U.S. patent application number 13/877925 was filed with the patent office on 2013-10-31 for peristaltic micropump and related systems and methods.
This patent application is currently assigned to VANDERBILT UNIVERSITY. The applicant listed for this patent is Erica L. Curtis, Parker A. Gould, Douglas J. Hall, Loi T. Hoang, Ayeeshik Kole, William J. Matloff, Ronald S. Reiserer, David K. Schaffer, Joseph R. Scherrer, Kevin T. Seale, Hunter Tidwell. Invention is credited to Erica L. Curtis, Parker A. Gould, Douglas J. Hall, Loi T. Hoang, Ayeeshik Kole, William J. Matloff, Ronald S. Reiserer, David K. Schaffer, Joseph R. Scherrer, Kevin T. Seale, Hunter Tidwell.
Application Number | 20130287613 13/877925 |
Document ID | / |
Family ID | 44906383 |
Filed Date | 2013-10-31 |
United States Patent
Application |
20130287613 |
Kind Code |
A1 |
Gould; Parker A. ; et
al. |
October 31, 2013 |
PERISTALTIC MICROPUMP AND RELATED SYSTEMS AND METHODS
Abstract
A peristaltic micropump comprising one or more conduits
configured to transfer one or more pumped fluids, wherein each
conduit comprises: an inlet (106), an outlet (107), a central
portion (102) between the inlet and the outlet, and an actuator
(103, 105) configured to engage the central portions of the one or
more conduits.
Inventors: |
Gould; Parker A.;
(Cambridge, MA) ; Hoang; Loi T.; (Antioch, TN)
; Scherrer; Joseph R.; (Nashville, TN) ; Matloff;
William J.; (Paradise Valley, AZ) ; Seale; Kevin
T.; (Nashville, TN) ; Curtis; Erica L.;
(Atlanta, GA) ; Schaffer; David K.; (Nashville,
TN) ; Hall; Douglas J.; (Chesterfield, MO) ;
Kole; Ayeeshik; (Columbia, MD) ; Reiserer; Ronald
S.; (Nashville, TN) ; Tidwell; Hunter;
(Nashville, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gould; Parker A.
Hoang; Loi T.
Scherrer; Joseph R.
Matloff; William J.
Seale; Kevin T.
Curtis; Erica L.
Schaffer; David K.
Hall; Douglas J.
Kole; Ayeeshik
Reiserer; Ronald S.
Tidwell; Hunter |
Cambridge
Antioch
Nashville
Paradise Valley
Nashville
Atlanta
Nashville
Chesterfield
Columbia
Nashville
Nashville |
MA
TN
TN
AZ
TN
GA
TN
MO
MD
TN
TN |
US
US
US
US
US
US
US
US
US
US
US |
|
|
Assignee: |
VANDERBILT UNIVERSITY
Nashville
TN
|
Family ID: |
44906383 |
Appl. No.: |
13/877925 |
Filed: |
October 7, 2011 |
PCT Filed: |
October 7, 2011 |
PCT NO: |
PCT/US11/55432 |
371 Date: |
July 16, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61390982 |
Oct 7, 2010 |
|
|
|
Current U.S.
Class: |
417/476 |
Current CPC
Class: |
F04B 43/12 20130101;
F04B 43/0054 20130101; F04B 43/0072 20130101; F04B 43/1269
20130101; F04B 43/1253 20130101; B01L 2300/123 20130101; B01L
2300/0819 20130101; F04B 43/1292 20130101; B01L 3/50273
20130101 |
Class at
Publication: |
417/476 |
International
Class: |
F04B 43/12 20060101
F04B043/12 |
Claims
1.-60. (canceled)
61. A peristaltic micropump comprising: a conduit configured to
transfer a pumped fluid; and an actuator configured to rotate about
a central axis, wherein: the actuator comprises a rolling element
and a driving element; the rolling element is disposed between the
conduit and the driving element; and the driving element and the
conduit have a coefficient of friction that is substantially
similar.
62. The peristaltic micropump of claim 61 wherein the driving
element and the conduit have coefficients of both elasticity and
friction that are substantially similar.
63. The peristaltic micropump of claim 61 wherein the driving
element and the conduit are comprised of a flexible polymeric
compound.
64. The peristaltic micropump of claim 61 wherein the driving
element and the conduit are comprised of polydimethylsiloxane
(PDMS).
65. The peristaltic micropump of claim 61 wherein the actuator
comprises a rolling element without an axle.
66. The peristaltic micropump of claim 61 wherein the rolling
element is configured to rotate about an axle.
67. The peristaltic micropump of claim 61 wherein the actuator
comprises one or more ball bearings.
68. The peristaltic micropump of claim 61 wherein the actuator
comprises one or more cylindrical rollers.
69. The peristaltic micropump of claim 61 wherein the actuator
comprises one or more conical rollers.
70. The peristaltic micropump of claim 61 wherein the actuator
comprises a plurality of rolling elements.
71. The peristaltic micropump of claim 70 wherein the driving
element comprises a cage configured to capture the plurality of
rolling elements.
72. The peristaltic micropump of claim 70 wherein the plurality of
rolling elements are located at substantially the same radius from
the center of the cage.
73. The peristaltic micropump of claim 70 wherein the plurality of
rolling elements are located at different radii from the center of
the cage.
74. The peristaltic micropump of claim 70 wherein the actuator
comprises a rotating drive mechanism and a centering component
configured to center the cage with respect to the rotating drive
mechanism.
75. The peristaltic micropump of claim 61 further comprising: one
or more conduits configured to transfer one or more pumped fluids,
wherein each conduit comprises: an inlet; an outlet; and a central
portion between the inlet and the outlet; wherein the actuator is
configured to engage the central portions of the one or more
conduits.
76. The peristaltic micropump of claim 61 further comprising one or
more valves configured to control flow of one or more pumped fluids
in the one or more conduits.
77. The peristaltic micropump of claim 76 wherein a first conduit
of the one or more conduits comprises a bypass line configured to
allow fluid to flow from the outlet of the first conduit to the
inlet of the first conduit.
78. The peristaltic micropump of claim 76 wherein: the one or more
conduits contains at least a first fluid and a second fluid; the
one or more valves can be opened and closed to control a flow rate
of the first and second fluids during operation of the peristaltic
micropump; and the outlets of the one or more conduits are in fluid
communication such that the first and second fluids can be mixed in
varying proportions.
79. The peristaltic micropump of claim 76 wherein the one or more
conduits are configured to provide sinusoidal or other output
concentration waveforms.
80. The peristaltic micropump of claim 61 wherein the conduit
comprises an expanded area configured to reduce pulsatility.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 61/390,982 filed Oct. 7, 2010, the entire
contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present disclosure relates generally to peristaltic
micropumps and valves and related systems and methods, including
microformulators mixers and other valved systems incorporating
peristaltic micropumps.
BACKGROUND INFORMATION
[0003] Fluid flow in microfluidic devices can be driven and
controlled by a variety of mechanisms, including differences in
external hydrostatic pressure between inputs and outputs of a
device, the use of electric forces with either dielectrophoresis or
electroosmosis, actuation by pistons and/or valves, or by
peristaltic action induced by a moving compressional wave induced
in an elastic fluidic conduit.
[0004] Microfluidic devices for chemical or biological research
offer the promise of automated complex analysis with fast reaction
times and small sample consumption. For example, optimization of
chemical synthesis pathways or formulation of chemical solutions on
a chip is potentially very fast since many alternatives can be
explored in a short time period, and only very small quantities of
expensive or rare drugs or reagents are required. In addition, drug
discovery experiments in which many chemical compounds and/or
combinations thereof are screened by the strength of a cellular
response may be conducted with greater speed and reliability. There
are virtually an infinite number of potential applications of
microfluidic devices since, in theory any biological assay may be
reduced in scale, even very complex functions that would normally
be studied in vivo. For example, Harvard researchers have recently
published extensive work on a lung on a chip that breathes, has its
own blood circulation and mounts its own immune response to
bacterial invasion (see "Reconstituting Organ-Level Lung Functions
on a Chip" Dongeun Huh, Benjamin D. Matthews, Akiko Mammoto, Martin
Montoya-Zavala, Hong Yuan Hsin and Donald E. Ingber).
[0005] However, for this type of technology (commonly referred to
as "Lab on a Chip") to be integral components of real, marketable
devices, it is important to be able to control and move many
discrete small volumes of fluid on the chip with little dead space
and without long time delays. It has been demonstrated that the
exemplary embodiments of rotary planar peristaltic micropumps
(RPPM) are capable of pumping a wide range of flows that are
appropriate for microfluidic experiments. An RPPM can also be
readily incorporated directly into a microfluidic chip, and its
functionality when integrated with microfluidic networks will be
enhanced by a proximal and reliable means of switching fluidic
inputs upstream or fluidic outputs downstream from the pump body.
An on-chip pump with switchable inputs and outputs lends
flexibility to microfluidic design and allows the construction of
more complex devices capable of more sophisticated
sample-processing tasks.
[0006] There are many examples of microvalves in the scientific
literature (see Oh et al., A Review of Microvalves, J. Micromech.
Microeng., 16, R13-R39, 2006, incorporated by reference herein)
that utilize a wide variety of materials and actuators. Embodiments
of a rotary planar valve (RPV) described herein are a unique
extension of RPPM technology. In certain embodiments, the actuator
comprises a caged thrust bearing with rolling elements turned by a
motor, crank or other rotational device. While similarities exist
between the technologies, one difference between RPPM and RPV
embodiments includes the geometry of the microfluidic channels that
are compressed by the rolling elements. Unlike prior art devices,
certain exemplary embodiments of the present invention utilize the
concept of a rolling element being rolled in a circle over one or
more channels in an elastomeric material by a rotating flange that
has a matched, elastomeric driving surface.
[0007] Exemplary embodiments of the RPV described herein are small
and can be located near an on-chip pump such as the RPPM. This
enables the design of low volume fluidic circuits with rapid
transit times, low dead volumes, and the possibility of
recirculation and feedback. Although popular existing technology
using pressurized, pneumatic control channels are also small-volume
(see Unger, et al., Monolithic Microfabricated Valves and Pumps by
Multilayer Soft Lithography, Science, 288, 113-116, 2000; and
Melin, et al., Microfluidic Large-Scale Integration: The Evolution
of Design Rules for Biological Automation, Annu. Rev. Biophys.
