U.S. patent application number 10/096179 was filed with the patent office on 2003-09-11 for microfluidic device including a micropump.
This patent application is currently assigned to The Board of Trustees of the Leland Stanford Junior University. Invention is credited to Simpson, Garth J., Wilson, Clyde F., Zare, Richard N..
Application Number | 20030170131 10/096179 |
Document ID | / |
Family ID | 27788289 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030170131 |
Kind Code |
A1 |
Zare, Richard N. ; et
al. |
September 11, 2003 |
Microfluidic device including a micropump
Abstract
Microfluidic devices are disclosed. The microfluidic devices
comprise pumps and mixers in which a microrotor rotated by coupled
dipoles induced by alternating electric fields moves fluids in
which it is immersed.
Inventors: |
Zare, Richard N.; (Stanford,
CA) ; Simpson, Garth J.; (W. Lafayette, IN) ;
Wilson, Clyde F.; (Stanford, CA) |
Correspondence
Address: |
Aldo J. Test
FLEHR HOHBACH TEST ALBRITTON & HERBERT LLP
Suite 3400
Four Embarcadero Center
San Francisco
CA
94111-4187
US
|
Assignee: |
The Board of Trustees of the Leland
Stanford Junior University
|
Family ID: |
27788289 |
Appl. No.: |
10/096179 |
Filed: |
March 8, 2002 |
Current U.S.
Class: |
417/423.1 |
Current CPC
Class: |
B01L 3/50273 20130101;
B01F 27/40 20220101; B01J 19/0093 20130101; B01F 27/27 20220101;
F04B 19/006 20130101; B01L 2400/0454 20130101; F04D 5/001 20130101;
B01J 2219/00853 20130101; B01L 2400/0475 20130101; B01F 33/30
20220101; B01F 35/32005 20220101; B01J 2219/00783 20130101; B01F
27/115 20220101 |
Class at
Publication: |
417/423.1 |
International
Class: |
F04B 035/04; F04B
017/00 |
Goverment Interests
[0001] This invention was made with Government support under Grant
No. DA09873-06 awarded by the National Institutes of Health. The
Government has certain rights to this invention.
Claims
What is claimed is:
1. A microfluidic device for moving a fluid comprising: a
polarizeable microrotor having a polarizability different than that
of the fluid disposed in said fluid, a polarizeable member
electrostatically coupled to said microrotor, spaced electrodes for
applying an alternating electric field to said rotor and said
member to induce alternating dipole fields in said rotor and
coupled member whereby the coupled dipole fields interact to cause
rotation of said microrotor to produce movement of said fluid.
2. A microfluidic device as in claim 1 in which said member is a
second rotor.
3. A microfluidic device as in claim 1 wherein said fluid is
disposed in a well whereby rotation of said microrotor mixes fluids
in said well.
4. A microfluidic device as in claim 1 wherein said fluid is
disposed in a microchannel and said member is a protrusion on the
wall of said microchannel, whereby rotation of said microrotor
pumps fluid along said channel.
5. A microfluidic device as in claim 1 wherein said fluid is
disposed in a microchannel and said member is a second microrotor
whereby rotation of said microrotor pumps fluid along said
channel.
6. A microfluidic device including: a dielectric motor, a coupled
member, electrodes on opposite sides of said rotor and coupled
member for applying electric fields to said rotor and coupled
member, and means for applying alternating voltages to said
electrodes thereby inducing alternating dipole fields in said rotor
and member which interact to cause rotation of said dielectric
rotor.
7. A microfluidic device as in claim 6 in which said microrotor is
disposed in a fluid whereby rotation of said microrotor causes
movement of said fluid.
8. A microfluidic device as in claim 7 in which the microrotor is
disposed in a microchannel and rotation of said microrotor pumps
fluid along said channel.
9. A microfluidic device as in claim 7 in which the microrotor is
disposed in a well to mix fluids in said well.
10. A microfluidic device as in claim 8 or 9 in which the coupled
member is a protrusion in the wall of said microchannel or wall to
position said microrotor.
11. A microfluidic device as in claim 8 or 9 in which said
microrotor is positioned in coupled relationship to said member by
optical tweezers.
12. A microfluidic device as in claim 6, 7, 8 or 9 in which said
coupled member comprises a second microrotor and said microrotors
are maintained in coupled relationship by optical tweezers.
Description
BRIEF DESCRIPTION OF THE INVENTION
[0002] The present invention relates to microfluidic devices using
electrically driven dielectric microrotors/impellers for pumping
and mixing fluids in microchannels.
