3D Turing nanowrinkles via anisotropic photopolymerization

Inspired by the diverse wrinkled surface patterns in nature, micro-nano scale wrinkled surfaces have become an essential part of materials science. Nowadays, it is still a challenge to flexibly fabricate three-dimensional (3D) nanowrinkled structures with precise configuration. Herein, we introduce a reaction-diffusion-based self-organized Turing mechanism integrated with femtosecond laser direct writing (FsLDW) to achieve controlled anisotropic photopolymerization, fabricating 3D hydrogel-based biomimetic Turing nanowrinkled structures. This approach enables precise spatial modulation of wrinkle periodicity, orientation, and amplitude. Furthermore, using methacrylated hyaluronic acid (MeHA) monomers, we elucidate the mechanistic interplay between anisotropic photopolymerization and Turing-patterned nanowrinkle formation. We further propose a theoretical framework—the polarization modulation of femtosecond laser pulses enables the anisotropic photopolymerization of Turing-patterned nanowrinkles, selectively generating aligned linear (Turing-line) and vertically ordered pillar (Turing-column) structures. According to this theoretical framework, we propose the concept of the nanowrinkle parameter (Wr), alongside an empirical formula derived from two-photon polymerization (TPP) fabrication parameters to predict Turing nanowrinkle emergence conditions. We also demonstrate the ability to create high-resolution, 3D nanowrinkled structures, including patterned structures, bio-inspired microvilli resembling those of the small intestine, cicada wing replicas, and moth-eye structures. Moreover, we functionalize Turing-patterned structures with magnetron-sputtered Ag coatings, creating micro/nano-devices for molecular surface enhanced Raman scattering (SERS) detection. The Turing-inspired SERS devices demonstrate ultra-trace detection capability for Rhodamine 6G (R6G) at concentrations as low as 10⁻⁹ M. This work provides a novel, high-precision methodology for the fabrication of complex, bionic, free-form Turing nanowrinkled structures.