(135e) Evaluating the Effectiveness of Microscale Herringbone Patterns for Reducing Protein Fouling on Ultrafiltration Membranes

Membrane biofouling occurs when biomass deposits on a membrane surface or within its pores. Accumulation of biofoulants such as proteins increases the mass-transfer resistance for fluid transport through the membrane, which increases operating costs. Membrane surface patterning is one approach to mitigate biofouling. In this presentation, we will present findings from a study that used a combination of flux decline measurements and experimental-computational visualization experiments to evaluate the effectiveness of microscale herringbone patterns for reducing protein fouling on ultrafiltration membranes.

Thermal embossing with woven mesh stamps was used for the first time to pattern membranes. Embossing process parameters were studied to identify conditions replicating the mesh patterns with high fidelity and to determine their effect on membrane permeability. Permeability increased or remained constant by patterning at low pressure (≤4.4 MPa) due to increased effective surface area; whereas, permeability decreased at higher pressures due to surface pore-sealing of the ultrafiltration membrane active layer upon compression. Spatiotemporal protein fouling data were collected by confocal laser scanning microscopy (CLSM) experiments for membranes patterned with different geometric features. Using separate fluorophore labels for the protein foulant and the membranes yielded three-dimensional CLSM images of membrane surface patterns and co-localized protein foulant. Numerical simulations were run in parallel to compare fouling patterns with visual analysis of the CLSM images. We utilized the customized simulator SUMs (Stanford University Membrane solver) within the OpenFOAM framework. The solver uses a finite volume method to study the dynamic couplings among flow, solute transport, and surface fouling. From the simulations, we found that herringbone style micropatterns reduce fouling through a fouling-focusing mechanism. Using an alternating flow field, we discovered that regions of foulant accumulation changed. We will illustrate how the innovative herringbone pattern design provides a possibility to consecutively alternate flow direction during operation to periodically clean zones of the membrane surface.

Overall, the combination of flux-decline experiments with visualization of protein fouling by CLSM and numerical simulations allowed us to explore the role of pattern geometry on fouling profiles and provided insights on the fouling mechanisms from the earliest stages of fouling, dominated by protein adsorption, to later stages, dominated by cake layer formation. We expect this approach to aid in the design of new membranes with tailored surface structures that prevent the irreversible deposition of foulants in prone-to-foul regions.