Biomol. Struct., 36, 213-231, 2007, each incorporated by reference
herein) exemplary embodiments of RPPM/RPV technology have an
advantage of being driven by electric motors--a small, inexpensive,
relatively simple, robust and mature technology, in contrast to the
solenoid bank and source of pressurized gas for the pneumatic valve
controller. While the pneumatic valves can be configured so that in
the absence of gas pressure the valve can either be normally open
or normally closed, the design determines the resting and activated
conductances--these pneumatic valves cannot be toggled to remain in
either state arbitrarily without the continual application of
pressurized gas to maintain one of the two states.
[0008] In contrast, embodiments of a motor-driven RPPM can function
as a valve when the motor is stopped. In certain embodiments, the
RPV is an extension of this concept in which multiple (e.g., up to
sixteen or more) separate fluidic channels or conduits are routed
through the compression zone of the thrust bearing of an RPPM. In
any given rotational position, the rolling element at rest
compresses and occludes a predetermined number of channels, and
rotation of the bearing into a set of rotational positions actuates
the valve. Importantly, the fluidic channels can be oriented and
sized so as to eliminate or minimize fluid displacement during
actuation of the RPV. Complete elimination of displacement removes
the possibility of errors in downstream chemical composition that
may arise from residual volumes of displaced fluid.
[0009] One type of valve that can be created from this mechanism is
an N-to-1 valve in which N input channels may be switched to
connect to one output channel. Reversed, the same device connects
one input to one of N outputs. This is similar in concept to a mux,
demux or mux/demux combination switch in electronics (an
abbreviation of multiplexers and demultiplexers). In the standard
pneumatically actuated microfluidic valve, multiple solenoids are
required to control multiple inputs. In this RPV embodiment, a
single motor can control sixteen or more inputs. Other more
specialized valve constructions that perform the microfluidic
equivalent of a large number of combinations of multi-pole,
multi-throw electronic switches can be built from the basic RPV
platform.
[0010] In certain embodiments, RPVs can be configured wherein
precise angular control of the caged bearing is provided by, for
example, a stepper motor or a DC gear-head motor with an angular
encoder, so that the balls or other rolling elements can be
positioned exactly over a particular channel at a particular time.
In some implementations, the balls would be rotated intermittently
in a single direction, whereas in others, the motion would be
alternately over a small angle to move a ball back and forth
against a particular channel. In that latter case, a means of
determining the exact position of the balls may improve the
performance of the device.
[0011] In other implementations, the continuous rotation of the
ball cage provides intermittent connection to multiple channels, so
that the exact angle is not as important as the angular velocity.
In these cases, a simple DC motor or a DC motor with gear head but
no encoder would be sufficient.
[0012] One feature of exemplary embodiments of the RPPM and the RPV
is that no pneumatic connection is required to control the
microfluidic device. Hence this approach is particularly suited for
applications wherein a disposable microfluidic cassette is inserted
into, for example, a point-of-care reader, and a lever or other
mechanical actuation means is provided to move the rolling elements
into contact with the PDMS or other elastomeric device such that
the underlying channels are compressed to allow pumping and valving
operations.
[0013] This disclosure includes a variety of designs that can be
implemented by various combinations of RPPMs and RPVs, or RPPMs
with pneumatic valves. Several of these implementations demonstrate
that the RPV and/or RPPM can be used to provide a concentration of
a chemical that varies in time either in a sinusoidal manner or
with some other chosen waveform, for example, to allow
large-amplitude, different-frequency modulation of various chemical
concentrations in a chemical reaction network to identify reactions
whose rates are determined by the product of two or more
concentrations. This would be difficult to achieve with
conventional peristaltic pumps and on-chip microvalves.
[0014] Exemplary embodiments of the present invention include
devices and methods of peristaltic pumping. In the classical,
macroscopic peristaltic pump (FIG. 1), a pump body (101) constrains
a deformable plastic tube (102) that is compressed by three or more
rollers (103). The rollers are caused to rotate by coupling to a
central rotor (104), which is caused to rotate about an axis (105).
As a result, fluid is drawn into one end of the tubing (106) and
expelled from the other (107). Many different techniques have been
developed to simplify and streamline this method of fluidic
pumping. In microfabricated devices, however, there have been only
a limited number of implementations of peristaltic pumps.
[0015] In Darby et al. (2010), this system is implemented in a
microfluidic device using either a rotating cam with the "tubing"
wrapped around the cam, or a linear screw drive pressed against a
series of microfluidic channels (FIGS. 2A and 2B). In the rotating
cam version, encapsulated channels (201) are created by bonding
together two thin layers (202) and (203) of a deformable
polydimethylsiloxane (PDMS) polymer (one flat layer and one layer
with channels). These encapsulated channels are analogous to the
classic peristaltic pump's tubing, and are wrapped around a thin
cylindrical mandrel and then cast in a thick PDMS layer (204) that
provides mechanical support and serves as the pump body (101) in
FIG. 1. After curing, a cam with an oval-shaped cross section
(205), with a transverse diameter greater than that of the diameter
of the original cylindrical cam, is fitted into the cylindrical
hole left by the original mandrel, producing two points of
compression (206 and 207). As this cam is turned (208), the two
points of compression drive fluid along the channels, achieving
peristaltic flow from 209 to 210. With the linear screw model, the
difficult process of wrapping the channels is eliminated. The basic
pumping concept is similar to the rotating cam version. A screw
(211) is placed such that its major axis is parallel to the fluid
channels (212), and fluid flow is then achieved by rotating the
screw (213). The screw is held in place over the channels by a cast
layer of PDMS (214), which also provides the requisite compression
(215 and 216). As the screw rotates, the threads move along the
channels, producing flow from 217 to 218.
[0016] Two other early implementations of peristaltic pumps in
microfluidic devices use either an array of solenoid-actuated pins
that sequentially compress zones along a microfluidic channel cast
in PDMS (Gu et al., 2004, and Takayama et al., 2010) (FIG. 3), or
three or more pneumatically actuated membranes that also provide
sequential compression of a channel (Chou et al., 2001) (FIG. 4).
In the former, a PDMS microfluidic device mounted on a rigid
substrate (301) has one or more channels (302) that are compressed
by pins (303-305) that are driven by solenoids, often using an
apparatus found in a tactile Braille-reader head. The sequential
compression of the pins draws fluid into the channels (306) and
drives fluid out of the other side (307). As for the latter, the
pins' functions are replaced by pneumatically actuated channels
(401-403) contained in a second PDMS membrane (404) bonded to the
membrane (405) containing the channels (406) to be compressed.
Pressure applied to channels in the second membrane causes the
channel to expand (401) and depress the membrane that foams the
bottom of the upper channel, and therefore induce compression (407)
along the lower channel within a microfluidic device backed by a
rigid substrate (408). When adjacent channels in the upper membrane
are sequentially actuated, a compression wave moves along the
channels in the lower membrane and fluid is drawn from 409 to 410.
In the event that pumping is not desired, both approaches require
the dissipation of power to keep at least one channel closed to
prevent passive flow or backflow through the pump.
[0017] Another method of inducing peristaltic compression is to
drive a roller linearly across the microfluidic channel (FIG. 5).
(Lim et al., 2004) When downward pressure (501) is applied to the
roller (502), a point of compression is created (503), which is
then made to move along a PDMS channel (504) by moving (505) the
roller with a motorized actuator (506). This technique requires a
large mechanical setup along with a fairly large roller. Also, the
roller's path is restricted linearly, which limits possible channel
geometries and eliminates the possibility of continuous or
recirculating flow.
[0018] One way to create continuous flow is to use magnets and
steel balls to create a circular compression zone that rotates
along a circular pathway (FIG. 6). Yobas et al. (2008), and
subsequently Du et al. (2009), present a peristaltic design that
achieves compression (601) by magnetically attracting small steel
balls (602) through a thin, channeled PDMS substrate (603) backed
by a rigid poly(methyl methacrylate) layer (604). The magnets (605)
are made to rotate (606) using a DC motor, which causes the balls
to roll in a circular trajectory (607) along the circular PDMS
channel, inducing flow from 608 to 609. However, this design has
many limitations. The total number of balls that can run along a
channel is limited by the minimum spacing needed to avoid adverse
magnetic interactions between the individual balls and the magnet
array. Rotating the balls at higher speeds (Yobas reported maximum
rotation speeds of 320 RPM) introduces the problem of the magnetic
field not providing the requisite centripetal force, thereby
allowing the balls to disengage from the device. The amount of
magnetic restoring force provided is limited by the strength of the
magnet and the separation distance (device thickness) from the
balls and the ball-to-ball spacing, and this force cannot be
reliably scaled higher without an increase in fabrication
complexity via thinner device layers or operational complexity via
the introduction of electromagnets. Using permanent magnets also
defines a single compression level for the channels, which must be
tuned to provide enough compression for flow, but not enough that
frictional forces hinder ball movement. Electromagnets would
require ferromagnetic cores, would produce heat that would need to
be dissipated, and would require electrical power both to operate
and to prevent passive flow or backflow through the device when
pumping is not desired.
SUMMARY
[0019] Exemplary embodiments include a peristaltic micropump
comprising one or more conduits configured to transfer one or more
pumped fluids, wherein each conduit comprises: an inlet; an outlet;
and a central portion between the inlet and the outlet. Exemplary
embodiments can also comprise an actuator configured to engage the
central portions of the one or more conduits. In certain
embodiments, the actuator is configured to rotate about a central
axis, and the central portions of the one or more conduits foam
concentric partial rings about the central axis. In particular
embodiments, the peristaltic micropump comprises at least two
conduits in fluid communication with each other, while in other
embodiments, none of the one or more conduits are in fluid
communication with each other.
[0020] In particular embodiments, the concentric partial rings are
partial circles, while in other embodiments the concentric partial
rings are non-circular configurations. In specific embodiments, the
actuator comprises one or more ball bearings, cylindrical rollers,
or conical rollers. In certain embodiments, the central portions of
the one or more conduits are arranged in a circumferential pattern
so that the actuator engages the central portions as the actuator
rotates. In particular embodiments, each of the one or more
conduits is a different length. In certain embodiments, the ratios
of the lengths of each of the one or more conduits is a non-integer
fraction. In specific embodiments, the one or more conduits are
configured to form an aperiodic pattern. In particular embodiments,
the aperiodic pattern is a Penrose Tile design.
[0021] In certain embodiments, the actuator comprises a driving
element and one or more rolling elements. In particular
embodiments, the one or more rolling elements comprises one or more
cylindrical rolling elements, and at least two of the cylindrical
rolling elements have different lengths. In specific embodiments,
the one or more rolling elements comprises one or more conical
rolling elements. In particular embodiments, the driving element
comprises a cage configured to capture the one or more rolling
elements. In specific embodiments, the one or more rolling elements
comprises one or more spherical rolling elements or cylindrical
rolling elements; and the one or more rolling elements is located
at substantially the same radius from the center of the cage.
