Meanwhile, the release efficiency by ultrasonication is saturated to about 40% under the experimental conditions (cf. Figures and). This would be due to that liposomes located on the deep inside of the pore are unlikely to be flushed out by cavitation or that cavitationgenerated energy is not enough to tear off the liposomes binding rigidly. The detail of the interaction between liposomes and AAO will be discussed in the next subsection.