A team of mechanical engineers at the University of California San Diego has successfully used acoustic waves to move fluids through small channels at the nanoscale. The devices employing the nanofluidic method could be integrated in a lab on a chip to sort cells, move liquids, manipulate particles, and sense other biological components, such as bacteria for rapid diagnosis.
Current methods of moving fluids at the nanoscale require bulky and expensive equipment, as well as high temperatures. Moving fluid out of a channel just a few nanometers high requires pressures of 1 megaPascal, or the equivalent of 10 atmospheres.
After a year of experimenting, post-doctoral researcher Morteza Miansari, now at Stanford University, built a device made of lithium niobate. Miansari bonded the material to itself at room temperature, creating nanoscale channels where fluids could be moved by the surface acoustic waves. The device is compatible with biological materials, cells and molecules.
Researchers used acoustic waves with a frequency of 20 megaHertz to manipulate fluids, droplets, and particles in 50- to 250-nanometer-tall slits. To fill the channels, researchers applied the acoustic waves in the same direction as the fluid moving into the channels. To drain the channels, the sound waves were applied in the opposite direction.
By changing the height of the channels, the device could be used to filter a wide range of particles, down to large biomolecules such as siRNA.