Ultrasonic photoacoustic emitter of graphene-nanocomposites film on a flexible substrateVella, Daniele (Avtor) Mrzel, Aleš (Avtor) Drnovšek, Aljaž (Avtor) Shvalya, Vasyl (Avtor) Jezeršek, Matija (Avtor) ultrasonic photoacoustic compositephotoacoustic materialslaser ultrasonicsphotoacoustic lensacoustic cavitationgraphene-polydimethylsiloxane compositePhotoacoustic devices generating high-amplitude and high-frequency ultrasounds are attractive candidates for medical therapies and on-chip bio-applications. Here, we report the photoacoustic response of graphene nanoflakes – Polydimethylsiloxane composite. A protocol was developed to obtain well-dispersed graphene into the polymer, without the need for surface functionalization, at different weight percentages successively spin-coated onto a Polydimethylsiloxane substrate. We found that the photoacoustic amplitude scales up with optical absorption reaching 11 MPa at ~ 228 mJ/cm$^2$ laser fluence. We observed a deviation of the pressure amplitude from the linearity increasing the laser fluence, which indicates a decrease of the Grüneisen parameter. Spatial confinement of high amplitude (> 40 MPa, laser fluence > 55 mJ/cm$^2$) and high frequency (Bw-6db ~ 21.5 MHz) ultrasound was achieved by embedding the freestanding film in an optical lens. The acoustic gain promotes the formation of cavitation microbubbles for moderate fluence in water and in tissue-mimicking material. Our results pave the way for novel photoacoustic medical devices and integrated components.20222022-10-19 10:54:56Članek v reviji142079sl