Active rheology of soft solids performed with acoustical tweezers

Fuente: arXiv
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Autori principali: Penneron, Antoine, Brunet, Thomas, Baresch, Diego
Natura: Preprint
Pubblicazione: 2025
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author Penneron, Antoine
Brunet, Thomas
Baresch, Diego
author_facet Penneron, Antoine
Brunet, Thomas
Baresch, Diego
contents Single-beam acoustical tweezers are used to manipulate individual microbubbles and provide quantitative measurements of the local shear modulus of soft hydrogels. The microbubbles are directly generated by electrolysis of the hydrogel and their displacement is detected using optical microscopy in the focal plane of a focused vortex beam. Microbubbles displaced off-axis can be pulled by a restoring radial force component that forms a stable two-dimensional trap. We also observe an off-axis tangential microbubble motion that is due to the transfer of the beam's angular momentum flux. A simple elastic model for the hydrogel deformation combined with radiation force calculations finally provide local values of the medium's shear modulus, which are found to be in good agreement with standard bulk measurements performed with a rheometer. Our results suggest that acoustical tweezers are relevant tools to characterize the local mechanical properties of complex soft materials opening new opportunities in the field of active rheology.
format Preprint
id arxiv_https___arxiv_org_abs_2501_18366
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Active rheology of soft solids performed with acoustical tweezers
Penneron, Antoine
Brunet, Thomas
Baresch, Diego
Soft Condensed Matter
Classical Physics
Single-beam acoustical tweezers are used to manipulate individual microbubbles and provide quantitative measurements of the local shear modulus of soft hydrogels. The microbubbles are directly generated by electrolysis of the hydrogel and their displacement is detected using optical microscopy in the focal plane of a focused vortex beam. Microbubbles displaced off-axis can be pulled by a restoring radial force component that forms a stable two-dimensional trap. We also observe an off-axis tangential microbubble motion that is due to the transfer of the beam's angular momentum flux. A simple elastic model for the hydrogel deformation combined with radiation force calculations finally provide local values of the medium's shear modulus, which are found to be in good agreement with standard bulk measurements performed with a rheometer. Our results suggest that acoustical tweezers are relevant tools to characterize the local mechanical properties of complex soft materials opening new opportunities in the field of active rheology.
title Active rheology of soft solids performed with acoustical tweezers
topic Soft Condensed Matter
Classical Physics
url https://arxiv.org/abs/2501.18366