Printing Flowers? Custom-Tailored Photonic Cellulose Films with Engineered Surface Topography

Abstract

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.

Flower Inspiration: Broad‐Angle Structural Color through Tunable Hierarchical Wrinkles in Thin Film Multilayers

“…Wrinkling, through the growth of cuticle on bulged epidermal cells, [25] gives rise to the tunability of hierarchical structures that control the broad angle spectrum of structural color in different regions. Recent examples in the literature [26][27][28][29][30][31] provide some of these attributes. For example, a bio-inspired structure resembling Queen of the Night tulip petals, formed by wrinkling a film containing a pre-etched nano-grating, mimicked the flower's iridescent effect of this flower and the angle broadening of diffraction.…”

When nanocellulose meets diffraction grating: freestanding photonic paper with programmable optical coupling

“…39,40 In the end, this deformed helical ordering will be preserved as a solid film, with the distance and amplitude of these grating lines imprinted and determined by the PDMS template. 35 In the chiral nematic film, the position of its photonic bandgap is optically tunable from UV-blue to visible regions by tuning the helical pitch. 20 By changing the CNC-PVA composition in its initial ink, we can easily manipulate the helix derived photonic band-gap in CNPF.…”

“… 39 , 40 In the end, this deformed helical ordering will be preserved as a solid film, with the distance and amplitude of these grating lines imprinted and determined by the PDMS template. 35 …”

“…After drying, these films are peeled off from the template with highly ordered grating lines imprinted onto the lower surface of the films, showing precisely controlled microstructures not only with a surface morphology but also with a bulk phase with deformed helical organization. 35 In particular, we describe that tuning the composition of initial CNC ink can be used to manipulate the photonic band-gap in the helical matrix which couples with diffraction derived from surface grating lines, showing programmable photonic-photonic colour mixing in reflection mode and affecting the diffuse appearance of the dual photonic paper. These bio-inspired films offer a convenient opportunity for the production of coupled photonic structures with complex polarization control, which may be of value in advanced optical devices.…”

Molecular‐Scale Design of Cellulose‐Based Functional Materials for Flexible Electronic Devices

“…Within plant cell walls, cellulose microfibers are packed in parallel with each other, and they can be directly used to prepare cellulose materials with applications in wastewater treatment, solar-steam-assisted desalination, energy storage systems, and intelligent electronics. [41][42][43] Simple pretreatments, such as diluted acid prehydrolysis, conventional organic acid swelling, deep-eutectic solvent fractionation, or enzyme-assisted hydrolysis, can depolymerize and dissolve lignin and hemicellulose, resulting in white microfibril bundles that comprise abundant elementary fibrils (Figure 1a). Due to the d-glucose repeat units linked via covalent bonds (Figure 1a), cellulose macromolecular chains have abundant hydroxyl groups (-OH) that can form strong inter-and intramolecular hydrogen-bond networks.…”