U.S. patent application number 10/121020 was filed with the patent office on 2003-09-11 for micro-dosing pumps and valves.
Invention is credited to Johnson, A. David.
Application Number | 20030170130 10/121020 |
Document ID | / |
Family ID | 27791235 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030170130 |
Kind Code |
A1 |
Johnson, A. David |
September 11, 2003 |
Micro-dosing pumps and valves
Abstract
A fluid mircro pump or valve of a two-stage pulsatile
peristaltic type. The pump body has an inlet port and an outlet
port. First and second layers of SiO are formed on an Si wafers
disposed in face-to-face relationship within the body. The first
layers define flexible diaphragms bulge, responsive to a first
fluid pressure, between a flat shape and a dome shape containing a
pumping chamber. The domes overlap laterally so that fluid is
pumped from on chamber to the other as the diaphragms are bulged in
serial fashion. Control chambers apply fluid pressure to bulge the
domes.
Inventors: |
Johnson, A. David; (San
Leandro, CA) |
Correspondence
Address: |
Law Offices of Richard E. Backus
The Monadnock Building
Suite 490
685 Market Street
San Francisco
CA
94105
US
|
Family ID: |
27791235 |
Appl. No.: |
10/121020 |
Filed: |
April 10, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60362972 |
Mar 7, 2002 |
|
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Current U.S.
Class: |
417/395 |
Current CPC
Class: |
F04B 43/14 20130101;
F04B 43/06 20130101; F04B 43/021 20130101 |
Class at
Publication: |
417/395 |
International
Class: |
F04B 043/06 |
Claims
1. A device for micro-dose pumping or valving of a fluid, the
device comprising a pump body having an inlet port and an outlet
port, first and second layers disposed in face-to-face relationship
within the body, the first layer being formed with a first
diaphragm having an outer side, the diaphragm being sufficiently
flexible to bulge, responsive to a first fluid pressure on a first
outer side, between a flat shape and a first dome shape which
projects away from the second layer and forms a first pumping
chamber therewith, the second layer being formed with a second
diaphragm having a second outer side, the second diaphragm being
sufficiently flexible to bulge, responsive to a second fluid
pressure on the second outer side, between a flat shape and a
second dome shape which projects away from the first layer forms a
second pumping chamber therewith, the first diaphragm being offset
laterally with respect to the second diaphragm sufficient so that
the first and second domes partially overlap to enable fluid
transfer between the domes, and a flow channel in the body for
communicating fluid from the inlet port to the first and second
pumping chambers and the outlet port.
2. A device as in claim 1 which further comprises control means for
producing the first and second fluid pressure.
3. A device as in claim 2 in which the control means comprises a
first control chamber for containing the first pressure and a
second control chamber for containing the second pressure, the
first and second control chambers being in fluid communication with
respective first and second outer sides.
4. A device as in claim 1 having a plurality of the pump bodies,
the first and second layers with the diaphragm in an array.
5. A method for fabricating a micro-dose pump or valve comprising
the steps of forming first and second flexible diaphragms of SiO on
surfaces of respective first and second Si wafers, placing the
surfaces in face-to-face relationship along a plane with the
diaphragms in lateral overlapping relationship, enabling the first
and second diaphragms to bulge from flat shapes toward respective
first and second dome shapes in directions away from the plane with
the domes enclosing respective first and second volumes and with
the volumes being in fluid communication when the diaphragms are
both bulged into the domes, causing a sample of fluid to enter the
first volume when the first diaphragm is in the first dome shape,
causing the sample to enter the second volume when the diaphragms
are both bulged into the domes, and directing the sample to egress
from the second volume when the second the diaphragm is in its flat
shape.
9. A device made by the method of claim 8.
Description
CROSS-REFERENCE TO PRIOR APPLICATION
[0001] This application claims the benefit under 35 USC
.sctn.119(e) of U.S. provisional application serial No. 60/362,972
filed Mar. 7, 2002.
BACKGROUND OF THE INVENTION
[0002] 1.0 Field of the Invention
[0003] This invention relates in general to microelectromechanical
systems (MEMS) pumps and valves, and more particularly to systems
capable of micro-dosing small aliquots of aqueous solutions for use
in fields such as genomics and proteomics.
[0004] 2.0 Description of the Related Art
[0005] The Human Genome Project and the Department of Health and
Human Services Protein Structural Initiative have stimulated rapid
growth in genomics and proteomics research. High-throughput systems
for drug discovery and DNA analysis employ channels to increase the
number of experiments done simultaneously. There is a growing need
for dispensing systems capable of micro-dosing small aliquots of
aqueous solutions. Sample size must become smaller because DNA is
expensive. Thus internal dead volume of the entire system becomes
critical because in a large volume, a small sample size is lost.
