From microchannels to high shear reactors: process intensification strategies for controlled nanomaterial synthesis

Nanomaterials (NMs) have catalyzed transformative advancements across diverse technological domains owing to their exceptional size-dependent mechanical, optical, electronic, and chemical properties. However, the scalable and controllable synthesis of NMs remains a major challenge due to the complex interplay of nucleation and growth processes, which are highly sensitive to mixing, mass transfer, and heat transfer dynamics. In this context, process intensification (PI) strategies-originally developed in chemical engineering-have emerged as a powerful approach to overcome the inherent limitations of traditional batch synthesis. This review comprehensively analyzed seven representative PI reactors: microreactors, confined impinging jet reactors, rotating packed beds, high shear mixers, spinning disk reactors, ultrasonic reactors, and microwave reactors. We systematically examine their operating principles, enhancement mechanisms, advantages, and limitations in the context of NM synthesis. Furthermore, their applications in key areas such as biomedicine, adsorption, catalysis, coatings, optics, and electrochemistry are critically reviewed. Through comparative analysis and synthesis-structure-function correlation, this review aims to provide essential guidance for the rational selection and engineering of PI reactors toward controllable, sustainable, and high-throughput NM manufacturing, thereby advancing the frontiers of precision nanotechnology.