Microfluidic printing directing photonic crystal bead 2D code patterns

We herein report a new method for the rapid preparation of photonic crystal patterns through microfluidic printing technology where the photonic crystal pixels of the patterns can be accurately manipulated. Poly(styrene-methyl methacrylate-acrylic acid)-generation 2 polyamidoamine-CdTe/ZnS (P(St-MMA-AA)-G2 PAMAM-CdTe/ZnS) hybrid microspheres were prepared by conjugating P(St-MMA-AA) and CdTe/ZnS quantum dots (QDs) with G2 PAMAM dendrimers as bridges through in situ reaction. Strong interactions between dendrimer-modified microspheres significantly reduce the cracking of photonic crystal films and the formation of coffee-ring pixels. In addition, taking advantage of a microfluidic printing device, we fabricated a fluorescent two-dimensional (2D) code pattern of photonic crystal (PC) beads by using the as-synthesized P(St-MMA-AA)-G2 PAMAM-CdTe/ZnS hybrid microspheres. This work developed a new microfluidic printing technology for the fabrication of multi-signal 2D code patterns with structural colors in daylight and fluorescence under UV light, which may have potential applications in the anti-counterfeiting and optoelectronic fields.