Figure 1.

Illustration of a typical engineered microbubble used in biomedical applications. Microbubbles are particles filled with gas, such as air, oxygen (O₂), nitric oxide (NO) or perfluorocarbon (PFC), with a diameter of 1–10 μm. They are stabilized by shells made of phospholipid (3–5 nm thick), protein (15–150 nm thick) or polymer (50–500 nm thick).