Further, samples must be of uniform volume, the wetted surfaces are
restricted to specific materials, and temperatures and electrical
potentials are limited.
[0006] In a wide variety of genomics and proteomics analysis
systems it is necessary convey nanoliter and picoliter samples from
the supply reservoir to the test apparatus. In some systems,
samples are transferred from the reservoir to a flat surface by
means of capillary tubes that are used to "print" on a flat
surface. In others, the fluid is ejected from nozzles into reaction
chambers. In both cases, a method of micro-dosing is required that
can move fluid volumes of sample from reservoir to reaction site in
a repeatable manner. Conventional valves, based on solenoid
actuation, besides being large compared to the samples to be
transferred, are difficult to "tune" so that uniform samples can be
transferred: sample sizes vary randomly from nozzle to nozzle and
from pulse to pulse within the same nozzle. Assembly of more than a
few channels, using discrete components, becomes prohibitively
labor intensive and expensive. Newer methods, such as
microfabrication techniques, are increasingly seen as cost
effective technologies for development and manufacture of
integrated Microsystems.
[0007] System design is in now transition. Conventional systems use
robots to load wells in genomics and proteomics analysis. This is
wasteful: a significant part of each load must remain in the well.
Eventually all processes will be integrated into a chip. But even
then there will be a need to transfer small quantities, under
computer control, from place to place. Thus the pump/valve system
described herein is needed for present robotics oriented systems
but will be just as critical to integrated systems.
OBJECTS
[0008] It is a general object of the invention to provide a new and
improved fluid valve/pump system for use in microelectromechanical
systems.
[0009] It is a further object to provide fluid valve/pump systems
capable of micro-dosing small aliquots of aqueous solutions for use
in fields such as genomics and proteomics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a side elevational view of a fluid mircro pump in
accordance with one preferred embodiment of the invention.
[0011] FIG. 2 is a side elevational view taken along the line 2-2
of FIG. 1.
[0012] FIG. 3 is a schematic cross sectional view of a unit cell in
a pump array showing one condition of the two diaphragms in the
pump of FIG. 1.
[0013] FIG. 4 is a schematic cross sectional view of a unit cell in
a pump array showing another condition of the two diaphragms in the
pump of FIG. 1.
[0014] FIG. 5 is a schematic cross sectional view of a unit cell in
a pump array showing another condition of the two diaphragms in the
pump of FIG. 1.
[0015] FIG. 6 is a schematic cross sectional view of a unit cell in
a pump array showing another condition of the two diaphragms in the
pump of FIG. 1.
[0016] FIG. 7 is a schematic side view of a linear array of four of
the pumps of FIG. 1.
[0017] FIG. 8 is a schematic cross section of one of the diaphragms
in the pump of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] In the drawings, FIGS. 1 6 illustrate generally at 10 a
fluid mircro pump which is shown within a micro-tier well 12 which
contains a sample fluid which is to be pumped. Pump 10 is of a
two-stage pulsatile peristaltic type. A microprocessor controller
is suitable for use in cycling the pumps.
[0019] Fluid intake is via a port 14 at the lower end below the
fluid surface 15. An outlet 16 at the upper end of the pump leads
to an accumulator, not shown. Control pressure ports 18 and 20 are
also at the upper end.
[0020] A plurality of the pumps 10 can be arrayed together in the
manner described in connection with FIG. 4. Each pump is comprised
of two chambers, a first chamber 22 (FIG. 4) and a second chamber
24 (FIG. 5). In the first phase of a pumping cycle, the first
chamber is filled from its reservoir through an intake port 26. In
the second phase of the cycle, the contents of the first chamber
are transferred to the second chamber 24. The second chamber is
then emptied into a capillary tube through an outlet port 27. The
dashed lines 23 and 25 shown vias formed in the wafers for
communication fluid between the ports and chambers.
[0021] The chambers 22 and 24 are formed in the surfaces of two
solid silicon (Si) wafers 21 and 23 using known microfabrication
techniques to etch thin diaphragms 30 and 32. The facing sides of
the wafers are oxidized, by exposure to H.sub.2O while heated, to
form a layer of SiO. Because the SiO layer occupies a greater
volume than the Si from which it is formed, the internal stresses
that are created cause the the SiO layer to buckle down into the
dome shaped diaphragms. The diaphragms are approximately 1 mm in
diameter and the domes are a few microns high. Each such dome has a
volume of about 25 picoliters. The domes formed by the diaphragms
are flexible and will change shape if pressure is applied. In an
array of the pumps, when the appropriate amount of pneumatic
pressure is applied to the front surface of the wafer then all of
the diaphragms will buckle toward the opposite side. Similarly,
pneumatic pressure applied to the reverse side of the wafer will
cause the volume inside the dome to diminish. This is the origin of
the pumping action.
