Acoustofluidics: Using Sound to Move Cells and Particles

What is acoustofluidics?

Acoustofluidics combines acoustics with microfluidics. An ultrasonic standing wave sets up pressure nodes and antinodes across a channel, and suspended particles drift toward them at a rate that depends on their size, density and compressibility — so different particles can be separated.

Bulk vs surface acoustic waves

Bulk acoustic wave (BAW) devices use a resonant chamber, often in a stiff material such as glass or silicon. Surface acoustic wave (SAW) devices use interdigitated transducers on a piezoelectric substrate for fine, localised control — sometimes called "acoustic tweezers".

Why it is attractive

• Label-free — no tags or beads needed.
• Contactless and gentle — biocompatible, important for living cells.
• Versatile — focus, separate by size, trap or concentrate particles.

Applications

Cell sorting, rare-cell separation (such as circulating tumour cells), cell washing, particle concentration and micro-assembly all use acoustofluidics.

Integration

Acoustofluidics works alongside other techniques and can be combined with droplet or lab-on-a-chip systems. Chips need a well-defined channel geometry and good acoustic coupling between transducer and fluid.

Frequently asked questions