Electrokinetic pump having capacitive electrodes
View Patent ↗An electrokinetic pump achieves high and low flow rates without producing significant gaseous byproducts and without significant evolution of the pump fluid. A first feature of the pump is that the electrodes in the pump are capacitive with a capacitance of at least 10 −4 Farads/cm 2 . A second feature of the pump is that it is configured to maximize the potential across the porous dielectric material. The pump can have either or both features.
1. A method of moving a liquid using an electrokinetic device comprising a pair of electrodes capable of having a voltage drop therebetween and a porous dielectric material between the electrodes, wherein the electrodes are comprised of a material having a capacitance of at least 10 −4 Farads per square centimeter, comprising the steps of:
(a) applying a positive current to the electrodes to charge the capacitance of the electrodes and to move the liquid through the porous dielectric material in a first direction;
(b) reversing the current applied to the electrodes prior to reaching a threshold voltage for a Faradaic process in the liquid; and
(c) applying a negative current to the electrodes to move the liquid through the porous dielectric material in a second direction that is opposite to the first direction.
2. The method of claim 1 wherein applying a negative current to the electrodes stops prior to the occurrence of a Faradaic process in the liquid.
3. The method of claim 1 wherein the liquid moves through the porous dielectric material at a rate of at least 1 mL/min.
4. The method of claim 1 , further comprising:
after applying a negative current, reversing the current applied to the electrodes prior to reaching a threshold voltage for a Faradaic process in the liquid.
5. The method of claim 1 , wherein moving a liquid through the porous dielectric material is the motive force in an indirect pumping system.
6. The method of claim 5 wherein the indirect pumping system is part of any one of: a glucose monitor system, a drug delivery system or a liquid dispensing system.
7. The method of claim 1 further comprising:
stopping the applying a positive current step when a predetermined amount of a second liquid has been moved in a second device, wherein the second device is in communication with the liquid moved through the porous dielectric material.
8. The method of claim 7 wherein the second device is any one of: a glucose monitoring device, a drug delivery device or a liquid dispensing device.
9. The method of claim 7 wherein the second liquid is either insulin or a drug.
10. A method of pumping a liquid through a porous dielectric material containing the liquid, comprising:
(a) applying a positive current to a pair of electrodes, wherein the electrodes sandwich the porous dielectric material and the capacitance of the electrodes is at least 10 −4 Farads/cm 2 , such that the liquid is pumped through the porous dielectric material in a first direction;
(b) stopping the applying a positive current to the pair of electrodes step before reaching a voltage drop across the electrodes that exceeds the threshold voltage for a Faradaic electrochemical reaction in the liquid; and
(c) applying a negative current to the electrodes such that the liquid is pumped through the porous dielectric material in a second direction, the second direction opposite the first.
11. The method of claim 10 further comprising:
stopping the applying a negative current to the pair of electrodes step before reaching a voltage drop across the electrodes that exceeds the threshold voltage for a Faradaic electrochemical reaction in the liquid.
12. The method of claim 10 wherein the steps are performed until a predetermined amount of liquid has been pumped.