MRI-R2: Developing Instrumentation for measuring decoupled normal and lateral retention forces for systems of drops on surfaces

0960229Tadmor“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。”摩擦学告诉我们，使两个表面相互滑动所需的侧向力（摩擦力）实际上与接触面积成正比。因此，阿蒙顿定律是一种特殊情况，在这种情况下，粗糙表面的接触面积恰好随着载荷的增加而线性增加。PI最近提出了一个系统，其中横向力随法向力而减小，尽管接触面积增加。这种情况发生在表面上的液滴，这一发现是通过一种仪器实现的，该仪器首次允许在正常和侧向保持力之间进行有限的解耦，即离心粘附平衡（CAB）。在本提案中，PI将开发CAB，使其首次能够完全独立地操纵法向和侧向保持力，这对于研究侧向保持力对法向力的依赖性至关重要。实现测量将改变我们考虑正交保持力相互影响的方式。这将在表面科学中创造一个新的范式（旨在找到正常和侧向保持力之间的关系），从而导致变革性的研究。这将增加到CAB的另一个功能是在零侧向力下减少法向力的可能性。在这种情况下，液滴只能垂直于表面运动，最终会以负的法向力飞离表面。这样的实验将是对表面科学的核心问题——杜普雷方程的第一次直接实验测试，因此有可能从根本上改变我们对杨-杜普雷方程的理解，从而再次导致一项变革性的研究。该仪器将用于研究表面上的液滴，以及任何其他两种正交保持力可能相互影响的情况。

0960229Tadmor"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Tribology teaches that the lateral force required to slide two surfaces against each other (friction force) is in fact proportional to the contact area. The Amonton law, therefore, is a special case in which the contact area of a rough surface happens to increase linearly with the load. The PI recently presented a system in which the lateral force decreases with the normal force in spite of the fact that the contact area increases. This happens for drops on surfaces, and the discovery was enabled using an instrument that allowed for the first time some limited decoupling between normal and lateral retention forces, namely the Centrifugal Adhesion Balance (CAB). In this proposal the PI will develop the CAB such that it will enable for the first time complete independent manipulations of the normal and lateral retention forces, which is essential for the study of the dependence of lateral retention forces on the normal forces. Enabling the measurement will change the way we consider the mutual influence of orthogonal retention forces. This will create a new paradigm in surface science (aiming to find relation between normal and lateral retention forces) leading to transformative research. Another feature that this will add to the CAB is the possibility to decrease the normal force under zero lateral force. In this configuration the drop can only move normal to the surface, and will eventually fly off the surface at some negative normal force. Such an experiment will be the first experimental direct test for the Dupre equation - a central issue in surface science - thereby bearing the potential to radically change our understanding of the Young-Dupre equation thereby leading again to a transformative research. This instrument will be used to study drops on surfaces and also any other case in which two orthogonal retention forces may influence each other.