Tunable Electroosmotic Pumping via Electrical Double Layer Charging

Here, we report a low-voltage, continuously tunable electroosmotic pump using a flexible carbon nanotube (CNT) membrane. By injecting electronic charge into the flexible CNT membrane, the sign and magnitude of the excess surface charge can be electrically controlled via the formation of an electrical double layer (EDL). The results indicate the dependence of electroosmotic flow (EOF) flux on applied current density, voltage gating, and electrolyte concentrations. This unique ability to control excess surface charge enables a bidirectional profile by applying a voltage greater than or lower than the potential of zero charge of the flexible CNT membrane. Moreover, by synchronously regulating the sign of the applied current density and gated voltage, the unidirectional pumping mode is achieved by mitigating the concentration polarization. Finally, the tunable transportation of rhodamine B and glucose across the flexible CNT membrane is performed, suggesting its significant potential for advancing biosensing, drug delivery, and integrated closed-loop systems.