[0022] In particular embodiments, the one or more rolling elements
comprises one or more spherical rolling elements or cylindrical
rolling elements, and the one or more rolling elements is located
at different radii from the center of the cage. In certain
embodiments, the actuator comprises a rotating drive mechanism and
a centering component configured to center the cage with respect to
the rotating drive mechanism. In particular embodiments, each of
the one or more rolling elements is configured to rotate about an
axle.
[0023] Certain embodiments further comprise one or more valves
configured to control flow of one or more pumped fluids in the one
or more conduits. In specific embodiments, a first conduit of the
one or more conduits comprises a bypass line configured to allow
fluid to flow from the outlet of the first conduit to the inlet of
the first conduit.
[0024] In particular embodiments, the one or more conduits contains
at least a first fluid and a second fluid; the one or more valves
can be opened and closed to control a flow rate of the first and
second fluids during operation of the peristaltic micropump; and
the outlets of the one or more conduits are in fluid communication
such that the first and second fluids can be mixed in varying
proportions. In specific embodiments, a conduit comprises an
expanded area configured to reduce pulsatility. In particular
embodiments, the one or more conduits are configured to reduce
pulsatility. In certain embodiments, the one or more conduits are
configured to provide sinusoidal or other output concentration
waveforms.
[0025] Specific embodiments comprise a peristaltic microformulator
comprising: a generally circumferential conduit; an actuator
configured to engage the generally circumferential conduit; one or
more inlets in fluid communication with the generally
circumferential conduit; an outlet in fluid communication with the
generally circumferential conduit, wherein the outlet comprises an
outlet valve; and a bypass conduit coupling the outlet and a first
inlet of the one or more inlets, wherein the bypass conduit
comprises a bypass valve and the first inlet comprises an inlet
valve.
[0026] In certain embodiments, the generally circumferential
conduit is configured as a circle. In particular embodiments, the
generally circumferential conduit is configured as a circle,
triangle, square, pentagon, hexagon, heptagon, octagon. In certain
embodiments, each of the one or more inlets comprises a valve; the
one or more inlets is configured to deliver at least a first fluid
and a second fluid to the generally circumferential conduit; and
the valves of the one or more inlets can be opened and closed to
control the amount of the first and second fluid that is pumped
through the outlet during operation.
[0027] Particular embodiments include a peristaltic micropump
comprising: a conduit configured to transfer a pumped fluid; and an
actuator configured to rotate about a central axis, wherein: the
actuator comprises a rolling element and a driving element; the
rolling element is disposed between the conduit and the driving
element; and the driving element and the conduit have a coefficient
of friction that is substantially similar. In certain embodiments,
the driving element and the conduit are comprised of a flexible
polymeric compound. In particular embodiments, the driving element
and the conduit are comprised of polydimethylsiloxane (PDMS).
[0028] Specific embodiments include peristaltic micropump
comprising: a conduit configured to transfer a pumped fluid; and an
actuator configured to rotate about a central axis, wherein: the
actuator comprises a rolling element and a driving element; the
rolling element is disposed between the conduit and the driving
element; and the driving element and the conduit have coefficients
of both elasticity and friction that are substantially similar. In
particular embodiments, the driving element and the conduit are
comprised of a flexible polymeric compound. In certain embodiments,
the driving element and the conduit are comprised of
polydimethylsiloxane (PDMS).
[0029] Specific embodiments include a peristaltic micropump
comprising: a circumferential conduit; an external conduit
comprising one or more valves, wherein the one or more valves are
in fluid communication with the circumferential conduit; and a
rotating actuator comprising one or more rolling elements
configured to engage the circumferential conduit and actuate the
one or more valves, wherein the one or more valves are configured
to control a fluid flow in the external conduit. In certain
embodiments, the circumferential conduit comprises one or more
ports in fluid communication with the one or more valves, and
wherein the spacing of the ports on the circumferential conduit can
be used to control the fluid flow in the external conduit.
[0030] In particular embodiments, the one or more valves are
normally closed and wherein a valve is opened when a rolling
element engages a port on the circumferential conduit. In specific
embodiments, during use the actuator rotates at a constant
rotational speed and the fluid flow in the external conduit varies
over time.
[0031] Particular embodiments include a microvalve comprising: a
first conduit comprising an inlet and an outlet; an actuator
configured to rotate about a central axis; and one or more rolling
elements coupled to the actuator, wherein the one or more rolling
elements are configured to rotate about the central axis at a first
radius, wherein: a first portion of the first conduit is located at
the first radius from the central axis; and a second portion of the
first conduit is located at a second radius from the central
axis.
[0032] In specific embodiments, the actuator comprises a driving
element, the rolling element is disposed between the first conduit
and the driving element, and the driving element and the first
conduit have a coefficient of friction that is substantially
similar. In particular embodiments, the driving element and the
conduit are comprised of a flexible polymeric compound.
[0033] In certain embodiments, the actuator comprises a driving
element; the rolling element is disposed between the first conduit
and the driving element; and the driving element and the first
conduit have a coefficient of elasticity that is substantially
similar. In particular embodiments, each of the one or more rolling
elements is configured to rotate about an axle. In certain
embodiments, the one or more conduits are configured to provide
sinusoidal or other output concentration waveforms. In the one or
more conduits are configured to provide droplets of a first fluid
encased in a second fluid. In particular embodiments, during
operation the one or more rolling elements engage the first portion
of the first conduit as the rolling element rotates about the
central axis. In specific embodiments, the one or more rolling
elements are configured to occlude a fluid flow between the inlet
and the outlet of the first conduit when the one or more rolling
elements engage the first portion of the conduit. Particular
embodiment comprise a second conduit extending between an inlet and
an outlet, wherein a first portion of the second conduit is located
at the first radius from the central axis; and a second portion of
the second conduit is located at a second radius from the central
axis.
[0034] In certain embodiments, the first and second conduits
comprise multiple portions at the first radius from the central
axis and multiple portions at the second radius from the central
axis. In specific embodiments, the outlet of the first conduit and
the outlet of the second conduit are in fluid communication. In
particular embodiments, a rotation of the actuator controls a first
fluid flow in the first conduit and a second fluid flow in the
second conduit. In certain embodiments, the first conduit and the
second conduit each comprise multiple portions at the first radius
from the central axis. In particular embodiments, the rolling
element is a ball bearing, a cylindrical roller, or a conical
roller. In particular embodiments, the driving element comprises a
cage configured to capture the one or more rolling elements.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0035] Referring now to FIG. 7, a peristaltic micropump 700
comprises a circumferential conduit or channel (701) with an inlet
(705), an outlet (706) and a series of rolling elements (702)
(e.g., roller bearings), driven by a motorized hub (704). During
operation, rolling elements (702) engage and compress a
circumferential channel (701) and pump a fluid from inlet (705) to
outlet (706). In the power-off mode when the pump is not operating,
one or more rolling elements prevent passive forward or reverse
flow through the device. In certain embodiments, the
circumferential channel (701) may be formed as a circle, and in
other embodiments circumferential channel (701) may be formed as a
polygon (e.g., a triangle, square, pentagon, hexagon, heptagon,
octagon, etc.). It is understood that the circular or polygonal
shape of circumferential channel (701) is used in general terms and
describes the shape of circumferential channel (701) if
circumferential channel (701) extended through the space between
inlet (705) and outlet (706).
[0036] During operation of pump 700, a z-axis stage control device
can be used for variable compression as well as continuous flow
capability. One limitation of this approach is the fabrication
complexity and cost of the mechanical roller mechanism. In FIGS. 5
and 7, the rolling elements (502 and 702) are moved by a mechanical
connection to the axle (506 and 703) that provides either
translation (505) or rotation (704). In FIG. 6, the ball is moved
by means of a rotating magnetic field gradient. FIG. 8 shows how
the rolling balls could be caused to rotate by turning a hard disk
(801) that is pressed (802) against steel balls (803) positioned
over PDMS channels (804). This configuration, however, lacks an
alignment system, which will eventually lead to the balls
disengaging from the channel-disk system, and the differences in
the coefficients of sliding friction and elasticity between the
PDMS, the balls, and the hard plate could lead to the plate
slipping against the balls, which then would not rotate or
roll.
[0037] FIG. 9 shows that a series of balls (901) could be pushed
simultaneously by capturing each ball in a circular array of
sockets (902) (a "cage"). This introduces a strict alignment
system; however, it also could produce substantial sliding
friction. Since the balls are captured by contact (903 and 904)
with the sides of the cage (903 and 904) and the top (905), the
sliding friction between the ball and the cage at these points
opposes the balls' tendency to roll (906), introducing the
possibility of the balls sliding across the PDMS surface rather
than rolling. Because of this friction, the torque required to
rotate a sliding ball and cage system is much greater than that of
the rolling ball and cage system. Varying the cage's size
introduces a trade-off between the ability of the ball to roll and
the chances of a ball disengaging from the cage.
[0038] Embodiments of the present invention comprise numerous
features that provide benefits over existing configurations. For
example, certain embodiments of the present invention include the
use of a deformable rotating disk to drive rolling elements, (e.g.,
steel balls in certain embodiments), as shown in FIG. 10. By using
PDMS or another elastomer for both this driving disk (1001) and the
microfluidic device (1002), the elastic deformations above and
below the steel balls (1003) are matched, drastically reducing the
incidence of sliding friction. The array of balls is kept in
alignment by a cage (1101) with a circular array of openings (1102)
for the balls (1103) (FIG. 11). The cage is free-floating and
therefore does not provide the force that causes the array of balls
to rotate. This force is provided instead by the deformable PDMS or
other elastomer disk (1104), which results in the balls moving with
rolling (1105) rather than sliding friction. A convenient analogy
of the two means to roll the balls, i.e., with a rigid or
deformable disk, is to consider rolling an apple between a book and
the palm of the hand, versus between two hands. In the former case,
the book is likely to slide against the apple due to the elastic
forces provided by the lower hand and the smaller sliding friction
between the book and the apple, as compared to that between the
apple and the hand. In the latter case, the elastic deformations of
both hands are matched to each other and the apple rolls easily.
With the deformable driving disk, the balls actually drive the
cage, and since little force is applied to the cage, little work is
required to rotate it and hence there is little power dissipation
associated with the cage. This system can in fact be constructed in
the same manner as a thrust bearing. The balls act as bearings
between the PDMS disk (1104) and channeled device (1106). The upper
PDMS disk drives the thrust bearing over a circular path above the
channels in the lower PDMS device. The cage simply keeps the balls
aligned, both radially and tangentially.
