Shear-Rolling Induced Unidirectional Alignment of Nanostructures in Block Copolymer Films for Quasi-Monograin Nanogyroid and Distortion-Free Stretchable Substrates

The ability to direct self-assembly of block copolymer (BCP) nanostructures into unidirectional or near-single-grain aligned configurations is crucial for practical optical and mechanical applications. In this study, we demonstrate a shear-rolling process capable of producing highly uniform and unidirectionally aligned sub-10 nm BCP nanostructures over a 4-inch-scale large area even on flexible substrates within 0.1 seconds at ultra-high temperatures of up to 280 °C.
Utilizing this method, we fabricated quasi-monograin gyroid thin films at a 4-inch scale through unidirectional alignment and solvent annealing for phase transformation. Structural analyses revealed preferential orientation with (111) planes parallel to the shear direction and (110) planes in the perpendicular direction, achieving monograin-level structures. Selective removal of the PDMS domain followed by gold electroplating enabled the creation of monograin gold gyroid films suitable for photonic crystals and metamaterials.
In addition to optical applications, we applied this shear-rolling process to address critical challenges in stretchable device substrates, particularly vertical contraction during stretching, which leads to image distortion. By aligning nanocylindrical structures in polystyrene-block-polyisobutylene-block-polystyrene thermoplastic elastomers, we achieved macroscopic mechanical anisotropy with a modulus ratio exceeding five times and a Poisson’s ratio below 0.07. This unprecedented reduction in vertical contraction ensures distortion-free deformation while maintaining high optical transmittance. The nanocylinders' size, being smaller than visible wavelengths, prevents optical haze or surface undulations, enabling transparent and monotonic stretchability.
This work bridges the gap between scalable nanostructure fabrication of BCPs and functional applications in optical and mechanical systems, offering a unified approach to creating quasi-monograin gyroid films and distortion-free stretchable substrates. These advancements unlock new possibilities of BCP nanostructure for roll-to-roll manufacturing of next-generation photonic and wearable devices.