Artificial joints implanted in patients usually have to be replaced after 10 years because a lack of good lubrication causes the joints to wear out. To find a better lubricant that’s also biocompatible, researchers have synthesized a polymer that mimics the structure and function of lubricin, a protein that occurs naturally in the fluid that cushions joints (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja501770y). Xavier Banquy of the University of Montreal and colleagues designed the polymer with two end domains that anchor it to surfaces, as well as a dense, springy area in the middle shaped like a bottlebrush. When two polymer-coated surfaces move toward each other, the bottlebrush domains touch and compress as the applied pressure increases. To test the lubricant, the researchers coated two mica plates with the polymer and measured the compressive force associated with squeezing the plates together and the frictional force caused by sliding one plate against the other. They then calculated the friction coefficient of the polymer. They found that the material lubricates much better than lubricin over a wide range of sliding speeds and pressures, Banquy says.