在玻璃上，的醋酸和丙酸表現出完全潤濕行為，並且其擴散係數超出了Tanner’s law。然而，在醋酸與丙酸的液滴中加入Silwet L-77三矽氧烷表面活性劑後，潤濕行為將從擴散轉變為自發性隨機運動。通過在兩側塗覆聚矽氮烷所構建之玻璃的線性跑道上，可以實現自發性移動液滴的定向運動。此自發性移動液滴沒有出現接觸線停滯，此現象可歸因於從液滴邊緣延伸的薄膜。因此我們提出了兩種簡單的方法來觀察完全潤濕之液滴和含有Silwet之自發性移動液滴的前軀膜：（1）觀察在液滴附近放置含有 pH 指示劑之水滴的顏色變化，以及（2）通過光學顯微鏡觀察到的非直接接觸相互作用。由於前軀膜的存在，自發性移動的液滴能夠在接觸線之間沒有直接接觸的情況下引起原本靜置的液滴運動。這一有趣的發現可以用由於前體膜和靜態液滴的接觸所造成的Marangoni應力相關的界面張力梯度來解釋。;Acetic and propionic acids on glass show a total wetting behavior with a large exponent beyond Tanner’s law. However, the incorporation of Silwet L-77 surfactant into the droplet of acids changes the wetting behavior from spreading to random motion. On a linear runway constructed by coating polysilazane on glass, the directed motion of the self-propelled droplet can be achieved. The absence of contact line pinning can be attributed to a thin film extending from the edge of the bulk droplet. Two simple methods are proposed to observe the precursor film associated with the spreading droplet and the self-running Silwet-laden droplet: (i) the color change of nearby water droplets containing pH indicator, and (ii) the noncontact interaction observed by optical microscope. Because of the precursor film, the self-running droplet is able to induce motion of a static droplet without the direct contact between their contact lines. This interesting finding may be explained by the interfacial tension gradient associated with Marangoni stress due to the contact of the precursor film and the static droplet.
