Scanning Electron Microscope (SEM) images of the dialysis membranes: cross-section (a) 6 kDa, no polyvinylpyrrolidone (PVP); (b) 12 kDa, 2% PVP; (c) 16 kDa, 3% PVP; thickness (d) 6 kDa, no PVP; (e) 12 kDa, 2% PVP; (f) 16 kDa, 3% PVP. Scanning Electron Microscope (SEM) images of the dialysis membranes: cross-section (a) 6 kDa, no polyvinylpyrrolidone (PVP); (b) 12 kDa, 2% PVP; (c) 16 kDa, 3% PVP; thickness (d) 6 kDa, no PVP; (e) 12 kDa, 2% PVP; (f) 16 kDa, 3% PVP. Anirban Roy et al. BMJ Innov 2016;2:84-92 Copyright © BMJ Publishing Group Ltd & British Cardiovascular Society. All rights reserved.