Measurement of liquid flow rate by self-generated electrokinetic potential on the microchannel surface of a solid

• Surface electric potential generated when liquid flows on solid surface.
• The electric potential generation depends on the shear force of fluid.
• Precise flow sensors can be integrated with microfluidic devices by using the proposed model.

A model to describe the interactions between the electrokinetic potential and the liquid ion slip is proposed. The model assumes that the electric charge at the liquid and solid interface causes an attraction force, whereas the fluid shear force at the wall induces a frictional force. Using the proposed model, the condition underlying liquid ion slip is described by analyzing the generation of the surface electric potential when the shear force of flow is above 0.1 mN. Once liquid ion slip occurs, the electric charges at the interface move in the direction of the flow but are retarded by electric resistance. Thus, there is a difference in the surface electric potential generated at the solid wall in the direction of the flow. In the water flowing through the microchannel, the velocity of the liquid ion slip was 5.09 × 10−5 to 2.19 × 10−3 m/s, whereas the generated surface electric potential varied from 0 to 64 μV. The proposed model and the experimental analyses provide the groundwork for precise flow sensors, which could easily be integrated into microfluidic systems.