Polymeric nanoparticles (NPs) are increasingly sought after in various scientific and industrial areas, such as biomedical drug delivery,^1,2  cosmetics,^3,4  and interfacial property modifiers in enhanced oil recovery.⁵  This broad scope of applications is achieved through the versatility of NP material properties and structures. One promising pathway for generating such tailored NPs in large quantities is flash nanoprecipitation (FNP).⁶  Here, hydrophobic polymers in solution are rapidly mixed with a miscible aqueous antisolvent in a confined environment, inducing supersaturation and subsequent aggregation of the polymers. This technique stands out as a one-step continuous process that operates at room temperature, consumes little energy, and has the potential to scale up. Further, the FNP process allows for a wide range of feed materials, which in turn can be used to achieve various particle structures, including Janus, core–shell, patchy, and lamellar morphologies.