Flow control systems

• US 20040163957A1
• Filed: 12/10/2003
• Published: 08/26/2004
• Est. Priority Date: 06/13/2001
• Status: Active Grant

• Current Assignee: AB Sciex LLC (Danaher Corporation)
• Original Assignee: AB Sciex LLC (Danaher Corporation)
• Inventors: Paul, Phillip H., Neyer, David W., Bailey, Christopher G., Arnold, Don Wesley
• Granted Patent: US 7,597,790 B2
• Time in Patent Office: Days
• US Class Current: 204/450
• CPC Class Codes: B01D 61/56 Electro-osmotic dewatering
• CPC Class Codes: G01N 2030/285 electrically driven carrier
• CPC Class Codes: G01N 2030/324 speed, flow rate
• CPC Class Codes: G01N 2030/326 pumps
• CPC Class Codes: G01N 30/32 of pressure or speed G01N30/36 takes precedence
• CPC Class Codes: G01N 30/34 of fluid composition, e.g. gradient G01N30/36 takes precedence
• CPC Class Codes: G05D 11/132 by controlling the flow of the individual components G05D11/133 takes precedence
• CPC Class Codes: G05D 7/0694 by action on throttling means or flow sources of very small size, e.g. microfluidics microvalves F16K99/0001; microstructural devices per se B81B
• CPC Class Codes: Y10T 137/85978 With pump
• CPC Class Codes: Y10T 137/85986 Pumped fluid control
• CPC Class Codes: Y10T 137/86027 Electric

Abstract

A flow controller which uses a combination of hydrostatic pressure and electroosmotic flow to control the flow of a fluid. A driving fluid (1204) whose flow rate is dependent on both hydrostatic pressures and electroosmotic flow can be used (a) directly as a working fluid in an operable device, for example a chromatograph, or (b) to displace a working fluid (1203) from a storage container (625) into an operable device (1301), or both (a) and (b). The driving fluid (1204) can be composed of one or more fluids. Part or all the driving fluid (1204) is passed through an electroosmotic device (100) so as to increase or decrease the flow rate induced by hydrostatic pressure.

Claims

1. A method of causing a working fluid to flow from a first point to a second point, which comprises applying a driving pressure to the working fluid at the first point, wherein at least part of the driving pressure is provided by a driving fluid whose rate of flow comprises

(i) a hydrostatic component, and

(ii) an electroosmotic component.

2. A method according to claim 1 wherein the driving fluid and the working fluid are the same.

3. A method according to claim 1 wherein the working fluid comprises a fluid which

(i) is stored in a storage element at the first point, and

(ii) is displaced from the storage element by the driving fluid.

4. A method according to any one of the preceding claims wherein the driving fluid flow is produced by a process which comprises

(1) supplying a stream of fluid by hydrostatic pressure, and

(2) removing some of the fluid from the stream by electroosmotic flow.

5. A method according to any one of claims 1 to 4 wherein the driving fluid flow is produced by a process which comprises passing a mixture of first and second fluids under hydrostatic pressure through a channel in which electroosmotic flow is generated in the mixture.

6. A method according to any one of claims 1 to 4 wherein the driving fluid flow is produced by a process which comprises mixing

(i) the working fluid whose flow rate depends on a pressure which is partly or wholly hydrostatic, and

(ii) a second fluid whose flow rate, before said mixing, depends on a pressure which is partly or wholly hydrostatic,

wherein a mixture is created that passes through a channel in which electroosmotic flow is generated.

7. A method according to claim 6 wherein

(i) the working fluid

(a) is supplied from a first source at a hydrostatic pressure P₁, and

(b) before it is mixed with the second fluid, passes through a first flow control element;

and

(ii) the second fluid

(a) is supplied from a second source at a hydrostatic pressure P₂, and

(b) passes through a second flow control element; and

wherein the first flow control element has a conductance k₁, the second flow control element has a conductance k₂, and the channel has a conductance k₃; and

1+k₃/k₁ is greater than P₁/P₂ and 1+k₃/k₂ is greater than P₂/P₁.

8. A method according to any one of claims 1 to 4, wherein the electroosmotic component is produced by passing an electrokinetic fluid through a channel in which the electroosmotic flow is generated in the electrokinetic fluid, and at least part of the electrokinetic fluid is

(i) stored in a storage element, and

(ii) is displaced from the storage element, before passing through the channel, by a fluid under hydrostatic pressure.