[0039] In certain embodiments of the present invention, the rotary
planar peristaltic micropump (RPPM) uses a thrust bearing (FIG. 12)
to compress microfluidic channels. As an upper disk is rotated, the
balls (1201) within the thrust bearing roll to create the moving
compressional wave that drives fluid through the underlying
channels that could be contained within the lower element (1204)
were it fabricated from an elastomeric material. The cage (1202) of
the thrust bearing confines the balls as they roll, but does not
provide enough friction to cause sliding. This is another advantage
of the RPPM. Many previous peristaltic pumps, including that of
Darby et al., involve significant frictional forces caused by the
dragging of the compressing object along the surface, an issue that
the matched rolling action of the RPPM's thrust bearing and the two
matched deformable surfaces avoids. With rolling friction, the wear
on the PDMS pieces, particularly the channeled device, is greatly
reduced as compared to a design with sliding friction, allowing for
prolonged use of the device. A standard thrust bearing also
contains two inelastic washers (1203 and 1204), usually metallic in
nature, that sit above and below the ball (1201) and cage assembly
(1202). In exemplary embodiments of the RPPM design (FIG. 13),
these washers are made of PDMS, with the bottom washer comprising
the channeled PDMS microfluidic device (1301), and the top washer
being the aforementioned disk (1302) that drives the rotation. The
bearing (1303) is turned by the frictional forces acted on it by
1302, which is attached to a coupler (1304) that is turned by a
stepper motor (1305). In specific embodiments, coupler (1304) may
be custom-machined metal or plastic.
[0040] In an ideal system with only rolling friction, the bearing
cage turns at exactly half the rate of the motor. The coupler
(1304) contains a shaft (1306) that provides axial registration for
the PDMS disk (1302), the thrust bearing (1303), and PDMS device
(1301). The shaft terminates within a circular opening at the
center of a disk (1307) that serves as the ultimate base of the
entire device. In certain embodiments disk (1307) may be formed
from polycarbonate or other material. Along with the center hole
(1308), disk (1307) contains tapped holes (1309 and 1310) along the
edge that correspond to openings (1311 and 1312) on the mounting of
the stepper motor. Altogether, the PDMS pieces, the stepper motor,
the metal or plastic coupler, the polycarbonate base piece, and the
mounting screws (1313 and 1314) comprise an exemplary embodiment of
an RPPM system.
[0041] In the embodiment shown in FIG. 14, the coupler 1304
comprises a shaft (1401) with a diameter just under the inner
diameter of the desired bearing and a hub (1404) at least as large
as the outer diameter of the bearing. The length of the shaft
(1402) determines the total allowable thickness of the PDMS washer,
bearing, and PDMS channels. Taking into consideration these
parameters, an additional distance (e.g., 2-5 mm) is needed so that
the shaft extends into the polycarbonate base. The diameter of this
shaft (1403) is determined by the inner diameter of the bearing
used. The shoulder on the coupler is of a diameter (1404) that is
larger than the bearing outer diameter. A center hole (1405) in the
coupler provides a connection to the motor shaft, and a tapped hole
(1406) and set screw (1407) secure the coupler to the motor.
[0042] The base piece (FIG. 15) shown here as a circular disk
(1501) has a centered hole (1502) that is just larger than the
metal or plastic shaft. Two threaded holes (1503 and 1504) match
the holes on the motor mount (1311 and 1312), and provide and
control compression to the device. Depending on the stability and
configuration of the mount and motor used, this base piece may
contain, for example, up to 4 mounting holes. Other configurations
of the base, motor mount, and drive components are also possible in
other exemplary embodiments.
[0043] The fabrication of the microfluidic device (FIG. 16) can be
accomplished with soft lithographic techniques and replica molding.
In certain embodiments, the master mold can be created in a
photolithographic process that uses a silicon wafer and SU-8
negative photoresist to produce a flat silicon base with raised
patterned structures composed of cross-linked photoresist. The
positive-relief pattern is created by shining UV light through a
patterned mask onto a thin layer of SU-8 negative photoresist
residing on the silicon wafer. Restricted by the usage of a thrust
bearing, the microfluidic design requires a circular compression
zone. The size of these radially arranged channels is determined by
the size of the thrust bearing. Exemplary embodiments contain
multiple concentric channels (1601) to ensure that a slightly
off-center placement of the thrust bearing will still cause flow,
or to allow increased flow rates for a given rotational
velocity.
[0044] In one exemplary embodiment, to create the microfluidic
device, a thin layer of PDMS (1602) (e.g., 100 .mu.m in certain
exemplary embodiments) is spun onto the silicon master. Pre-cured
tubing-support cubes of PDMS (1603 and 1604) are then placed over
the input and output holes of the master and the entire device is
allowed to cure. The cured PDMS is then carefully removed from the
wafer and I/O holes (1605 and 1606) are punched through the PDMS
cubes. The punched device is then plasma bonded to another thin
layer of cured PDMS (1607). Lastly, a hole for the metal or plastic
shaft (1608) is punched at the center of the bonded device.
[0045] Altogether, the components described above comprise an
exemplary embodiment of a rotary planar peristaltic micropump.
Assembly instructions for the exemplary embodiment described above
follow. It is understood that the following assembly description is
merely one example of assembly, and that other suitable
alternatives may be substituted for certain components or steps.
For example, the retainers may be configured differently than shown
and described.
[0046] To assemble the pump, the coupler (1304) is slid onto the
motor's (1305) shaft (1315) and secured using a retainer (1316)
(e.g., a set screw). The PDMS washer (1302) can then be added onto
the shaft of the coupler (1304), followed by the thrust bearing
(1303), followed by the channeled PDMS device (1301). The end of
the coupler's shaft (1306) fits into the center hole (1308) of the
base piece (1307). The pieces can then be secured together with
adjustable retainers (e.g., machine screws) (1313 and 1314) passing
through the motor mount (1311 and 1312) and terminating in the
tapped holes (1309 and 1310) in the polycarbonate base (1307).
Loosening or tightening the adjustable retainers (1313 and 1314)
controls the amount of compression felt by the channels.
[0047] Exemplary embodiments of the present invention offer
numerous advantages over other peristaltic pumps used in
microfluidic devices. Many current microfluidic systems are driven
by computerized mechanical pumps, for example, linear syringe
pumps, or by banks of computer-controlled solenoids to deliver
pressure to selected control channels. Compared to these expensive
pumps, which require a computer or microprocessor and either
complex mechanical actuators or expensive valve banks and a
pressure regulator, exemplary embodiments of the present invention
require a simple motor to turn the assembled device. In contrast to
many peristaltic pumps in microfluidic devices, when the motor
driving various embodiments of the present invention is turned off,
regions of compression remain in the channels and block passive
forward or reverse flow through the pump. Also, with peristalsis,
the system does not directly pump from a reservoir, thus allowing
for the possibility of a recirculating setup that addresses the
problem of a finite reservoir and permits prolonged experimentation
that requires little to no maintenance.
[0048] Exemplary embodiments of the present microfluidic
peristaltic pump may be used for microfluidic mixing. By
reconfiguring the channeled PDMS device and replacing the ball
thrust bearing (FIG. 12) with a roller thrust bearing (schematics
shown in FIGS. 17A and 17B), many different mixer designs can be
fabricated. The roller thrust bearing features a cage (1701 and
1705) and rolling elements configured as cylindrical rollers (1702
and 1706) coupled, for example, to the cage via pins (1703 and
1707) that pass through a central hole (1704 and 1708) in each of
the cylindrical rollers. FIG. 17B shows rollers of variable length
and placement (1709-1711), which prove useful in mixing
applications.
[0049] FIG. 18A shows a multipath-design mixer, with three channels
(1801-1803) with a path length ratio of roughly 1:2:3. A series of
13 valves (depicted by rectangles, e.g., 1804) controls each of the
six modes for the pump. One exemplary configuration of the valves
for each mode is shown in FIG. 18B (Table 1). 1805-1807 are three
possible inputs for this design, and 1808-1810 are the three
possible outputs. The nodes denoted by asterisks (1811 and 1812)
are connected via tubing and used only during the series
recirculation mode. This design would most likely utilize the
roller thrust bearing shown in FIG. 17A. A second possible mixer
design would use a pattern derived from Roger Penrose's aperiodic
set of thick and thin rhombus tiles. This design, shown in FIG.
19A, has multiple inputs (1901-1903) to allow for parallel loading
of mixing components, and a circular Penrose design (1904) that is
compressed by a roller bearing as shown in FIG. 17A or 17B. A
series of valves similar to those used in FIG. 18 could also be
incorporated in this design for greater control of mixing modes.
Using the variable length rollers (1709-1711) of FIG. 17B along
with the aperiodic pattern of FIG. 19 can create a unique scenario
of splitting and recombining flow streams that will increase mixing
efficiency. The long rollers would ensure that the solution had a
net tangential flow around the pump and was completely expelled
from the pump at the end of the mixing process, and the short
rollers would provide a local circulation that would enhance mixing
efficiency. Combining either of the mixing designs with a valve
bank would also allow for the fabrication of a rotary reagent
formulator.
[0050] It is important in many biological and chemical research
projects to be able to produce solutions that contain a large
number of different chemical substances at differing
concentrations. Historically, preparation of these solutions would
be done by separate weighing, volume measurements, serial
dilutions, and mixing. More recently, this process has been
automated by the use of either manual pipetting with controlled
dispensing, or by acoustic droplet generators.
[0051] Two main types of microformulator devices have been created.
One type is a junction at which multiple input channels of fluid
are combined into a single channel and then mixed, either by
lateral diffusion over the length of a long channel, or by other
mixing approaches, such as chaotic mixers or three-dimensional
mixers. The concentration of each fluid can be controlled by the
input velocity of their respective channels. Junction mixers are
fast but are accurate for only two different fluid inputs. The
second type is in the style of the Hansen et al. (2004) device,
which at present represents the state of the art in microfluidic
formulators. Hansen devised a microfluidic microformulator that
utilized a large number of pneumatically operated valves and pumps
to mix picoliter volumes from 32 reservoirs that could be loaded
with different chemical solutions. In this type of microformulator,
fluids from multiple input channels are serially loaded into a
mixer system, the output of which is then pumped from the device.
The Hansen-style microformulator creates accurate mixtures,
although it is slow due to its serial nature. Other limitations of
this system include the large number of valves, the low volume of
the device, and the time required to produce and mix a microliter
of solution.
