Parametric Study on Electric Field-Induced Micro-/Nanopatterns in Thin Polymer Films
Parametric Study on Electric Field-Induced Micro-/Nanopatterns in Thin Polymer Films
复制标题
聚合物薄膜中电场感应微/纳米图案的参数化研究
DOI：
10.1021/acs.langmuir.8b00007
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发表时间：
2018
期刊：
影响因子：
3.9
通讯作者：
Yang Qingzhen
中科院分区：
文献类型：
--
作者：
Song Fenhong;Ju Dapeng;Gu Fangwei;Liu Yan;Ji Yuan;Ren Yulin;He Xiaocong;Sha Baoyong;Li Ben Q.;Yang Qingzhen
电场诱导聚合物薄膜中的微/纳米结构，有时被称为电流体图案化，是一种很有前途的微/纳米结构制备技术。由于其具有微接触(易拆卸)、成本低等优点，受到了广泛的关注。尽管在这项技术上已经做了大量的工作，包括实验和理论上的工作，但仍然需要了解电流体动力学图案化的机理。因此，我们利用数值相场模型系统地研究了不同参数对电流体图案化的影响。以往的研究人员通常采用润滑近似(即长波近似)来简化数值模型。然而，如果结构高度与波长相同或大于波长，则这种近似将失去有效性，这种情况在大多数情况下都会发生。因此，我们放弃了润滑近似，而是求解了流体流动和电场的完整控制方程。在该模型中，聚合物薄膜的变形用相场模型来描述。对于电场，采用了同时考虑电介电常数和电导率的漏电介质模型。流体流动与电场在相场框架内耦合在一起。利用该模型，详细研究了外加电压、模板结构高度、聚合物电导率等物理参数对聚合物电导率的影响。然后，对控制方程进行了无量纲化处理，分析了各参数之间的关系。定义了一个无量纲参数--电雷诺数ER，对于该参数，较大的值将使电场简化为理想的介电模型，较小的值将导致稳定的泄漏模型。这些发现和结果可能会加深我们对电流体图样的理解，并可能对实验有意义的指导。
Electric field-induced micro-/nanopatterns in thin polymer films, sometimes referred as electrohydrodynamic patterning, is a promising technique to fabricate micro-/nanostructures. Extensive attention has been attracted because of its advantages in microcontact (easy demolding) and low cost. Although considerable work has been done on this technique, including both experimental and theoretical ones, there still appears a requirement for understanding the mechanism of electrohydrodynamic patterning. Thus, we systematically studied the effect of different parameters on electrohydrodynamic patterning with a numerical phase field model. Previous researchers usually employed lubrication approximation (i.e., long-wave approximation) to simplify the numerical model. However, this approximation would lose its validity if the structure height is on the same scale or larger than the wavelength, which occurs in most cases. Thus, we abandoned the lubrication approximation and solved the full governing equations for fluid flow and electric field. In this model, the deformation of polymer film is described by the phase field model. As to the electric field, the leaky dielectric model is adopted in which both electrical permittivity and conductivity are considered. The fluid flow together with electric field is coupled together in the framework of phase field. By this model, the effect of physical parameters, such as external voltage, template structure height, and polymer conductivity, is studied in detail. After that, the governing equations are nondimesionalized to analyze the relationship between different parameters. A dimensionless parameter, electrical Reynolds numberER, is defined, for which, a large value would simplify the electric field to perfect dielectric model and a small value leads it to steady leaky model. These findings and results may enhance our understanding of electrohydrodynamic patterning and may be a meaningful guide for experiments.