9. A method according to any one of the preceding claims wherein at least part of the driving fluid passes through a flow control element.

10. A method according to any one of the preceding claims which comprises

(a) monitoring at least one variable by one or more of a pressure transducer, a flowmeter, a temperature sensor, a heat flux sensor, a displacement sensor, a load cell, a strain gauge, a conductivity sensor, a selective ion sensor, a pH sensor, a flow spectrophotometer, and a turbidity sensor, and

(b) changing, in response to said monitoring, an electrical potential which generates at least part of the electroosmotic component.

11. A method according to any one of the preceding claims wherein variations in the electroosmotic component at least partially compensate for variations in the hydrostatic component.

12. A method according to any one of preceding claims wherein the rate of flow of the working fluid at the second point is less than 50 microliters/minute.

13. A method according to any one of the preceding claims wherein the working fluid has at least one of the following characteristics:

(a) it comprises a liquid having an ionic strength of least 25 millimolar;

(b) it comprises a liquid having an ionic strength less than 0.5 millimolar;

(c) it comprises a liquid having a dynamic viscosity greater than 5 centipoise;

(d) it comprises a substantially pure organic liquid;

(e) it comprises a liquid having a dielectric constant less than 20;

(f) it comprises a liquid containing polyvalent ions;

(g) it comprises a liquid having a pH value less than 7; and

(h) it comprises a liquid having a pH value less than 4.

14. A method according to any one of preceding claims wherein the fluid from the second point passes into a chromatograph.

15. A method according to any one of preceding claims wherein apparatus operating under a first set of conditions causes the working fluid to flow from the first point to the second point and through an operable device during a first time period, and thereafter the same apparatus operating under a second set of conditions causes the working fluid to flow from the first point to the second point and through an operable device during a second time period, the working fluid during the first time period being different from the working fluid during the second time period and/or the operating conditions of the operable device during the first time period being different from the operating conditions of the operable device during the second time period, and/or the operable device during the first time period being different from the operable device during the second time period.

16. Apparatus suitable for use in a method as claimed in any one of preceding claims, the apparatus comprising

(1) a channel which includes an inlet and an outlet, and through which a fluid under pressure can flow from the inlet to the outlet;

(2) a porous solid dielectric material which is positioned within the channel between the inlet and the outlet; and

(3) electrodes which are positioned so that, when an electrokinetic fluid under pressure is flowing through the channel between the inlet and the outlet, the rate at which the fluid flows can be changed by changing an electric potential connected to the electrodes;

said apparatus having at least one of the following characteristics;

(a) it comprises a flow control element through which a fluid under pressure can flow before reaching the inlet;

(b) it comprises a flow control element through which a fluid under pressure can flow after leaving the outlet;

(c) it comprises an operable device which employs a pressurized fluid in its operation and is connected to

(i) the outlet, so that when pressurized fluid flows from the outlet, it passes through the device, or

(ii) a first outlet of a conduit having a second outlet connected to the channel and an inlet which can be connected to a source of pressurized fluid;

(d) it comprises a first source for a first fluid and a second source for a second fluid, both the first source and the second source being connected to the inlet so that pressurized fluid from the sources can pass through the inlet into the channel;

(e) it comprises a variable power supply connected to the electrodes;

(f) it comprises at least one sensor for monitoring a control signal, and a feedback control mechanism operatively connected to the sensor, whereby, when the apparatus includes a power supply connected to the electrodes, the feedback control mechanism modulates the electric potential supplied by the power supply;

(g) it comprises a conduit having (i) a first conduit outlet which is connected to the inlet, (ii) a second conduit outlet which can be connected to an operable device or a plurality of operable devices, and (iii) a conduit inlet which can be connected to a source of pressurized fluid, whereby, when pressurized fluid enters the conduit, a part of the pressurized fluid flows through the channel and the remainder of pressurized fluid flows through the device or devices;

(h) it comprises two or more said channels and a conduit having (i) a plurality of conduit inlets connected to an inlet or an outlet of each of said channels, and (ii) a conduit outlet which can be connected to an operable device or a plurality of operable devices;

(i) it comprises two or more said channels, the dielectric materials in the channels being different from each other;

(j) it comprises a pressure transducer through which a fluid under pressure can flow before reaching the inlet;

(k) it comprises a check valve through which a fluid under pressure can flow before reaching the inlet; and

(l) it comprises an accumulator through which a fluid under pressure can flow before reaching the inlet.