[0052] Exemplary embodiments of the invention using a rotary planar
peristaltic micropump can be extended to create a microformulator
of a different design: a system that can rapidly combine, mix, and
dispense a solution that contains an arbitrary number of solutions
combined at controlled volumes to achieve the desired concentration
of each component.
[0053] The rotary planar peristaltic micropump (RPPM) (FIGS. 13-16)
can be combined with microfluidic channels and a loading system to
form a microformulator, identified as a rotary microformulator. The
use of the RPPM as the driver of a microformulator is an
improvement of current microformulators, in part due to its speed,
versatility, accuracy, and small size.
[0054] The functionality of the rotary microformulator (FIG. 20) is
accomplished with a circular channel (2001) containing radially
arranged inputs (2002). The RPPM compresses this channel to cause
fluid flow. The rotation of the bearings (2006) or rollers of the
RPPM over the flow channel (2007) causes fluid to be pumped through
the channel. This driving action of the bearings allows for precise
control over the flow rate of the fluid, facilitating precise
metering of both input and output solutions. The RPPM also allows
for high flow rates compared to those of alternative methods,
allowing for fast mixing of larger volumes of liquid.
[0055] Valves are used to control the flow configuration of the
rotary formulator. When the valve on the connecting or bypass
channel (2005) is closed and the others are open, fluid flows from
the input channel (2007) to the output channel (2008). When the
input valve (2004) and the output valve (2003) are closed and the
connecting valve (2005) is open, the main channel forms a closed
path through which the RPPM can induce continuous recirculatory
flow. The recirculation of flow allows for rapid solution mixing.
Multiple input solutions can be loaded into the channel either in
flow configurations using methods involving such structures as
multiplexers or in radially arranged inputs (2002).
[0056] Alternatively, the device can be used to mix an arbitrary
number of solutions in a strictly linear path as opposed to a
recirculating loop. The RPPM can draw fluid in from a multiplexer
or radially positioned inputs, which lets various solutions into
the mixture in quantities controlled by varying the time and
frequency that the channel to each reservoir of solution is open.
As the pump runs, it draws in each solution in proportion to the
time that each reservoir channel is open. To facilitate the mixing
process, the opening of the reservoirs is alternated so that the
distance that each bolus of solution must diffuse is minimized.
Once the correct ratios of solutions are drawn from their
respective reservoirs, the mixture is pumped through a long,
meandering pathway so that when the fluid is pumped out of the
device, it is fully mixed. Using such a device, the composition of
the mixture can be dynamically varied (i.e., sinusoidal variation
of certain solutions) simply by varying the solution inputs. Such a
device would be advantageous because the rotary peristaltic pump
eliminates the need for multiple pumps, while still maintaining a
high pumping rate.
[0057] An almost sinusoidal concentration of an output mixture of
two solutions is accomplished with two converging channels whose
widths vary according to sinusoidal relationships. The flow rate of
the channels produced by the rotating bearings or rollers of the
RPPM varies according to the widths, causing the converged mixture
to have sinusoidal concentrations over time.
[0058] Solution input into the device is accomplished by connecting
channels to the main fluid flow channel. Valves are used to control
the opening and closing of these input channels. Implementations of
this general input structure can be accomplished in a number of
ways. The simplest approach that is sufficient for serial output of
mixtures is the use of a single multiplexer that connects to the
input of the device, functioning similarly to the Hansen et al.
(2004) formulator. The bearings rotate a certain amount to load
solutions from the multiplexer serially to achieve the desired
mixture. A multiplexer can also be used along the perimeter of the
circle to allow for very rapid input. In this configuration, the
multiplexer loads channels connected to the main fluid flow path in
defined amounts. As the RPPM rotates, the fluid is drawn in.
[0059] Another method for fluid input, shown in FIG. 21, is through
the use of recirculating fluid input holder channels (2103) that
remain in contact with the rollers (2104) of the RPPM. The fluid
input holder channel (2103) is connected to the main flow channel
(2101) through a valved angled channel (2102). When a single path
is formed between the fluid input supply (2108) and the main fluid
channel (2102) by closing only one valve (2106), the roller meters
solution into the mixture. When the path is closed from the fluid
input supply (2108) to the fluid channel (2101) by closing the
connecting valve (2105) and the supply valve (2107), the fluid in
the input holder (2103) simply recirculates along the closed path.
Hence the roller is continuously moving fluid in a peristaltic
fashion, and the selection of which valves are open or closed
determines whether injection or recirculation is recurring, but in
no case are large pressures developed by having a peristaltic pump
attempt to move fluid past a closed valve.
[0060] An additional fluid input method, shown in FIG. 22, uses a
valve (2204) with an input (2202) and output (2201) channel on
either side. As a roller (2205) of the RPPM rolls over the valve
(2204) and past it, fluid in the main channel (2203) is directed
out of the output channel (2201) and fluid from the input channel
(2202) is directed into the mixer at main channel (2203).
[0061] Alternatively, as shown in FIG. 23, the fluid inputs can be
arranged radially along the perimeter of the circular channel
(2303), each inlet (2301) being immediately preceded by an outlet
(2302) and a valve (2304). To load fluid, the device is initially
loaded with an arbitrary solution, such as water. As a roller
(2305) moves across the valve, the valve blocks the main channel
and forces fluid out through the outlet (2302). A vacuum is then
formed between the PDMS and the substrate, so when the rollers move
past the solution inlet (2301), fluid is drawn in. Using this
method, the volume of each solution input can be varied by
actuating the valves in a certain sequence and precisely varying
the rotation of the bearings.
[0062] The use of pneumatic microfluidic valves with the rotary
microformulator can be accomplished with a multi-layer PDMS device.
In the multiple layers the control channels of the valves are
protected such that compression of the closed valve does not fully
close the control channel. This allows a channel to be compressed
by the RPPM despite being closed.
[0063] An implementation of this valve protection for a valve
outside of the main flow loop is shown in FIG. 24. As rollers
depress the pump channel (2407), the valve channel cover (2406) is
also depressed, therefore protecting the valved channel (2405). The
four-layer PDMS structure shown consists of a pump layer (2401), a
valved channel layer (2402), a control layer (2403), and a base
layer (2408). The channel in the control layer (2403) contains the
control channel (2404), which expands with air to close the valved
channel (2405). The pump channel (2407) is in the same layer as the
valved channel cover (2406).
[0064] An implementation for a valved pump channel is shown in FIG.
25. Whether or not the main flow channel (2505) in the pump layer
(2501) is compressed by the control valve (2504), there remains
sufficient space in the control valve (2504) in the control layer
(2502) for proper functionality, regardless of the RPPM state. The
base of the control valve (2504) is provided by the base layer
(2503).
[0065] The rollers or bearings can be designed in conjunction with
external structures, such as closed channels, to provide
functionality in addition to the pumping. This can be used, for
example, to control metering. FIG. 26 shows an implementation of
this hardwired functionality. As the rollers of the RPPM (2602)
rotate around the flow channel (2601), they sequentially depress
the closed valves (2605, 2604, 2603). The compression of the closed
valves on one side by the rollers (2602) allows the closed valves
to act as a pneumatically actuated peristaltic pump on a different
channel (2606). Using this technique, an entire sequence of fluid
flow handling events can be encoded in the rotation of the RPPM.
This allows for complex devices to be controlled by a simple motor
running at an arbitrary rate.
[0066] A mixer driven by an RPPM can be useful in experiments
requiring a steady flow of a precise combination of solution
components, even when those components must be dynamically and
precisely varied. Previous mixers have used either a single
pneumatically actuated microfluidic pump to draw fluid from
different reservoirs, which cannot handle higher flow rates, or
individual syringe pumps for each input solution, which are costly
and complicated. Our device eliminates both of these limitations by
using a single high flow rate peristaltic pump to draw each
solution, eliminating the expense of multiple pumps. In addition,
the use of an easily controlled motor and the lack of
pressure-actuated valves allow the device to remain compact and
suitable for on-site or low-resource settings. The device can be
used to expand the repertoire of fluid flow operations that
point-of-care microfluidic devices can perform.
[0067] FIGS. 27 and 28 illustrate the first implementation of the
RPPM, and FIGS. 29 and 30 show a more recent implementation, with
FIG. 29 showing a simple rotary pump, and FIG. 30 showing a Penrose
mixer.
[0068] Referring now to the exemplary embodiment shown in FIG. 31,
the microfluidic portion of the RPPM can be configured to provide
support for separate, but simultaneous pumping for multiple
external devices. Fluid can be drawn in through the inlets or
inputs (3101-3104) and pumped through concentric channels (3109) to
the outlets or outputs (3105-3108). The angular extent of the
channels (3109) in each section can be different to provide
different pumping rates or duty cycles, depending upon the
configuration of rollers (FIGS. 17A and B).
[0069] In the exemplary embodiment of FIG. 32A, a microfluidic
design is shown that could be used with the RPPM to pump a fluid
from 3201 to 3202. This embodiment has multiple concentric channels
(3203) to increase flow rate and protect against channel
blockage.
[0070] The embodiment illustrated in FIG. 32B shows a slight
variation of 32A, with each of the concentric channels (3206)
connected directly to the input (3204) and output (3205) nodes.
[0071] The embodiment of FIG. 32C provides a microfluidic design
that could be used to pump several different fluids simultaneously
and without crosstalk. Each of the inputs (3207-3210) has a
corresponding output (3211-3214). In function, this embodiment is
similar to the one shown in FIG. 31.
[0072] The embodiments shown in FIGS. 33A and 33B provide two
different microfluidic configurations for a multiple channel device
that allows crosstalk between channels, for example, to allow
mixing. In 33A, fluid is drawn in through an input node (3301),
allowed to split into multiple channels (3303), and then forced to
recombine as the channels collapse to a single channel (3304)
toward the center of the design. A flow is then allowed to split
again and recombine at a single channel (3305) toward the outer rim
of the design. During operation, the process can be repeated twice
more until the fluid exits at 3202. The differences in path length
result in longitudinal mixing.
[0073] In the embodiment of FIG. 33B, the splitting (3308) and
recombination of the flow can occur in the middle of the concentric
channel region (3309). Fluid enters at 3306 and exits at 3307.
[0074] The embodiment of FIG. 34A shows a schematic of conical
(3401) and cylindrical (3405) rollers between two layers of PDMS
(3402 and 3403, 3406 and 3407). During operation, these rollers can
be depressed so that they compress their respective microfluidic
channels (3404 and 3408).
