Using Electroosmotic Pumps to Control the Flow Velocity in Cotton Thread‐Based µTADs

ABSTRACT Flow velocity control is of great interest for passive microfluidic devices that are used in point‐of‐care diagnostics. Various methods have been developed for the flow velocity control of microfluidic paper‐based analytical devices (µPADs), whereas fewer attempts have been made for microfluidic thread‐based analytical devices (µTADs). In this research, we attempt to control the flow velocity in cotton thread‐based µTADs with electroosmotic pumping. Utilizing electroosmotic pumps, the flow velocity in the cotton thread‐based µTADs can be decreased or increased by 13% and 106%, respectively. Moreover, the dynamic control of the flow velocity in the cotton thread‐based µTADs is achieved by adjusting the real‐time magnitude and direction of the voltage. Furthermore, we demonstrate that electroosmotic pumps can be used to overcome the hydrophobic valves in the cotton thread‐based µTADs. We show that the delivery sequence of different liquid samples for a three‐branch µTAD can be controlled. Finally, we show the potential application in lithium detection with a colorimetric assay. This method for flow velocity control shows promise for customizing the flow velocity and reaction time of cotton thread‐based µTADs, and this method can potentially increase the sensitivity of detection.