A low-cost viscosity sensor based on electrowetting on dielectrics(EWOD) forces

We study the fluid dynamics of polar high-k fluids immersed in non-polar insulating fluids, which areexcited by Electrowetting-On-Dielectric (EWOD) forces inside a tube with pressure compensation chan-nels (PCCs). The fluids are set in motion using the electrowetting effect resulting in a pressure differenceinside the tube. A model of the pressure field for various viscosities of the surrounding fluid is obtained byfinite element analysis of the Navier-Stokes equation. From the time-dependent pressure response andthe associated viscous damping, a correlation with the fluid’s dynamic viscosity is obtained. In the nextstep, we study the pressure evolution after driving the polar fluid in one direction and stopping it rapidlyat the edge of the driving electrode. The decay time of the pressure induced height difference insidethe PCCs can also be related to the surrounding non-polar fluid’s viscosity. Subsequently, an alternativelow-cost fabrication process of an EWOD stack is used to build the device simulated. The built deviceis tested by measuring silicon oils and a comparison between already established methods for viscositysensing and our “tube” method is made.