Characterization of a high-Q in-liquid longitudinal-mode film bulk acoustic resonator for real-time in-situ monitoring of competitive protein adsorption

We report the characterization results of in-liquid longitudinal-mode FBAR (L-FBAR) for real-time in-situ monitoring of the Vroman effect, a competitive adsorption and exchange of proteins on a surface. The change of resonant frequency of the L-FBAR, ~1.55 GHz, is a direct function of the proteins' molecular weight, and thus we monitor the resonant frequency shifts to estimate the adsorption and exchange behavior. A low molecular weight (LMW) protein, albumin, initially covers the surface and is displaced by a high molecular weight (HMW) protein, IgG; sequentially, the highest molecular weight protein, fibrinogen displaces IgG. However, the reverse sequence does not occur.