IE84902B1 - A microfluidic droplet queuing network - Google Patents
A microfluidic droplet queuing networkInfo
- Publication number
- IE84902B1 IE84902B1 IE2007/0072A IE20070072A IE84902B1 IE 84902 B1 IE84902 B1 IE 84902B1 IE 2007/0072 A IE2007/0072 A IE 2007/0072A IE 20070072 A IE20070072 A IE 20070072A IE 84902 B1 IE84902 B1 IE 84902B1
- Authority
- IE
- Ireland
- Prior art keywords
- droplets
- bridge
- draft
- conduit
- bridges
- Prior art date
Links
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Abstract
ABSTRACT The invention relates to control of flow of small discrete quantities of liquids (“droplets”) at the microfluidic scale.
Description
A Microfluidic Droplet Queuing Network
INTRODUCTION
Field of the Invention
The invention relates to control of flow of small discrete quantities of liquids
(“droplets”) at the microfluidic scale.
Prior Art Discussion
There are many applications emerging for the use of flowing liquid droplets for uses
such as chemical reactors. The liquid droplets may be controlled in such a way that
they are separated from one another by an immiscible carrier oil which also wets the
inner channel or tube surface. The droplets are thereby completely wrapped by the oil
phase and any chemical interaction with the surface, including carryover and cross-
contamination between droplets is eliminated.
It is known to provide droplets by, for example, segmenting a single phase
homogeneous droplet into multiple smaller droplets of the same composition.
However the art provides little guidance for controlling flow of multiple droplets,
particularly where droplets contain different chemical compositions.WO2005/00273O
describes a microfluidic device in which droplets are provided by shearing force
between an aqueous liquid from a channel and oil flowing in the channel into which
the aqueous liquid enters.
The invention is directed towards providing improved control of such droplets.
SUMMARY OF THE INVENTION
According to the invention, there is provided a method for managing a queue of
droplets in a network comprising; a draft conduit for flow of droplets with a carrier
liquid; at least one liquid bridge in the draft conduit, the bridge having a chamber in
which there is a draft inlet formed by the draft conduit, a draft outlet fonned by the
draft conduit, an inlet port, and a compensation port;
the method comprising delivering a sequence of droplets flowing in carrier
liquid to each bridge via the inlet port so that said droplets are added to carrier
liquid in the draft conduit, carrier liquid is withdrawn via the compensation
port of each bridge to compensate for added liquid, and the separations of the
inlet droplets are sufficient to achieve an adequate separation of droplets in the
draft conduit.
In one embodiment, there are a plurality of bridges in the draft conduit. and droplets
of the same type are added substantially simultaneously to the draft conduit via the
bridges so that there is a sequence of droplets of similar type in the draft conduit.
In another embodiment, droplets of different types are added substantially
simultaneously to the draft conduit, providing a sequence of droplets of selected
different types in the draft conduit.
In a further embodiment, there is a uniform target flow in the draft conduit.
In one embodiment, there are a plurality of bridges in the draft conduit and a liquid
supply delivers liquid to the inlet port of each bridge.
In another embodiment, the inlet port and the draft conduit are co-planar.
In a further embodiment, the compensation port is at an angle to the plane of the inlet
port and the draft conduit.
In one embodiment, the compensation port is at an angle of substantially 90° to the
plane of the draft conduit and the inlet port.
In another embodiment, the network comprises a plurality of draft conduits in parallel
and the bridges are used to provide a plurality of sequences of droplets.
In a further embodiment, each bridge inlet port diameter is in the range of 0.1mm to
.6mm.
In one embodiment, each bridge compensation port diameter is in the range of 0.1mm
to 0.6mm.
In another embodiment, the separation of the compensation port from the axis of the
draft conduit is in the range of 21m to 81nm.
In a further embodiment, the method comprises the steps of segmenting a large droplet
or a stream into droplets and delivering said droplets to the inlet port of the bridge.
In one ernbodiment, the segmenting is performed by a bridge having a chamber with
an inlet and an outlet, and a droplet temporarily adheres to the inlet and transfers to
the outlet when it becomes unstable.
In another embodiment, carrier liquid is contained in the space between the inlet and
the outlet.
In a further embodiment, the network comprises a plurality of bridges in the draft
conduit, at least one of said bridges being a mixing bridge downstream of at least one
other bridge, and in which the mixing bridge mixes a droplet with a droplet flowing in
the draft conduit.
