Hierarchically non-uniform structures determine the hydro-actuated bending deformation of camel hair

Nature uses efficient strategies to produce complex structures for hydration-induced reversible deformation. One such example is camel hair, a keratinous fiber with remarkable water-triggered shape memory. Herein, we unravel the effect of non-uniform structures on the shape memory of camel hair. By extraction and quantitative analysis of the deformation of camel hair, we describe that the shape memory of camel hair is a bending mode instead of shrinking along the long fiber axis. The shape memory process is based on anisotropic swelling, caused by the non-uniform distribution of disulfide bonds and the non-uniform thickness of the cortex layer along the cross-section. This natural actuation structure inspires the design of complex shape-memory materials with simple simulation strategies and has better biocompatibility to meet the requirements of biological applications. [Display omitted] •Shape memory of camel hair follows a bending mode instead of supercontraction•Camel hair features non-uniform structures at both molecular and nanofibrillar scale•The non-uniform structures of camel hair are important in its hygroscopic movements Due to the non-uniform distribution of disulfide bonds and the non-uniform thickness of the cortex layer, the anisotropic swelling of the cortex layer causes bending of the hair in humidity. Inspired by this natural actuation structure, Zhang et al. design complex shape-memory materials with good biocompatibility via simple simulation strategies.