[0022] For each pump, the two wafers 21 and 23 are bonded
face-to-face, positioned to form pairs of chambers that partially
overlap. When the first chamber of each pair is changed from flat
shape to dome shape, fluid is drawn into it. When the first chamber
is flattened while the second is domed, its contents are
transferred to the other member of the pair. If both diaphragms of
a pair are flattened in sequence, the contents are forced out
through the outlet ports into a capillary tube (not shown). Cycling
is accomplished by sequentially changing pressures on opposing
sides of the wafer sandwich.
[0023] The dome shape is controlled by modulating fluid pressure in
a control chamber 34 for diaphragm 32 and in a control chamber 36
for diaphragm 30.
[0024] The silicon/silicon oxide diaphragms change between two
shapes--either domed or flattened. The volumes below the diaphragms
comprise the control chambers that are sequentially pressurized and
de-pressurized to force the diaphragms to flatten or bend. As the
diaphragms change shape, the volumes change. Fluid is transported
from the intake port, through the intake via, into the first
chamber, then into the second chamber, then the output via and out
through outlet port 27.
[0025] FIGS. 3-6 show four different stages for the two diaphragms.
In the first stage of FIG. 3, both diaphragms are in closed
position so that the volume they enclose is minimum. In transition
to the second stage of FIG. 4, pressure on the lower diaphragm is
decreased so that it forms a downwardly convex dome shape, causing
pressure in chamber 22 to decrease which draws fluid in through the
intake port.
[0026] In transition to the third stage of FIG. 5, the upper
diaphragm is opened while simultaneously closing the lower
diaphragm so that the quantity of fluid is transferred from chamber
22 to chamber 24. The cycle is completed by increasing pressure in
control chamber 34 above diaphragm 32 so the fluid is forced
through the outlet port. Completion of this stage returns the pump
to the first stage in preparation for another cycle.
[0027] FIG. 6 shows the pump with both diaphragms un-pressurized so
that there is a clear flow path through the two diaphragms and the
inlet and outlet channels. This stage may be used of flushing the
system between uses.
[0028] FIG. 7 shows any array of four identical pumps 42, 44, 46
and 48. Each array is shown in four possible states from states 50,
52, 54, and 56. Pumping is accomplished by iteratively repeating
stages 52, 54 and 56. In state 50 the diaphragms are open for
flushing. State 52 is the intake phase for each pump. State 54
transfer the contents of first chamber 58 to second chamber 60 in
each pump. State 56 transfers the contents of chamber 60 through
the outlet port of each pump into capillaries.
[0029] The volume enclosed by the curved membrane which forms the
diaphragms can be approximately calculated if the curvature is
assumed to be spherical. FIG. 8 show a cross section of a typical
diaphragm of the invention having a wall thickness t, length L and
height h. The radius of curvature is approximately L.sup.28h. This
radius is to be limited so that the strain in the surface of the
membrane is about 0.5%.
[0030] Strain=0.005=t/R=8th/L.sup.2
[0031] Then if L is one millimeter and t is 10 microns, h=50
microns, and the volume enclosed is about 25.times.10.sup.6
microns.sup.3 or 25 picoliters.
[0032] Therefore one cycle of each pump can deliver about 25
picoliters of DNA-containing aqueous solution. Uniformity from one
pump to another and from one cycle to another is extremely close.
All pumps in an array operate in unison. Each pump can supply a
fixed-volume aliquot of solution to a print head through a
capillary tube or through a nozzle into a reaction site.
[0033] The pump system is capable of being flushed for cleaning and
re-use. This may involve exposure to strongly basic solutions. The
solutions contain NaOH at a pH of approximately 12. All materials
wetted by fluids in the pumps must be compatible with biological
basic fluids and basic chemistry. Acceptable material include glass
(silicon dioxide), PEEK plastic, polystyrene, stainless steel and
polypropylene plastic.
[0034] Since DNA links have two dangling negative charges, it is
imperative that all material with which the liquid comes in contact
have no net positive charge or the molecules will adhere to the
surface and not easily be moved.
[0035] The system of dome shaped diaphragms in face-to-face
relationship as described can also be applied as a valve for
control of fluids.
* * * * *