Surface Topography, Surface Energy and Wettability of Magnetron‐Sputtered Amorphous Carbon (a‐C) Films and Their Relevance for Platelet Adhesion

Abstract

Diamond-like carbon (DLC) and amorphous carbon (a-C, a-C:H) coatings, respectively, have been proposed since many years as potential materials for biomedical applications due to their chemical inertness, low friction coefficient, high wear resistance, bio-and haemocompatibility. [1][2][3][4][5][6] The feasibility of amorphous carbon coatings was investigated for a variety of applications like surgical needles, [2] orthopaedic implants and prostheses, [7][8][9][10][11] medical guidewires, [12][13][14][15] coronary artery stents [16,17] and also for mechanical heart valve replacement and other solid implants. [18][19][20][21][22][23] The functionality, performance and durability of artificial surfaces in vivo are determined and often limited by their interaction with blood or tissue. However, the coagulation mechanism of blood on amorphous carbon (DLC) films in such a biomedical environment is not understood in detail even if the biocompatibility of DLC coatings was described early by many reports. [1,3,[24][25][26] Extensive information on individual aspects, like protein adsorption, platelet adhesion and activation on carbonaceous surfaces has been accumulated in the literature. [27][28][29] Since a few years more sophisticated approaches to the scientific understanding of the complex interaction of blood and inorganic surfaces are emerging by addressing this field through fundamental and interdisciplinary research efforts offering synoptical views based on materials science, chemistry, biology, physics, physical chemistry and medicine. [30][31][32] Main factors have been recognised to influence significantly the cell adhesion and interaction on amorphous carbon: these include the constitution of the carbon films and the fraction of the sp 3 bonds, [12,30] the surface energy and hydrophobicity, [27] and the surface roughness and topography. [26,31] The properties of a-C and DLC coatings, especially the biofunctional ones, can further be modified by incorporating other elements in the coatings, such as H, N, F, P, Si and metals. [4,5,[33][34][35][36][37][38][39] It is well known that the incorporation of additional elements into an amorphous carbon matrix has a very strong impact on the surface energy and wettability of such coatings. [40][41][42] Combining various surface modification methods should thus offer new tools for a future engineering design of biofunctional thin film materials, covering a wide range of properties, for example from strongly hydrophilic to extremely hydrophobic. Recently, it was shown that the modification of the inherent surface topography of carbon films on the nano-scale by proper adjusting of the deposition process and kinetics can strongly impact the wetting behaviour. [43] Similar or complementary effects were achieved through creating an artificial micro-or nano-scale surface topography by laser-patterning or plasma-etching or by subsequent thermal processing of carbon coatings. [44][45][46] From the biological perspective, the competitive adsorption of several plasma proteins (al...

Evaluation of wettability and surface energy of native Nitinol surfaces in relation to hemocompatibility

“…Interestingly, the correlation between the patterns in platelet adhesion and spreading in the sequence Ce-CeWb-CeWbHt surfaces with the behavior of the polar energy agrees with the results of the study of amorphous carbon films [40] where platelet activation gradually decreased with γ p .…”

Deposition and characterization of NiOx coatings by magnetron sputtering for application in dye-sensitized solar cells

“…With the change in deposition pressure, target current and substrate bias voltage, there was a change in the surface roughness and an associated variation in the water contact angle and surface energy as shown in Fig. 8a, b and c. A similar finding was reported by Stüber et al who observed a linear change in the surface energy of the sputtered coatings with increasing surface roughness [36]. From this study it was concluded that of the deposition parameters investigated the deposition pressure had the most significant influence on enhancing both surface roughness and energy of the NiO x coatings.…”

Exploring the potential of high power impulse magnetron sputtering for growth of diamond-like carbon films

“…Due to these attributes, DLC films are widely used for surface protection in cutting tools [2;3], magnetic storage discs [4], biomedical devices [5][6], antireflection coatings, and optical sensors [7]. Various mechanisms have been proposed in order to describe the formation of sp 3 bonds in DLC films [1,[8][9][10][11]; among them, the most accepted view for amorphous carbon films without significant hydrogen incorporation is that the sp 3 formation is triggered by subsurface densification generated by subplantation of energetic deposited species [1,[9][10][11].…”