________________________________________________________________Countless lives have been saved by implantable medical devices (e.g., total artificial hearts, ventricular assist devices, pacemakers, cardioverterdefibrillators, and central lines) and extracorporeal devices that flow whole human blood outside the body through indwelling catheters and external circuits, during cardiopulmonary bypass (CPB), hemodialysis, and extracorporeal membrane oxygenation (ECMO) 1,2 . However, the need to co-administer soluble anticoagulant drugs, such as heparin, with many of these procedures, significantly reduces their safety and hampers their effectiveness 3,4 . Without systemic anticoagulation, these extracorporeal and indwelling devices can rapidly occlude due to thrombosis because clots form when fibrin and platelets in the flowing blood adhere to the surfaces of these artificial materials 5 . Unfortunately, heparin causes significant morbidity and mortality including post-operative bleeding, thrombocytopenia, hypertriglyceridemia, hyperkalemia and hypersensitivity 6 , and its use is contraindicated in several patient populations 7 . In fact, the majority of drug-related deaths from adverse clinical events in the UnitedStates are due to systemic anticoagulation 8 .This need to prevent blood clotting while minimizing administration of anticoagulant drugs has led to the search for biomaterial surface coatings that can directly suppress blood clot formation. The most successful approach to date has been to chemically immobilize heparin on blood-contacting surfaces to reduce thrombosis and lower anticoagulant administration 9,10 . Although this approach has been widely adopted, major limitations persist because the surface-bound heparin leaches, resulting in a progressive loss of anticoagulation 24,25 . Importantly, the TP continues to retain the free LP as a thin mobile liquid layer even when the surface is challenged with a flowing immiscible fluid, such as blood (Fig. 1a). We refer to this unique anti-thrombogenic bilayer composed of the TP and LP coating as a Tethered-Liquid Perfluorocarbon (TLP) surface.
RESULTS
A generic blood repellent surface coatingTo test the anti-adhesive properties of the TLP coating method, we examined surface adhesion of fresh whole human blood on an acrylic surface sloped at an angle of 30 degrees, with or without a TLP coating composed of tethered perfluorohexane and liquid perfluorodecalin. Blood droplets immediately adhered to the control uncoated acrylic surface and left a trail of blood components over the course of 5 sec (Fig. 1b, top, Supplementary Fig. 1 and
Supplementary Movie 1).In contrast, when the same surface was coated with TLP, the blood droplet almost immediately slid off the surface (< 0.3 sec), and remarkably, there was no evidence of any residual blood trail (Fig. 1b, Supplementary Fig. 1 and Supplementary Movie 2). We quantified blood adhesion to surfaces by measuring the minimum angle required to cause a droplet to slide ("sliding angle") ( Fig. 1c). Control uncoated s...