17. Apparatus according to claim 16 wherein the porous dielectric material comprises a fused silica capillary, silica particles, an organic polymer, or a product made by lithographic patterning, lithographic etching, direct injection molding, sol-gel processing, or electroforming.

18. Apparatus according to claim 16 or 17 which comprises a power supply having electrodes, the power supply having one or both of the following characteristics

(i) it is a variable power supply, and

(ii) its electrodes are connected to the channels through a bridge.

19. Apparatus according to any one of claims 16 to 18 which comprises at least one sensor for monitoring a control signal, and a feedback control mechanism operatively connected to the sensor, whereby, when the apparatus includes a power supply connected to the electrodes, the feedback control mechanism maintains the control signal within a predetermined range by modulating the electric potential supplied by the power supply, the sensor being one or more of a pressure transducer, a flowmeter, a temperature sensor, a heat flux sensor, a displacement sensor, a load cell, a strain gauge, a conductivity sensor, a selective ion sensor, a pH sensor, a flow spectrophotometer, and a turbidity sensor.

20. The use of electroosmotic flow to modify the rate at which a pressurized working fluid is delivered to an operable device which employs the pressurized fluid in its operation.

21. A flow controller system, comprising:

(a) a first conduit having;

(i) a first fluid inlet in fluid communication with a first fluid source at pressure P₁;

(ii) a first fluid outlet at pressure P₃ in fluid communication with the first fluid inlet, wherein P₃<

P₁; and

(iii) a first flow element disposed between the first fluid inlet and a first node; and

(b) a second conduit having;

(i) a second fluid inlet in fluid communication with a second fluid source at pressure P₂, wherein P₃<

P₂;

(ii) a second fluid outlet in fluid communication with the second fluid inlet and, at the first node, with the first conduit;

(iii) a second flow element disposed between the second fluid inlet and the second fluid outlet; and

(iv) a third fluid outlet at pressure P_4, wherein P₄<

P₁ and P₄<

P₂, the third fluid outlet being in fluid communication at a second node with the second flow element outlet

wherein α

₁=θ

₁ν

₁, where ν

₁ is the internal volume of the first node an θ

₁ is the sum of apparent compressibilities within ν

₁, α

₂=θ

₂ν

₂ where ν

₂ is the internal volume of the second node and θ

₂ is the sum of apparent compressibilities within ν

₂, the first flow element has a conductance of k₁, the second flow element has a conductance of k₂, and wherein α

₁/k₁>

α

₂/k₂.

22. A flow controller system, comprising:

(a) a first conduit having;

(i) a first fluid inlet in fluid communication with a first fluid source at pressure P₁;

(ii) a first fluid outlet at pressure P₃ in fluid communication with the first fluid inlet, wherein P₃<

P₁; and

(iii) a first flow element disposed between the first fluid inlet and a first node; and

(b) a second conduit having;

(i) a second fluid inlet in fluid communication with a second fluid source at pressure P₂, wherein P₃<

P₂;

(ii) a second fluid outlet in fluid communication with the second fluid inlet and, at the first node, with the first conduit;

(iii) a second flow element disposed between the second fluid inlet and the second fluid outlet; and

(iv) a third fluid outlet at pressure P₄, wherein P₄<

P₁ and P₄<

P₂, the third fluid outlet being in fluid communication at a second node at pressure P_N2, with the second flow element outlet;

(c) a pressure transducer located at either the first or the second node; and

(d) an accumulator located at the opposite node as the pressure transducer;

wherein α

₁=θ

₁ν

₁, where ν

₁ is the internal volume of the first node and θ

₁ is the sum of apparent compressibilities within ν

₁, α

₂=θ

₂ν

₂ where ν

2 is the internal volume of the second node and θ

₂ is the sum of apparent compressibilities within ν

₂, the first flow element has a conductance of k₁, the second flow element has a conductance of k₂, and wherein α

₁/k₁>

α

₂/k₂.

