High throughput synthesis of uniform biocompatible polymer beads with high quantum dot loading using microfluidic jet-mode breakup.

Uniform polymer microbeads with highly loaded quantum dots (QDs) are produced using high-throughput coherent jet breakup of a biocompatible poly(ethylene glycol) diacrylate (PEGDA) prepolymer resin, followed by in-line photopolymerization. A spiraling and gradually widening channel enables maximum absorption of radiated UV light for the in-line photopolymerization without coalescence and clogging issues. Although the dripping mode in general provides superior uniformity to the jet mode, our nozzle design with tapered geometry brings controlled jet breakup leading to 3% of uniform particle size distribution, comparable to dripping-mode performance. We achieve a maximum production rate of 2.32 kHz, 38 times faster than the dripping mode, at a same polymer flow rate. In addition, the jet-mode scheme provides better versatility with 3 times wider range of size control as well as the compatibility with viscous fluids that could cause pressure buildup in the microsystem. As a demonstration, a QD-doped prepolymer resin is introduced to create uniform biocompatible polymer beads with 10 wt % CdSe/ZnSe QD loading. In spite of this high loading, the resulting polymer beads exhibits narrow bandwidth of 28 nm to be used for the ultrasensitive bioimaging, optical coding, and sensing sufficiently with single bead.