Ganging electrokinetic pumps

Abstract

An electrokinetic system includes a first electrokinetic pump, a second electrokinetic pump, a reservoir having delivery fluid therein, and a controller. The first electrokinetic pump is configured to provide a first range of flow rates. The second electrokinetic pump is configured to provide a second range of flow rates. The second range includes flow rates that are greater than the flow rates of the first range. The reservoir is fluidically attached to the first electrokinetic pump and the second electrokinetic pump. The controller is configured to apply voltage to one of the first or second electrokinetic pumps and then apply voltage to the other of the first or second electrokinetic pumps so as to vary the flow rate range of delivery fluid pump from the reservoir.

1 . An electrokinetic pump system, comprising:
 a reservoir configured to have a delivery fluid therein;   a first electrokinetic pump assembly fluidically connected to the reservoir and configured to pump the delivery fluid from the reservoir at a first range of flow rates;   a second electrokinetic pump assembly fluidically connected to the reservoir and configured to pump the delivery fluid from the reservoir at a second range of flow rates, the second range including flow rates that are greater than the flow rates of the first range; and   a controller configured to apply voltage to one of the first or second electrokinetic pump assemblies and then apply voltage to the other of the first or second electrokinetic pump assemblies so as to vary the flow rate of delivery fluid pumped by the electrokinetic pump system.   
     
     
         2 . The electrokinetic pump system of  claim 1 , wherein a total flow rate range of the system is between approximately 0.0001 ml/hr and 1,200 ml/hr. 
     
     
         3 . The electrokinetic pump system of  claim 2 , wherein the total flow rate range of the system is between approximately 0.0001 ml/hr and 1,000 ml/hr. 
     
     
         4 . The electrokinetic pump system of  claim 3 , wherein the total flow rate range of the system is between approximately 0.01 ml/hr and 30 ml/hr. 
     
     
         5 . The electrokinetic system of  claim 1 , further comprising a third electrokinetic pump assembly fluidically connected to the reservoir and configured to provide a third range of flow rates, the third range of flow rates including flow rates that are greater than the flow rates of the second range, wherein the controller is configured to apply voltage to one of the first or second or third electrokinetic pump assemblies and then apply voltage to the another of the first or second electrokinetic pump assemblies so as to vary the flow rate of delivery fluid pumped by the electrokinetic pump system. 
     
     
         6 . The electrokinetic system of  claim 1 , wherein the flow rate range of the first electrokinetic pump assembly is between approximately 0.01 and 5 ml/hr and the flow rate range of the second electrokinetic pump assembly is between approximately 0.1 ml/hr and 15 ml/hr. 
     
     
         7 . The electrokinetic system of  claim 1 , wherein the first and second pump assemblies are electrically connected in parallel. 
     
     
         8 . The electrokinetic system of  claim 1 , wherein the first electrokinetic pump assembly includes a first pressure sensor configured to detect a flow rate of delivery fluid pumped with the first electrokinetic pump assembly, and wherein the second electrokinetic pump assembly includes a second pressure sensor configured to detect a flow rate of delivery fluid pumped with the second electrokinetic pump assembly. 
     
     
         9 . The electrokinetic system of  claim 1 , wherein the first electrokinetic pump assembly includes a first check valve to control the flow rate of delivery fluid pumped from the first electrokinetic pump assembly, and wherein the second electrokinetic pump assembly includes a second check valve configured to control the flow rate of delivery fluid pumped from the second electrokinetic pump assembly. 
     
     
         10 . The electrokinetic system of  claim 1 , wherein the controller is further configured to apply voltage to both of the first and second electrokinetic pump assemblies simultaneously to increase the flow rate of delivery fluid pumped by the electrokinetic pump system. 
     
     
         11 . A method of pumping fluid in an electrokinetic pump system, comprising:
 applying voltage with a controller to a first electrokinetic pump assembly to pump delivery fluid from a reservoir at a first flow rate; and   applying voltage with the controller to a second electrokinetic pump assembly to pump delivery fluid from the reservoir at a second flow rate, the second flow rate different than the first flow rate.   
     
