Bioinspired structural hydrogels with highly ordered hierarchical orientations by flow-induced alignment of nanofibrils

Natural structural materials often possess unique combinations of strength and toughness resulting from their complex hierarchical assembly across multiple length scales. However, engineering such well-ordered structures in synthetic materials via a universal and scalable manner still poses a grand challenge. Herein, a simple yet versatile approach is proposed to design hierarchically structured hydrogels by flow-induced alignment of nanofibrils, without high time/energy consumption or cumbersome postprocessing. Highly aligned fibrous configuration and structural densification are successfully achieved in anisotropic hydrogels under ambient conditions, resulting in desired mechanical properties and damage-tolerant architectures, for example, strength of 14 ± 1 MPa, toughness of 154 ± 13 MJ m⁻³, and fracture energy of 153 ± 8 kJ m⁻². Moreover, a hydrogel mesoporous framework can deliver ultra-fast and unidirectional water transport (maximum speed at 65.75 mm s⁻¹), highlighting its potential for water purification. This scalable fabrication explores a promising strategy for developing bioinspired structural hydrogels, facilitating their practical applications in biomedical and engineering fields.