Diffusiophoretic Fast Swelling of Chemically Responsive Hydrogels.

Acid-induced release of stored ions from polyacrylic acid hydrogels (with a free surface fully permeable to the ion and acid) was observed to increase the gel osmotic pressure that leads to rapid swelling faster than the characteristic solvent absorption rate of the gel. The subsequent equilibration of the diffusing ion concentration across the gel surface diminishes the osmotic pressure. Then, the swollen gel contracts, thereby completing one actuation cycle.

Colony-like Protocell Superstructures.

We report the formation, growth, and dynamics of model protocell superstructures on solid surfaces, resembling single cell colonies. These structures, consisting of several layers of lipidic compartments enveloped in a dome-shaped outer lipid bilayer, emerged as a result of spontaneous shape transformation of lipid agglomerates deposited on thin film aluminum surfaces. Collective protocell structures were observed to be mechanically more stable compared to isolated spherical compartments.