Nucleating cavitation from laser-illuminated nano-particles

Vapor bubble generation from laser-illuminated gold nano-particles has been investigated as a means of providing nucleation sites for cavitation induced by high-intensity focused ultrasound (HIFU). Pulses from a 532-nm Nd:Yag laser were synchronized with a pulsed 1.1-MHz HIFU source in an acrylamide phantom seeded with 82-nm-diameter gold particles. Emissions from bubble collapses were detected by a 15-MHz focused transducer at a laser pulse energy and HIFU focal pressure of 0.10 mJ and 0.92 MPa, respectively. In comparison, a HIFU peak focal pressure of 4.50 MPa was required to nucleate detectable cavitation without laser illumination.