Fiber networks amplify active stress

TLDR

Living organisms generate forces to move, change shape, and maintain internal functions, typically produced by molecular motors embedded in fiber networks. The study demonstrates that the surrounding fiber network, not just motors, plays a central role in biological force generation. Fiber networks amplify stresses, converting small extensile forces into large‑scale contraction, and this behavior is quantitatively explained by the authors' theory, matching experimental measurements.

Abstract

Significance Living organisms generate forces to move, change shape, and maintain their internal functions. These forces are typically produced by molecular motors embedded in networks of fibers. Although these motors are traditionally regarded as the defining elements of biological force generation, here we show that the surrounding network also plays a central role in this process. Indeed, rather than merely propagating forces like a simple elastic medium, fiber networks produce emergent, dramatically amplified stresses and can go so far as reversing small-scale extensile forces into large-scale contraction. Our theory quantitatively accounts for experimental measurements of contraction.