Effect of Backing on Carbon-Polymer Nanocomposite Sources for Laser Generation of Broadband Ultrasound Pulses

Light absorbing polymer nanocomposites have been widely investigated as a source of broadband and high amplitude ultrasound generated via pulsed laser excitation. Biomedical applications of such sources include both imaging and ablative therapies. Fabrication of light absorbing nanocomposite sources has mostly involved elaborate chemistry. Here, a nanocomposite composed of multi-walled carbon nanotubes mechanically dispersed in polydimethylsiloxane polymer is used. The nanocomposite film was backed on optically clear polydimethylsiloxane and laboratory grade glass slides. The two backed sources were investigated using two lasers whose full-width half maximum durations were 2.6 and 4.0 ns. It was found that the characteristics of the acoustic field generated from the nanocomposite source showed a significant dependence on the backing when the stress confinement criterion is not satisfied.