US20100254830A1

US20100254830A1 - Magnetically driven micro-pumping method using external rotating stirrer

Info

Publication number: US20100254830A1
Application number: US11/545,189
Authority: US
Inventors: David J. Beebe; Ivar Meyvantsson; Dongshin Kim
Original assignee: Individual
Current assignee: Wisconsin Alumni Research Foundation
Priority date: 2006-10-10
Filing date: 2006-10-10
Publication date: 2010-10-07

Abstract

A device and method for conducting peristaltic pumping of a fluid in a body is provided. The body includes a channel having an input and an output and being partially defined by a flexible layer. A plurality of contacts are spaced along the layer and the channel is filled with the fluid. The plurality of spaced contacts is magnetically coupled to a magnetic field in sequence so as to translate peristaltic motion to the layer thereby pumping the fluid through the channel.

Description

REFERENCE TO GOVERNMENT GRANT

This invention was made with United States government support awarded by the following agencies: NAVY/ONR N00014-04-1 0659. The United States has certain rights in this invention.

FIELD OF THE INVENTION

This invention relates generally to microfluidic devices, and in particular, to a device and method for the peristaltic pumping of a fluid within a microfluidic device.

BACKGROUND AND SUMMARY OF THE INVENTION

As is known, microfluidic components that perform a wide variety of operations have been developed for use in micro-total analysis systems aimed at genomic, proteomic and cellulomic applications. However, the successful integration of different microfluidic components on a single platform has been limited. It is noted that the fabrication processes for each of the microfluidic components can be somewhat difficult. As a result, essential fabrication processes such as bonding, aligning, and clamping have caused significant failure rates in these systems.
Further, it can be appreciated that practically all of these prior attempts at providing a functional microfluidic system require the continuous flow of a fluid through a channel of a microfluidic device. Consequently, several non-traditional pumping methods have been developed for pumping fluid through a channel of a microfluidic device, including some that have displayed promising results. However, the one drawback to almost all pumping methods is the requirement for expensive and/or complicated external equipment, be it the actual pumping mechanism (e.g., syringe pumps), or the energy to drive the pumping mechanism (e.g., power amplifiers).
The most popular method of moving a fluid through a channel of a microfluidic device is known as electrokinetic flow. Electrokinetic flow is accomplished by conducting electricity through the channel of the microfluidic device in which pumping is desired. While functional in certain applications, electrokinetic flow is not a viable option for moving biological samples through a channel of a microfluidic device. The reason is twofold: first, the electricity in the channels alters the biological molecules, rendering the molecules either dead or useless; and second, the biological molecules tend to coat the channels of the microfluidic device rendering the pumping method useless. Consequently, the only reliable way to perform biological functions within a microfluidic device was by using pressure-driven flow.
In order to provide a more elegant and efficient method of pumping fluid through a channel of a microfluidic device, it has been contemplated to incorporated a plurality of spaced deformable membranes in series along the channel of the microfluidic device. The pumping of the fluid in the channel can be realized by providing regulated external pressures that communicate with the deformable membrane units through corresponding operating channels. The deformable membranes act as springs in response to the application of the external pressures thereon. In order to pump the fluid through the channel, the deformable membranes are actuated sequentially such the deformable membranes exhibit peristaltic-like motion. The peristaltic motion of the deformable membranes is translated to the fluid in the channel of the microfluidic device, thereby urging the fluid downstream in the channel.
While functional for its intended purpose, the prior attempt at peristaltic pumping of fluid through a channel of a microfluidic device has certain limitations. For example, in order for the deformable membrane units to communicate with the regulated external pressures, the deformable membrane units and operating channels must be incorporated into the mircofluidic device. As previously noted, however, manufacturing processes such as bonding, lining, clamping and the like used in fabrication of microfluidic devices have significant failure rates. Further, providing the necessary, regulated external pressures to the deformable membranes of the microfluidic device requires a central processing unit to control the pre-programmed actuating pattern of the deformable membranes. This, in turn, increases the complexity of the microfluidic device.
