Dynamic Creation of 3D Hydrogel Architectures via Selective Swelling Programmed by Interfacial Bonding

The
topological features of material surfaces are crucial to the
emergence of functions based on characteristic architectures. Among
them, the combination of surface architectures and soft materials,
which are highly deformable and flexible, has great potential as regards
developing functional materials toward providing/enhancing advanced
functions such as switchability and variability. Therefore, a simple
yet versatile method for creating three-dimensional (3D) architectures
based on soft materials is strongly required. In this study, hydrogels
are selected as the soft materials and hydrogel film/rigid substrate
layer composites are fabricated to obtain a 3D hydrogel architecture
based on swelling instability. When a hydrogel film weakly attached
to a rigid substrate is exposed to water, swelling-driven compressive
stress induces buckle-delamination of the film from the substrate.
Utilizing the chemical modification of a rigid substrate and a conventional
photolithography technique, the delamination location is successfully
controlled, resulting in a high-aspect-ratio folding architecture
at an arbitrary position. In addition, we systematically designed
the delamination geometry and chemically tuned the swelling ratio
of the hydrogel, leading to the discovery of several new morphology
transitions and relationships between the morphologies and the controllable
parameters. This work provides a new approach to fabricating highly
programmable 3D architectures of soft materials.