What is Acoustic Streaming?

Acoustic streaming is a phenomenon that occurs when sound waves are propagated in a fluid medium, generating a flow pattern. This flow pattern is caused by the interaction of sound with the fluid, which leads to a transfer of momentum and energy from the sound field to the fluid. Acoustic streaming is characterized by a steady and continuous flow motion, which can be used for various applications, including mixing, particle manipulation, and cell sorting.

How Does Acoustic Streaming Work?

Acoustic streaming can be generated using various techniques, such as ultrasonic transducers, surface acoustic waves, and acoustic resonators. When a sound wave is propagated in the fluid, it generates a pressure field that creates fluid motion. The fluid motion is caused by the interaction of the sound pressure gradient with the fluid’s viscosity and inertia. Depending on the frequency and intensity of the sound wave, different types of acoustic streaming patterns can be generated, including symmetric and asymmetric flows.

Applications of Acoustic Streaming

Acoustic streaming has various applications in different fields, including biotechnology, microfluidics, and acoustics. In biotechnology, acoustic streaming can be used for cell sorting, drug delivery, and tissue engineering. In microfluidics, acoustic streaming is used for mixing, particle manipulation, and droplet formation. In acoustics, acoustic streaming can be used for flow visualization, acoustic levitation, and non-destructive testing.

Example: Acoustic Streaming in Microfluidics

One of the most common applications of acoustic streaming is in microfluidics, where it is used for mixing and particle manipulation. Acoustic streaming can be generated using a piezoelectric transducer, which is placed at the bottom of a microfluidic channel. When an AC voltage is applied to the transducer, it generates an ultrasonic wave that propagates through the fluid, creating an acoustic streaming flow. This flow can be used for mixing different fluids or for trapping and manipulating small particles or cells. Acoustic streaming in microfluidics is a promising technique for various biomedical and chemical applications, such as drug discovery, diagnostics, and lab-on-a-chip devices.