Kidney-inspired anti-fouling strategies for membrane-based water filtration.
Doctoral thesis (Ph.D), UCL (University College London).
Access restricted to UCL open access staff until 1 December 2023.
Membrane technologies possess inherent advantages over other separation techniques as no phase change is needed, saving energy. However, fouling is a ubiquitous problem faced by membranes, which limits their life span and increases their operating costs.
Nature is increasingly turned to as a source of inspiration for problems faced by society. The adaptations of natural systems provide a platform for engineering to base solutions on to its own problems. One such problem is membrane fouling, which can be alleviated through the use of inspiration from the kidney. The kidney was chosen for this work as it can produce 140 L of primary urine filtered from the blood stream daily without degradation. The endothelial surface layer present in the lumen of the glomerular blood vessels was determined as a dominant factor in its anti-fouling property.
The inspiration from the glomerulus was taken methodologically by first determining the importance of physicochemical properties before moving up in scale to physical properties. Based on the conceptual lessons learnt at these scales, adaptations were made to create antimicrobial surfaces.
Modification with oligomers and polymer brushes allowed for a reduction of fouling propensity by combining different energetic and entropic barriers. Hydrophilic and charged oligomers were shown to resist adsorption of lysozyme by 79%. Hydrophilic, negatively charged dense polyacrylic acid brushes resisted 95% of the bovine serum
albumin (BSA) present in the feed. Furthermore, the immobilisation of gold nanoclusters within the polymer brush allowed for the stable integration of antimicrobial properties with a reduction of 99.997% and 99.989% of E. coli and S. aureus colony forming units (CFU), respectively, within just one hour.
The research presented herein provides a platform to improve anti-fouling properties of membranes, and more general surfaces. Additionally, integrating inspiration from the kidney at larger scales could further advance this technology.
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