The morphology of coatings created by electrostatic deposition can be generally divided into three categories: wire mats, particles, and films. At intermediate regimes, there should exist nanowire forests as a mixture of wire and particulate deposition, but these have yet to be observed as a dominant morphology. We utilized electrostatic dissipative particle dynamics simulations to reveal that the barrier to forming nanowire forests is the directional nature of evaporation, implying that they should form if evaporation is homogeneous. Experimentally, we utilized electrospray deposition (ESD) to explore the spray of a fibril gel former, methylcellulose (MC) in water:ethanol mixtures. MC possesses a lower critical solution temperature (LCST) in water and water:ethanol blends. Above the LCST, MC and water phase separate concurrently with the rapid evaporation of ethanol, forming a shear-thickening, homogeneous gel phase. In the ESD process, the strongly entangled polymer solution resulting from gelation electrospins on a drop-by-drop basis to create forests of individual nanowires. To verify this mechanism, we employed different viscosities of MC by ESD through changes in spray temperatures, molecular weight, loading concentration, flow rates, spray distances, and additive content. The results reveal that lowering the viscosity of the gel increases the aspect ratio of formed nanowires. Similarly, the incorporation of additives that lead to too high or too low a viscosity prevents the formation of nanowires in ESD. Our study indicates that the homogenous evolution of viscosity is necessary for nanowire forest formation and that the specific viscosity further controls the morphology of the forests.

中文翻译：

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均相凝胶化在电喷雾和电纺之间的过渡中导致纳米线森林

通过静电沉积产生的涂层形态可以大致分为三类：金属丝垫，颗粒和薄膜。在中间状态下，应该以线和颗粒沉积的混合物的形式存在纳米线森林，但尚未观察到它们是主要形态。我们利用静电耗散粒子动力学模拟来揭示形成纳米线森林的障碍是蒸发的方向性，这意味着如果蒸发是均匀的，则应形成纳米线森林。在实验上，我们利用电喷雾沉积（ESD）探索了原纤维凝胶形成剂甲基纤维素（MC）在水：乙醇混合物中的喷雾。MC在水和水：乙醇混合物中的临界溶液温度（LCST）较低。在LCST上方，MC和水相在乙醇快速蒸发的同时分离，形成剪切增稠的均匀凝胶相。在ESD过程中，凝胶电纺丝逐滴产生的强力缠结聚合物溶液会形成单个纳米线的林。为了验证这种机理，我们通过改变喷涂温度，分子量，负载浓度，流速，喷涂距离和添加剂含量，通过静电放电采用了不同粘度的MC。结果表明，降低凝胶的粘度可增加形成的纳米线的长径比。类似地，掺入导致粘度太高或太低的添加剂会阻止在ESD中形成纳米线。