本計畫將結合模擬與理論方法，探討接觸線遲滯現象。此現象雖已經過多年研究，最近的實驗數據顯示出本現象的經典研究確有需要補強之處。新的實驗研究使用在奈米尺度下粗糙的固體表面，以不同液體量測接觸線運動與外力的關係。結果顯示經典理論與實驗結果有若干不同處。本計畫將先以電腦模擬釐清若干基本問題，例如 (一) 在實驗中接觸線遲滯的發生需要固體表面的粗糙度超過一臨界值，(二) 實驗發現外力在接觸線運動時的遲滯量與接觸線移動時外力的漲落有冪次關係，(三) 接觸線移動時外力滑落的"雪崩"強度分布。這些問題在過去接觸線遲滯研究都沒有討論到，本計畫的模擬將可有極大幫助。在電腦模擬執行後，我們會接著建立統計物理的理論模型來幫助理解接觸線遲滯現象與其他系統如在無序材質裡的介面或高分子，以及地震等問題的關聯。 ;Motivated by recent experimental detailed data, I plan to study the statistical properties of stick-slip motion of the contact line on a surface with collective weak pinning sites. The aim is to clarify the following issues: (1) The critical roughness of solid surface for the onset of contact line hysteresis. The existence of this critical roughness was different from the prediction of the classic scaling theory proposed by Robbins and Joanny. (2) The scaling relation between the hysteresis in the force-displacement relation and the fluctuation of force during contact line stick-slip motion. To the best of my knowledge, this relation has not been predicted by any existing theory. (3) the size distribution of avalanches during stick-slip motion. Experimental data shows a scaling relation that is well-described by extreme-value statistics, but there is no rigorous theoretical explanation for this phenomena.I propose that a combination of numerical and theoretical study can be applied to compare theoretical and experimental results, clarifying the crossover regime predicted in the previous scaling theory, and providing detailed statistical properties of contact line hysteresis that cannot be obtained by scaling arguments. The results will be important for further understanding of a broad range of disorder systems from interfaces and polymers in disordered medium to rupture of solids and earthquake.