23. A flow controller system, comprising:

(a) a first conduit having;

(i) a first fluid inlet in fluid communication with a first fluid source at pressure P₁;

(ii) a first fluid outlet at pressure P₃ in fluid communication with the first fluid inlet, wherein P₃<

P₁; and

(iii) a first flow element disposed between the first fluid inlet and a first node; and

(b) a second conduit having;

(i) a second fluid inlet in fluid communication with a second fluid source at pressured P₂, wherein P₃<

P₂;

(ii) a second fluid outlet in fluid communication with the second fluid inlet and, at the first node, with the first conduit;

(iii) a second flow element disposed between the second fluid inlet and a second fluid outlet; and

(iv) a third fluid outlet at pressure P_4, wherein P₄<

P₁ and P₄<

P₂, the third fluid outlet being in fluid communication at a second node with the second flow element outlet;

(c) a pressure transducer located at either the first or the second node; and

(d) a check valve between the first and second nodes;

wherein α

₁=θ

₁ν

₁, where ν

₁ is the internal volume of the first node and θ

₁ is the sum of apparent compressibilities within ν

₁, α

₂=θ

₂ν

₂ where ν

₂ is the internal volume of the second node and θ

₂ is the sum of apparent compressibilities within ν

₂, the first flow element has a conductance of k₁, the second flow element has a conductance of k₂, and wherein α

₁/k₁>

α

₂/k₂.

24. A flow controller system, comprising:

(a) a first channel having;

(i) a first channel fluid inlet in fluid communication at a node with a first fluid source at pressure P₁ and a second fluid source at pressure P₂;

(ii) a first channel fluid outlet in fluid communication with the first channel fluid inlet and, at pressure P_3, with a fluid terminus, wherein P₃<

P₁ and P₃<

P₂; and

(iii) a porous dielectric material disposed in the first channel;

(b) a second channel having;

(i) a second channel fluid inlet in fluid communication with the second fluid source;

(ii) a second channel fluid outlet in fluid communication with the second channel fluid inlet and, at the first node, with the first channel inlet and

(iii) a porous dielectric material disposed in the second channel; and

(c) a power supply in electrical communication with spaced electrodes for applying an electrical potential to the electrodes, the electrodes being positioned so that the channels are electrokinetically active when the power supply applies an electric potential to the electrodes;

wherein the electric potential generates an electroosmotically-driven flow component through at least one of the first and the second channels, wherein the electroosmotically-driven flow component modulates at least one pressure-driven flow component resulting from the P₁−

P₃ and the P₂−

P₃ pressure differentials.

25. A flow controller system, comprising:

(a) a first channel having;

(i) a first channel fluid inlet in fluid communication at a first node with a first fluid source at pressure P₁ and a second fluid source at pressure P₂;

(ii) a first channel fluid outlet in fluid communication with the first channel fluid inlet and, at pressure P₃, with a fluid terminus, wherein P₃<

P₁ and P₃<

P₂; and

(iii) a porous dielectric material disposed in the first channel;

(b) a second channel having;

(i) a second channel fluid inlet in fluid communication with the second fluid source;

(ii) a second channel fluid outlet in fluid communication with the second channel fluid inlet and, at the first node, with the first channel; and

(iii) a porous dielectric material disposed in the second channel;

(c) a first power supply in electrical communication with a first set of spaced electrodes for applying a first electric potential to the first set of spaced electrodes, the first set of spaced electrodes being positioned so that the first channel is electrokinetically active when the first power supply applies an electric potential to the first set of spaced electrodes;

(d) a second power supply in electrical communication with a second set of spaced electrodes for applying a second electric potential to the second set of spaced electrodes, the second set of spaced electrodes being positioned so that the second channel is electrokinetically active when the second power supply applies an electric potential to the second set of spaced electrodes;

wherein the first electric potential generates a first electroosmotically-driven flow component through the first channel, the first electroosmotically-driven flow component modulating at least one pressure-driven flow component resulting from the P₁−

P₃ and the P₂−

P₃ pressure differentials and the second electric potential generates a second electroosmotically-driven flow component through the second channel, the second electroosmotically-driven flow component modulating at least one pressure-driven flow components resulting from the P₁−

P₃ and the P₂−

P₃ pressure differentials.

26. A flow controller system, comprising:

(a) a channel having;

(i) a fluid inlet in fluid communication at a node with a fluid source at pressure P₁;

(ii) a fluid outlet in fluid communication with the fluid inlet and, at pressure P₂, with a first fluid terminus, wherein P₂<

P₁; and

(iii) a porous dielectric material disposed in the channel;

(b) a power supply in electrical communication with spaced electrodes for applying an electric potential to the spaced electrodes, the spaced electrodes being positioned so that the channel is electrokinetically active when the power supply applies an electric potential to the electrodes; and

(c) a first fluid storage element being disposed between the node and a second fluid terminus at pressure P_3, wherein P₃<

P₁, wherein the first fluid storage element has a first fluid storage element inlet in fluid communication at the node with the fluid source, and wherein the first fluid storage element also has a first fluid storage element outlet in fluid communication with the first fluid storage element inlet and the second fluid terminus;

wherein the electric potential generates an electroosmotically-driven flow component through the channel that modulates at least one pressure-driven flow component resulting from the P₁−

P₂ and the P₁−

P₃ pressure differentials.

