Hollow Colloid Assembled Photonic Crystal Clusters as Suspension Barcodes for Multiplex Bioassays.

Barcode particles have a demonstrated value for multiplexed high-throughput bioassays. Here, a novel photonic crystal (PhC) barcode is presented that consists of hollow colloidal nanospheres assembled through microfluidic droplet templates. Due to their gas-filled core, the resultant barcode particles not only show increased refractive index contrast, but also remain in suspension by adjusting the overall density of the PhC to match that of a detection solution. In addition, magnetic nanoparticles can be integrated to give the barcodes a magnetically controllable motion ability. The encoding ability of the barcodes is demonstrated in microRNA detection with high specificity and sensitivity, and the excellent features of the barcodes make them potentially very useful for biomedical applications.