In one embodiment, a manifold delivers droplets from a well to a plurality of bridges.
In another embodiment, an infusion pump delivers carrier liquid to the manifold.
In a further embodiment, the bridges and the draft conduit are arranged in an array and
there is a well adjacent each bridge.
In one embodiment, said wells are arranged in a pattern of an assay well plate.
In another embodiment, there are a plurality of wells and associated manifolds, and
they deliver droplets of different types to the bridges to achieve a serial flow of
droplets of different types in the draft conduit.
In a fiirther embodiment, droplets are added simultaneously at spaced-apart locations
along the draft conduit.
In one embodiment, the length of conduit between said supply and each bridge is
chosen according to modelling of an electric circuit, in which conduit length is
equivalent to electrical resistance.
In another aspect of the invention, there is provided a microfluidic network for
queuing a sequence of droplets in an immiscible carrier liquid, the network
comprising:
a draft conduit for flow of droplets with a carrier liquid;
a plurality of liquid bridges along the draft conduit, each of said bridges
comprising a chamber, a draft inlet, a draft outlet, a droplet inlet port, and a
compensation port,
a liquid supply connected to the bridge inlet ports;
a liquid supply delivering a flow of liquid along the draft conduit; and
wherein the compensation ports are at an angle to the plane of the inlet ports
and the draft conduit.
In one embodiment, the compensation port is at an angle of substantially 90° to the
plane of the draft conduit and the inlet port.
In another embodiment, each bridge inlet port diameter is in the range of 0.1mm to
.6mm.
In a further embodiment, each bridge compensation port diameter is in the range of
.1mm to 0.6mm.
In one embodiment, the network further comprises a segmenter for segmenting a large
droplct or a stream into droplets and delivering said droplets to the inlet port of the
bridge.
In another embodiment, the segmenter comprises a bridge having a chamber with an
inlet and an outlet, and a droplet temporarily adheres to the inlet and transfers to the
outlet when it becomes unstable.
In a further embodiment, the segmenter comprises a chamber, for containing carrier
liquid in the space between the inlet and the outlet.
In one embodiment, the network further comprises a manifold for delivering droplets
from a well to a plurality of bridges.
In another embodiment, the network further comprises an infusion pump for
delivering carrier liquid to the manifold.
In a further embodiment, the bridges and the draft conduit are arranged in an array and
there is a well adjacent each bridge.
In one embodiment, said wells are arranged in a pattern of an assay well plate.
DETAILED DESCRIPTION OF THE INVENTION
Brief Description of the Drawings
The invention will be more clearly understood from the following description of some
embodiments thereof, given by way of example only with reference to the
accompanying drawings in which:-
Fig. l is an illustration of a multi-port liquid bridge of a liquid droplet network;
Fig. 2 shows queuing configuration of droplets in a tube in which droplets are
grouped into sets of similar chemistry;
Fig. 3 shows queuing configuration of droplets in a tube in which droplets of
different types are arranged in sequence;
Fig. 4 shows queuing configuration of droplets in a tube in which droplets are
arranged in repeat sequence;
Fig. 5 shows time progression, left to right, of a queue formation of droplets
with different chemistry in each;
Fig. 6 shows queuing of different droplets formed in identical parallel lines;
Fig. 7 shows a queuing system having an upstream liquid bridge segmenter to
form droplets, queuing bridges, and a downstream bridge mixer to add
chemistry to each of the queued droplets;
Fig. 8 shows network having wells, manifolds, segmenter bridges, and queuing
bridges to produce a queue of droplets with different chemistry in each;
Fig. 9 shows the physical construction of the bridge of Fig. 1;
Fig. 10 shows a bridge having three in-plane with three ports at 120° to each
other and a compensating port at 90° to this plane;
Fig. 11 is an external perspective view of an array plate of a network; Fig. 12
shows junction caps and a fluorinated ethylene propylene (FEP) well inserts of
the well plate, and Fig. 13 is a more detailed perspective view;
Fig. 14 is a perspective view of a 11111 microfluidic system;
Fig. 15 shows a syringe pump system which supplies the system with fluid
flow;
Figs. 16 and 17 shows a multiple syringe and manifold infuse array in use;
Fig. 18 shows a manifold used to convert fluid flow into multiple equal lines of
fluid flow; and
Fig. 19 is a diagram illustrating operation of electrical analysis software
modelling microfluidic networks.
