Electrowetting with Atomic Layer Deposition (EWALD)

在该项目中，疏水表面结构应在电润湿的特殊情况下进行研究。疏水表面的一个属性是流体的低流动阻力，流体可以很容易地通过毛细管移动，最终提供高体积的塞流。疏水性的产生是通过特定设计的表面结构来完成的。此外，可以在边界界面处使用合适的材料来调节这种效果。最后，这种效果可以通过电润湿来调节和控制。这种控制是通过表面下的电极和流体之间的电场来完成的。在这个项目中，将研究表面结构，其中所有三种方法都结合起来，以创建一个理想的可控表面。表面结构应该用牺牲层技术构建，由此电极将用原子层沉积（ALD）沉积，通过电介质隔离层隔离，也通过ALD沉积。通过在电极顶部沉积额外的电介质层，可以额外地影响润湿性。EWOD原理适用于控制表面的润湿性，由于层薄，电压较低。在由多个电极组成的微流体系统中，可以通过调制控制产生，移动和分离流体液滴。本项目的范围就是开发这样的概念。应该用原型示出，由于非常薄的ALD介电层（1个单层到几纳米），可以降低液滴移动所需的电压。由于层高度的收缩，控制电压从ca. 40伏到几伏。此外，可以用不同的拓扑结构来构造表面，使得疏水性将增加。这种结构也是CMOS兼容的。通过这些主题，该项目为复杂的芯片实验室应用提供了高效可控微流控芯片的基础。该项目的工作包包括表面结构和布局的建模，材料选择，电润湿模拟以及此类结构的原型和测量。此外，原型评估的测量系统的设计也包括在工作包中。

Within the project, hydrophobic surface structures should be researched in the special case of electrowetting on dielectrics (EWOD). One attribute of hydrophobic surfaces is the low flow resistivity of fluids and the fluid can easily move through capillaries and finally providing a high volume plug flow.The creation of hydrophobicity is done by a specific designed surface structure. Furthermore, it is possible to tune this effect with suitable materials at the boundary interface. Finally, this effect can be tuned and controlled by electrowetting. This controlling is done by an electrical field in between the electrode under the surface and the fluid.In this project surface structures will be investigated, where all three methods are combined to create an ideal controllable surface. The surface structures should be built with sacrificial layer technology, whereby the electrodes will be deposited with atomic layer deposition (ALD), isolated by ultrathin isolating layers, also deposited by ALD.With depositing an extra dielectric layer on top of the electrode it is possible to influence the wettability additionally. The EWOD-Principle is suitable for controlling the wettability of the surface with a low electrical voltage due to the thin layers.In a microfluidic system consisting of multiple electrodes it is possible to generate, move and divide fluidic driblets with a modulated control.Scope of this project is to develop such a concept. It should be shown with prototypes that the voltage, necessary for the movement of the driblet could be reduced due to the very thin ALD dielectric layers (1 monolayer up to a few nanometres). Due to the shrinking of layer height the control voltage decreases from ca. 40V to a few volts. Additionally, it is possible to structure the surface with different topologies so that the hydrophobicity will be increased. This structures are also CMOS compatible. With these topics the project creates the fundamentals for efficient controllable microfluidic chips with integrated control electronics for complex lab-on-chip-applications.The work packages of this project reach from modelling the surface structure and layout, the material choice, simulation of electrowetting to prototyping and measurement of such structures. Furthermore, the design of measurement systems for prototype evaluation is included in the working packages also.