Читать книгу Materials for Biomedical Engineering - Mohamed N. Rahaman - Страница 185

Surface properties and characteristics, together with bulk properties, have a strong influence on the performance of biomaterials in vivo. In this chapter, we discussed important surface properties relevant to biomaterials, including surface chemistry, surface energy, surface topography, and surface charge.

 Surface chemistry is the most important surface property because it influences the behavior of a biomaterial in any given environment. We discussed a variety of techniques for characterizing surface chemistry of a material, but it should be noted that because most of these techniques require the use of an ultrahigh vacuum, the measured surface chemistry is often different from that of biomaterials implanted in vivo.

 Surface energy is difficult to measure for many materials and, consequently, it is often considered more simply in terms of the extent to which a liquid will wet and spread over a surface. The contact angle between a liquid (water) droplet and a solid surface is often taken as a measure of the wettability of the system. Overall, hydrophilic materials (low contact angle) show good wetting and spreading by water whereas hydrophobic materials (high contact angle) show poor wetting by water.

 When placed in an aqueous environment, such as the physiological fluid, biomaterials develop a surface charge that can influence subsequent adsorption of ions and molecules from the medium.

 Certain surface topographical features, such as certain roughness features, have been shown to have beneficial effects on the response of certain cells in vitro and in vivo, a topic that is discussed further in Chapter 21.