     
         12 . The method of  claim 11 , wherein a total flow rate range of the electrokinetic pump system is between approximately 0.0001 ml/hr and 1,200 ml/hr. 
     
     
         13 . The method of  claim 12 , wherein the total flow rate range of the electrokinetic pump system is between approximately 0.0001 ml/hr and 1,000 ml/hr. 
     
     
         14 . The method of  claim 13 , wherein the total flow rate range of the electrokinetic pump system is between approximately 0.01 ml/hr to 30 ml/hr. 
     
     
         15 . The method of  claim 11 , further comprising applying voltage with the controller to a third electrokinetic pump assembly to pump delivery fluid from the reservoir at a third flow rate, the third flow rate different than the first and second flow rates. 
     
     
         16 . The method of  claim 11 , wherein a flow rate range of the first electrokinetic pump assembly is between approximately 0.01 ml/hr and 5 ml/hr, and wherein a flow rate range of the second electrokinetic pump assembly is between approximately 0.1 ml/hr and 15 ml/hr. 
     
     
         17 . The method of  claim 11 , wherein the first and second electrokinetic pump assemblies are electrically connected in parallel. 
     
     
         18 . The method of  claim 11 , further comprising measuring the flow rate of delivery fluid pumped by the first electrokinetic pump assembly with a first pressure sensor and measuring the flow rate of delivery fluid pumped by the second electrokinetic pump assembly with a second pressure sensor. 
     
     
         19 . The method of  claim 11 , further comprising controlling the flow of delivery fluid pumped by the first electrokinetic pump assembly with a first check valve and controlling the flow of delivery fluid pumped by the second electrokinetic pump assembly with a second check valve. 
     
     
         20 . The method of  claim 11 , wherein the voltage is applied with the controller to the first and second electrokinetic pump assemblies simultaneously to increase the flow rate of delivery fluid pumped by the electrokinetic pump system. 
     
     
         21 . An electrokinetic pump system comprising:
 a reservoir configured to have a delivery fluid therein;   a first electrokinetic pump assembly fluidically connected to the reservoir and configured to pump the delivery fluid from the reservoir;   a second electrokinetic pump assembly fluidically connected to the reservoir and configured to pump the delivery fluid from the reservoir; and   a controller configured to apply voltage in a first cycle to the first electrokinetic pump assembly and to apply voltage in a second cycle to a second electrokinetic pump assembly, the controller configured to stagger the start-time of the first and second cycles so as to provide substantially continuous flow of the delivery fluid from the electrokinetic pump system.   
     
     
         22 . The electrokinetic pump system of  claim 21 , further comprising a third electrokinetic pump and a fourth electrokinetic pump, wherein the reservoir is fluidically attached to the third and fourth electrokinetic pumps, and wherein the controller is configured to apply voltage in a third cycle to the third electrokinetic pump and to apply voltage in a fourth cycle to the fourth electrokinetic pump, the controller configured to stagger the start-times of the first, second, third, and fourth cycles so as to provide substantially continuous flow of the delivery fluid pumped from the electrokinetic pump system. 
     
     
         23 . The electrokinetic pump system of  claim 22 , wherein the controller is configured to synchronize the cycles such that the first cycle includes an intake or outtake stroke only when the second cycle includes a zero-voltage phase, the second cycle includes an intake or an outtake stroke only when the first cycle includes a zero-voltage phase, the third cycle includes an intake or an outtake stroke only when the fourth cycle includes a zero-voltage phase, the fourth cycle includes an intake or an outtake stroke only when the third cycle includes a zero-voltage phase. 
     
     
         24 . The electrokinetic pump system of  claim 23 , wherein the controller is further configured to synchronize the cycles such that the first cycle includes an intake stroke when the third cycle includes an outtake stroke, and the third cycle includes an intake stroke when the first cycle includes an outtake stroke. 
     
     
         25 . The electrokinetic pump system of  claim 21 , wherein the controller is configured to synchronize the cycles such that the first cycle includes an intake stroke while the second cycle includes an intake stroke. 
     
     
         26 . The electrokinetic pump system of  claim 25 , wherein the third cycle includes an intake stroke while the second cycle includes an intake stroke. 
     
