A microfluidic concentration-gradient droplet array generator for the production of multi-color nanoparticles

A microfluidic concentration-gradient droplet array generator (CDrAG) with parallel multi-channels and multi-layers was developed with 64 outlet channels producing 33 droplet gradient concentrations. A droplet production rate of 5 × 10⁴ min⁻¹ was obtained, and the RSD value of droplet diameters in 64 groups is 5.5% (n = 64). Using the concentration gradient droplet array as parallel microreactors, 33 Au/Ag ratio nanoparticles were synthesized. The absorption spectra of the Au/Ag nanoparticles shifted from the spectrum of pure gold to one of pure silver. This demonstrates the CDrAG platform's promising potential to produce specific nanoparticle barcodes for high-throughput screening in chemistry, biology and a broad range of life science applications.