Fluid inertia limits microporous flow efficiency

With the continual development of novel materials—graphene membranes are a notable example—we approach the holy grail of filtration: a system that combines the seemingly antagonistic functions of high permeance and strong selectivity. Through emerging filtration techniques, it becomes possible to significantly reduce the energy loss caused by viscous dissipation when separating solutes and solvants. However, despite these advancements, there is still a lack of comprehensive understanding regarding the fundamental limits of flow efficiency through micropores. In this study, we examine inertia—the process of accelerating a fluid particle as it passes through the porous membrane. We show that there exists an upper limit to flow efficiency through pores due to the effects of inertia. While strategies such as optimizing the filtration system’s geometry and applying surface treatments can help mitigate the energy cost associated with overcoming viscous drag, the energy associated with fluid momentum remains unavoidable. Our results highlight the importance of area scalability in emergent filtration technology. Graphic abstract