Therefore, it is a primary object and feature of the present invention to provide a device and method for performing peristaltic pumping of a fluid within a channel of a microfluidic device.
It is a further object and feature of the present invention to provide a method and device for peristaltic pumping of a fluid within a channel of the microfluidic device that does not require any connections external of the microfluidic device.
It is a still further object and feature of the present invention to provide a device and method for the peristaltic pumping of a fluid in the channel of a microfluidic device that is simple and inexpensive to fabricate.
In accordance with the present invention, a device is provided for conducting peristaltic pumping of a fluid. The device includes a body defining a channel therein from receiving the fluid therein. The channel has an input end and an output end. A flexible layer partially defines the channel and a plurality of spaced magnetic contacts are spaced along the layer.
The channel may have a generally arcuate path and the plurality of spaced magnetic contacts may be bonded to the layer. For example, adhesive tape may be used for bonding the plurality of magnetic contacts to the layer. The device may also include a movable magnetic source. The magnetic source magnetically couples to the plurality of spaced magnetic contacts sequentially. The magnetic source includes a rotating magnetic stirrer.
In accordance with a further aspect of the present invention, a method is provided for conducting peristaltic pumping of a fluid in a body. The method includes the step of providing a channel in the body having an input and an output. The channel is partially defined by a flexible layer. A plurality of contacts are spaced along the layer and the channel is filled with the fluid. Thereafter, the plurality of spaced contacts are magnetically coupled in sequence to a magnetic field so as to translate peristaltic motion to the layer.
The step of magnetically coupling the plurality of spaced contacts with the magnetic field includes the additional step of rotating a magnet in close proximity to the body. The magnet generates the magnetic field. The magnet includes a first end having a first polarity such that the first end sequentially draws each of the plurality of contacts towards the magnet. In addition, the magnet includes a second end having a second polarity such that the second end sequentially urges each of the plurality of contacts away from the magnet.
The magnet may be a magnetic stirrer and the channel may have a generally arcuate configuration. The plurality of contacts may be affixed to the layer. Alternatively, the step of spacing a plurality of contacts along the layer includes the step of electroplating the plurality of contacts on the layer.
In accordance with a further aspect of the present invention, a method is provided for conducting peristaltic pumping of a fluid in a body. The method includes the step of providing a channel in the body having an input and an output. The channel is partially defined by a flexible layer. A plurality of contacts are spaced along the layer. The channel is filled with the fluid and the body is positioned in close proximity to a rotating magnetic field such that the rotating magnetic field magnetically couples with each of the plurality of spaced contacts sequentially.
The magnetic field draws each of the plurality of spaced magnetic towards a magnetic source when magnetically coupled thereto. Alternatively, the magnetic field urges each of the plurality of spaced contacts away from the magnetic source when magnetically coupled thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings furnished herewith illustrate a preferred construction of the present invention in which the above advantages and features are clearly disclosed as well as others which will be readily understood from the following description of the illustrated embodiment.

In the drawings:

FIG. 1 is a isometric view of a microfluidic device in accordance with the present invention positioned on a magnetic stirrer;

FIG. 2 is a top plan view of the microfluidic device of FIG. 1;

FIG. 3 is a cross sectional view of the microfluidic device of the present invention taken along line 3-3 of FIG. 2;

FIGS. 4 a-4 h are schematic views of a method for the peristaltic pumping of a fluid within the microfluidic device of FIG. 1; and

