Water in solid form is 1 atom thick crystals of 3xH2O + 3xOH-, with 3xH3O+ between the sheets, holding them together. Water in "gel-phase" is 1 atom thick crystals of 3xH2O + 3xOH-, without 3xH3O+ in between the sheet. The 3xH3O+ instead forms a positively charged layer adjacent to the gel-layer. This is what "surface tension" is, a gel-layer on top of the water. Osmosis is driven by the membrane potential that results because the thickness of the gel-layer (and therefore the hydronium ion concentration next it) diminishes with colloids. An electrical gradient "pushes" (Greek ōsmos, "push") hydronium ions through the membrane.
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From @johan-nygren