Low-Voltage Nongassing Electroosmotic Pump and Infusion Device with Polyoxometalate-Encapsulated Carbon Nanotubes

A low-voltage nongassing electroosmotic pump was assembled by sandwiching a silica frit between two carbon paper electrodes that were dip-coated with a paste consisting of phosphomolybdic acid/phosphotungstic acid (PMA/PTA)-encapsulated multiwalled carbon nanotubes (MWCNTs) and Nafion. The PMA/PTA encapsulation was a combined effect of their thermomigration and nanocapillary action in MWCNTs. The encapsulated MWCNTs retained desirable redox and charge transfer characteristics of PMA/PTA. The stable voltammogram in 1 M H2SO4 solution exhibited 77% charge retention. A total of three different possible pump configurations, namely, PUMP-I = PMA//SiO2//PMA, PUMP-II = PTA//SiO2//PTA, and PUMP-III = PMA//SiO2//PTA were put together. They are in the sequence of the anode, silica frit, and cathode. All pumps showed a linear dependence on the flow rate with a minimum operating voltage of 1 V, which is well below the thermodynamic potential of water splitting. PUMP-I provided an electroosmotic flux of 43.57 μLmin–1 V–1 cm–2 that matched the requirement of an infusion device like an insulin pump. The device was fabricated and its applicability has been demonstrated by delivering ∼1.8 mL of water at a 10 ± 2 μLmin–1 flow rate at 2 V constant applied voltage over a period of 3 h. Such a wearable device can be programed to deliver model insulin or pain medication drugs for chronic diseases.