     
         27 . The electrokinetic pump system of  claim 26 , wherein the fourth cycle includes an intake stroke while the third cycle includes an intake stroke. 
     
     
         28 . The electrokinetic pump system of  claim 21 , wherein the first electrokinetic pump assembly includes a first electrokinetic engine and two electrokinetic pumps, and wherein the second electrokinetic pump assembly includes a second electrokinetic engine and two additional electrokinetic pumps, the first and second engines being reciprocating engines. 
     
     
         29 . The electrokinetic pump system of  claim 1 , wherein the controller is configured such that an instantaneous flow rate of the delivery fluid pumped from the electrokinetic pump system never drops to zero during pumping of the delivery fluid. 
     
     
         30 . The electrokinetic pump system of  claim 21 , wherein the controller is configured such that an instantaneous flow rate delivery fluid pumped from the electrokinetic pump system varies by less than 20% from a target flow rate. 
     
     
         31 . The electrokinetic pump system of  claim 30 , wherein the controller is configured such that the instantaneous flow rate varies by less than 10%. 
     
     
         32 . The electrokinetic pump system of  claim 31 , wherein the controller is configured such that the instantaneous flow rate varies by less than 5%. 
     
     
         33 . A method of pumping fluid with an electrokinetic pump system, comprising:
 applying voltage in a first cycle to a first electrokinetic pump assembly to pump delivery fluid from a reservoir with the first electrokinetic pump assembly;   applying voltage in a second cycle to a second electrokinetic pump assembly to pump delivery fluid from the reservoir with the second electrokinetic pump assembly;   wherein the start-time of the second cycle is delayed relative to the start-time of the first cycle so as to provide substantially continuous flow of the delivery fluid from the electrokinetic pump system.   
     
     
         34 . The method of  claim 33 , further comprising applying voltage in a third cycle to a third electrokinetic pump assembly to pump delivery fluid from the reservoir with the third electrokinetic pump assembly and applying voltage in a fourth cycle to a fourth electrokinetic pump assembly to pump delivery fluid from the reservoir with the fourth electrokinetic pump assembly, wherein the start-times of third and fourth cycles are delayed relative to the start-time of the first and second cycle so as to provide substantially continuous flow of the delivery fluid from the electrokinetic pump system. 
     
     
         35 . The method of  claim 34 , further comprising synchronizing the cycles such that the first cycle includes an intake or outtake stroke only when the second cycle includes a zero-voltage phase, the second cycle includes an intake or an outtake stroke only when the first cycle includes a zero-voltage phase, the third cycle includes an intake or an outtake stroke only when the fourth cycle includes a zero-voltage phase, the fourth cycle includes an intake or an outtake stroke only when the third cycle includes a zero-voltage phase. 
     
     
         36 . The method of  claim 35 , further comprising synchronizing the cycles such that the first cycle includes an intake stroke when the third cycle includes an outtake stroke, and the third cycle includes an intake stroke when the first cycle includes an outtake stroke. 
     
     
         37 . The method of  claim 34 , further comprising synchronizing the cycles such that the first cycle includes an intake stroke while the second cycle includes an intake stroke. 
     
     
         38 . The method of  claim 37 , further comprising synchronizing the cycles such that the third cycle includes an intake stroke while the second cycle includes an intake stroke. 
     
     
         39 . The method of  claim 38 , wherein the fourth cycle includes an intake stroke while the third cycle includes an intake stroke. 
     
     
         40 . The method of  claim 33 , wherein, when applying the voltage in the first cycle and the second cycle, an instantaneous flow rate of delivery fluid from the electrokinetic pump system never drops to zero. 
     
     
         41 . The method of  claim 33 , wherein applying the voltage in the first cycle and the second cycle causes variations in an instantaneous flow rate of the delivery fluid from the electrokinetic pump system of less than 20% from a target flow rate. 
     
     
         42 . The method of  claim 41 , wherein the instantaneous flow rate varies by less than 10%. 
     
     
         43 . The method of  claim 42 , wherein the instantaneous flow rate varies by less than 5%.