A challenge with implantable medical devices is preventing the formation of blood clots. One strategy to mitigate the problem has been to attach the anticoagulant heparin to device surfaces, but the sulfated glycosaminoglycan can leach away and cause unintended bleeding. As an alternative to heparin, Donald E. Ingber, founding director of the Wyss Institute at Harvard University, and coworkers have developed a tethered liquid perfluorocarbon (TLP) coating that repels blood and reduces clot formation (Nat. Biotechnol. 2014, DOI: 10.1038/nbt.3020). The coating is made up of a tethered layer of perfluorohexane topped with a thin liquid layer of perfluorodecalin. A blood droplet will immediately slide off a TLP-coated acrylic surface tilted at a 30° angle. The blood droplet would otherwise leave a trail of adhered blood on an uncoated acrylic surface. The coating decreases fibrin adhesion and polymerization on acrylic and polysulfone substrates relative to uncoated surfaces and relative to surfaces coated only with tethered perfluorohexane. The researchers used the coating on materials that were assembled into a femoral artery shunt in pigs. Blood circulated through the tubing for more than eight hours without clotting and without the use of an anticoagulant.