Sophisticated oil film geometries through incomplete electrical dewetting by feedback control and Fourier construction
Sophisticated oil film geometries through incomplete electrical dewetting by feedback control and Fourier construction
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DOI：
10.1039/c5lc00274e
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发表时间：
2015-01-01
期刊：
影响因子：
6.1
通讯作者：
Heikenfeld, Jason
中科院分区：
文献类型：
--
作者：
Hsieh, Wan-Lin;Chen, Kuo-Ching;Heikenfeld, Jason
用于电子控制两种不混溶流体之间的界面的现有技术通常限于简单的周期性几何形状（对称波）或球形几何形状（仅两个主曲率半径）。这里介绍的是一种新的技术，具有更复杂的电子控制流体弯月面的几何形状。先前未展示的两种流体界面，如不对称的锯齿形轮廓，是通过动态调制覆盖控制电极阵列的油膜的不完全去湿状态而产生的，其中油膜本身由充当接地电极的导电流体覆盖。展示了两种不同的方法：（1）施加电压，电容感测弯月面几何形状，然后基于感测到的电容进一步反馈控制施加的电压;（2）使用多个周期性电压波形和跨弯月面的波传播，通过傅立叶构造来建立复杂的弯月面几何形状。这些方法在这项工作中证明了一个行之有效的电流体动力学建模方法，耦合的最大井应力张量与层流相场的油-水双相。这项工作可以用于许多应用，包括粒子或流体传输（例如芯片实验室）或自适应光学表面（例如液体棱镜阵列）。重要的是，可以使用常规材料实现该结果，并且流体以足够慢的速度（ms-mu s）响应，使得甚至常规控制电子器件（mu s-ns）也绰绰有余。此外，因为导电流体从不使油膜从固体表面去湿，所以可能消除介电劣化问题。
Existing techniques for electronic control of the interface between two immiscible fluids are typically limited to simple periodic geometries (symmetric waves) or spherical geometries (only two principle radii of curvature). Presented here, is a new technique with much more sophisticated electronic control of fluid meniscus geometry. Previously undemonstrated two-fluid interfaces, such as asymmetric saw-tooth profiles, are created by dynamic modulation of an incomplete dewetting state for an oil film covering an array of control electrodes, with the oil film itself covered by an electrically conductive fluid acting as the ground electrode. Two distinct approaches are demonstrated: (1) application of voltages, electrical capacitance sensing of meniscus geometry, followed by further feedback control of the applied voltages based on the sensed electrical capacitance; (2) use of multiple periodic voltage waveforms and wave propagation across the meniscus to build up complex meniscus geometries by Fourier construction. These approaches are demonstrated in this work by a proven electro-hydrodynamic modeling method, which couples the Max-well stress tensor with the laminar phase field of the oil-water dual phase. This work could serve numerous applications including particle or fluid transport (e.g. lab-on-chip), or adaptive optical surfaces (e.g. liquid prism arrays). Importantly, the results can be achieved using conventional materials, and the fluids respond with speeds that are adequately slow (ms-mu s) such that even conventional control electronics (mu s-ns) are more than adequate. Furthermore, because the conducting fluid never dewets the oil film from the solid surface, dielectric degradation issues are likely eliminated.