The strength of the technology lies in the fact that there are several key parameters that can be adjusted to tailor the separation for a wide range of applications. This can be used to wash cells by moving them from one liquid to another. Cells can also be removed from a liquid to, for instance, generate clean plasma from blood. By fine-tuning parameters such as the flow rate or density of the medium, cells with different physical properties such as size or density can be separated from each other.
The acoustic separation chip consists of a microfluidic glass or silicon chip coupled to a piezoelectric transducer. The microfluidic channel is typically half a millimeter wide and a couple of centimeters long, with two inlets and two outlets. As the flow is laminar, particles move through the channel in separate flow paths without any mixing. An electrical signal is applied to the piezoelectric transducer to generate ultrasonic vibrations. The frequency is matched to the width of the channel to create a standing wave between the side walls. The acoustic field exerts acoustic forces on the particles, moving them towards the pressure node in the center of the channel.
The force is dependent on the size of the particle and its density and compressibility relative to the surrounding liquid. By adjusting parameters such as the flow rates, acoustic power and density of the media, this principle can be used to separate particles with different physical properties. Particles that are large or dense enough will be moved to the center and can be collected from the center outlet, while the other particles stay in their flow paths and are collected from the side outlet.