FIGS. 5 a-5 h are schematic views of the method for the peristaltic pumping of a fluid within an alternate embodiment of the microfluidic device of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, a microfluidic device in accordance with the present invention is generally designated by the reference numeral 10. Microfluidic device 10 includes first and second ends 12 and 14, respectively, and first and second sides 16 and 18, respectively. Microfluidic device 10 is further defined by upper and lower surfaces 20 and 22, respectively. Channel 24 is provided in void 25 that extends through microfluidic device 10. As hereinafter described, channel 24 may take the form of a single channel extending through microfluidic device 10. Alternatively, channel 24 may take the form of a series of channels or a channel network within microfluidic device 10, without deviating from the scope of the present invention.
Channel 24 includes a first vertical portion 26 terminating at an input 28 that communicates with upper surface 20 of microfluidic device 10 and a second vertical portion 30 terminating at an output 32 also communicating with upper surface 20 of microfluidic device 10. First and second vertical portions 26 and 30, respectively, of channel 24 are interconnected by and communicate with horizontal portion 34 of channel 24. In the depicted embodiment, horizontal portion 34 of channel 24 has a generally U-shaped configuration. However, other configurations are possible without deviating from the scope of the present invention. For example, channel 24 may have a generally circular shaped configuration so as to allow for the recirculation of fluid flowing therethrough. The dimensions of channel 24 connecting input 28 and output 32 are arbitrary.
Referring to FIG. 2, horizontal portion 34 of channel 24 is defined by first and second sidewalls 36 and 38, respectively, and lower surface 40. Flexible membrane 42 is positioned within void 25, extends between first and second sidewalls 36 and 38, respectively, and is vertically spaced from lower surface 40. Membrane 42 may be fixed within void 25 or be removable from microfluidic device 10. This, in turn, allows the peristaltic pumping of fluid in channel 24 (hereinafter described) to be stopped simply by removing membrane 42. In addition, it can be appreciated that an alternate membrane may be substituted for membrane 42 in order to conduct peristaltic pumping of the fluid at a different location of channel 24.
Membrane 42 includes inner surface 44 communicating with horizontal portion 34 of channel 24 and an outer surface 46. It is contemplated to fabricate membrane 42 from polydimethyl siloxane. However, membrane 42 may be fabricated from other materials without deviating from the scope of the present invention. A plurality of contacts 48 a-48 c are spaced along outer surface 46 of membrane 42. In the depicted embodiment, contacts 48 a-48 c take the form of magnets affixed to outer surface 46 of membrane 42 by an adhesive 50. However, contacts 48 a-48 c may be fabricated from other magnetically attractable materials without deviating from the scope of the present invention. In addition, it can be appreciated that contacts 48 a-48 c maybe affixed to outer surface 46 of membrane 42 by doping, by electroplating contacts 48 a-48 c directly onto outer surface 46 of membrane 42, or by embedding contacts 48 a-48 c within membrane 42, without deviating from the scope of the present invention.
In the depicted embodiment, it is intended to generate the flow of fluid in channel 24 from input 28 to output 32 of microfluidic device 10, in a first direction as indicated by arrows 52 and 54. As such, it is contemplated to generate peristaltic motion of membrane 42 such that the motion of membrane 42 is translated to and pumps the fluid in the first direction. In order to generate the peristaltic motion of membrane 42, contacts 48 a-48 c are sequentially attracted to and repelled by a magnetic source. By way of example, magnetic stirrer 56 may be used to generate the peristaltic motion of membrane 42. However, other types of magnetic sources such as microelectrodes or microcoils may be used without deviating from the scope of the present invention.