Description of the Embodiments
lf liquid droplets are added to a tube or channel at different axial locations then the
flow rate and velocity would increase in the flow direction, giving an undesirable
summing of flow rates when queuing a number of droplets. To overcome this, equal
volumes of liquid are added and subtracted simultaneously to keep the axial velocity
in the queuing tube constant. A droplet network has bridges such that wherever a
droplet is added to a draft flow excess carrier liquid (silicone oil) is removed via a
compensating port. An aqueous phase entering from an inlet port will be delivered to
an exit port, likewise for an aqueous phase arriving at an upper inlet port. By this
means aqueous droplets can be introduced into the draft stream and delivered straight
through all of the downstream bridges. In a single device, with steady inlet flows, a
queue of droplets can be formed and delivered. Furthennore, a downstream segmenter
can then be used to break a stream of droplets into droplets of a different size.
A multi-port liquid bridge 1 is illustrated in Fig. 1. Arrows indicate flow direction.
Aqueous phase droplets 10 are distinctly shown with an enveloping oil phase carrier
liquid 11, implied in all of the drawings. A chamber 3 links four ports, and it is
permanently full of oil 11 when in use. Oil phase is fed in a draft flow from an inlet
port 4 and exits through a draft exit port 6 and a compensating flow port 7. The oil
carrier and the sample droplets (“aqueous phase”) flow through the inlet port 5 with an
equivalent fluid flow subtracted through the compensating port 7. The latter is
perpendicular to the plane of the page, and the manner of representing this used in Fig.
l is also used in the remainder of the drawings.
The ports of the bridge 1 are formed by the ends of capillaries held in position in
plastics housings. as described in more detail below. In one embodiment the inner
diameter of the chamber is 2.4mm and the height of the chamber is 2.5mm. The ports
-7 are 0.4mm in diameter and generally in the order of 0.1 to 0.6mm in diameter.
The phases are density matched. Density matching creates a near weightless
environment where gravitational forces are negligible. This results in droplets l0
adopting spherical forms when suspended from capillary tube tips. Furthermore, the
equality of mass flow is equal to the equality of volume flow. The phase of the inlet
flow (from the droplet inlet port 5 and the draft inlet port 4) is used to determine the
outlet port 6 flow phase.
Fig. 2, Fig. 3 and Fig. 4 represent a range of queuing configurations of droplets in a
tube. Fig. 2 shows droplets grouped into sets, Fig. 3 shows droplets arranged in
sequence, and Fig. 4 shows droplets arranged in repeat sequence.
A queuing network is illustrated in Fig. 5, which shows a column of three bridges l at
four instances in time, left to right. At a time t; the droplets taken from a well are
approaching the bridges from the left inlet port 5 in phase. At time t3 the droplets
bridge to the lower port 6. The compensating port 7 is out of plane and too far from
any inlet to bridge with the droplets, it therefore only takes the oil phase. At time t3 the
droplets are shown queued in the draft tube. At time t4 the inlet port 4 is shown
bridging with the outlet port 6, and therefore any droplet that enters from the top. or
from the left, always exits from the exit port 6. A queue of different droplets of the
aqueous phase is thereby formed. Operation of the compensating port 7 ensures
uniformity of flow down through the draft conduits 4, 6.
Many lines can be configured in parallel as shown in Fig. 6 to give a high-throughput
system. This is particularly useful for managing queuing of droplets as micro—reactors
for thermal cycling through multiple thermal cyclers in parallel. This is very
advantageous for achieving a high throughput, and it avoids need to cyclically heat
and cool reaction vessels.
A network which performs segmentation of a continuous aqueous phase into droplets,
and also queuing and mixing of the droplets, is shown in Fig.7. This embodiment
shows how the queue bridge configaration of Fig. 5 can be integrated with other
bridges, and how this network can be arranged in parallel. In the arrangement of Fig. 7
there are segmentation bridges 20 having ports 21 to 24, but only ports 21, 23 and 24
are operational as there is no flow through port 22. The bridges 20 are arranged
upstream of the queuing system, one for each well, to segment the continuous phase
drawn from a well. The segmentation is achieved by a droplet forming within a
chamber between the ports 23 and 24, and due to inter-facial tension and inuniscibility
between the aqueous and oil phases, breaking off and entering the port 24.
