Rodahl M, Höök F, Fredriksson C, Keller C A, Krozer A, Brzezinski P, Voinova M, Kasemo B
Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden.
Faraday Discuss. 1997(107):229-46. doi: 10.1039/a703137h.
We have measured the energy dissipation of the quartz crystal microbalance (QCM), operating in the liquid phase, when mono- or multi-layers of biomolecules and biofilms form on the QCM electrode (with a time resolution of ca. 1 s). Examples are taken from protein adsorption, lipid vesicle adsorption and cell adhesion studies. Our results show that even very thin (a few nm) biofilms dissipate a significant amount of energy owing to the QCM oscillation. Various mechanisms for this energy dissipation are discussed. Three main contributions to the measured increase in energy dissipation are considered. (i) A viscoelastic porous structure (the biofilm) that is strained during oscillation, (ii) trapped liquid that moves between or in and out of the pores due to the deformation of the film and (iii) the load from the bulk liquid which increases the strain of the film. These mechanisms are, in reality, not entirely separable, rather, they constitute an effective viscoelastic load. The biofilms can therefore not be considered rigidly coupled to the QCM oscillation. It is further shown theoretically that viscoelastic layers with thicknesses comparable to the biofilms studied in this work can induce energy dissipation of the same magnitude as the measured ones.
我们测量了在液相中运行的石英晶体微天平（QCM）的能量耗散情况，此时生物分子和生物膜的单层或多层在QCM电极上形成（时间分辨率约为1秒）。实例取自蛋白质吸附、脂质囊泡吸附和细胞黏附研究。我们的结果表明，即使是非常薄（几纳米）的生物膜，由于QCM振荡也会耗散大量能量。本文讨论了这种能量耗散的各种机制。考虑了对测量到的能量耗散增加的三个主要贡献。（i） 一种粘弹性多孔结构（生物膜），在振荡过程中发生应变；（ii）由于膜的变形而在孔隙之间或进出孔隙移动的截留液体；（iii）来自本体液体的负载，其增加了膜的应变。实际上，这些机制并非完全可分离，相反，它们构成了一种有效的粘弹性负载。因此，不能认为生物膜与QCM振荡是刚性耦合的。理论上进一步表明，厚度与本工作中研究的生物膜相当的粘弹性层可以引起与测量值相同量级的能量耗散。