[0075] The embodiment shown in FIG. 34B illustrates some of the
advantages of using conical rollers for a rotary pump. A conical
roller (3409) rolls in a circle (3410) because of the differences
in radii at its end points. A thrust bearing using conical rollers
also has the advantage of being self-centering when depressed by
the coupler and PDMS washer system. On the other hand, cylindrical
rollers (3411) roll in a straight line (3412), implying that, when
included in a thrust bearing, a restoring force on its outer edge
is required for rotary motion, and that there can be differential
slippage along the length of the roller if it is forced to roll in
a circle.
[0076] The embodiments illustrated in FIG. 35 show a variety of
cage designs for custom thrust bearings. The physical cage
assemblies for the designs are denoted as 3501, 3503, 3506, 3508,
and 3511.
[0077] The embodiments of FIGS. 35A and 35B show designs that would
contain rollers. The equivalently sized and spaced openings (3502)
in FIG. 35A would accommodate 20 rollers of equal length, whereas
the smaller openings (3505) in FIG. 35B would accommodate shorter
rollers in a staggered fashion. Longer rollers (3504) are inserted
at regular intervals to push flow along.
[0078] FIGS. 35C, 35D, and 35E show embodiments that can contain
spherical balls as the rolling elements. FIG. 35C shows an
embodiment with a cage configuration for a standard ball thrust
bearing, with openings at regular intervals (3507) for balls. The
embodiment of FIG. 35D has a staggered configuration of openings
(3509), akin to that shown in FIG. 35B. Three openings (3510),
spanning from the inner to the outer radius, mimic the flushing
action of the longer rollers. FIG. 35E uses the three-ball-span
configuration (3512) around the entirety of the cage. Such a
bearing has the low friction advantages of a spherical ball but
would allow multiple concentric channels to be pumped at similar
compression levels.
[0079] The principle of operation and a diagram of one embodiment
of an RPV microvalve are shown in FIGS. 36A-36C. FIG. 36A
illustrates a four-channel valve in which the fluidic connections
between inputs (3601) and outputs (3602) are interrupted by
compression from the ball in the bearing at certain locations and
contiguous at other locations (3603) such that only one channel of
the valve's four channels is open at any given rolling element
position. The principle of operation is illustrated in FIG. 36C
with four rolling elements (3625) shown in four different positions
(3621-3624) in which only one channel (3626-3629, respectively) is
open to flow between the inputs and outputs. FIG. 36B is a
schematic drawing of a 16-port valve in which the outputs from 16
switched inputs (3611) are combined at a single point in the center
(3612). The meandering channels (3613) crisscross the radial
position of the rolling element compression zone and are precisely
positioned such that at each of sixteen angular positions of 8
rolling elements, only one input channel is open to the output and
the remaining channels are compressed by one or more rolling
elements, forming a 16-port valve.
[0080] FIGS. 37A-37C show the concept, design, and functioning of
one embodiment of a pulse-width modulation RPV waveform generator.
FIG. 37A illustrates how the generator is composed of a continuous
mixer that uses alternating discrete pulses of two solutions as
inputs. The boluses mix together in a meander by diffusion and
Taylor dispersion, forming an axial output concentration waveform.
By dynamically changing the length of the discrete pulses, multiple
different concentration waveforms can be produced at a wide range
of temporal resolution. FIG. 37B is an image of an axial gradient
in a meander produced by manually alternating between DI water and
black dye. FIG. 37C is a schematic of the implementation of
discrete bolus mixing of two solutions using RPVs. As the
compression zones of the rolling elements (3705) rotate, the two
channels (3706, 3707) are alternately closed. Positions 3701, 3702,
3703, and 3704 show the four different states of the device formed
by 11.25.degree. clockwise rotation of the rolling elements (3705).
In positions 3701 and 3703, 3706 is closed, allowing fluid from
3707 to enter the meander (3708). In positions 3702 and 3704, 3707
is closed, allowing fluid to enter from 3706. The discrete boluses
of the two solutions mix in the meander (3708) and exit through the
output port (3709). By dynamically varying the speed of the motor,
arbitrary bolus sizes can be created, allowing generation of
different waveforms.
[0081] FIGS. 38A-38D illustrate the design and operation of a
variable flow rate RPPM. FIG. 38A illustrates a device that pumps
two fluids through two separate channels (3807, 3808) from
respective fluid inputs (3801, 3803) to fluid outputs (3802, 3804),
using two rolling elements (3805, 3806) rotating at constant speed
around a central axis and positioned opposite each other such that
each fluid channel is always compressed by exactly one bearing.
FIGS. 38B-38D illustrate device operation, as the rolling element
(3812) traverses the fluid channels (3811, 3821, 3831) and
encounters an increasing number of channels as it progresses from
FIGS. 38B-38D. As the number of channels that rolling element
(3812) compresses changes, pumping speed through the fluid channel
changes proportionally, such that any flow waveform can be created
with a specific variation in channel multiplicity.
[0082] FIGS. 39A-D illustrate a pulse regulating device with an
input (3905) and an output (3906). As shown in FIG. 39A, when the
standard device (3901) is operated, there is a period where the
rolling element (3902) occludes the channels as they exit the
device, which causes a stoppage in flow (3903). This in turn causes
the flow from the device (3901) to be pulsatile. However, the pulse
regulator design shown in 39B phases the channels out at different
stages of rotation (3904), decreasing the pulsatility of flow from
input (3905) to output (3906). A detailed view of the phased exits
is shown in FIGS. 39C-39D. As shown in FIG. 39C, the rolling
element (3902) is early in the cycle, and is occluding the exit of
the third channel (3909) while the others remain open and allow
flow. FIG. 39D shows the rolling element (3902) late in the cycle
of rotation, occluding the exit of the last channel (3911).
[0083] FIG. 40A illustrates an RPPM configured as a two- or
three-phase droplet generator. During operation, the actuator with
six rolling elements (4001) (shown filled with hatch marks) rotates
in a clockwise direction. The compression zones for each of the six
rolling elements move continuously around the radius defined by the
bearing geometry. Three compression zones for each rolling element
(eighteen total) are depicted as unfilled circles. Three
microfluidic channels with inputs (4002-4004) follow precise
pathways through the bearing compression zones and converge at a
single output (4005). Fluid can be pumped from the inputs of all
three channels to the output in the pumping zone (4006) in reverse
sequential order (4004, then 4003, then 4002).
[0084] During operation, each channel is occluded to prevent
backflow with meanders in the compression zones of non-pumping
rolling elements (4007). The positioning of the compression zones
ensures that the channel being pumped in the pumping zone is not
occluded, while the other two channels are occluded. This can
ensure forward flow at the nexus and an interleaving of fluids from
the three input channels. If immiscible liquids are used on the
inputs, droplets can be formed on the outputs. Two-phase droplet
mixtures can be obtained by eliminating one of the three
microfluidic channels, and if desired, enlarging the remaining two
to maintain continuous, uninterrupted flow. If more than three
fluidic phases or solutions are desired, additional channels may be
added in a similar configuration.
[0085] FIG. 40B illustrates a RPPM and RPV system that can act as
both a fluid multiplexer and a demultiplexer, depending upon the
direction of rotation. This extends the concept shown in FIG. 40A
and demonstrates the use of a single set of ball actuators to work
as both a pump and a valve. With the balls rotating in a clockwise
direction, the device acts as a multiplexer and draws fluid from
three inputs and expels it through a single output. fluid is first
drawn from port 4011, with the pumping section 4014 providing the
pressure to move the fluid, in contrast with the device in FIG. 40A
where an external pressure source is required. The return path 4016
allows the fluid to flow through to the output 4017 by crossing the
path of the balls at a location where the flow is not blocked by a
ball when that section is pumping. After the ball moves from
position A to position C, the pumping from 4011 stops because the
ball (shaded) encounters the blocking valve section 4015. Fluid is
pumped from input 4012 when another ball reaches position B, and
continues until that ball passes position A. Fluid is pumped from
input 4013 when another ball reaches position C, and continues
until that ball passes position B. The output 4017 contains the
summed flow from 4011, 4011, and 4013, as shown in FIG. 40C. The
exact timing of the beginning and end of each pumping phase is
determined by the exact angular position of the pumping and
blocking valve regions, and can be adjusted as desired in the
design of the device. Hence, in this configuration, three different
solutions can be multiplexed from the three inputs into a common
output. Similarly, rotation of the balls in a counterclockwise
direction causes the device to act as a demultiplexer that draws
fluid from a single input 4017 and expels it through three separate
outputs 4011-4013. Other embodiments could produce multiplexers and
demultiplexers with different numbers of solutions and different
timing.
[0086] FIG. 41A shows a profile view of one embodiment of a
peristalsis system in microfluidics. The microfluidic channel
(4101) is compressed by a rolling element (4102) (e.g., a ball
bearing in certain embodiments) that is receiving downward force
applied by a brass flange (4103) and a PDMS washer (4104). As
rolling element (4102) rotates and moves along the microfluidic
channel, the fluid or contents of the channel also move along. FIG.
41B shows two schematics of embodiments of the RPPM. In the upper
schematic, a single channel design depicts input and output punch
pads (4111, 4112). Rolling elements (4113) show theoretical
placement of the balls within a thrust bearing. The lower schematic
of FIG. 39B replaces a single channel configuration with five
concentric channels (4114) that combine on ends. FIG. 41C is an
exploded profile view of one embodiment of an RPPM system. In this
particular embodiment, a stepper motor (4121) is attached to a
polycarbonate base piece (4122) by a set of four M3 screws (4123),
and a brass flange (4124) is attached to the motor shaft by an 0-80
screw (4125). In the embodiment shown, the brass flange's shaft
provides alignment and support for the PDMS washer (4126) and
thrust bearing (4127). The microfluidic pump (4128) with tubing
(4129) is placed between the thrust bearing and polycarbonate
piece. FIG. 41D is a assembled version of FIG. 41C, while FIG. 41E
shows a perspective view.
[0087] FIG. 42A shows a schematic for a compact embodiment of an
RPPM. 4201 and 4202 are the input/output ports for this design,
which are connected to 5 concentric channels (4203). Additional
concentric circles (4204, 4205) are included for alignment. FIG.
