Sifan Yin | Searcharxiv

arXiv2026

Elastohydrodynamic instability of a spinning elastic disk

A soft thin elastic disk spinning in a viscous fluid experiences centrifugal tension generated by rotation together with viscous shear generated by the surrounding flow. While the former stabilizes the flat state, the latter can destabilize it. We combine the linearized F\"{o}ppl-von K\'{a}rm\'{a}n equations for a rotating elastic disk with the shear stresses arising from the classical von K\'{a}rm\'{a}n swirling flow to derive an elastohydrodynamic stability problem. Linear stability analysis identifies the onset of buckling in terms of two dimensionless control parameters measuring centrifugal stiffening and fluid-induced shear. Above threshold the disk buckles into azimuthally periodic saddle-like modes whose wavenumber increases with increasing rotational tension. The buckled configuration also supports retrograde traveling waves that rotate more slowly than the material frame. These results identify a simple mechanism whereby fluid shear destabilizes rotating elastic structures.

physics.flu-dyn↗

arXiv2022

Contractility-induced phase separation in active solids

A combination of cellular contractility and active phase separation in cell-matrix composites is thought to be an enabler of spatiotemporal patterning in multicellular tissues across scales, from somitogenesis to cartilage condensation. To characterize these phenomena, we provide a general theory that incorporates active cellular contractility into the classical Cahn--Hilliard-Larch{é} model for phase separation in passive viscoelastic solids. We investigate the dynamics of phase separation in this model and show how a homogeneous mixture can be destabilized by activity via either a pitchfork or Hopf bifurcation, resulting in stable phase separation and/or traveling waves. Numerical simulations of the full equations allow us to track the evolution of the resulting self-organized patterns, in both periodic and mechanically constrained domains, and in different geometries. Altogether, our study underscores the importance of integrating both cellular activity and mechanical phase separation in understanding patterning in soft, active biosolids, and might explain previous experimental observations of cartilage condensation in both in-vivo and in-vitro settings.

cond-mat.soft↗