基于接触区几何形貌的微纳粘着和界面现象演化规律的AFM研究

Micro-nano adhesion is a major reason for the failure of micro-electromechanical systems (MEMS) in manufacture and in use. The research of micro-nano adhesion is of great theoretical significance in the exploration of micro-friction mechanisms. The adhesion force measurements by an atomic force microscopy (AFM) have poor repeatability. Based on the geometry of the contact zone, the project will establish a computational model of the nanoscale adhesion. The model will be solved by numerical methods. The solution will be compared with the results of AFM experiments, to deepen the understanding of the single-asperity contact. The study of the influence of AFM parameter on the adhesion force has some shortcomings. Based on different environments and contact geometries, using the separation technology of the interaction and influencing factors, the project will study the coupling effect of every two of the loading rate, dwell time and separation speed. The evolution laws of interfacial phenomena have not been understanded yet. Based on the adjustment of the relative position of two contacting surfaces and the comparison method for changing parameters, by repeated contact-separation on the same position and the analysis of force-displacement curves, the project will investigate the occurrence mechanism and evolution process of the formation and rupture of capillary liquid bridges, contact electrification, the structural morphology of molecular adsorption films, in order to further the understanding of the microscopic adhesion. This project will have theoretical significance in understanding the mechanism of the adhesion, reference value for adhesion force experiments, and guiding significance in solving adhesion problems in various engineering cases.

微纳粘着是微机电系统(MEMS)在制造和使用中失效的一个主要原因。它的研究在微观摩擦机理的探索方面也有重大的理论意义。本项目以原子力显微镜(AFM)粘着力测量较差的重复性为出发点，基于接触区几何形貌建立纳米级粘着计算模型，数值求解并与AFM实验作对比，以深化对单峰接触的认识。针对以往参数影响研究的片面性，基于不同的环境和接触区几何形貌，采用相互作用和因素的分离技术，研究加载速率、停留时间和分离速度三者中两两间的耦合效应。针对界面现象规律认识不足的现状，基于接触区两表面相对位置的调节和改变参数作对比的方法，通过在同一位置上多次重复的接触-分离和力-位移曲线的分析，来探讨毛细液体桥的形成与破裂、接触起电和分子吸附膜的结构形态等表面现象的发生机理及其演化过程，以达到进一步地认识微纳粘着的目的。本项目将对粘着机理的认识有理论意义，对粘着力实验有参考意义，对解决各种工况下的粘着问题有指导意义。

微纳粘着是微机电系统应用中的一个关键的基础问题，是其失效的一个主要原因。本项目围绕微纳粘着的现象和机理开展研究，取得如下进展情况：(1) 粘着接触计算模型：建立了纳米级粘着接触计算模型，揭示了对称性表面轮廓的纳米级粘着力的非对称性；(2) 粘着力的时间依赖性：揭示了具有时间依赖性和无时间依赖性的粘着力发生的条件，提出了低湿度下粘着力的对数接触时间依赖性及其主导作用，并在阐明粘着力时间依赖性形成机理的基础上，揭示了利用受限液体的时间依赖性动力学行为来实现粘着调控的规律；(3) 液膜对粘着力的影响：阐明了固体表面上吸附的液膜对粘着力行为的影响规律，揭示了基底温度对膜厚的影响规律及异常大粘着力的产生原因；(4) 横向动力对粘着力的影响：揭示了不同湿度下粘着力随横向速度呈对数减小的规律，阐明了横向速度对不同湿润性表面的粘着力影响的差异性；(5) 重复接触时粘着力的演变：揭示了极端干燥环境下的重复接触时粘着力的演化现象，阐明了粘着力分层及其幅值变化的机理。相关研究成果不仅可以丰富微纳粘着的基础研究，而且有助于推动微机电系统的实用化进程，尤其对硅基微机电系统的抗粘着设计和粘着调控有指导意义。