Systems and methods for cleansing blood are disclosed herein. The methods include acoustically separating undesirable particles bound to capture particles from formed elements of whole blood. After introducing the capture particles to whole blood containing undesirable particles, the whole blood and capture particles are flowed through a microfluidic separation channel. At least one bulk acoustic transducer is attached to the microfluidic separation channel. A standing acoustic wave, imparted on the channel and its contents by the bulk acoustic transducer, drives the formed elements and undesirable particles bound to capture particles to specific aggregation axes. After aggregating the particles, the formed elements exit the separation channel through a first outlet and are returned to the patient. The undesirable particles, bound to the capture particles, exit through a second outlet and can be discarded to saved for later study.
