Tuning Synthetic Semiflexible Networks by Bending Stiffness

TL;DR

This study introduces tunable DNA nanotube networks to explore the mechanics of semiflexible polymers, validating key properties and revealing new scaling behaviors that challenge existing theories.

Contribution

It provides the first experimental characterization of persistence length in synthetic semiflexible networks, enabling validation of theoretical models and revealing unexpected scaling relations.

Findings

Persistence length scales with elastic modulus as G_0 ∝ l_p.

Elastic modulus scales with concentration as G_0 ∝ c^{7/5}.

DNA nanotube networks validate key semiflexible polymer properties.

Abstract

The mechanics of complex soft matter often cannot be understood in the classical physical frame of flexible polymers or rigid rods. The underlying constituents are semiflexible polymers, whose finite bending stiffness ($\kappa$) leads to non-trivial mechanical responses. A natural model for such polymers is the protein actin. Experimental studies of actin networks, however, are limited since the persistence length ($l_{\text{p}} \propto \kappa$) cannot be tuned. Here, we experimentally characterize this parameter for the first time in entangled networks formed by synthetically produced, structurally tunable DNA nanotubes. This material enabled the validation of characteristics inherent to semiflexible polymers and networks thereof, i.e., persistence length, inextensibility, reptation and mesh size scaling. While the scaling of the elastic plateau modulus with concentration $G_0 \propto c^{7/5}$ is consistent with previous measurements and established theories, the emerging persistence length scaling $G_0 \propto l_{\text{p}}$ opposes predominant theoretical predictions.