Flexible and rapid generation of multiple concentration gradients for the protein nanoparticle synthesis

The effective control of concentration gradient of diffusible reactants is essential in chemical and biochemical processes, necessitating the flexible and rapid generation of concentration gradients for the subsequent analysis. Herein, A novel microfluidic concentration gradient generator, Circular Multi-Concentration Gradient Generator (CMCGG), is developed to create multiple concentration gradients simultaneously. This unique design features an expandable circular distribution channel for splitting external incoming fluid into distinct flow ratios, a radial channel for even splitting of internal incoming fluid, and multiple groove-patterned connecting S-channels for pairing and mixing the two split fluids, forming multiple concentration gradients. Through detailed numerical simulations and experimental characterizations, we have showed that the combination of stable flow distribution and rapid micromixing contributes significantly to creating multiple concentration. In addition, a decreased concentration gradient of variable mode can be easily obtained on demand by merely adjusting the incoming flow rates, providing guidelines for controlling the reactant concentration in the subsequent analysis. Furthermore, multi-size and highly monodisperse nanoparticles are successfully synthesized in one step, demonstrating the practicability in concentration-dependent nanoparticle crystallization. The presented concentration generator provides a highly efficient mixing and highly adaptable concentration platform, making it highly suitable for the chemical and biological analysis reliant on flexible concentrations.