  Monodisperse lipid-coated microbubbles are a promising route to unlock the
full potential of ultrasound contrast agents for medical diagnosis and therapy.
Here, we present a stand-alone lab-on-a-chip instrument that allows
microbubbles to be formed with high monodispersity at high production rates.
Key to maintaining a long-term stable, controlled, and safe operation of the
microfluidic device with full control over the output size distribution is an
optical transmission based measurement technique that provides real-time
information on production rate and bubble size. We feed the data into a
feedback loop and demonstrate that this system can control the on-chip bubble
radius (2.5 to 20 $\mu$m) and the production rate up to $10^6$ bubbles/s. The
freshly formed phospholipid-coated bubbles stabilize after their formation to a
size approximately two times smaller than their initial on-chip bubble size
without loss of monodispersity. The feedback control technique allows for full
control over the size distribution of the agent and can aid the development of
microfluidic platforms operated by non-specialist end users.