A single bridge 1 operating as a mixing bridge is arranged downstream of each draft
flow, so that a single phase from a well X is segmented and then mixed with each of
the queued droplets A B, in succession in the mixer bridge 1. The mixer bridges 1
are arranged so that there is simultaneous anival of droplets at them. This will also
work if the phase from well X is continuous. Within each mixer bridge. droplets form
at the ends of the ports 4 and 6, they mix due to their internal pressures and inter-facial
tension, and the mixed droplet exits via the exit ports 6.
The end result is the delivery of a queue of mixed droplets which flow downstream to
be further processed by, for example, a thermal cycler. An application of this is the
arrangement of primers in a well for queuing, then the addition of a patient’s sample
along with the other required premix occurring in the mixer. A continuous thermal
cycler for DNA amplification using the polymerase chain reaction (PCR) may be
downstream from the mixers.
Referring to Fig. 8, a network has two wells 30 and manifolds 31 to produce a queue
of droplets with alternative chemistry in each. The manifolds 31 distribute the flow to
segmenter bridges 20 so that each line carries the same flow rate. Downstream of the
segmenter bridges 20 are the queue-bridges 1 which operate in the same way as those
shown in Fig. 5.
Fig. 9 is a three dimensional view of the bridge 1. The bridge chamber 3, the upper
draft inlet 4, left droplet inlet port 5, lower draft exit 6 and the compensation port 7 are
all clearly illustrated. The outer cylinder is a solid plastics wall, in this case
polycarbonate.
However, other configurations are possible, and Fig. 10 illustrates one example in
which three in-plane ports 41, 42 and 43 are at an equal angular separation of 120°,
and the compensating port 44 is again at 90°
In one embodiment the tubing used for the fluid flow has an exterior diameter of 0.8
mm and an interior diameter of 0.4 mm, the distance between bridges is 9 mm, the
bridge chamber is of diameter 2.4 mm, and the outer diameter is approximately 6 mm.
In one embodiment, the flow rates and droplet volumes for the apparatus as follows,
with reference to the bridge 1: flow rate in the draft inlet 4, the droplet inlet 5, the
draft exit 6, and the compensating exit 7 are all equal (i.e. q4 = q5 = q,; = q7); the sum
of the inlet flow rates is also equal to the sum of the outlet flow rates (q4+q5 = q,5+q7);
droplet or plug volumes are between 30-300nl; and volumetric flow rate is3 ,ul/min
with velocities of the order 1 mm/s. These are the conditions used when the queue is
used to array primers upstream of a PCR DNA amplifier.
A network may segregate primers into a controlled and orderly flow of droplets.
Multiple wells of differing primers feed into a single tube of main fluid flow. With an
applied force to the primers in each well, a set of primer droplets will be formed at
each bridge in the tube of main fluid flow. This can be used to give a very consistent
and predictable flow of queued primer droplets. It will be appreciated that multiple
wells in multiple parallel tubes of fluid flow can achieve a large number and/or
arrangement of differing primers. A number of well array plates can be used in
parallel to acquire a sufficient number of primers for a required DNA test. Groups of
multiple droplets (approximately 10) are used to increase the sample size and thus
increase the certainty of the final test results. The queuing system receives fluid flow
from the infuse manifold of the pumping system, flows through a distribution head
into a queuing cartridge and fluid is then withdrawn from the queuing cartridge,
through the distribution head and back to the withdrawal manifold of the pumping
system.
As illustrated in Figs. 11 and 12 a plate 50 has integrally mounded bases 51 for wells
and 52 for bridges. A cap 53 is provided to complete a bridge 63 (shown in Fig. 13)
and a well insert 54 is provided to complete each well 64 (also shown in Fig. 13). Fig.
13 shows capillaries 61 interconnecting the wells 64 and the bridges 63, all in a
queuing network cartridge 60. The draft flow is along each line of bridges 63. The
overall configuration mimics that of a conventional 96-well assay plate, and so
samples can be dispensed by conventional dispensing equipment onto the wells 51.
The cartridge 60 consists of fluoropolymer tubing 61 and three injection moulded
parts: a polycarbonate array plate 62, 48 polycarbonate caps 53 and 48 fluorinated
ethylene propylene (FEP) wells 54. All parts are manufactured using standard
injection moulding. Gate and ejector pin locations were placed at sites that did not
interfere with the operation of the components. A flatness tolerance of 200
micrometers was applied to the upper face of the array plate to ensure a uniform
interface with mating fluidic ports.
