arXiv subjects

Claude Inserra

Publications and source records attributed to Claude Inserra.

5 recordsLinked to original sources

arXiv2025

Contactless micro-elastography of single cells using oscillating microbubbles as shear wave sources

The mechanical properties of cells play key roles in their physiology, function, physiological and pathological transformations. Micro-elastography has recently emerged as a promising tool to estimate cellular viscoelastic properties within a millisecond, without the need for mechanical modeling. Here, we report a fully contactless approach to single-cell micro-elastography, using acoustically oscillating gas microbubbles positioned near individual cells (20~\textmu m diameter megakaryocytes) as localized shear wave sources. Using this approach, we successfully performed micro-elastography on cells up to five times smaller than those studied in previous works, establishing the smallest single-cell elastography measurements to date. Spherical or non-spherical bubble oscillations generated 15~kHz elastic waves, which we detected using a high-speed camera coupled to a standard bright-field microscope. Noise correlation elastography enabled the measurement of average and local shear-wave velocities within single cells. Our results demonstrate that this method is robust and reproducible across multiple cells from the same cell line, paving the way for real-time, label-free mechanical monitoring of single cells during fast biological processes.

physics.app-ph↗

arXiv2025

Resonance behavior of a bubble near a spherical inclusion

We present an analytical model for the frequency response of a gas microbubble oscillating near a spherical inclusion of arbitrary size and mechanical nature (rigid, fluid, or viscoelastic) immersed in a viscous compressible fluid. The model considers both radial and nonspherical oscillations in the linear regime and predicts how their resonance frequencies and oscillation amplitudes are altered by the bubble size, material properties, and distance to the nearby sphere. As a key application, we demonstrate that scanning the frequency response of a bubble near a viscoelastic object, such as an erythrocyte-like particle mimicking a biological cell, offers a way to recover its mechanical properties through inverse modeling, opening new possibilities for high-resolution elastography at the microscale.

physics.flu-dyn↗

arXiv2025

Mathematical modelling for acoustic microstreaming produced by a gas bubble undergoing asymmetric oscillations

An exact solution is developed for the bubble-induced acoustic microstreaming in the case of a gas bubble undergoing asymmetric oscillations. The modeling is based on the decomposition of the solenoidal, first- and second-order, vorticity fields into poloidal and toroidal components. The result is valid for small amplitude bubble oscillations without restriction on the size of the viscous boundary layer $(2{\nu}/{\omega})^{(1/2)}$ in comparison to the bubble radius. The nonspherical distortions of the bubble interface are decomposed over the set of orthonormal spherical harmonics ${Y_n^m} ({\theta},{\phi})$ of degree $n$ and order $m$. The present theory describes the steady flow produced by the nonspherical oscillations $(n,{\pm}m)$ that occur at a frequency different from that of the spherical oscillation as in the case of a parametrically-excited surface oscillation. The three-dimensional aspect of the streaming pattern is revealed as well as the particular flow signatures associated to different asymmetric oscillations.

physics.flu-dyn↗

arXiv2025

Acoustic microstreaming and shear stress produced by the interaction of an oscillating gas bubble with a viscoelastic particle

An analytical theory is developed that describes acoustic microstreaming produced by the interaction of an oscillating gas bubble with a viscoelastic particle. The bubble is assumed to undergo axisymmetric oscillation modes, which can include radial oscillation, translation and shape modes. The oscillations of the particle are excited by the oscillations of the bubble. No restrictions are imposed on the ratio of the bubble and the particle radii to the viscous penetration depth and the separation distance, as well as on the ratio of the viscous penetration depth to the separation distance. Capabilities of the developed theory are illustrated by computational examples. The shear stress produced by the acoustic microstreaming on the particle surface is calculated. It is shown that this stress is much higher than the stress predicted by the formula of Nyborg, which is commonly used to evaluate the time-averaged shear stress produced by a bubble on a rigid wall.

physics.flu-dyn↗

arXiv2024

Phenomenon of self-oscillation in bubble dynamics: Bouncing acoustic bubbles

Self-oscillations underlie many natural phenomena such as heartbeat, ocean waves, and the pulsation of variable stars. From pendulum clocks to the behavior of animal groups, self-oscillation is one of the keys to the understanding of synchronization phenomena and hence the collective behavior of interacting systems. In this study, we consider two closely spaced bubbles pulsating in the kHz range in response to ultrasonic excitation. A translational bouncing motion emerges from their interaction with a much lower frequency than the bubble pulsation frequency. Our analysis reveals that the observed bubble bouncing exhibits the main features of self-oscillation, such as negative damping and the emergence of a limit cycle. These results highlight unexpected nonlinear effects in the field of microbubbles and give insights into the understanding of synchronization in large bubble clouds.

physics.flu-dyn↗