| Most microbubble (MB) theoretical models that assume fixed viscoelastic properties for shells have not been proven to successfully describe MB behaviour. Experimental data are not available in this area and therefore research often resource to fitting shell parameters to acoustic or optical data. Data on shell properties first were collected using the Atomic Force Microscope (AFM) for static experiments and relatively hard shelled MBs (BiSphere®). The force resolution of sub-nanonewtons is adequate to study the mechanical properties of soft lipids. MBs of the experimental agent BR14 were interrogated with tipless cantilevers using the MFP-1D AFM. Stiffness measurements of MBs between 1-10 ìm showed that forces above 10nN caused MB damage. The stiffness (effective spring constant) of the MBs averaged at 0.06 N/m, which is 50 times lower than the hard shelled BiSphere®. No dependence on size was observed. Using linear elasticity theory the Young’s modulus of the shell ranged around 0.5 and 4.0 GPa, which appears to contradict other findings. |