Nanoscale diameter control of sensory polydiacetylene nanoparticles on microfluidic chip for enhanced fluorescence signal

Abstract

Owing to its stimulus-induced fluorescence 'turn-on' feature, polydiacetylene (PDA) has been actively investigated as a label-free sensor matrix. Fabrication of monodisperse PDA particles is important for the efficiency of microarray or microfluidic-based PDA sensor chips. Conventional bulk methods inevitably produce polydisperse mixtures of PDA nanoparticles. Herein we report the synthesis of size-controlled PDA nanoparticles on a microfluidic chip using a staggered herringbone micromixer (SHM), a well-known chaotic mixer. PDA particles of diameters ranging from 36 to 84 nm were readily prepared by adjusting the flow conditions. In addition, use of the SHM method remarkably increased the productivity of the PDA nanoparticles, by about 40 times relative to PDA nanoparticles prepared by means of a hydrodynamic focusing method. The fluorescence intensity of the PDA nanoparticles was found to be dependent upon their size distribution, and a microfluidic channel containing smaller PDA particles was found to emit stronger fluorescence than one containing larger PDA particles.