Fabrication of Large-Area, Crack-Free Inverse Opals on Microfluidic Chips via Wet Infiltration

Inverse opals (IOs) exhibit attractive optical properties and high interconnected porosity; however, the large-area fabrication of continuously ordered IOs remains challenging. This study presents a method for preparing crack-free IO hydrogel films using a microfluidic chip. Through a "wet infiltration" technique, the drying process of the template is eliminated, thereby avoiding dense cracks that result from particle shrinkage. The fabricated IO films achieve long-range order with lateral dimensions of 1 × 1.2 cm² and thicknesses of 1 mm, with thickness precisely controlled using the dimensions of the microfluidic chamber. The absence of a covering layer exposes the highly porous photonic structures on the surface of the film. Additionally, this preparation method adopts varying ratios of hydrogel precursors, making it suitable for various applications. This study represents a simple, cost-effective, and scalable approach for generating thick IO films suitable for diverse applications.