A method of removing bio films from a surface is disclosed. The method includes a source of bubbles in a liquid medium being provided. The bubbles having a predetermined size. A source of ultrasound waves at a predetermined frequency also being provided. The bubbles in the liquid medium being output toward the surface. The ultrasound waves also being directed toward the surface so that the bubbles vibrate at the predetermined frequency of the ultrasound waves. The predetermined size of the bubbles is approximately related to the frequency of the ultrasound waves.