BACKGROUND OF THE INVENTION
[0003] The fabrication and use of microchannels in the manipulation
of small fluid volumes in chemical and biochemical analysis is well
known. Small fluid volumes have been moved through microchannels
employing electro-kinetic flow. Mechanical pumping systems have
also been used to move and direct fluids within microchannels.
These systems employ microscale devices utilizing external and
internal microfabricated pumps and valves. The microfabrication
methods are costly because they require bulky and expensive
equipment. There is a need for a microfluidic device which can pump
and mix fluids in microchannels for chemical and biochemical
analysis and synthesis.
SUMMARY OF THE INVENTION
[0004] It is a general object of the present invention to provide a
microfluidic device having at least one microchannel in which the
fluid in the microchannel is pumped and/or mixed by electrically
driven dielectric micro-rotor/impellers.
[0005] It is another object of the present invention to provide a
microfluidic device employing microchannels in which a micro rotor
is employed to pump fluid along the channels.
[0006] It is a further object of the present invention to provide a
microfluidic device in which a dielectric rotor/impeller mixes
fluid in the vicinity of the rotor/impeller.
[0007] A microfluidic device having at least one microchannel is
provided. A microrotor/impeller is disposed in said microchannel
and driven by dipole field induced coupled electrorotation to pump
and/or mix the fluid in said channel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing and other objects of the invention will be
more clearly understood from the following description when read in
conjunction with the accompanying drawings in which:
[0009] FIG. 1 is a top plan view of a capillary channel formed in a
substrate with a microfluidic pump employing a
microrotor/impeller.
[0010] FIG. 2 is a sectional view of the capillary channel and
microfluidic pump taken along line 2-2 of FIG. 1 with a cover not
shown in FIG. 1.
[0011] FIG. 3 is a sectional view of the capillary channel
microfluidic pump taken along the line 3-3 of FIG. 1 with a cover
not shown in FIG. 1.
[0012] FIG. 4 is an enlarged view of the region microrotor/impeller
of FIG. 1.
[0013] FIG. 5 shows another embodiment of a capillary channel
formed in a substrate with a microfluidic pump.
[0014] FIG. 6 is a top plan view of a capillary channel and
microfluidic pump having a constant channel dimension.
[0015] FIG. 7 is a top plan view of another capillary channel with
another microfluidic pump.
[0016] FIG. 8 is a top plan view of microfluidic device with a
micropump at the fluid supply reservoir.
[0017] FIG. 9 is a top plan view of a microrotor/impeller disposed
in a well for mixing fluids.
[0018] FIG. 10 is a schematic illustration of microfluidic device
incorporating micropumps in accordance with the present
invention.
DESCRIPTION OF PREFERRED EMBODIMENT
[0019] Microfluidic device of the present invention includes at
least one microchannel of capillary dimensions with a micropump
comprising a microrotor/impeller rotated by dipole field induced
coupled electrorotation for pumping and/or mixing fluid in the
microchannel. The device may include a number of microchannels for
transferring fluid to intersections where chemical reactions or
chemical or biological reactions can be carried out using
microquantities of reagents or samples. By way of example the
microchannels may have cross sectional dimensions in the range of 1
micron to 500 microns and the rotor/impellers have diameters from
0.5 microns to perhaps 50 microns or more.
[0020] Referring to FIGS. 1-4, a microchannel 11 is formed in a
substrate 12. The substrate can be any material which does not
react with the fluid which is being pumped. The substrate can, for
example, be an insulator a semiconductor material. The microchannel
can be formed by photolithography and etching which is well known
in the semiconductor art. Alternately the substrate may be plastic
and the microchannel may be formed in the plastic material by
injection molding, stamp molding and embossing. Referring to FIG.
1, the channel 11 is formed with a bulge or protruding wall portion
13. The substrate is provided with a cover plate 15, FIG. 2, to
form a capillary passage. A dielectric microrotor/impeller 14 is
located adjacent to bulge. The rotor/impeller is selected to have a
different polarizability than the fluid in the microchannel 11. In
one embodiment the rotor/impeller comprises microspheres obtainable
from Molecular Probes (Eugene, Oreg.), Polysciences, Inc.
(Warrington, Pa.) or Bangs Laboratories, Inc. (Fishers, Ind.). The
bulge 13 and rotor 14 are in close proximity so that they are
electrostatically coupled to one another. Spaced electrodes 16 and
17 may be formed on the upper surface of the substrate. In the
examples shown in FIGS. 1-4 the electrodes 16 and 17 are embedded
in the piece so that they lie substantially opposite the spherical
rotor to provide substantially uniform linear electric fields
through the microrotor/impeller 14 and the bulge 13. However, it is
apparent that, in view of the fact that the microchannels are
involved, the electrodes can be formed on the surface of the
substrate.
