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

0960229 Tadmor“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。“摩擦学教导说，使两个表面相互滑动所需的横向力（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载荷线性增加。PI最近提出了一个系统，其中，尽管接触面积增加，但横向力随法向力减小。这种情况发生在表面上的液滴，并且使用第一次允许法向和侧向保持力之间的一些有限解耦的仪器，即离心粘附天平（CAB），实现了这一发现。在本提案中，PI将开发CAB，以便首次实现法向和侧向固位力的完全独立操作，这对于研究侧向固位力对法向力的依赖性至关重要。启用测量将改变我们考虑正交固位力相互影响的方式。这将在表面科学中创建一个新的范式（旨在找到正常和横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的另一个特征是在零横向力下减小法向力的可能性。在这种配置中，液滴只能垂直于表面移动，并且最终将在一些负的法向力下飞离表面。这样的实验将是第一个实验直接测试的杜普雷方程-一个中心问题，在表面科学-从而承担的潜力，从根本上改变我们的理解杨杜普雷方程，从而再次导致一个变革性的研究。该仪器将用于研究表面上的液滴以及两个正交固位力可能相互影响的任何其他情况。

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.