27. A flow controller system, comprising:

(a) a channel having;

(i) a fluid inlet in liquid communication with a fluid source at pressure P₁;

(ii) a fluid outlet in liquid communication with a first fluid terminus at pressure P₂, wherein P₂<

P₁; and

(iii) a porous dielectric material disposed in the channel;

(b) a power supply in electrical communication with spaced electrodes for applying an electric potential to the spaced electrodes, the spaced electrodes being positioned so that the channel is electrokinetically active when the power supply applies an electric potential to the electrodes; and

(c) a fluid storage element fluid disposed between the fluid source and the channel, the fluid storage element having a fluid storage element inlet in fluid communication with a fluid source, the fluid storage element also having a fluid storage element outlet in fluid communication with the fluid storage element inlet and the fluid inlet;

whereby the electric potential generates an electroosmotically-driven flow component through the channel that modulates a pressure-drive flow component resulting from the P₁−

P₂ pressure differential.

28. A method for controlling a flow of a fluid, comprising:

applying an electric potential to spaced electrodes in electrical communication with a channel, the channel having a porous dielectric material disposed therein, the channel also having a fluid inlet in fluid communication with a first fluid source at pressure P₁ and a second fluid source at pressure P₂, the channel also having a fluid outlet in fluid communication with the fluid inlet and, at pressure P_3, with a terminus, wherein P₃ <

P₁ and P₃<

P₂, wherein the electric potential generates an electroosmotically-driven flow component through the channel that modulates at least one pressure-driven flow component resulting from the P₁−

P₃ and the P₂−

P₃ pressure differentials.

29. A method of controlling the flow of a fluid comprising:

(a) placing a first accumulator at a first node, wherein the first node is in a first conduit having;

a first fluid inlet in fluid communication with a first fluid source at pressure P₁, a first fluid outlet at pressure P₃, wherein P₃<

P₁, and a first flow element disposed between the first fluid inlet and the first fluid outlet;

(b) placing a second accumulator at a second node;

wherein, the second node is in a second conduit having;

a second fluid inlet in fluid communication with a second fluid source at pressure P₂, wherein P₃<

P₂, a second fluid outlet in fluid communication with the first conduit at the first node, a second flow element disposed between the second fluid inlet and the second fluid outlet, and a third fluid outlet at pressure P₄, wherein P₄<

P₁ and P₄<

P₂, the third fluid outlet being in fluid communication at the second node with the second fluid inlet.

30. A method of controlling a flow of a fluid, comprising:

applying an electric potential to spaced electrodes in electrical communication with a channel, the channel having a porous dielectric material disposed therein, the channel also having a fluid inlet in fluid communication at a node with a fluid source at pressure P₁, the channel also having a fluid outlet in fluid communication with the fluid inlet and, at pressure P₂, with a first fluid terminus, wherein P₂<

P₁, and wherein a fluid storage element is disposed between the node and a second fluid terminus at pressure P₃, wherein P₃<

P₁, the fluid storage element having a fluid storage element inlet in fluid communication at the node with the fluid source, the fluid storage element also having a fluid storage element outlet in fluid communication with the fluid storage element inlet and the second fluid terminus, wherein the electric potential generates an electroosmotically-driven flow component through the channel that modulates at least one pressure-driven flow component resulting from the P₁−

P₂ and the P₁−

P₃ pressure differentials.

31. A method for controlling a flow of fluid, comprising:

applying an electric potential to spaced electrodes in electrical communication with a channel, the channel having a porous dielectric material disposed therein, the channel also having a fluid inlet in fluid communication at a node with a fluid source at pressure P₁, the channel also having a fluid outlet in fluid communication with the fluid inlet and, at pressure P₂, with a first fluid terminus, wherein P₂<

P₁, and wherein a fluid storage element is disposed between the node and the fluid inlet, the fluid storage element having a fluid storage element inlet in fluid communication at the node with the fluid source, the fluid storage element also having a fluid storage element outlet in fluid communication with the fluid storage element inlet and the fluid inlet, wherein the electric potential generates an electroosmotically driven flow component through the channel that modulates a pressure-driven flow component resulting from the P₁−

P₂ pressure differential.