Anomalous normal stresses in biopolymer networks with compliant cross-links
School of Engineering, Brown University - Providence, RI 02912, USA and Intel Corporation - Chandler, AZ 85226, USA
Received: 2 December 2013
Accepted: 31 January 2014
Cross-linked biopolymer filament networks that constitute the cytoskeleton in living cells show rich mechanical response including large strain stiffening and negative normal stresses. Here, we have studied these phenomena in the case where the cross-links act as flexible worm-like chain springs. We find that in contrast to the well-studied case of sparse networks with rigid cross-links that display negative normal stresses when subject to shear loading, flexible cross-links give rise to positive normal stresses during early stages of deformation. With increased loading, we observe a transition where the normal stresses become negative. In this regime, the ratio of the normal stresses to the shear stress is found to increase with increase in the density of cross-links, in distinct contrast to the behavior observed for rigid cross-links. We show that these anomalous properties can be understood by considering the way in which the applied load is shared by the extension of the cross-links and the bending and stretching of the filaments.
PACS: 87.10.Kn – Finite element calculations / 87.16.Ln – Cytoskeleton / 87.16.Ka – Filaments, microtubules, their networks, and supramolecular assemblies
© EPLA, 2014