Microfluidic synthesis of metal oxide nanoparticles: process control, product quality, and clogging mitigation–a systematic review

Metal oxide nanoparticles are essential functional materials for environmental, energy storage, catalytic and sensing applications. Conventional synthesis lacks control over nucleation and growth leading to broad particle size and - poor reproducibility. Microfluidic platforms offers regulation of flow behavior improving control over the material properties. This systematic review summarizes recent studies on microfluidic synthesis of Metal oxide nanoparticles with emphasizing control, quality, and clogging prevention during continuous operating conditions under long term reactor operation. Peer reviewed articles from the last decade were considered,80 studies were retained for qualitative synthesis. The review shows that microreactors enable effective control of mixing time, residence time, temperature, and precursor concentration.Compared to traditional synthesis methods, microfluidic techniques offer superior crystallinity, control over particle morphology and improved reproducibility. However, channel clogging, nanoparticle deposition remain major challenges at high concentrations and long operation. Surface functionalisation, segmented flow, periodic flow reversal, ultrasonic assistance, use of stabilisers, chelating agents as mitigation techniques are discussed. Microfluidic synthesis show link between reactor geometry, operating parameters, product quality. The review evaluates methods for clogging control. This review provides a framework for designing and developing microfluidic platforms for high quality metal oxide nanomaterials synthesis.