Abstract
Photoinduced shape morphing has implications in fields ranging from soft robotics to biomedical devices. Despite considerable effort in this area, it remains a challenge to design materials that can be both rapidly deployed and reconfigured into multiple different three-dimensional forms, particularly in aqueous environments. In this work, we present a simple method to program and rewrite spatial variations in swelling and, therefore, Gaussian curvature in thin sheets of hydrogels using photoswitchable supramolecular complexation of azobenzene pendent groups with dissolved α-cyclodextrin. We show that the extent of swelling can be programmed via the proportion of azobenzene isomers, with a 60% decrease in areal swelling from the all trans to the predominantly cis state near room temperature. The use of thin gel sheets provides fast response times in the range of a few tens of seconds, while the shape change is persistent in the absence of light thanks to the slow rate of thermal cis–trans isomerization. Finally, we demonstrate that a single gel sheet can be programmed with a first swelling pattern via spatially defined illumination with ultraviolet light, then erased with white light, and finally redeployed with a different swelling pattern.
Highlights
In this work, we present a simple method to program and rewrite spatial variations in swelling and, Gaussian curvature in thin sheets of hydrogels using photoswitchable supramolecular complexation of azobenzene pendent groups with dissolved α-cyclodextrin
By introducing inhomogeneous in-plane swelling profiles, thin gel sheets can be programmed to buckle into shapes with essentially arbitrary distributions of Gaussian curvature, providing great flexibility for the design of targeted three-dimensional (3D) shapes.[3−5] the majority of work to date has focused on transformation through closely related families of shapes that are permanently programmed into the material through variations in cross-link density,[6−10] alignment of anisotropic inclusions,[11,12] or the presence of nonswelling components,[13,14] and it remains a challenge to rationally design stimuli-responsive hydrogel platforms that are amenable to adopting multiple distinct 3D configurations.[15,16]
The most promising approach to date has relied on spiropyran derivatives, where photoreversible ringopening and -closing reactions drive large changes in hydrophilicity and swelling.[29−32] realization of robust photochemical responses has been complicated by narrow pH operational ranges and photoswitching fatigue in these systems
Summary
We present a simple method to program and rewrite spatial variations in swelling and, Gaussian curvature in thin sheets of hydrogels using photoswitchable supramolecular complexation of azobenzene pendent groups with dissolved α-cyclodextrin.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
