Isolation of microbubbles of selected size range from polydisperse microbubbles

A method for isolating target microbubbles having a predetermined size range from polydisperse microbubbles, comprising:

• applying a first centrifugal field having a first field strength to a suspension comprising the polydisperse microbubbles for a first duration of time, thereby forming a first infranatant comprising at least a portion of target microbubbles and a first supernatant cake comprising microbubbles having a greater size than the target microbubbles;
• removing the first supernatant cake;
• applying a second centrifugal field having a second field strength to the first infranatant for a second duration of time, the second field strength being greater than the first field strength, thereby forming a second infranatant comprising at least a portion of target microbubbles and a second supernatant cake comprising microbubbles having a greater size than the target microbubbles;
• removing the second supernatant cake;
• applying a third centrifugal field having a third field strength to the second infranatant for a third duration of time, the third field strength being greater than the second field strength, thereby forming a third supernatant cake comprising at least a portion of the target microbubbles and third infranatant comprising microbubbles having a smaller size than the target microbubbles;
• and
• isolating the third supernatant cake.