Electrokinetic pump designs and drug delivery systems
One embodiment of the present invention provides a piston assembly having a piston housing filled with an electrolyte; a housing within the piston housing that divides the piston housing into a first portion and a second portion, the housing having apertures, a shaft connecting the housing to a piston head outside of the piston housing; and a porous material inside of the housing in contact with the electrolyte. Additionally, there are provided a method for filling the delivery chamber with a delivery fluid by withdrawing the piston head from within the delivery chamber. Yet another embodiment provides a method for filling a fluid delivery assembly by withdrawing a shaft from within the fluid delivery assembly to simultaneously displace a moving pump element within the delivery chamber and bypass fluid around a housing in the pump chamber.
1 . A piston assembly, comprising:
A piston housing;
A housing within the piston housing that divides the piston housing into a first portion and a second portion, the housing having apertures that provide fluid communication between the first portion and the second portion;
A shaft connecting the housing to a piston head outside of the piston housing; and
A porous material inside of the housing.
2 . The piston assembly of claim 1 where in the piston housing is filled with an electrolyte.
3 . The piston assembly of claim 1 where in the porous material inside of the housing is in contact with the electrolyte.
4 . The piston assembly according to claim 1 wherein the porous material is a porous dielectric material adapted for operation as part of an electrokinetic pump.
5 . The piston assembly according to claim 1 further comprising:
A sealing element around the piston head or the housing.
6 . The piston assembly according to claim 1 further comprising a second shaft connecting the housing to a handle outside of the piston housing.
7 . The piston assembly according to claim 6 further comprising a valve within the second shaft wherein actuation of the valve provides a flow path between the first portion and the second portion.
8 . The piston assembly according to claim 7 wherein the flow path from one side of the housing to the other side of the housing includes a bypass through the porous material contained in the housing.
9 . The piston assembly according to claim 7 wherein the valve is actuatable from a handle attached to the second shaft.
10 . The piston assembly according to claim 1 wherein the shaft extends through a wall in the piston housing.
11 . The piston assembly according to claim 5 wherein the sealing element around the material housing seals the housing to a wall of the piston housing.
12 . The piston assembly according to claim 1 further comprising an electrode in the first portion and an electrode in the second portion.
13 . The piston assembly according to claim 12 wherein the electrodes have a double layer capacitance of greater than 10 4 microfarad/cm 2 .
14 . A pump, comprising:
a delivery chamber, a pump chamber and a wall separating the pump chamber from the delivery chamber;
a piston assembly having a piston head in the delivery chamber, a housing in the pump chamber and a shaft connecting the piston head to the housing and passing through the wall separating the pump chamber from the delivery chamber; and
a dielectric material in the housing.
15 . The pump according to claim 14 further comprising:
a pair of electrodes in the pump housing.
16 . The pump according to claim 15 wherein one electrode is on each side of the housing.
17 . The pump according to claim 15 wherein the pair of electrodes are made from a material selected to electrokineticly move a fluid in the pump chamber.
18 . The pump according to claim 14 wherein the delivery chamber and the pump chamber are in a single housing.
19 . The pump according to claim 14 wherein the housing divides the pump chamber into a first portion and a second portion.
20 . The pump according to claim 19 further comprising apertures in the housing that provide fluid communication between the first portion and the second portion.
21 . The pump according to claim 14 further comprising an electrolyte in the pump chamber.
22 . The pump according to claim 15 wherein each electrode in the pair of electrodes has a double layer capacitance of more than 10 4 microfarad/cm 2 .
23 . The pump according to claim 14 further comprising:
a bypass valve in the shaft that provides a fluid pathway from one side of the housing to the other side of the housing.
24 . The pump according to claim 14 further comprising:
a bypass valve in the shaft that provides a fluid pathway from the first portion to the second portion.
25 . The pump according to claim 14 wherein the delivery chamber is filled with a delivery fluid by relative movement between the pump chamber and the delivery chamber.
26 . The pump according to claim 17 wherein application of an electric field across the electrodes moves the fluid in the pump chamber from one side of the housing to the other side of the housing.
27 . The pump according to claim 17 wherein application of an electric field across the electrodes moves the piston head in the delivery chamber.
28 . The pump according to claim 17 wherein application of an electric field across the electrodes moves the housing relative to the pump chamber.
29 . A method for operating a fluid delivery system, comprising:
inserting a piston assembly into a delivery chamber, the piston assembly having a pump housing, a piston head outside of the pump housing and attached to a shaft extending through a wall in the pump housing, a housing attached to the shaft and between electrodes in the pump housing; and filling the delivery chamber with a delivery fluid by withdrawing the piston head from within the delivery chamber.
30 . A method for operating a fluid this delivery system according to claim 29 , further comprising:
fixing the position of the pump housing relative to the delivery chamber.
31 . A method for operating a fluid delivery system according to claim 29 further comprising:
advancing the piston head in the delivery chamber by moving fluid in the pump chamber.
32 . A method according to claim 31 wherein moving fluid within the pump chamber comprises electrokineticly moving fluid through the housing.
33 . A method according to claim 31 wherein moving fluid within the pump chamber comprises providing an electric field between the electrodes.
34 . The method according to claim 29 wherein the filling step comprises withdrawing the pump assembly.
35 . A method for operating a fluid delivery assembly having a pump chamber and a delivery chamber, comprising:
withdrawing a shaft from within the fluid delivery assembly to simultaneously displace a moving pump element within the delivery chamber and bypass fluid around a housing in the pump chamber.
36 . A method for operating a fluid delivery assembly according to claim 35 wherein withdrawing a shaft from the pump assembly introduces a delivery fluid into the delivery chamber and into contact with the moving pump element.
37 . A method of operating fluid delivery assembly according to claim 35 further comprising:
advancing the moving pump element in the delivery chamber by applying an electrical field across electrodes in the pump chamber and on either side of the housing.
38 . A method of operating a fluid delivery assembly according to claim 35 , further comprising:
electrokineticly moving fluid in the pump chamber to dispense fluid from the delivery chamber.
39 . The method of claim 35 further comprising:
Actuating a bypass in the shaft during the withdrawing step.