Anshul Shrivastava | Search arXiv

arXiv2026

Viscous Dissipation Governs Bubble Morphology and Failure in Soft Matter

Cavitation, the growth of bubbles in fluids and soft matter, plays a central role in tissue damage, ultrasound therapies, and material failure, yet the influence of viscoelastic dissipation on bubble dynamics remains unclear. Here, we investigate cavitation in polyacrylamide hydrogels with identical elastic moduli but different viscous dissipation. We observe a striking symmetry breaking transition: elastic gels rapidly develop ellipsoidal cavities before rupture, whereas viscoelastic gels sustain large, nearly spherical bubbles. A modified Rayleigh Plesset framework shows that viscous stresses suppress shape instabilities and delay symmetry breaking, whereas elastic stresses accelerate cavity deformation. Finite element simulations independently validate these findings. The Deborah number (De) further captures the competition between material relaxation and cavity growth, with higher De associated with predominantly elastic growth and lower De with greater relaxation. Together, our results establish viscous dissipation as a key stabilizing mechanism that governs bubble morphology and failure in soft materials. These results have direct implications for understanding cavitation-mediated damage in biological tissues, optimizing therapeutic ultrasound, and advancing mechanical characterization of hydrogels for engineering and food processing applications.

cond-mat.soft↗

arXiv2022

Crosslinks increase the elastic modulus and fracture toughness of gelatin hydrogels

Hydrogels have the ability to undergo large deformations and yet fail like brittle materials. The development of biocompatible hydrogels with high strength and toughness is an ongoing challenge in many applications. We crosslinked bovine gelatin using glutaraldehyde (control) and methylglyoxal (MGO) and assessed changes in their fracture toughness. Swelling experiments show ~710% retention of water in MGO hydrogels as compared to ~450% in control specimens. We used FTIR to identify the presence of chemical groups that may be involved in the crosslinking of gelatin gels. Scanning electron micrographs of lyophilized MGO hydrogels show large pores with plate-like intact walls that help retain water as compared to control specimens. Monotonic compression tests demonstrate nonlinear stress-strain behaviors for both hydrogel groups. MGO samples had 96% higher moduli as compared to control hydrogels that had moduli of 4.77+-0.73 kPa (n=4). A first order Ogden model fit the stress-strain data well as compared to Mooney-Rivlin and neo-Hookean models. We used cavitation rheology to quantify the maximum pressure for bubble failure in the hydrogels using blunt needles with inner radii of 75, 150, 230, and 320 μm respectively. Pressures inside the bubbles increased linearly with time and dropped sharply following a critical value. Bubbles in MGO gels were small and penny-shaped as compared to large spherical bubbles in control samples. We used the critical pressures to quantify the fracture energies of the hydrogels. MGO treatment increased the fracture energy by 187% from 13.09 J/m2 for control gels. Finally, we discuss the challenges in using the Ogden and Mooney-Rivlin models to compute the failure energy for gelatin hydrogels.

physics.bio-ph↗