A novel surface-flow filter has been designed to take advantage of a combination of both diffusion and lateral flow permeation, since active coatings, even if porous, tend to be far less permeable than through-flow constructs. The formation of a continuous coating layer virtually excludes any fluid transport into the coating other than by planar diffusion for gases or capillarity for liquids. This study considers the additional potential advantage of creating a pixelated/patterned coating, applied using a pin coater to form printed dots onto a highly permeable cellulose fibrous paper-like substrate. The coating—fine particulate calcium carbonate combined with micro-nanofibrillated cellulose as binder and humectant—reacts on exposure to NO₂ gas to form calcium nitrate. Experimental results show an effective doubling of nitrate-forming efficiency using pixelated coating compared with a reference continuous layer coating. To establish an understanding of the comparative mechanisms of gas-coating contact, computational fluid dynamic modelling is used to generate surface pressure profiles combined with a pore network model of the coating to estimate theoretical fluid permeability and gas diffusion coefficients. Although pressure-driven permeation was calculated to be approximately two orders of magnitude less than the diffusive flow, it is concluded that patterned aerofoil pressure differential effects can reduce the impact of surface stagnant layering and so aid fluid transfer, boosting the diffusive transport, which in turn delivers greater contact efficiency based on the increased accessibility to the active coating.

一种新型的表面流过滤器被设计为利用扩散和侧流渗透的组合，因为活性涂层，即使是多孔的，其渗透性往往远低于通流结构。除了气体的平面扩散或液体的毛细作用之外，连续涂层的形成实际上排除了任何流体输送到涂层中。该研究考虑了创建像素化/图案涂层的额外潜在优势，使用针式涂布机将印刷点涂在高渗透性纤维素纤维纸状基材上。涂层——细颗粒碳酸钙与作为粘合剂和湿润剂的微纳原纤化纤维素结合——在暴露于 NO _{2 时发生}反应气体生成硝酸钙。实验结果表明，与参考连续层涂层相比，使用像素化涂层的硝酸盐形成效率有效加倍。为了了解气体-涂层接触的比较机制，使用计算流体动力学模型生成表面压力分布，并结合涂层的孔隙网络模型来估计理论流体渗透率和气体扩散系数。尽管计算出的压力驱动渗透比扩散流低大约两个数量级，但可以得出结论，图案化的翼型压差效应可以减少表面停滞分层的影响，因此有助于流体传输，促进扩散传输，