Preparation Of Superhydrophobic Surfaces And Their Effects On Anticoagulation

Superhydrophobic surfaces were usually defined as a water contact angle (WCA) larger than 150°and sliding angles (SA) smaller than 10°. Such new surfaces showed anti-pollution, anti-oxidation and self-cleaning, which would make people's lives much convenient. Many studies have been carried out on wettibility of pure or deionized water on such surfaces, but few studies reported the wettability of blood on them. Besides, there was no conclusion that superhydrophobic surfaces had effect on anticoagulation. Some researchers tested that these surfaces exhibited plasma-repellent property by using in vitro static platelets adhesion and in vivo transplantation tests; while others disagreed with such result by using in vivo transplantation and in vitro blood circulation tests.In this paper, poly(dimethylsiloxane) (PDMS) stamps were firstly prepared by replica molding against fresh lotus leaves. Then the Nano-TiO₂/low-density polyethylene (Nano-TiO₂/LDPE) surface was prepared by thermal replica-molding against such featured PDMS stamp assisted by TiO₂ Nano-particles. SEM images showed that such structured surface was exactly like Lotus leaf surface. Contact angle measurements showed that Nano-TiO₂/LDPE surface had stable superhydrophobicity and good repellency against high pressure water stream. The circuit shaped High-density polyethylene (HDPE) and needle cluster shaped Polystyrene (PS) superhydrophobic surfaces were prepared by thermal micromolding using anodic aluminum oxidation foils as the tamplate.The wettability of Platelets-rich Plasma (PRP) onto the prepared Nano-TiO₂/LDPE and HDPE superhydrophobic surfaces were tested according to the water contact angle measurement method. The wettability and wetting velocity were also observed by immersing both surfaces into PRP vertically. Besides, the hemolysis rate was tested by using a spectrophotometer to examine light-absorbing value of the diluted blood which was previously immersed by the prepared superhydrophobic surfaces. LDPE smooth surface, Nano-TiO₂/LDPE and HDPE superhydrophobic surfaces were immersed into PRP for 3 h both at dynamic and static experimental conditions. Then platelets adhesion onto these surfaces was evaluated by a field emission scanning electron microscopy (SEM).The results showed both superhydrophobic surfaces didn't exhibit plasma-repellent property. The PRP contact angles (PRP-CAs) of Nano-TiO₂/LDPE and HDPE superhydrophobic surfaces were 127.2°and 121.3°, respectively, and showed unstability. When both surfaces were immersed into PRP, the Nano-TiO₂/LDPE surface was completely wetted only after 2 min and the HDPE surface was completely wetted immediately. Observing hemocyte variation, the hemolysis rate of both samples was below 5%. The platelets adhesion test showed that, when both superhydrophobic surfaces were immersed in PRP at static experimental condition, much more platelets adhesion on both of them than on the smooth LDPE surface. However, less platelet was found on both superhydrophobic surfaces than on the LDPE smooth surface when they were immersed in PRP at dynamic experimental condition. It showed microconvexed structure of superhydrophobic surfaces had effects on anticoagulation.The main reason they believed was that the microscopic multiscale surface remodeled the boundary conditions for ?ow, higher flow velocity of the boundary layer, lower the chance for platelets contact with the surface, thereby largely suppressing platelet adhesion. Therefore, under dynamic condition, it's more accurate to say that it was microscale rough structure played a role on anticoagulation than the superhydrophobic surfaces themself. For blood flows in the body with dynamic circulation, superhydrophobic artificial blood vessels should have effects on anticoagulation, which would direct a new way to develop new type artificial blood vessel.