The wetting transition behaviors of polymeric droplets on microcavity surfaces are familiar and play a vital role in micromanufacturing, microfluidics, and printing industries. Despite previous research indicating that microcavity surfaces can precisely control the droplet wetting state, the understanding of the complex effects of droplet spreading, surface morphology, and property of polymeric droplet on wetting transitions remains incomplete. The air–liquid interfaces (ALIs) typically arise from the entrapped air beneath the droplet on microcavity surfaces, adopting a metastable wetting state caused by either bubble escape or dissolution. Here, we discovered a previously unobserved phenomenon: the time-dependent evolution of regularly arranged ALIs with discontinuous wetting states, along with the pronounced directional wetting transitions from the Cassie–Baxter state to the Wenzel state upon deposition of polymeric droplets on heterogeneous microcavity surfaces. The durability of ALIs in microcavities was quantified, illustrating that the wetting transitions associated with droplet spreading processes obeyed power laws. By integrating the wetting theory and the viscoelastic effect of polymeric droplet, we have proposed a phenomenological coevolution model for wetting transitions that emphasizes the synergistic interaction between adjacent microcavities, resulting in the observed cluster evolution behavior of ALIs within droplets. Our study holds great significance in guiding soft manufacturing techniques utilizing internal ALIs as templates. The established mechanism opens up avenues for investigating the intricate wetting phenomena of polymeric droplets on microtextured substrates.

中文翻译：

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异质微腔表面聚合物液滴中的不连续定向润湿转变


聚合物液滴在微腔表面上的润湿转变行为是众所周知的，在微制造、微流体和印刷行业中起着至关重要的作用。尽管先前的研究表明微腔表面可以精确控制液滴润湿状态，但对液滴扩散、表面形态和聚合物液滴特性对润湿转变的复杂影响的理解仍然不完整。气-液界面 （ALI） 通常由微腔表面液滴下方的滞留空气产生，采用由气泡逸出或溶解引起的亚稳态润湿状态。在这里，我们发现了一个以前未观察到的现象：具有不连续润湿状态的规则排列的 ALI 的时间依赖性演变，以及在聚合物液滴沉积在异质微腔表面上时从 Cassie-Baxter 状态到 Wenzel 状态的明显定向润湿转变。ALI 在微腔中的耐久性被量化，表明与液滴扩散过程相关的润湿转变服从幂律。通过整合润湿理论和聚合物液滴的粘弹性效应，我们提出了一种润湿转变的现象协同进化模型，该模型强调相邻微腔之间的协同相互作用，从而观察到液滴内 ALI 的簇进化行为。我们的研究对于指导利用内部 ALI 作为模板的软制造技术具有重要意义。已建立的机制为研究微纹理基材上聚合物液滴的复杂润湿现象开辟了途径。