equipment can be relatively expensive, especially for industrial-scale applications or specialized setups.

Precautions

1. It should be carried out in a soundproof chamber to minimize noise and any potential hazards from the ultrasonic energy.
2. Use appropriate personal protective equipment (PPE) to protect from high-frequency energy.
3. Always carry out ultrasonication in a sonication vessel in order to avoid spillage of the sample.

Reference

1. Sandhya. M, Ramasamy. D, Sudhakar. K, Kadirgama. K, Harun W.S.W. Ultrasonication an intensifying tool for preparation of stable nanofluids and study the time influence on distinct properties of graphene nanofluids – A systematic overview. 73: 1-16, 2021. DOI: https://doi.org/10.1016/j.ultsonch.2021.105479.