[0021] Application of alternating electric voltage to the
electrodes generates linear electric fields 18, FIG. 4. These
electric fields induce dipoles 21 and 22 in the dielectric rotor 14
and substrate bulge 13, respectively. With the rotor offset from
the bulge, the dipole fields attract and the rotor rotates in the
direction shown by the arrow 24. When the fields alternate there
are still attracting forces which cause the rotor to continue to
rotate at a rotational velocity which is dependent upon the
alternating frequency of the electric fields, the viscosity and
polarizability of the fluid and the dielectric properties of the
rotor. In order for rotation to occur the fluid and the rotor and
bulge need to be polarizeable. The direction of rotation depends on
the relative positions of the rotor and bulge within the electric
field.
[0022] As seen in FIG. 4, rotation of the rotor viscously drags the
fluid to pump the fluid in the direction of the arrows 26 and along
the channel 11. Additionally as the rotor rotates it will mix fluid
in the vicinity of the rotor. The rotor is maintained adjacent the
bulge by mechanical restriction or an optical trap. Thus, there has
been provided a simple pump which operates by dipole field induced
coupled electrorotation for causing fluid to flow along
microchannels or microcapillaries.
[0023] Referring to FIG. 5, electrodes 31 and 32 are placed at the
bottom of the channel 11 and provide longitudinal alternating
electric fields which induce the dipoles 33 in the bulge and 34 in
the rotor which cause the rotor to rotate in a counter-clockwise
direction as indicated by arrow 36 and pumps fluid as indicated by
the arrow 37.
[0024] By way of example, the alternating frequency of the electric
field can be in range of 400 kHz to 700 kHz and the voltage between
1.5 and 3.5 peak-to-peak. In one example, this caused rotation of
the microrotor at 800 to 1800 rpm for a microsphere having 0.75
.mu.m diameter. It is apparent that the rotor/impeller can take
other shapes such as a disc-shaped rotor, hexagonal-shaped,
octagonal, etc. to provide more efficient pumping.
[0025] In certain applications, it is desirable to have a channel
of uniform dimensions. FIG. 6 shows a channel 40 having a zig-zag
shape with the microrotors/impellers 41, 42 located at one edge of
the protruding walls 43, 44. The electrodes 46, 47 are on opposite
sides of the rotors 41, 42. The rotors pump by dipole field induced
coupled rotation as indicated by the arrows 49.
[0026] In another embodiment, FIG. 7, two microrotors 51, 52 are
held next to each other in electric fields generated by the
electrodes 53 and 54 by an optical trap, not shown. Induced dipoles
56, 57 cause the rotors to rotate in opposite directions and pump
fluid along the channel in the direction of rotation of the
microrotor closest to a wall (in the illustrated example, in the
direction of arrow 58).
[0027] The end 61 of a microchannel 62 is shown in FIG. 8
cooperating with a fluid reservoir 63. A pump formed by the
microrotor/impeller 64, bulge 66 and electrodes 67, 68 rotate the
impeller and pump fluid from the reservoir into the
microchannel.
[0028] In many applications, it is necessary to mix fluids in
wells. The present invention provides an excellent mixing device
for use in microwells. Referring to FIG. 9, a microwell 71 is shown
formed in a substrate 72. A microrotor/impeller 73 is disposed in
the well and held adjacent the well wall by an optical trap (not
shown). Spaced electrodes 76, 77 provide linear electric fields
which induce dipoles 78, 79 in the microrotor/impeller 73 and well
wall. This caused the impeller to rotate at a rotational velocity
which depends upon the frequency of the applied electric fields.
The rotating microrotor/impeller mixes the fluids.
[0029] FIG. 10 shows a schematic illustration of microchip
including a plurality of fluid reservoirs, 71, 72, 73, 74
cooperating with microchannels 76, 77, 78 and 79. Different fluids
can be applied to the fluid reservoirs and pumping and mixing along
the channel can occur by employing the micropumps of the type
described associated with each of the wells. Suitable detection
means such as fluorescent detectors which detect labeled cells or
molecules can be located along the channel. Alternatively,
electrophotometric detectors can be placed along the channel to
read changes in the chemical composition due to the reaction of
chemicals which are mixed in the channels. It is apparent that
other configurations of microchips can employ micropump/mixers in
accordance with the present invention to pump, mix, direct and
otherwise manipulate fluids in microchannels.
[0030] The foregoing descriptions of specific embodiments of the
present invention are presented for the purposes of illustration
and description. They are not intended to be exhaustive or to limit
the invention to the precise forms disclosed; obviously many
modifications and variations are possible in view of the above
teachings. The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
applications, to thereby enable others skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. It
is intended that the scope of the invention be defined by the
following claims and their equivalents.
* * * * *