Pinned Boundaries Delay Contraction and Shape Stress Relaxation in Active Gels
Researchers used reconstituted actomyosin gels with pinned boundary conditions to show that mechanical constraints delay contraction, produce intermittent dynamics, and generate nonuniform strain fields. The work mimics supracellular actomyosin networks found in tissues and embryos, filling a gap in prior studies that focused on freely contracting systems. The findings shed light on how boundary conditions and spatial heterogeneity govern stress regulation at cellular and tissue scales, with potential implications for soft materials and bioinspired robotics.
A new preprint posted to arXiv investigates how mechanical boundary constraints shape the behavior of active contractile gels made from actomyosin, the protein system that drives cell mechanics. By adhering gels transversely between two opposing surfaces — a configuration called pinned boundary conditions — the researchers found that stress builds up progressively, delaying contraction and producing intermittent, spatially nonuniform deformation. Stress is ultimately relieved through multiple pathways, including symmetric constriction driven by active stress and defect-driven events such as boundary detachment and internal rupture. The team developed a hydrodynamic model incorporating elastic, viscous, and active stress contributions that distinguishes stress-accumulation from stress-release phases and links variations in active stress to the observed intermittent dynamics. Numerical simulations reproduced the experimental behavior and revealed how internal energy is generated and dissipated during each phase. The results provide mechanistic insight into stress regulation in biological tissues and embryos, and the authors suggest the findings could inform the design of adaptive soft materials and bioinspired robotic systems.
What's missing
As a preprint, this work has not yet undergone peer review, so the validity of the hydrodynamic model and the generalizability of the reconstituted gel system to living cells remain to be independently assessed.
What different sources said
- arXiv physicsCenter
Pinned Boundaries Delay Contraction and Shape Stress Relaxation in Active Gels
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