Absorption Based Characterization Method for Fluid Properties Using Electrowetting-on-Dielectric Forces: Modeling and Fabrication

Electrowetting-on-Dielectrics (EWOD) can be used to build a device, where a polar fluid droplet gets actuated between two EWOD electrodes. In our setup, each electrode is located between a laser diode and an oppositely arranged photo diode. In that manner, the presence of a fluid droplet located above one certain electrode can be optically detected by means of this transmission setup. The droplet’s viscosity dependent switching time, i.e., the time it takes to move the droplet between these two electrodes can be obtained by a time difference measurement of both transmission signals. CFD simulations of the switching time, which depends on the droplet’s viscosity, and furthermore absorption simulations according to the Beer Lambert law have been carried out with DI water as a sample fluid. A low-cost and rapid fabrication method of the so called absorption EWOD (aEWOD) switch is reported and the fabricated EWOD stack is characterized with the aid of surface profilometry.