Viscous Boundary Lubrication of Hydrophobic Surfaces by Mucin
Viscous Boundary Lubrication of Hydrophobic Surfaces by Mucin
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DOI：
10.1021/la8018666
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发表时间：
2009-02-17
期刊：
影响因子：
3.9
通讯作者：
Ramsden, Jeremy J.
中科院分区：
文献类型：
--
作者：
Yakubov, Gleb E.;Mccoll, James;Ramsden, Jeremy J.
采用软接触摩擦学方法研究了带弱电荷的短侧链糖蛋白粘蛋白Orthana（M-w = 0.55 MDa）在亲水性和疏水性PDMS基底之间的润滑行为。结果发现，粘蛋白促进疏水性PDMS表面之间的润滑，导致粗糙表面的边界摩擦系数降低10倍。粘蛋白的存在还导致混合润滑状态向较低夹带速度的转变。所观察到的粘蛋白的边界润滑行为被发现依赖于体浓度，我们将其与吸附的粘蛋白膜的结构和动力学，这是使用光波导光光谱评估。我们观察到的复合结构的吸附粘蛋白层，其内部结构由纠缠。该吸附层的膜厚度随浓度增加，而粗糙表面的边界摩擦系数被发现是成反比的吸附膜的厚度。润滑和膜的结构之间的这种联系与粘性边界润滑机制一致，即，在给定的滑动速度下，较厚的吸附膜导致较低的局部剪切速率，并因此导致较低的局部剪切应力。由摩擦测量和聚合物层密度得到的吸附层的估计局部粘度彼此一致。
The lubricating behavior of the weakly charged short-side-chain glycoprotein mucin "Orthana" (M-w = 0.55 MDa) has been investigated between hydrophobic and hydrophilic PDMS substrates using soft-contact tribometry. It was found that mucin facilitates lubrication between hydrophobic PDMS surfaces, leading to a 10-fold reduction in boundary friction coefficient for rough surfaces. The presence of mucin also results in a shift of the mixed lubrication regime to lower entrainment speeds. The observed boundary lubrication behavior of mucin was found to depend on the bulk concentration, and we linked this to the structure and dynamics of the adsorbed mucin films, which are assessed using optical waveguide light spectroscopy. We observe a composite structure of the adsorbed mucin layer, with its internal structure governed by entanglement. The film thickness of this adsorbed layer increases with concentration, while the boundary friction coefficient for rough surfaces was found to be inversely proportional to the thickness of the adsorbed film. This link between lubrication and structure of the film is consistent with a viscous boundary lubrication mechanism, i.e., a thicker adsorbed film, at a given sliding speed, results in a lower local shear rate and, hence, in a lower local shear stress, The estimated local viscosities of the adsorbed layer, derived from the friction measurements and the polymer layer density, are in agreement with each other.