Acoustic Tweezers: optical calibration and applications

Recently, the acoustic manipulation of micro and nanoparticles has emerged as a promising area in scientific research and practical applications. Acoustic tweezers, which use sound waves to manipulate objects without direct contact, are a cutting-edge technology based on the principle of acoustic radiation. This technology can manipulate a wide range of materials, enabling numerous applications. The capability of measuring the trapping forces requires a careful calibration of the trap. This procedure, while well established in other micromanipulation techniques such as optical trapping, in acoustic case is only seldom carried out. To cover this gap, in this thesis we adapt the calibration protocols tipically used in optical tweezers to the acoustic case. We measure trap stiffnesses in the mN/m range that are consistent with calculations of acoustic forces based on a simple dipole approximation approach. In addition, we will show that acoustic tweezers can be integrated with a portable Raman spectrometer, allowing to obtain Raman spectra of particles far from any interaction with a substrate. We will show some results regarding the recognition of different mineral phases in samples of interest in astrophysics and the high-resolution spectroscopy of molecular species adsorbed on a plasmonic suface.