A complete microfluidic system is depicted in Fig. 14. A distribution head 71
containing mating ports is milled from polycarbonate. A very tight flatness tolerance
is applied to the lower surface of the distribution head 71 in order to mate with the
upper surface of the array plate 60. A stepper motor 72 with gearing 73 which is
situated on a gear train mount 74 is used to drive a cradle base 75 containing the
queuing cartridge 60 against a support head 76 containing the distribution head 71. By
doing so the necessary connections are made between the queuing cartridge 60 and the
distribution head 71. The gear train mount 74, the cradle base 75 and the support head
76 are all made from aluminium. Steel bars 77 and collars 78 are used to position the
plates and act as guides. Bearings 79 on the cradle base 75 allow for motion to and
from the distribution head 71. The queuing cartridge sits on a cradle 80 which is fitted
onto the cradle base. The cradle 80 is a two-part piece with the top half manufactured
from polycarbonate and the bottom half manufactured from aluminium. The rotational
force of the motor 72 is converted to an upwards force acting on the array plate
through a gear and cam mechanism 73
Assembling the queuing cartridge 60 involves fastening the polycarbonate caps 53 and
the FEP wells 54 to the appropriate locations. Contact between mating parts is made
via a compression press—fit between the pins on the array plate 60 and the holes on the
well and caps. Short lengths of rigid PEEK tubing are then inserted into the
withdrawal ports of the array plate. These lengths of tubing provide a cylindrical
geometry for spacing the tubing tips. The microfluidic network of tubing 61 is then
formed by placing tubing in the appropriate ports. The tubing 61 connecting each
bridge typically measures 8mm. The tubing 61 connecting the wells to the bridges
typically measures 12mm. Sealing of the tubing network is achieved with the use of a
poly dimethyl siloxane (PDMS) encapsulant. This encapsulant is mixed as a two-part
resin, degassed in a vacuum chamber and poured into the array plate cavity. The
assembly is then cured in an oven at 80°C for 1 hour. The cured encapsulant forms an
elastomeric seal to ensure primer and oil flow only through tubing and not between
array plate—tubing interfaces. Finally, the PEEK tubing used to space the tubing tips is
removed.
Assembly of the distribution head involves the connection of tubing to the appropriate
connectors. Again sealing of the tubing network is achieved with the use of a poly
dimethyl siloxane (PDMS) encapsulant. The same method of mixing, pouring and
curing of the PDMS as mentioned above is used.
The distribution head performs the task of distributing the flow from the 48 tubes of
the manifold system to the top of the wells on the queuing cartridge. This fluid flow
from the manifold system, through the distribution head to the top of the well, is used
to pump the primer from the wells down the connecting tubes and into the bridges.
The assembled queuing cartridge 60 and distribution head 71 are primed with AS100
silicone oil prior to first use. This step removes trapped air from tubing and liquid
bridge cavities. Primer is then loaded into wells of the queuing cartridge via a standard
pipette. The pipette tip is submerged under the level of the oil and in contact with the
throat of the well such that the sample is transferred directly into the tubing. Any
backflow thereafter is accommodated by the expanding conical section of the wells.
Care must be exercised not to introduce large quantities of air into the tubing after the
primer has been infused. The cartridge is then ready to be loaded into the cradle with
the distribution head to be loaded into the support head.
The queuing cartridges 60 are designed to supply enough primer for a number of tests.
After the cartridge is depleted of primers, either a new cartridge can be used or the old
cartridge can be refilled. The distribution head, platform plates and motor system are
all permanent features of the system.
There are many ways of pumping fluid through the system. A singular plate with
indentations can be used to feed oil flow into the queuing cartridge. By placing the
plate in a bath of oil into the queuing system, the compression force applied to the
queuing system can create a constant fluid flow. Also a multiple syringe system can
be applied in order to get a multiple fluid flow through tubing into the queuing system.
However the current design uses syringe pumps to deliver the necessary flow to the
input lines of the queuing system. It is done either directly or by back-pressuring a
storage well. For the multiple line fluid flow a limited number of syringes are used to
pressurise a reservoir or manifold with many outlets. A Harvard pump with stepper-
motor drive is used to drive the limited number of syringes.