As best seen in FIGS. 1-3, magnetic stirrer 56 includes upper surface 58 for receiving microfluidic device 10 thereon. As is conventional, magnetic stirrer 56 houses rotatable bar magnet 60. As is conventional, bar magnet 60 has first and second ends 60 a and 60 b, respectively, having opposite polarities. Magnetic stirrer 56 includes a control device (not shown) operatively connected to bar magnet 60 for rotating bar magnet 60 about central axis 61 at a user selected frequency. An input device such as rotatable knob 62 may be provided to allow a user to input the selected frequency.
In operation, microfluidic device 10 is positioned on magnetic stirrer 56 such that lower surface 22 of microfluidic device 10 engages upper surface 58 of magnetic stirrer 56. Preferably, horizontal portion 34 of channel 24 is aligned with and overlaps the rotational path of ends 60 a and 60 b of bar magnet 60. Fluid is provided in channel 24 of microfluidic device 10. Magnetic stirrer 56 is actuated such bar magnet 60 rotates about central axis 61.
Referring to FIGS. 4 a-4 h, in it initial configuration, membrane 42 is generally flat, FIG. 4 a. As first end 60 a of bar magnet 60 approaches contact 48 a, contact 48 a magnetically couples to first end 60 a of bar magnet 60 such that contact 48 a is attracted to and moves toward first end 60 a of bar magnet 60, FIG. 4 b. As bar magnet 60 continues on its path, first end 60 a of bar magnet 60 magnetically decouples from contact 48 a and magnetically couples with contact 48 b. With contact 48 b magnetically coupled to first end 60 a of bar magnet 60, contact 48 b is attracted to and moves toward first end 60 a of bar magnet 60, FIG. 4 c. Once again, as bar magnet 60 continues on its path, first end 60 a of bar magnet 60 magnetically decouples from contact 48 b and magnetically couples with contact 48 c. With contact 48 c magnetically coupled to first end 60 a of bar magnet 60, contact 48 c is attracted to and moves toward first end 60 a of bar magnet 60, FIG. 4 d. Thereafter, as bar magnet 60 continues on its path, bar magnet 60 magnetically decouples from contact 48 c and membrane 42 returns to its original, generally flat configuration, FIG. 4 e.
As bar magnet 60 continues on its path and second end 60 b of bar magnet 60 approaches contact 48 a, contact 48 a magnetically couples to first end 60 b of bar magnet 60 such that contact 48 a is repelled from and moves away from second end 60 b of bar magnet 60, FIG. 4 f. As bar magnet 60 continues on its path, second end 60 b of bar magnet 60 magnetically decouples from contact 48 a and magnetically couples with contact 48 b. With contact 48 b magnetically coupled to second end 60 b of bar magnet 60, contact 48 b is repelled and moves away from second end 60 b of bar magnet 60, FIG. 4 g. Once again, as bar magnet 60 continues on its path, second end 60 b of bar magnet 60 magnetically decouples from contact 48 b and magnetically couples with contact 48 c. With contact 48 c magnetically coupled to second end 60 b of bar magnet 60, contact 48 c is repelled and moves away from second end 60 b of bar magnet 60, FIG. 4 h. Thereafter, as bar magnet 60 continues on its path, bar magnet 60 magnetically decouples from contact 48 c and membrane 42 returns to its original, generally flat configuration, FIG. 4 a.
The process heretofore described is repeated during each rotation of bar magnet 60. It can be appreciated that rotation of bar magnet 60 generates the peristaltic motion of membrane 42. The peristaltic motion of membrane 42 is translated to and pumps the fluid in channel 24 in the first direction, as shown by arrows 52 and 54 in FIG. 2. By controlling the rotational frequency of bar magnet 60, it is understood that a user can control the flow rate of the fluid flowing through channel 24. It is noted that in the event that channel 24 has a circular configuration, it is also contemplated to replace contacts 48 a-48 c with a ferrofluid in void 25. This, in turn, will allow for the smoother or more “analog” pumping of the fluid in channel 24. It is also noted that the direction of the flow in channel 24 is dependent on the conditions provided at the time of actuation of the magnetic stirrer. More specifically, it can be appreciated that certain factors, e.g., the strength of the magnetic field, the size of contacts 48 a-48 c, the distance between contacts 48 a-48 c, the compliance and thickness of membrane 42, and the rotational frequency of bar magnet 60, may influence the direction of fluid flow in channel 24. As a result, it can be understood that a channel network within microfluidic device 10 may demonstrate fluid flow in several different directions concurrently.
