diluted [@LeDuc1995]. The effect has been documented both on hydrophilic and hydrophobic interfaces [@LeDuc1995; @Green1999] being more evident the more hydrophilic the material, but with stronger protein binding the more hydrophobic the surfaces [@Noh2007; @Ding2011]. However, no universality is found in the experiments and the results strongly depend on the details of the experiments [@Lassen1996; @Lassen1997; @Barnthip2009]. It is generally accepted that proteins with smaller molecular weight and at higher concentration adsorb first to the surface, but later are replaced by other proteins with, generally, larger molecular weight and size. After the adsorption, the protein can undergo conformational changes and denaturation, especially at a hydrophobic interface, eventually leading to irreversible adsorption [@Green1999].

Many experimental techniques have been used to investigate the effect from blood plasma or model solutions with a limited number of components and many models have been proposed to rationalize the experiments [@Lu1994; @Brash1995; @Slack1995; @LeDuc1995; @Dejardin1995; @Green1999]. However, the mechanisms of the phenomenon are still debated and no existing model can fully explain it [@Jung2003; @Barnthip2009; @Hirsh2013].

Volumetric effects, due to non-deformable proteins trying to fit on the available surface, can account for competitive adsorption of proteins [@Barnthip2009]. However, they do not reproduce the maxima of absorption 