Laser-generated focused ultrasound for arbitrary waveforms

Abstract

Transducers for laser generated focused ultrasound can achieve photoacoustic waves with several hundred bars positive pressure in water. Previous designs employed concave glass substrates decorated with catalytically grown carbon nanotubes. Here, we show that arbitrarily shaped surfaces made of polymers and printed with 3d printers allow the generation of waveforms with complex temporal and spatial shape. We first present three different polymer materials together with a simplified deposition technique. This is achieved by painting layers of carbon-nanotube powder and polydimethylsiloxane. Together with a clear resin (Formlabs Photopolymer Clear Resin), pressure amplitudes of 300 bar peak positive were obtained. With the flexibility of polymer substrates, complex waveforms can be generated. This is demonstrated with a stepped surface which launches two waves separated by 0.8 μs. Detailed pressure measurements are supported with shadowgraphy images and simulations of the wave.

Review of Laser-Generated Ultrasound Transmitters and Their Applications to All-Optical Ultrasound Transducers and Imaging

“…(v) Focused ultrasound with complex temporal and spatial waveforms can be generated by utilizing arbitrarily shaped surfaces of polymers made by three-dimensional (3D) printing [72]. high-intensity and high-frequency LGUS focused transmitters [71].…”

“…high-intensity and high-frequency LGUS focused transmitters [71]. (v) Focused ultrasound with complex temporal and spatial waveforms can be generated by utilizing arbitrarily shaped surfaces of polymers made by three-dimensional (3D) printing [72]. …”

Acoustical characterisation of carbon nanotube-loaded polydimethylsiloxane used for optical ultrasound generation

“…Consequently, optical acoustic sources are ideally suited to broadband material characterisation [5] and detector calibration. In addition, optical ultrasound sources have been successfully applied to biomedical imaging [3], [6]- [8] and therapeutic settings [9], [10].…”

Generating arbitrary ultrasound fields with tailored optoacoustic surface profiles

“…The same work demonstrated that 3-D printing with transparent materials is well suited to the creation of these surface profiles. 10 The question of how to generate a desired acoustic field using different configurations of piezoelectric arrays has been addressed via optimisation in a number of previous works. 11,12 However, an approach has yet to be developed for the design of optoacoustic surface profiles.…”

“…While not a focus of this work, it has been shown previously that the pressure can be increased up to MPa levels with appropriate design of the optical absorber. 10 The signal to noise ratio (SNR) in the target plane of the experimental data is 4.1. This was quantified by creating a mask encompassing the target pattern and calculating the ratio of the average peak pressure within the mask to outside it.…”