Fouling in microstructured devices: a review

Microstructured devices are widely used for manufacturing products that benefit from process intensification, with pharmaceutical products or specialties of the chemical industry being prime examples. These devices are ideally used for processing pure fluids. Where particulate or non-pure flows are involved, processes are treated with utmost caution since related fouling and blocking issues present the greatest barrier to operating microstructured devices effectively. Micro process engineering is a relatively new research field and there is limited understanding of fouling in these dimensions and its underlying processes and phenomena. A comprehensive review on fouling in microstructured devices would be helpful in this regard, but is currently lacking. This paper attempts to review recent developments of fouling in micro dimensions for all fouling categories (crystallization, particulate, chemical reaction, corrosion and biological growth fouling) and the sequential events involved (initiation, transport, attachment, removal and aging). Compared to fouling in macro dimensions, an additional sixth category is suggested: clogging by gas bubbles. Most of the reviewed papers present very specific fouling investigations making it difficult to derive general rules and parameter dependencies, and comparative or critical considerations of the studies were difficult. We therefore used a statistical approach to evaluate the research in the field of fouling in microchannels.