Motor systems as shown in Fig. 15 give a constant feed rate to infuse and withdraw oi I
phase from the queuing system70. The motor is a stepper motor 100 driving a lead
screw 101 via a belt 102. The rotating lead screw drives a pusher block 103 which in
turn applies a constant velocity to the syringes 104. The constant flow from the infuse
syringes is pumped through manifolds l05 as depicted in Fig. 16 which will separate
the fluid flow into multiple tubes with equal flow rates. The fluid flow then enters the
queuing system. The fluid is then withdrawn at the same flow rate using a similar
motor system in reverse. A manifold 105 is now used to reduce the number of
withdrawal tubes which is in turn connected to withdrawal syringes as shown in Fig
17. This system uses multiple syringes for infuse and withdrawal, however a singular
syringe with a larger manifold can also achieve the same task.
The manifold 105 is shown in more detail in Fig. 18. It is milled from polycarbonate.
The tubing is cut square. Equal length tubing is inserted into holes in the manifold and
are positioned flush with an inside chamber 106. A spare tube is inserted flush with
the surface at an inverted cone section 107 of the chamber. This inverted cone collects
the trapped air in the system and allows for the air to be drained via the spare tube.
The tubes are then held in place with PDMS. Again the same mixing, pouring and
curing method as in the queuing system are used. A cap array 108 with PEEK tubing
flush with the inside surface is press fitted into the opposite end of the chamber. The
cap is then fixed in place with epoxy encapsulant. This encapsulant is mixed as a two-
part resin, degassed in a vacuum chamber and poured into the array plate cavity. The
assembly is then cured in an oven at 50°C for 1 hour. The cured encapsulant forms a
solid seal to ensure no leaks occur to the chamber.
Syringes 109 are placed on top of the motor system and the manifold PEEK tubing is
connected. The entire tubing array of the pumping system is primed prior to the tubes
exiting from the manifold are connected to the queuing system. Priming the system
involves driving fluid through the system and then draining the air from the system via
the spare tubing in each chamber. This must be done before the pumping system is
ever used. After the initial priming, the system should not need to be primed again
unless air is trapped in the tubing. The same process must be then repeated. After the
fluid has run through the system the flow is then withdrawn from the system back
through the withdrawal manifolds, into the withdrawal syringes which are attached to
another motor system for withdrawal. At present the infuse and withdrawal are
powered by separate motors however since the infuse and withdrawal are at the same
flow rate the same can he achieved from a single motor adapted to suite both infuse
and withdrawal.
In summary, the pumping mechanism of Figs. 16 and 17 pump oil through the
manifolds 105, and from there into the system 70 of Fig. 14. Within this system the
liquids are processed in a network such as illustrated in Figs. 5 to 8.
Referring to Fig. 19, a queuing system employing a pressurized source, or sources, to
address multiple pressurised lines or wells may be modelled by drawing an electrical
analogy with fluidic and geometric characteristics of the system.
The following may be regarded as equivalent electrical and fluidic parameters:
Electrical Resistance, R = Fluidic Resistance, where ,u denotes fluid
viscosity, L the conduit length and R the conduit radius.
— Electrical Current, I = Fluid Flowrate, Q.
— Voltage Drop, AV = Pressure Drop, AP.
The electrical analogy permits the use of electrical engineering software to model a
droplet network. Hence, electrical engineering software may be used to predict
theoretically correct flowrates in every pressurised line within a microfluidic network.
Fig. 19 presents a section of an electrical circuit used to model a microfluidic network.
The correct selection of electrical resistance within each branch of the circuit may be
used to define appropriate lengths and radii of conduits. For example, the tubing
leading from the manifold to the upstream bridges needs to be longer than that leading
to downstream bridges, in proportion to the lower resistances illustrated.
It will be appreciated that a network of the invention allows for a queue of aqueous
droplets to be formed with a different chemical composition in each droplet. Serial
line of bridges can be arranged in parallel to give a high throughput. A network may
have a segmenter so that plugs of aqueous phase are formed upstream of the queuing
devices Also, liquid bridge mixers may be provided downstream of each serial line for
adding chemical or biological samples to the queued droplets. A network may be fed
from a small number of wells through a manifold to give a queue of droplets which
differs from the one given above, for example, with every other droplet having a
different chemistry. The network may be manufactured to have a simple geometry of
bridges that can be connected together in a variety of ways with interconnecting
circular tubing.
The invention is not limited to the embodiments described but may be varied in
construction and detail. It will be appreciated by persons skilled in the art that
variations and/or modifications may be made to the invention without departing from
the scope of the invention.