Referring to FIGS. 5 a-5 h, an alternate embodiment of microfluidic device 10 is provided. In its initial configuration, it is contemplated for inner surface 44 of membrane 42 to be engaged with lower surface 40 of horizontal portion 34 of channel 24, FIG. 5 a. As first end 60 a of bar magnet 60 approaches contact 48 a, contact 48 a magnetically couples to first end 60 a of bar magnet 60 such that contact 48 a is repelled and moves away from first end 60 a of bar magnet 60, FIG. 5 b. As bar magnet 60 continues on its path, first end 60 a of bar magnet 60 magnetically decouples from contact 48 a and magnetically couples with contact 48 b. With contact 48 b magnetically coupled to first end 60 a of bar magnet 60, contact 48 b is repelled and moves away from first end 60 a of bar magnet 60, FIG. 5 c. Once again, as bar magnet 60 continues on its path, first end 60 a of bar magnet 60 magnetically decouples from contact 48 b and magnetically couples with contact 48 c. With contact 48 c magnetically coupled to first end 60 a of bar magnet 60, contact 48 c is repelled and moves away from first end 60 a of bar magnet 60, FIG. 5 d. Thereafter, as bar magnet 60 continues on its path, bar magnet 60 magnetically decouples from contact 48 c and membrane 42 returns to its original configuration, FIG. 5 e.
As bar magnet 60 continues on its path and second end 60 b of bar magnet 60 approaches contact 48 a, contact 48 a magnetically couples to first end 60 b of bar magnet 60 such that contact 48 a is attracted to and attempts to move toward second end 60 b of bar magnet 60 such that membrane 42 remains in its initial configuration, FIG. 5 f. As bar magnet 60 continues on its path, second end 60 b of bar magnet 60 magnetically decouples from contact 48 a and magnetically couples with contact 48 b. With contact 48 b magnetically coupled to second end 60 b of bar magnet 60, contact 48 b is attracted to and attempts to move toward second end 60 b of bar magnet 60 such that membrane 42 remains in its initial configuration, FIG. 5 g. Once again, as bar magnet 60 continues on its path, second end 60 b of bar magnet 60 magnetically decouples from contact 48 b and magnetically couples with contact 48 c. With contact 48 c magnetically coupled to second end 60 b of bar magnet 60, contact 48 c is attracted to and attempts to move toward second end 60 b of bar magnet 60 such that membrane 42 remains in its initial configuration, FIG. 5 h. Thereafter, as bar magnet 60 continues on its path, bar magnet 60 magnetically decouples from contact 48 c and membrane 42 remains in its initial, generally flat configuration, FIG. 5 a.
The process heretofore described is repeated during each rotation of bar magnet 60. It can be appreciated that rotation of bar magnet 60 generates the peristaltic motion of membrane 42. The peristaltic motion of membrane 42 is to translated to and pumps the fluid in channel 24 in the first direction, as shown by arrows 52 and 54 in FIG. 2. By controlling the rotational frequency of bar magnet 60, it is understood that a user can control the flow rate of the fluid flowing through channel 24.
It can be appreciated that the number and location of the contacts affixed to membrane 42 may be varied. For example, groups of contacts may be provided at various locations along the channel or channel network within microfluidic device 10 so as to allow for pumping of the fluid at these various locations. In addition, magnetic stirrer 56 may be replaced with microcoils positioned adjacent to these multiple locations along the channel. The microcoils could be actuated sequentially, thereby attracting or repelling the contacts at the various locations and producing a sweeping effect similar to that of the bar magnet 60. Further, its is contemplated to achieve peristaltic pumping by utilizing magnets as the contacts and positioning the magnets adjacent the channel with alternating polarity and exposing the magnets to a spatially uniform, sinusoidal magnetic field produced by a single external coil.
Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter, which is regarded as the invention.