42B shows the physical implementation of the compact embodiment
illustrated in FIG. 42A. This implementation includes a small
stepper motor (4206), which is enclosed in a hollow threaded rod
(4207, secured to motor housing with a set screw) and is screwed
into the top half of a partially threaded hollow sleeve (4208). A
brass flange (4209, secured to motor shaft with a set screw),
allows a PDMS washer (4210) and ball thrust bearing (4211) to be
placed concentric to the motor's axis of rotation. The PDMS
microfluidic device (4212) is placed on top of another hollow
threaded rod (4213), which is then screwed into the bottom half of
4208. Tubing (4214) can then be added to facilitate fluid flow.
Threaded rod (4213) provides structural support and height
adjustment to tubing (4212). Both threaded rods (4213) and (4207)
can be used to control the amount of compression between tubing
(4211) and PDMS microfluidic device (4212), which is a major factor
in controlling flow.
[0088] FIG. 42C shows the unassembled parts used in another
implementation of the embodiment shown in FIG. 42A. In this
embodiment, a motor (4215) is directly attached to an acrylic
housing (4216) with two hex socket head screws (4217, 4218). A
brass adapter (4221) is attached to the shaft of the motor with a
set screw and supports the PDMS washer (4220) and thrust bearings
(4219). In this embodiment, the microfluidic device and tubes
(4222) are presented to the bearings and held in place by a hollow
set screw (4223). FIG. 42D shows the assembled device, including
4215-4223.
[0089] FIGS. 43A-C show a design for a multi-pump array. This
embodiment includes three pairs of two pumps (4301 and 4302, 4303
and 4304, 4305 and 4306), each of which is run through serpentine
mixers (4307-4309). The middle pair is also run through a meander
(4310) to allow for contemporaneous flow. In this embodiment, the
three channels are then combined in a fourth serpentine mixer
(4311). Parts of the larger structure (43C) are shown with dotted
lines. These include screws (4312), motor heads (4313), and
fastening plates (4314). FIG. 42B shows the motor used in the array
(4315) and a ruler for scale. FIG. 43C shows a 3-D cutaway model of
the array, which shows array (4315), the fastening plates (4316),
brass adapters (4317), PDMS washers (4318), thrust bearings (4319),
PDMS device layer (4320), glass base (4321), and metal base (4322).
The fastening plates are supported by springs from underneath and
held down by adjustable screws.
[0090] FIG. 44 shows the excellent linear relationship between flow
rate (microliters/minute) and motor speed (revolutions/minute)
exhibited by one embodiment of an RPPM. 4401 shows a photograph of
the pump used to gather this data. Each set of points (4402) (e.g.,
square, triangle, asterisk, large circle, and small circle data
points, as shown from top to bottom in the legend) has a linear
trendline fitted to it. The equations and R.sup.2 values for these
trendlines (4403) are shown on the left-hand side of the graph.
[0091] FIGS. 45A-45C show an embodiment exhibiting how two RPPMs
may be arranged to provide two-dimensional control of particles in
a microfluidic device. FIG. 45A shows a schematic for the
microfluidic device (known as a "crossflow" divide) used in 2-D
control. One input and one output of the first pump are connected
via tubing to ports (4501) and (4502), respectively. The second
pump's input and output are connected to ports (4503) and (4504).
The open chamber (4505) in the middle of the device allows for
particles to move freely based on the flow streams provided by the
two RPPMs.
[0092] FIG. 45B shows the crossflow device and two RPPMs (4506 and
4507) configured to perform a 2-D control experiment. Tubing (4508)
connects the two pumps to the crossflow device (4509). The
microcontroller platform used to control this pump system (4510) is
also shown. FIG. 45C shows several kymographs created using this
2-D crossflow setup. By setting each RPPM to provide a sinusoidal
input stimulus (with a 90 degree phase shift between the two),
particles can be moved in a circle, as shown in 4511. The 3-D graph
(4512) shows the path of the particle in the x- and y-axis and the
progression of time in the z-axis. 4513 and 4514 show 2-D side
views taken from the 3-D kymograph.
[0093] FIGS. 46A-46C illustrate the design and operation of one
embodiment of an RPPM- and RPV-driven batch mode microformulator.
In this embodiment, fluid inputs are selected from inputs (4601) of
a rotary multiplexer (4602) and are drawn with an RPPM (4605) into
a loading shuttle (4603) that holds inputs while RPPM (4605)
flushes rotary multiplexer (4602) with solvent to the waste port
(4606). Inputs in loading shuttle (4603) are then drawn into the
mixing chamber (4604) and recirculated with RPPM (4605) until
sufficiently mixed, at which point they are pumped out with RPPM
(4605) through the output port (4607). In this exemplary
embodiment, mode switching of the device is achieved with an RPV
(4608) that sequentially opens and closes channel paths with a
thrust bearing located in the compression zone (4609). FIGS. 46B
and 46C illustrate RPV operation, as rolling elements (4611, 4612,
4621, 4622) sequentially pass over compression zones (4613, 4623)
of fluid channels (4614, 4615, 4624, 4625) and successively open
and close channel paths to switch between device operation
modes.
[0094] FIG. 47 illustrates a schematic representation of an
alternative embodiment of a high-density array of microfluidic
single-cell yeast traps. In this schematic, 112 traps are shown in
7 rows of 16. In this exemplary embodiment, each trap is 10
.mu.m.times.10 .mu.m, and the channel above each trap is 10 .mu.m
wide. The ports are configured as pairs connected to a push-pull
pump, using an on-chip peristaltic pump with either pneumatic or
rotary mechanical actuation or a syringe pump pair, so that the
flow from one port is matched by the fluid removed from the other
port of the pair. In one exemplary method of use, a small number of
yeast cells can be loaded by laminar flow along L1-L2 while all
other ports are blocked. Once the cells are loaded in a line along
the left edge of the array, pumps S1-S2 and S3-S4 are actuated
transiently to move these yeast from left to right into the
array.
[0095] In this embodiment, actuation of the transverse parallel
flow from T1 to T2 will sweep the cells into the nearest trap.
Adjustment of the T1-T2 transverse flow can control the ability of
the device to hold cells in the traps, or modulate the trapping
efficiency. S1-S2 and S3-S4 can pump different media formulations,
e.g., different glucose concentrations. A gradient generator could
be used to provide a different concentration for each row. In this
schematic, there are four adult yeast cells trapped, one of which
is budding, and another whose bud has already moved to the adjacent
downstream trap.
[0096] In the embodiment shown, adjustment of the pumping rates of
S1-S2 and S3-S4 relative to T1-T2 can lead to cells being trapped
or swept all the way to the right, where a vertical fence of small
posts detains the cells. Then optical sensing and
computer-controlled valves V-A and V-B can direct flow from C1
cells to either outlet ports C2 or C3, depending upon the cell type
or genealogy. More outlet ports can be used to sort into more
categories. Adequate perfusion for low-density cultures can be
readily maintained with total flow through S1-S2 and S3-S4 of only
2 mL/min. Activation of T1-T2 can provide perfusion without
translation. Alternatively, flow from S1 to S2 and S3 to S4 will
shift to the right cells displaced from a trap by division. At
20.times. magnification, a typical automated fluorescence
microscope can, in 40 ms, image a 430 .mu.m.times.345 .mu.m field
of view (FoV, each) in four colors with 0.3 .mu.m.times.0.3 .mu.m
pixels. By sequentially imaging 12 fields of view in 10 seconds,
the high-speed translation of an automated microscope can allow a
user to image 4000 traps over a 1.3 mm.times.1.4 mm area in 10
seconds. The imaged area can either be configured as one large trap
array, or multiple, individually controllable trap sub-arrays. One
advantage of the latter is that vertical perfusion can be
continuous for all traps, but horizontal flow could be limited to
the interval where each sub-region is being viewed multiple times
by the microscope to track the cells as they move.
[0097] FIGS. 48A-F illustrate steps towards implementation of the
embodiment of FIG. 47. FIG. 48A illustrates an overall schematic of
the device, while FIGS. 48B-48F provide more detailed views of
different sections. While the figures in the present disclosure are
generally not to scale, FIGS. 48A-48E are shown to scale for one
exemplary embodiment. In FIG. 48A, the scale bar represents 1 cm.
In FIG. 48B, fluid flow is driven by an on-chip RPPM, and the scale
bar is equal to 500 .mu.m. In FIG. 48C, a Moire interference
pattern for accurate low-cost mask alignment is illustrated, with a
scale bar equal to 400 .mu.m. In FIG. 48D, a valve system is shown
to allow for integrated cell sorting. In this Figure, the scale bar
equals 800 .mu.m. In FIG. 48E, an array of cell trap devices is
illustrated with a scale bar equal to 60 .mu.m. FIG. 48F
illustrates a Comsol hydrodynamic model of cell retention force
under perfusion in a selection of trap designs. Surface shading
represents fluid velocity magnitude, and vector arrows represent
normalized average total shear stress on primary trapped cells (top
row) and secondary trapped cells (bottom row).
[0098] FIG. 49A shows an embodiment utilizing rotary thrust ball
bearings as planar valves to drive serial switching between three
different flow configurations. In this embodiment, rolling element
spacing within the cage (4901) allows for three unique positions.
Rolling element spacing can be modified to allow for more
configurations. Additionally, this configuration of nanobioreactor
and channel positioning can be arrayed around the cage to control
multiple switching events in a single rotation. A compression
between the rolling element-PDMS interface forces any underlying
microfluidic flow channels shut. Rotation of the bearing cage
allows for only one open flow path at branch sites (4902, 4903) so
that nanobioreactor A and B (4904, 4905) can operate separately, as
shown in FIG. 49B, or in series, as shown in FIGS. 49C-49D.
[0099] FIG. 49B shows a rolling element (e.g., ball bearing)
configuration that allows for independent perfusion of
nanobioreactor A and B. These unique rolling element positions
close off channels that connect flow between the nanobioreactors
(4911, 4912) and the outlet port used while operating in series
from nanobioreactor A to B (4913). Thus, this rotation state leaves
only two open outlets for independent perfusion of nanobioreactor A
(4914) and nanobioreactor B (4915).
[0100] Subsequent clockwise rotation of the rolling element cage to
the next unique state is shown in FIG. 49C. Rolling element
positions (4921, 4922) close output flow channels for
nanobioreactor B and re-route output flow of B to nanobioreactor A
(4923). Flow from nanobioreactor A to B is occluded as well (4924),
forcing flow to a single output channel (4914).
[0101] Further clockwise rotation of the rolling element cage to
the last unique state is shown in FIG. 49D. Rolling element
position (4931) blocks the outlet port downstream of nanobioreactor
A, forcing flow through a connecting channel (4932) from A to
nanobioreactor B. Series flow from nanobioreactor B to A is
prevented as this channel (4932) is forced shut due to ball bearing
compression (4933). Additionally, a single outlet port (4934)
remains open as ball bearing (4932) shuts flow to the second outlet
port of nanobioreactor B (4915).
