**3.5 Sonophoresis**

Sonophoresis uses sound waves to increase the permeability of the skin. Similar to electroporation, sonophoresis also targets the lipid bilayer underneath the stratum corneum [112]. Sound waves (20–100 kHz) increases the pore sizes on the skin due to the increased fluidity of the lipid bilayers. Thus, sound waves allow the transcellular entry of drug molecules through the stratum corneum [114].
