Fig. 2. A constant concentration gradient of a valence-symmetric electrolyte ∇n^∞_i induces diffusioosmosis in a channel that comprises two parallel, hydrophobic plates with a constant surface charge density and a length L separated by a distance 2H. Diffusioosmosis is parallel to ∇n^∞_i along the x-direction. The induced electric field E is parallel to ∇n^∞_i and note that it may be in the same or opposite direction as ∇n^∞_i depending on the electrolyte and channel surface charge.