Biomaterials are characterized by hierarchical order that spans angstroms to meters to impart properties essential for organism survival. Among these, aligned bundles of mesoscale fibrils, with cross-sectional dimensions of 10-7-10-4 meters, are ubiquitous. Yet, despite striking natural examples, few synthetic analogues exist due to fabrication challenges at the mesoscale. Specifically, mesoscale components are too large to sample the energy landscape via thermal motion, precluding spontaneous assembly pathways like crystallization, but too small for macroscale strategies like textile spinning. In this work, we describe a novel fabrication paradigm, termed a “photocrease,” that offers spatiotemporal shape change of mesoscale polymer (MSP) ribbons from distinct, unentangled filaments into topologically linked bundles. This vision is realized by synthesizing novel copolymers with pendent near-UV-active photoacid generators, printing them from solution to form substrate-bound MSPs, then embedding photomask-defined microscale domains (photocreases) that guide local MSP curvature and twist upon application of a stimulus. When prepared at regular intervals and a uniform tilt angle φ with respect to the MSP long axis, photocreases drive MSP deformation into helices of tunable radius, pitch, and chirality, all with UV dose-dependent coiling kinetics. When printed in close proximity (i.e., spacing d ≤ 100 μm), MSPs entangle as they coil to afford collectively twisted bundles. Notably, the pitch and radius of bundled MSPs exceed those of un-bundled helices up to 4-6-fold, suggesting a compressive stress that reinforces the aggregate structure. Moreover, bundles exhibit a high degree of topological linking, exceeding 270 pairwise links in a 500 μm segment of a 10-MSP bundle; mechanical resilience is confirmed by repeated agitation and deformation in solution without visible deterioration. At the individual scale, the photocrease platform offers spatiotemporal programming of local radius and curvature, offering a route to designer 3-dimensional shapes from 1-dimensional mesoscale filaments. At the scale of collective structures and bundles, photocreases offer a path to programmed self-spinning of mesoscale filaments that are expected to underpin a new generation of meso-to-macroscale bioinspired assemblies.

Programmed self-spinning of mesoscale polymer filaments

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.