Preprogrammed microfluidic system for parallel anti-reflection coating by layer-by-layer assembly

Layer-by-layer (LbL) assembly is a widely used method of nanofilm coating in various technology applications; however, the coating process is typically time-consuming and labor-intensive. This study presents a microfluidic platform that performs LbL assembly in a fast, parallel, preprogrammed manner, with only water-head pressure as the driving force. The platform generates periodic sequential outflows with four solutions (TiO2 and SiO2 nanoparticle solutions and two washing solutions), and simultaneously applies 12 different conditions of coating period (0.6-4 min) and shear stress (0.7-15 dyn cm(-2)) for anti-reflection coating in the visual spectrum. The thickness and roughness of the coated films are well regulated at the nanoscale using shear stress, coating period, and the number of bilayers. In this way, our study reveals the substantial influence of shear stress on the relative composition of the nanoparticles and void volume in the films, thereby varying the film transmittance with a maximum value of 98%. Compared to the conventional immersive coating method, the coating duration of our method was 15 times faster. This parallel coating method is highly effective for determining optimized coating conditions.

Automated summary

This study introduced a microfluidic platform for fast and parallel Layer-by-Layer assembly, demonstrating the significant impact of shear stress on the thickness and transmittance of coated films. The platform allows for efficient determination of optimized coating conditions, with coating duration 15 times faster than conventional methods.