Multifunctional photonic crystal barcodes from microfluidics

Barcode particles have a demonstrated value for multiplexed high-throughput bioassays. Attempts to develop this technology tend to focus on the generation of featured barcodes both with a large number of identifications to increase the throughput and with novel functions to improve the assays. Here, we report a new class of barcodes that are composed of multiple photonic crystal or magnetic-tagged ethoxylated trimethylolpropane triacrylate (ETPTA) cores and polyethylene glycol (PEG) hydrogel shells. These barcodes are prepared by polymerizing microfluidic multiple double emulsions. As the photonic crystal cores possess distinct reflection peaks, our barcodes allow for a substantial number of coding levels for multiplexing applications. The hydrogel shells surrounding the barcodes enable the creation of three-dimensional scaffolds for immobilizing probes. Moreover, the presence of magnetism in the barcodes confers their controllable movement under magnetic fields, which can be used to significantly increase the sensitivity of the bioassays and to simplify the processing. These features make photonic crystal barcodes ideal for biomedical applications. NPG Asia Materials (2012) 4, e25; doi:10.1038/am.2012.46; published online 7 September 2012