Size distribution of microbubbles as a function of shell composition

•We present an optical method for measure the size distribution of microbubbles.•We measure the size distribution of microbubbles with different shell compositions.•Microbubble size distributions are monomodal and nearly Gaussian in shape.•Microbubble size distributions are insensitive to changes in shell composition.•Microbubble size is generally determined by the synthesis method.

The effect of modifying the shell composition of a population of microbubbles on their size demonstrated through experiment. Specifically, these variations include altering both the mole fraction and molecular weight of functionalized polymer, polyethylene glycol (PEG) in the microbubble phospholipid monolayer shell (1–15 mol% PEG, and 1000–5000 g/mole, respectively). The size distribution is measured with an unbiased image segmentation program written in MATLAB which identifies and sizes bubbles from micrographs. For a population of microbubbles with a shell composition of 5 mol% PEG2000, the mean diameter is 1.42 μm with a variance of 0.244 μm. For the remainder of the shell compositions studied herein, we find that the size distributions do not show a statistically significant correlation to either PEG molecular weight or mole fraction. All the measured distributions are nearly Gaussian in shape and have a monomodal peak.