[0102] FIG. 50 illustrates the design of an RPPM-driven and
Quake-style valve-controlled batch mode microformulator. Fluid
inputs are selected from inputs (5001) of a multiplexer (5004)
controlled with Quake valve channels (5002) and are drawn with an
RPPM (5007) into a loading shuttle (5009) that holds inputs while
5001 is flushed with solvent to the waste port (5005). Inputs in
5004 are then drawn with 5007 into the mixing chamber (5008) and
recirculated with 5007 until sufficiently mixed, at which point
they are pumped out with 5007 through the output port (5006). Mode
switching is achieved with Quake valve channels (5003) that
sequentially open and close channel paths.
[0103] FIG. 51 shows the concept, design, and operation of a
Quantum Dot Hybridizer. FIG. 51A is a schematic showing the
agglomeration of quantum dots (QDs) and antigens in a closed
recirculating microfluidic channel. With each hybridization cycle,
the agglomerates grow larger until they can be easily detected.
FIG. 51B is a schematic showing how an RPPM and pneumatic valves
are combined to implement re-circulatory flow. The device consists
of connected flow channels (5104) and three control channels that
act as valves (5101, 5102, 5108). When 5101 and 5108 are
pressurized, the fluidic inputs (5103) are closed, allowing for
circulation of fluid by rotation of the RPPM's bearings (5105).
When only 5102 is pressurized, fluid can enter and exit the system
through the fluid ports (5103). The branched mixer (5107), which is
composed of multiple meanders of varied lengths (5106), allows for
rapid mixing.
[0104] FIG. 51C shows the device (5109) with the motor and rolling
elements set up to re-circulate and mix lighter and darker dyes
(with the darker dyes being at the upper portions of the meanders).
5110, 5111, and 5112 are time series images of the mixer at the
start, middle, and end of mixing by counter-clockwise rotation of
the bearings. FIG. 51D is an image of the device after mixing
lighter and darker dyes.
[0105] Rotary planar peristaltic micropumps (RPPMs) and rotary
planar valves (RPVs) technologies can also be combined into a
well-plate assay controller. Since the same DC gear-head or
stepping motor configuration can be used to drive either the RPPMs
and the RPVs, the development on an integrated microfluidic control
unit is attainable. The RPPMs and RPVs can be used in tandem to
create general purpose instrumentation that can deliver, for
example, within one minute a microliter of solution that is metered
and mixed from multiple reservoirs whose relative contributions can
be controlled on demand. The RPPMs can be used to drive the fluid
through the systems and the RPVs will regulate flow to the desired
inlet/outlets. Various reagent reservoirs for priming buffer,
coating channels with desired matrix, cells, cell media, test
sample and wash buffer will be considered to facilitate the
implementation of assay protocols.
[0106] A typical well-plate assay with live cells can involve two
modes. The first mode is a "preparation mode," which consists of
priming the device, cell matrix injection, and cell injection
followed by media injection until cells are confluent. A wash and
suction step is integrated for waste removal. The second mode is an
"assay mode," which refers to the test conditions where different
samples (nutrients, xenobiotic compounds, drugs, and pathogens) are
evaluated for their effects on the cells being cultured.
[0107] In this embodiment, each of these modes is supported by a
separate RPPM-RPV device. FIG. 52A shows the device that supports
the Preparation Mode. RPV 1 (5201) selects one of six inputs
(5211-5216), RPPM 1 (5202) with rotating elements (5203) provides
the pumping through the device, and a Y-channel or connector header
(5204) provides the connection of the Preparation inputs to the
input ports (5205) of the well plate, shown in FIG. 54A. While 12
chambers are shown for convenience, the actual number could be
different, either larger or smaller.
[0108] The Assay Mode shown in FIG. 52B has RPV 2 (5206) that
selects from six inputs (5217-5222), and the output of this valve
goes to RPPM 2 (5207). The output of this pump then goes into a
selector valve RPV 3 (5208), which determines which input fluid is
injected through the connector 5209 and hence well-plate assay
ports 5210 and then to the selected, individual chamber in the well
plate.
[0109] FIG. 52C shows an alternative embodiment for the Assay Mode,
in which the output from RPPM 2 (5207) connects to RPV 3' that is
similar to 5208 but with an additional valve position (5230) that
is connected to a common set of ports 5234 in RPV 4 (5232). This
12-position RPV (5232) switches from random access to parallel flow
for media flow, in a manner designed to eliminate crosstalk between
the bioreactors until they are fed by the common line from the
13.sup.th position in RPV 3' (5231). For the serial loading of
individual chambers in the well plate, as described in FIG. 52B,
the selection of connections (5235) in RPV 4 (5232) connects each
of the first 12 output of RPV 3' (5231) valve inputs (5233) to the
corresponding well-plate connector and port in 5209 and 5210. In
this embodiment, when RPV 4 is switched to the other position, the
connections 5235 are made to the common ports (5234), and the
output of RPPM 2 (5207) is directed in parallel to all twelve of
the chambers through each line in 5209 and 5210. A particular
advantage of this particular arrangement is that the 12 chambers in
the well plate can be either addressed individually for loading,
drug dosing, or analysis without cross contamination, but can also
be perfused in parallel to allow long-term culture without the need
to use the RPVs actively to multiplex perfusion through all wells
individually.
[0110] The well-plate controllers in FIGS. 52A-C could be connected
to the well plate in FIG. 53. The connector from the Preparation
Mode controller (FIG. 52A) connects to the ports 5205, while those
from the Assay Mode Controller (FIGS. 52B-C) connect to ports 5210.
Each of these ports is connected to perfusion line, for example,
5201 and 5202, respectively. The use of two separate lines reduces
the possibility that cell debris or other materials from the
loading process will interfere with the assay process, and could be
eliminated if desired. Each of the preparation and loading lines
converges on an individual microfluidic chamber, device, or fluidic
network, as shown for example by 5303. Each chamber, device, or
network is connected to an individual drain line, e.g., 5304, and
these lines are gathered together to form drain connections 5305
from the device. Other embodiments would be possible based upon
this example.
[0111] The discussion below summarizes an automated well-plate
loading and assay process, using the controller in FIG. 52 and the
12-well plate in FIG. 53 as an example. The process comprises the
following sequences:
[0112] Preparation Mode
[0113] 1. Stainless steel Y connectors into the inlet of each
device with sealable plug to choose the port for injection in the
12 wells.
[0114] 2. Four reservoirs for priming media, cell growth matrix,
cells and cell culture media/harvesting media connected to a
6-position RPV for: Off, wash, matrix, cells, media, harvest.
[0115] 3. An RPPM draws fluid from the valve and pressurizes the
well plate for initiating the valve-based sequential operation.
[0116] 4. A single tube goes to a disposable output connector with
a built-in splitter for 12 Y-As. A blank termination tube goes to
the 12 Y-Bs for use in the assay mode.
[0117] Assay Mode
[0118] In this embodiment, we illustrate how to investigate the
effects of four different drugs on a total of twelve separate cell
populations.
[0119] 1. Five reservoirs for media+four drug solution
reservoirs.
[0120] 2. Six-way RPV for Off, media, 4 drug solution.
[0121] 3. An RPPM interconnected to a 13-position RPV for
individual well addressing or parallel addressing of all wells.
[0122] 4. An RPV that can switch from serial individual loading to
parallel, simultaneous perfusion.
[0123] Using the layout in FIG. 43, a set of six of motors that
could be mounted in a manner to implement FIGS. 52A-C, with
different microfluidic channels, to create a compact RPPM-RPV
microfluidic control unit, which would thereby replace with a
single unit all the hardware and tubing required by macroscopic
laboratory implementations of microfluidic well-plate loading. Such
a system would result in an integrated fluidic controller for a
high-throughput assay. This system could then be utilized in
standard microscopes, automated microscopes, high-throughput plate
readers, and high-content screening automated microscopes, as well
as being integrated into stand-alone instruments that contain the
requisite optical and mechanical components.
[0124] One notable feature of this pump and valve system over other
approaches is that a common motor and controller design can be used
to control either a pump or a valve; the components are of
sufficiently low cost that they can be implemented as individual
support units for each well plate being assayed, and the devices
are sufficiently compact that they could be placed inside a
sterile, cell-culture incubator.
[0125] FIGS. 54A-D illustrate an embodiment of an RPPM device that
maintains a constant flow rate without pulsatility. FIG. 54A
depicts an RPPM with a U-shaped channel (5401) compressed by
rotating bearings (5402) that pumps fluid from an inlet (5403) to
an outlet (5404). FIG. 54B illustrates the mechanism by which
pulsatility forms in such a device. As the bearing (5412) rotates
and travels away from the fluid channel (5411), the area of the
channel once compressed by 5412 is no longer compressed and expands
to its normal height, thereby drawing in fluid to fill the
expanding channel and temporarily reducing output flow. One method
to eliminate this output pulse is to temporarily increase rolling
element rotation speed as the event in 54B occurs, thus increasing
output flow by an amount equal to the pulsed reduction in flow.
FIG. 54C illustrates a second device, identical to 54A except for a
channel modification (5431), designed to eliminate pulsatility
while maintaining constant bearing rotation. FIG. 54D illustrates
the function of the device, as rotating rolling elements (5441,
5444) compress a channel (5442) and pump fluid through 5442. As the
last rolling element (5444) leaves the channel area, the previous
rolling element (5441) compresses an expanded area of the channel
(5443) and pumps an additional volume of fluid equal to the fluid
lost through pulsatility.
[0126] While exemplary embodiments of the present invention have
been shown and described in detail above, it will be clear to the
person skilled in the art that changes and modifications may be
made without departing from the scope of the invention. As such,
that which is set forth in the preceding description and
accompanying drawings is offered by way of illustration only and
not as a limitation.
[0127] In addition, one of ordinary skill in the art will
appreciate upon reading and understanding this disclosure that
other variations for the invention described herein can be included
within the scope of the present invention.
[0128] In the preceding Detailed Description of Disclosed
Embodiments, various features are grouped together in several
embodiments for the purpose of streamlining the disclosure. This
method of disclosure is not to be interpreted as reflecting an
intention that exemplary embodiments of the invention require more
features than are expressly recited in each claim. Rather, as the
following claims reflect, inventive subject matter lies in less
than all features of a single disclosed embodiment. Thus, the
following claims are hereby incorporated into the Detailed
Description of Exemplary Embodiments, with each claim standing on
its own as a separate embodiment.
REFERENCES
[0129] The following documents are incorporated herein by
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