  Single-filament tracing has been a valuable tool to directly determine
geometrical and mechanical properties of entangled polymer networks. However,
systematically verifying how the stiffness of the tracer filament or its
molecular interactions with the surrounding network impacts the measurement of
these parameters has not been possible with the established experimental
systems. Here, we use mechanically programmable DNA nanotubes embedded in
crosslinked and entangled F-actin networks, as well as in synthetic DNA
networks, in order to measure fundamental, structural network properties like
tube width and mesh size with respect to the stiffness of the tracers. While we
confirm some predictions derived from models based purely on steric
interactions, our results indicate that these models should be expanded to
account for additional inter-filament interactions, thus describing the
behavior of real polymer networks.
