论文标题
弹性涂层在流体介导的载荷下通过球形探针的弹性涂层
Elastohydrodynamics of a soft coating under fluid-mediated loading by a spherical probe
论文作者
论文摘要
在柔软的壁附近的物体运动与中间流体的运动是弹性水力动力学中的典型问题,在跨越生物学的受试者中存在存在。特别是,在扫描探针显微镜的背景下,通常会遇到球体向具有中间流体的软底物运动的运动。尽管对该设置进行了基本的理论研究,但它们仍专注于特定的应用,因此进行了适当的简化。在这里,我们提出了一个多功能的半分析框架,用于研究刚性球的轴对称载荷的弹性水力动力学,靠近柔软的弹性底物涂在涂有水解溶液介导的刚性平台上。考虑了三种加载模式 - 方法,衰退和振荡。该框架结合了 - 大振荡频率和振幅,压力和底物变形之间的双向耦合以及DLVO力的存在。从使用框架的计算中,我们可以洞悉DLVO力,底物厚度,底物材料可压缩性(通过Poisson的比率量化)和高振荡频率对于SPM和喜欢的不同物理设置的高振荡频率。我们列出了一些关键观察。较厚,更可压缩的底物可以使更大的变形,即有效地更柔软。 DLVO力的存在导致高达两个数量级的力量,并在低频下以低频和低速下的接近/衰退加载的振荡载荷的底物变形至数量级。对于高频的振荡载荷,DLVO力不会明显影响系统的力和挠度行为。在证明了我们框架的多功能性和实用性后,我们希望它能够发展为解决软润滑问题的多样化和有用的工具。
Motion of an object near a soft wall with intervening fluid is a canonical problem in elastohydrodynamics, finding presence in subjects spanning biology to tribology. Particularly, motion of a sphere towards a soft substrate with intervening fluid is often encountered in the context of scanning probe microscopy. While there have been fundamental theoretical studies on this setup, they have focussed on specific applications and thus enforced suitable simplifications. Here we present a versatile semi-analytical framework for studying the elastohydrodynamics of axisymmetric loading of a rigid sphere near a soft elastic substrate coated on a rigid platform mediated by an aqueous electrolytic solution. Three loading modes are considered - approach, recession and oscillatory. The framework incorporates - large oscillation frequency and amplitude, two-way coupling between pressure and substrate deformation, and presence of DLVO forces. From computations using the framework, we gain insights on the effects of DLVO forces, substrate thickness, substrate material compressibility (quantified by Poisson's ratio) and high oscillation frequency for different physical setups encountered in SPM and the likes. We list some key observations. A substrate that is thicker and more compressible allows for larger deformation, i.e. is effectively softer. Presence of DLVO forces lead to magnification in force of upto two orders of magnitude and in substrate deformation of upto an order of magnitude for oscillatory loading at low frequencies and approach/recession loading at low speed. For oscillatory loading at high frequencies, DLVO forces do not appreciably affect the force and deflection behaviour of the system. Having demonstrated the versatility and utility of our framework, we expect it to evolve into a diverse and useful tool for solving problems of soft-lubrication.