Scalable Nacre-Like Photonic Paper with Enhanced Mechanical Stability for Rewritable Printing

Hydrochromic photonic paper is a promising substitution for traditional paper due to its eco-friendly coloration technique and potential compatibility with inkjet printing. However, it is highly desired yet very challenging to fabricate photonic paper with robust mechanical stability in a scalable manner for commercial popularity. Inspired by nacre, a scalable photonic paper is fabricated with a highly aligned "brick-and-mortar" architecture via roll-to-roll-assisted blade-coating. This hierarchical architecture is constructed by high-content (≈50 wt.%), low-aspect-ratio (≈33.2) α-zirconium phosphate nanoplates bonded to poly(acrylamide-co-diacetone acrylamide) via interfacial hydrogen-bonds. The resultant photonic paper features a near-equal "brick-mortar" ratio, effectively balancing the conflict between high strength (≈24.2 MPa), toughness (≈13.1 MJ m^{- 3}), and structural color. Therefore, it demonstrates high-contrast multicolor output and spatiotemporal color evolution through hygroscopic salt ink self-sustaining layer spacing. Importantly, the robust mechanical stability supports over 100 cycles of high-resolution rewritable printing using commercial printers, along with proof-of-concept demonstrations of Braille printing and erasure. Moreover, the hierarchical nanoplates endow the photonic paper with excellent flame retardancy, meeting higher storage safety requirements. This work presents an enlightening biomimetic design to integrate scalable assembly, structural color, and mechanical enhancement in photonic paper via low-aspect ratio nanoplates, offering a promising platform for the sustainable paper industry.