$(1$ pt$)$ What is the diffusion coefficient and what does it depend on$?$

$(1$ pt$)$ What is a material design strategy to maximize differences in diffusion coefficients between two molecules?

$(1$ pt$)$ What is a material design strategy to maximize permeate flux?

$(1$ pt$)$ What can be done to membrane thickness to maximize permeate flux?

$(1$ pt$)$ What is the main energy penalty associated with membrane separation?