Transport Through Fluctuating and Defective Materials

Transport of water and protons through fluctuating and defective materials are areas of great scientific importance. First, we perform comprehensive atomistic simulations to understand coupling between the fluid transport and mechanics of the membrane. For a membrane separating a salt solution and fresh water, we show that considerable deformation and fluctuation in the membrane results in an enhanced water permeability. Calculations on a harmonically vibrating membrane indicate that the coupling between the vibrational density of states between water and the membrane plays an important role. Second, we investigate proton transport across nanometer thick membranes with defects by using ab-initio molecular dynamics simulations. We demonstrate bidirectional translocation of protons which occurs through the interstitial sites in the surface. We show that water dissociation and the subsequent movement of the dissociated proton through the interstitials sites results in bidirectional transport. We also show that this interstitial proton transport results in an induced electric field that is modulated depending on the proton gradient across the membrane.