Sonication

Sonication is the use of sound energy, typically ultrasonic frequencies above 20 kHz, to agitate particles in a sample. When applied to liquids, the acoustic energy induces cavitation, the formation, growth, and collapse of microscopic bubbles. The collapse generates localized temperatures and pressures and intense shear forces, capable of breaking up agglomerates, dispersing particles, or rupturing cells.

Equipment and modes vary. Bath sonicators use a transducer to emit ultrasonic energy into a liquid surrounding the sample, providing broad-area exposure. Probe or horn sonicators insert a titanium probe directly into the sample for higher energy delivery, enabling rapid dispersion or disruption. Operation can be continuous or pulsed to control energy input and temperature.

Typical applications cover materials processing, chemistry, and biology. In materials science, sonication disperses nanoparticles, exfoliates layered materials such as graphene, and promotes mixing. In chemistry and biochemistry, it assists degassing solvents, accelerates reactions by increasing interfacial area, and aids extraction. In biology, it can lyse cells and homogenize tissues or shear DNA; it is also used to ultrasonically disperse emulsions and to prepare samples for analysis.

Parameters and effects depend on frequency, power, duration, and temperature. Lower frequencies (around 20–40 kHz) produce stronger cavitation and are suited for disruption or exfoliation, while higher frequencies yield milder effects. Prolonged exposure can heat samples and cause damage or degradation; cooling and pulsing mitigate this risk. Probe tips may introduce metal contaminants if not cleaned, and bath systems may deliver gentler but less intense energy.

Safety and limitations include the risk of aerosolization, noise, and unintended sample damage. Proper enclosure, ventilation, and personal protective equipment are recommended, along with careful optimization of energy input to avoid overheating or degradation.