Physics & Astronomy ETDs


Debra Cox

Publication Date



Micron-sized bubbles are of some interest for applications in ultrasound contrast and ultrasound-targeted drug delivery. Bubbles must be coated to remain stable; otherwise the surface tension induces an internal Laplace pressure that rapidly drives the bubble gas into solution. We have studied the behavior of bubbles made with different phospholipid coat molecules, subjected to repeated, brief pulses of 1.1 MHz focused ultrasound. Bubbles show rapid initial shrinkage, followed by a slower (or even stationary) phase. For essentially all bubbles, the rate of initial rapid shrinkage exceeds the limit imposed by gas diffusion into the surrounding medium; this rapid shrinkage may be evidence of nanoscopic bubble fragmentation. Upon reaching a fraction of their initial size, bubbles begin a slower shrinkage phase with behavior depending on the resting phase state of the coat lipid. Fluid DMPC monolayers give a more rapid shrinkage than gel phase DMPC. When coated with the long chain saturated lipid DSPC (solid phase), the bubbles are stable indefinitely, but bubbles with shorter or unsaturated lipid coats are eventually destroyed.

Degree Name


Level of Degree


Department Name

Physics & Astronomy

First Committee Member (Chair)

Hossein-Zadeh, Mani

Second Committee Member

Thomas, James

Third Committee Member

Prasad, Sudhakar

Fourth Committee Member

Rudolph, Wolfgang

Project Sponsors

Integrating Nanotechnology with Cell Biology and Neuroscience Integrative Graduate Education and Research Traineeship (INCBN IGERT); Spatio Temporal Modeling Center (STMC)




bubble, lipid, ultrasound, diffusion, dissolution, convection, fragmentation, drug delivery, contrast agent, monolayer, stability, lipid saturation, monolayer phase

Document Type