Electrowetting with Atomic Layer Deposition (EWALD)

• Applicant: Professor Dr.-Ing. Holger Vogt
• Subject Area: Microsystems ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 325152037

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.

• DFG Programme: Research Grants
• Co-Investigators: Erik Verheyen; Dr.-Ing. Reinhard Viga