Shear flow induced long-range ordering of rod-like viral nanoparticles within hydrogel

Controlling the alignment of anisotropic nanoparticles within a three-dimensional (3D) environment over large-scale is still a challenge. In this paper, a facile method to align rod-like nanoparticles in hydrogel via shear flow to afford a long-range order is reported. The rod-like tobacco mosaic virus (TMV) was employed as a prototypical anisotropic particles in the study, and the shear force provided by the unidirectional flow of the precursor solution direct the alignment of TMVs, which could be quickly fixed through the fast sol-gel transition in situ. The degree of orientation and the distance between the TMV particles could be regulated by adjusting the concentration of hydrogels and TMVs. While the introduction of TMVs could reduce the degree of swelling of the hydrogel and help maintaining the mechanical strength of resultant hydrogels, both repulsion interaction and shear flow contributed synergistically to the assembly. This method does not require the usage of strong magnetic or electric fields, nor does it require the use of specialized lithography, thus offers a facile way to the fabrication of hydrogel materials with control of anisotropic structural features.