The ability to modulate polyacrylamide hydrogel surface morphology, rheological properties, adhesion and frictional response is demonstrated by combining acrylic acid copolymerization and network confinement via grafting to a surface. Specifically, atomic force microscopy imaging reveals both micellar and lamellar microphase separations in grafted copolymer hydrogels. Bulk characterization is conducted to reveal the mechanisms underlying microstructural changes and ordering of the polymer network, supporting that they stem from the balance between hydrogen bonding in the substrate‐grafted hydrogels, electrostatic interactions, and a decrease in osmotically active charges. The morphological modulation has direct impacts on the spatial distribution of surface stiffness and adhesion. Furthermore, lateral force measurements show that the microphase separations lead to speed and load‐dependent lubrication regimes as well as spatial variation of friction. A proof of concept via salt screening demonstrates the dynamic control of surface morphology and adhesion. This work advances the knowledge necessary to design complex hydrogel interfaces that enable spatial and dynamic control of surface morphology and thereby of friction and adhesion through modulation of hydrogel composition and surface confinement, which is of significance for applications in biomedical devices, soft tissue design, soft robotics, and other engineered tribosystems.

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Despite recent advances in polyelectrolyte systems, designing responsive hydrogel interfaces to meet application requirements still proves challenging. Here, semicrystalline colloidal gels composed of poly(methacrylamide‐co‐methacrylic acid) are investigated in water with storage moduli in the MPa range. A combination of SEM, X‐ray scattering, and NMR reveals the evolution of the colloidal microstructure, crystallinity, and hydrogen bonding with varying monomer ratio. The gels with the finest colloidal microstructure exhibit the most dissipative rheological behavior and are selected for the study of their interfacial characteristics and underlying interactions. Microstructure stabilization and dynamics results from short‐range (attractive) hydrogen bonding and hydrophobic forces, and long‐range (repulsive) electrostatic interactions—the “SALR” pair potential. Further, the gel's surface exhibits a submicron colloidal topography that greatly determines (colloidal‐like) friction as a result of the viscoelastic deformation of the colloidal network, while electrostatic near‐surface interactions propagate in lamellar adhesion. The dynamic and reversible nature of the involved interactions introduces a stimulus responsive behavior that enables the electrotunability of adhesion and friction. This study advances the knowledge necessary to design complex hydrogel interfaces that enable spatial and dynamic control of surface properties, which is of relevance for applications in biomedical devices, soft tissue design, soft robotics, and other engineered tribosystems.

Spherical powders (with diameters 95% of the theoretical density) and showed both tetragonal and/or cubic x-ray phases. The bulk density values of these ceria-doped zirconia sintered pellets are much higher than those obtained for the CaO-or Y2Oa-doped zirconia samples prepared by the same process.Fully and partially stabilized ZrO2 solid solutions are one of the most extensively studied solid oxide electrolyte systems due to the many practical applications of these materials. In order to stabilize the high temperature, high conductive tetragonal, and/or cubic phases, CaO, Y20~, or MgO have been extensively utilized as dopants. Recently, the addition of CeO2, as a stabilizer of ZrO2, has demonstrated the capability for producing a fairly large-grained (20-40 p~m) pure tetragonal solid solution with high flexure strength and fracture toughness.