Simulation-guided design of a 3D flow focusing chip for the uniform production of polymer dots.

Semiconducting polymer dots (Pdots) are fluorescent conjugated polymer nanoparticles that exhibit high photoluminescence and biocompatibility, making them promising for high photoluminescence and biocompatibility, giving them high potential in biomedical applications such as bioimaging, drug delivery, and phototherapy. Accordingly, the size of the Pdots has become a critical factor in determining their bioavailability, biodistribution, and clearance. Towards this goal, microfluidic technologies have gained attention for the precise control of their size. However, the limitations of conventional glass capillary systems still inhibit the production of uniform and small nanoparticles. Here, computational fluid dynamics (CFD) simulations were used to guide the design of a 3D printed master for the fabrication of a solvent resistant 3D flow focusing microfluidic chip. Compared to glass capillary microfluidics, the developed chip offers more flexibility towards optimization of the design. Small and homogeneous Pdots (<50 nm) from commercially available MEH-PPV, CN-PPV, F8BT, and custom synthesized Pttc-4O-TTQ were produced. Large red shifts in the emission spectra of some Pdots suggest an efficient and tight packing of the polymers within the particles. Coprecipitation of the polymers with chitosan or PMSA enhanced their cell uptake, with complete cell uptake achieved in less than an hour in some cases. Furthermore, the spectral properties of both aggregation-induced quenching-prone and aggregation-induced emission-prone Pdots were observed, highlighting the chip's flexibility with different types of Pdots. The 3D flow focusing chip offers an accessible and cost-effective alternative to traditional microfluidic systems for the production of smaller Pdots.