Cartilage-inspired, lipid-based boundary-lubricated hydrogels

Slippery surfaces using lipids In engineered systems, a reduction in friction can come from the use of lubricants or through surface coatings that are inherently slippery. For most hydrogels, which are cross-linked polymers heavily swelled with water, surface lubrication typically comes from trapped liquids that help to form a slippery surface. Drawing inspiration from articular cartilage that in part uses a lipid boundary layer, Lin et al. designed hydrogels with small concentrations of lipids that are continuously exuded toward the surface to make a slippery layer (see the Perspective by Schmidt). Friction and wear of the hydrogels was reduced by up to a factor of 100, and the effect was observed even after the hydrogels were dried and rehydrated. Science , this issue p. 335 ; see also p. 288