Switchable Electroosmotic Delivery via Capillary Shrunken Reduced Graphene Oxide Membrane

Abstract A capillary-force-assisted reduced graphene oxide (rGO) membrane is developed for electrically controlled electroosmotic flow (EOF). By combining capillary drying with subsequent freeze-drying, structural shrinkage is used to continuously control the pore size and channel density of the membrane. The resulting membrane shows enhanced EOF together with switchable transport behavior enabled by electrical parameter regulation. Under the optimized 20 h capillary drying condition, the membrane exhibits an EOF intensity of about 1.15 μL min−1 cm−2 and enables symmetric four-mode electrical switching of EOF direction and intensity through independent regulation of driving current and membrane-bias polarity. This switchable EOF is further translated into switchable molecular delivery, allowing reversible regulation of glucose and FITC-dextran (MW: 10 kDa) transport between opposite directions; in the transport-favorable direction, the transported amounts are 3.23 and 5.06× higher, respectively, than those in the opposite direction. Together, these results provide a practical route for flexible electroosmotic systems requiring electrically switchable and reversible molecular transport.