Claims

1. A device for conducting peristaltic pumping of a fluid, comprising:

a body defining a channel therein for receiving the fluid therein, the channel having an input end and an output end;

a flexible layer partially defining the channel;

a plurality of spaced contacts spaced along and operatively connected to the layer; and

a magnetic source movable along the layer and having at least one of a first polarity and a second opposite polarity, the magnetic source magnetically coupling the plurality of spaced contacts sequentially in response to movement along the layer;

wherein:

each of the plurality of spaced contacts moves axially toward the magnetic source in response to magnetically coupling with the magnetic source having the first polarity such that the sequential magnetic coupling of the magnetic source to the plurality of spaced contacts causes peristaltic motion of the layer to pump the fluid through the channel; and

each of the plurality of spaced contacts moves axially away from the magnetic source in response to magnetically coupling with the magnetic source having the second polarity such that the sequential magnetic coupling of the magnetic source to the plurality of spaced contacts causes peristaltic motion of the layer to pump the fluid through the channel.

2. The device of claim 1 wherein the channel has a generally arcuate path.

3. The device of claim 2 wherein the plurality of contacts are bonded to the layer.

4. The device of claim 3 further comprising adhesive tape for bonding the plurality of contacts to the layer.

5. (canceled)

6. The device of claim 1 wherein the magnetic source includes a rotating magnetic stirrer.

7. A method for conducting peristaltic pumping of a fluid in a body, comprising the steps of:

providing a channel in the body having an input and an output and being partially defined by a flexible layer;

spacing a plurality of contacts along the layer in operable contact therewith;

filling the channel with the fluid; and

magnetically coupling the plurality of spaced contacts with a magnetic field in sequence, the magnetic field having at least one of one of a first polarity and a second opposite polarity;

wherein:

each of the plurality of spaced contacts moves axially toward the magnetic field in response to magnetically coupling with the magnetic field having the first polarity such that the sequential magnetic coupling of the magnetic field to the plurality of spaced contacts causes peristaltic motion of the layer to pump the fluid through the channel; and

each of the plurality of spaced contacts move axially away from the magnetic field in response to magnetically coupling with the magnetic field having the second polarity such that the sequential magnetic coupling of the magnetic field to the plurality of spaced contacts causes peristaltic motion of the layer to pump the fluid through the channel.

8. The method of claim 7 wherein the step of magnetically coupling the plurality of spaced contacts with a magnetic field includes the additional step of rotating a magnet in close proximity to the body, the magnet generating the magnetic field.

9. The method of claim 8 wherein the magnet includes a first end having the first polarity such that the first end sequentially draws each of the plurality of contacts towards the magnet.

10. The method of claim 9 wherein the magnet includes a second end having the second polarity such that the second end sequentially urges each of the plurality of contacts away from the magnet.

11. The method of claim 8 further comprising a magnetic stirrer for housing the magnet.

12. The method of claim 7 wherein the channel has a generally arcuate configuration.

13. The method of claim 7 comprising the additional step of affixing the plurality of contacts to the layer.

14. The method of claim 7 wherein the step of spacing a plurality of contacts along the layer includes the step of electroplating the plurality of contacts on the layer.

15. A method for conducting peristaltic pumping of a fluid in a body, comprising the steps of:

positioning magnetic material along the layer in a spaced relationship and in operable contact therewith;

filling the channel with the fluid; and

positioning the body in close proximity to a magnetic field having at least one of a first polarity and second polarity such that the magnetic field having the first polarity draws the magnetic material axially towards the magnetic field when magnetically coupled thereto and such that the magnetic field having a second polarity urges the magnetic material axially away from the magnetic field when magnetically coupled thereto;

wherein movement of the spaced magnetic material generates peristaltic motion of the layer thereby pumping the fluid through the channel.

16. The method of claim 15 wherein the step of positioning the magnetic material includes the step of providing a plurality of spaced contacts along the layer.

17-18. (canceled)

19. The method of claim 15 comprising the additional step of removing the layer from the microfluidic device.

20. The method of claim 15 wherein the channel is further defined by a lower surface, the layer being in contact with the lower surface in the absence of the magnetic field.

21. The method of claim 15 wherein the channel is further defined by a lower surface, the layer being spaced from the lower surface in the absence of the magnetic field.