4D Printing of Seed Capsule-Inspired Hygro-Responsive Structures via Liquid Crystal Templating-Assisted Vat Photopolymerization

The creatures in nature exhibit dynamic responses to environmental stimuli through their hierarchical architectures. Benefiting from gradient porous structures, Delosperma nakurense opens its protective valves of the seed capsules when hydrated with liquid water, increasing the likelihood that seeds are dispersed under conditions favorable to germination. Here, a versatile 4D printing technology, namely liquid crystal templating-assisted vat photopolymerization (LCT-VPP), which can fabricate bioinspired porous structures with hygro-responsive capabilities by utilizing photopolymerization induced phase separation (PIPS) and liquid crystals (LCs) electro-alignment is reported. PIPS within the LCs/nanofiller composites leads to the formation of submicrometer gradient porous structures after extracting nonreactive LCs. The electric field enables the programmable alignment of LCs, which in turn elongates the porous structures and aligns nanofillers. In addition, the programmable arranged nanofillers by the templated LCs enhance the degree of deformation and thus the resulting composites exhibit high shape control accuracy, fast dynamic response, and high reliability. This study opens a perspective for designing bioinspired smart materials with the special spatial distribution of porous structures. The results reported here can give rise to various potential applications in soft robots, smart anticounterfeiting devices, flexible sensors, and ultrafiltration membrane.