  Shape-morphing networks of mesoscale filaments are a common hierarchical
feature in biology and hold significant potential for a range of technological
applications, from micro-muscles to shape-morphing optical devices. Here, we
demonstrate both experimentally and computationally that the shape-morphing of
highly-ordered 2D networks constructed of thermoresponsive mesoscale polymeric
fibers strongly depends on the physical attributes of the single fiber, in
particular on its diameter, as well as on the network's density. We show that
based on these parameters, such fiber-networks exhibit one of two thermally
driven morphing behaviors: (i) the fibers stay straight, and the network
preserves its ordered morphology, exhibiting a bulk-like behavior; or (ii) the
fibers buckle and the network becomes messy and highly disordered. Notably, in
both cases, the networks display memory and regain their original ordered
morphology upon shrinking. This hierarchical principle, demonstrated here on a
range of networks, offers a new way for controlling the shape morphing of
materials with mesoscale resolutions and elucidates that minute changes in the
mesoscale structural attributes can translate to a dramatic change in the
morphing behaviors at the macroscale.
