High intensity laser-ultrasound

Laser ultrasound is based on the photoacoustic effect to generate high frequency, broadband and high pressure acoustic waves. In a laser ultrasound transducer, a material absorbs pulsed laser energy, leading to a transient thermal expansion and generating an ultrasonic wave propagating out from the absorber. The laser light can shine on the flat or concave absorbing film to generate un-focused or focused ultrasound, respectively.

In laser ultrasound transducers, the optical absorbing thin film with high optical absorption and high thermal expansion is a critically important component. In this study, we investigated a carbon nanofibers–PDMS (CNFs-PDMS) composite thin film for high intensity ultrasound generation. The results strongly suggest that CNFs-PDMS thin film is promising for efficient laser ultrasound transducers for a broad range of ultrasound applications.

Laser-Ultrasound

(a) Non-focused and (b) Focused laser generated ultrasound transducer; (c) Experimental setup for laser ultrasound generation; (d) Scanning electron microscopy (SEM) photograph of the CNFs thin film (10000×); (e) Waveforms of laser generated ultrasound by CNFs-PDMS thin film and carbon black PDMS film.

References:

Huang, W., W.-Y Chang, J. Kim, S. Li, S. Huang, and X. Jiang, “A Novel Laser Ultrasound Transducer Using Candle Soot Carbon Nanoparticles”, IEEE Transactions on Nanotechnology, (2016). Accepted
Chang, W.-Y., W. Huang, J. Kim, S. Li, X. Jiang, “Candle Soot Nanoparticles-PDMS Composites for Laser Ultrasound Transducers“, Applied Physics Letters, 107(16), 161903, (2015).
Hsieh, B.-Y., J. Kim, J. Zhu, S. Li, X. Zhang, X. Jiang, “A laser ultrasound transducer using carbon nanofibers-polydimethylsiloxane composite thin film“, Applied Physics Letters, 106(2), 021902, (2015).