Abstract
A versatile and scalable fabrication method for laser-generated focused ultrasound transducers is proposed. The method is based on stamping a coated negative mold onto polydimethylsiloxane, and it can be adapted to include different optical absorbers that are directly transferred or synthesized in situ. Transducers with a range of sizes down to 3 mm in diameter are presented, incorporating two carbonaceous (multiwalled carbon nanoparticles and candle soot nanoparticles) and one plasmonic (gold nanoparticles) optically absorbing component. The fabricated transducers operate at central frequencies in the vicinity of 10 MHz with bandwidths in the range of 15–20 MHz. A transducer with a diameter of 5 mm was found to generate a positive peak pressure greater than 35 MPa in the focal zone with a tight focal spot of 150 μm in lateral width. Ultrasound cavitation on the tip of an optical fiber was demonstrated in water for a transducer with a diameter as small as 3 mm.
Highlights
A versatile and scalable fabrication method for lasergenerated focused ultrasound transducers is proposed
A key challenge with interventional applications remains in those areas where lateral diameters are highly constrained (e.g.,
Polydimethylsiloxane (PDMS) has been highlighted due to its high thermal expansion coefficient [20] ( β ≈ 300 × 10−6 C−1), optical transparency (400–1100 nm) [21], and an acoustic impedance well matched to biological tissue [22]
Summary
A versatile and scalable fabrication method for lasergenerated focused ultrasound transducers is proposed. Laser-generated focused ultrasound (LGFU) transducers utilize optically absorbing materials to produce ultrasound via the photoacoustic effect. A key challenge with interventional applications remains in those areas where lateral diameters are highly constrained (e.g.,
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