  Wrought by nature's wondrous hand, surface topographies are discovered on all
length scales in living creatures and serve a variety of functions. Inspired by
floral striations, here we developed a scalable means of fabricating
custom-tailored photonic cellulose films that contained both cholesteric
organization and microscopic wrinkly surface topography. Free-standing films
were prepared by molding cellulose nanocrystal ink onto an oriented wrinkled
template through evaporation-assisted nanoimprinting lithography, yielding
morphology-induced light scattering at a short wavelength as well as optically
tunable structural color derived from the helical cellulose matrix. As a
result, the interplay between the two photonic structures, grating-like surface
and chiral bulk, led to selective scattering of circularly polarized light with
specific handedness. Moreover, the wrinkled surface relief on cholesteric
cellulose films could be precisely controlled, enabling engineered printing of
microscopic patterned images.
