The impact of nanoscale chemical features on micron-scale adhesion: Crossover from heterogeneity-dominated to mean-field behavior
The impact of nanoscale chemical features on micron-scale adhesion: Crossover from heterogeneity-dominated to mean-field behavior
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DOI：
10.1016/j.jcis.2009.05.046
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发表时间：
2009-09-15
影响因子：
9.9
通讯作者：
Santore, Maria M.
中科院分区：
文献类型：
--
作者：
Duffadar, Ranojoy;Kalasin, Surachate;Santore, Maria M.
这项工作探讨了纳米级表面异质性的影响，相对于两个表面之间的有效接触面积小，成对的胶体规模的相互作用。聚阳离子为基础的积极补丁，直径为10 nm的顺序，随机排列，平躺在其他负基板上，被用来创建表面的竞争吸引力和排斥力的功能，确定与相对表面的净相互作用。缓慢流动的稀释负微粒的粘附的实验室实验和模拟改变了颗粒尺寸（0.5-2 μ m）、离子强度（kappa（-1）= 1-12 nm）和收集器上的异质性密度。报道了从高离子强度下的非均匀性控制到低离子强度下的类平均场相互作用的限制行为。当异质性是重要的，成对的相互作用是更有吸引力的比预测的平均表面性能（例如，每DLVO），和粘附阈值，描述的最小平均密度的阳离子功能所需的单粒子捕获（粘附），强烈依赖于德拜长度。在相反的限制，阈值变得不敏感的德拜长度，和平均表面字符近似的相互作用。一个分析处理，减少到一个简单的缩放参数预测一个-1/2幂律依赖的德拜长度和颗粒大小的粘附阈值。在实验和模拟结果中，流体动力学贡献沿着有一个稍强的颗粒尺寸依赖性，静电力、货车德瓦尔斯力和流体动力学力具有轻微的标度差异。对于异质性主导的限制，与生物配体进行类比：发现对于该特定系统，少至20-100个阳离子贴片的接合决定颗粒粘附（细节取决于流动、颗粒大小和离子强度），类似于炎症途径期间选择素介导的白色血细胞滚动的报道。还发现了离子强度对颗粒捕获的影响中的异质性依赖性交叉，其中添加的盐在大多数情况下促进颗粒粘附，但当异质性变得相对密集时稳定颗粒。(C)2009 Elsevier Inc. All rights reserved.
This work explores the impact of nanoscale surface heterogeneity, small relative to the effective contact area between two surfaces, on pairwise colloid-scale interactions. Polycation-based positive patches, of order 10 nm in diameter, arranged randomly and lying flat on otherwise negative substrates, were used to create surfaces whose competing attractive and repulsive features determined the net interactions with opposing surfaces. Lab experiments and simulations of the adhesion of gently flowing dilute negative microparticles varied particle size (0.5-2 mu m), ionic strength (kappa(-1) = 1-12 nm) and the density of heterogeneity on the collectors. Limiting behaviors from heterogeneity-controlled at high ionic strength to mean-field-like interactions at low ionic strength are reported. When heterogeneities are important, pairwise interactions are more attractive than predicted by average surface properties (e.g. per DLVO), and an adhesion threshold, describing the minimum average density of cationic features needed for single particle capture (adhesion), depends strongly on Debye length. In the opposite limit, the threshold becomes insensitive to the Debye length, and the average surface character approximates the interactions. An analytical treatment, reduced to a simple scaling argument predicts a -1/2 power-law dependence of the adhesion threshold on Debye length and particle size. A slightly stronger particle size dependence in experiments and simulations results from hydrodynamic contributions along with slight scaling differences in electrostatic, van der Waals, and hydrodynamic forces. An analogy to biological ligands is made for the heterogeneity-dominated limit: it is discovered, for this particular system, that engagement of as few as 20-100 cationic patches dictates particle adhesion (with details depending on flow, particle size, and ionic strength), similar to reports for selectin-mediated rolling of white blood cells during the inflammatory pathway. Also discovered is a heterogeneity-dependent crossover in the effect of ionic strength on particle capture, where added salt promotes particle adhesion in most cases but stabilizes the particles when the heterogeneity becomes relatively dense. (C) 2009 Elsevier Inc. All rights reserved.