Claims (1)
- Claims A method for managing a queue of droplets in a network comprising; a draft conduit for flow of droplets with a carrier liquid; at least one liquid bridge in the draft conduit, the bridge having a chamber in which there is a draft inlet formed by the draft conduit, a draft outlet formed by the draft conduit, an inlet port, and a compensation port; the method comprising delivering a sequence of droplets flowing in carrier liquid to each bridge via the inlet port so that said droplets are added to carrier liquid in the draft conduit, carrier liquid is withdrawn via the compensation port of each bridge to compensate for added liquid, and the separations of the inlet droplets are sufficient to achieve an adequate separation of droplets in the draft conduit. A method as claimed in claim 1, wherein there are a plurality of bridges in the draft conduit, and droplets of the same type are added substantially simultaneously to the draft conduit via the bridges so that there is a sequence of droplets of similar type in the draft conduit. A method as claimed in claim 1, wherein droplets of different types are added substantially simultaneously to the draft conduit, providing a sequence of droplets of selected different types in the draft conduit. A method as claimed in any preceding claim, wherein there is a uniform target flow in the draft conduit. A method as claimed in any preceding claim, wherein there are a plurality of bridges in the draft conduit and a liquid supply delivers liquid to the inlet port of each bridge. A method as claimed in any preceding claim, wherein the inlet port and the draft conduit are co-planar. A method as claimed in claim 6, wherein the compensation port is at an angle to the plane of the inlet port and the draft conduit. A method as claimed in claim 7, wherein the compensation port is at an angle of substantially 90° to the plane of the draft conduit and the inlet port. A method as claimed in any of claims 1 to 8, wherein the network comprises a plurality of draft conduits in parallel and the bridges are used to provide a plurality of sequences of droplets. A method as claimed in any preceding claim, wherein each bridge inlet port diameter is in the range of 0. 1mm to 0.6mm. A method as claimed in any preceding claim, wherein each bridge compensation port diameter is in the range of 0. 1m to 0.6mm. A method as claimed in any preceding claim, wherein the separation of the compensation port from the axis of the draft conduit is in the range of 2mm to 8mm. A method as claimed in any preceding claim, comprising the steps of segmenting a large droplet or a stream into droplets and delivering said droplets to the inlet port of the bridge. A method as claimed in claim 13, wherein the segmenting is performed by a bridge having a chamber with an inlet and an outlet, and a droplet temporarily adheres to the inlet and transfers to the outlet when it becomes unstable. A method as claimed in claim 14, wherein carrier liquid is contained in the space between the inlet and the outlet. A method as claimed in any preceding claim, wherein the network comprises a plurality of bridges in the draft conduit, at least one of said bridges being a mixing bridge downstream of at least one other bridge, and in which the mixing bridge mixes a droplet with a droplet flowing in the draft conduit. A method as claimed in any of claims 5 to 16, wherein a manifold delivers droplets from a well to a plurality of bridges. A method as claimed in claim 17, wherein an infusion pump delivers carrier liquid to the manifold. A method as claimed in any preceding claim, wherein the bridges and the draft conduit are arranged in an array and there is a well adjacent each bridge. A method as claimed in claim 19, wherein said wells are arranged in a pattern of an assay well plate. A method as claimed in any of claims 17 to 20, wherein there are a plurality of wells and associated manifolds, and they deliver droplets of different types to the bridges to achieve a serial flow of droplets of different types in the draft conduit. A method as claimed in claim 21, wherein droplets are added simultaneously at spaced-apart locations along the draft conduit. A method as claimed in any of claims 5 to 22, wherein the length of conduit between said supply and each bridge is chosen according to modelling of an electric circuit, in which conduit length is equivalent to electrical resistance. A microfluidic network for queuing a sequence of droplets in an immiscible carrier liquid, the network comprising: a draft conduit for flow of droplets with a carrier liquid; a plurality of liquid bridges along the draft conduit, each of said bridges comprising a chamber, a draft inlet, a draft outlet, a droplet inlet port, and a compensation port, a liquid supply connected to the bridge inlet ports; a liquid supply delivering a flow of liquid along the drafi conduit; and wherein the compensation ports are at an angle to the plane of the inlet ports and the draft conduit. A microfluidic network as claims in claim 24, wherein the compensation port is at an angle of substantially 90° to the plane of the draft conduit and the inlet port. A microfluidic network as claimed in either of claims 24 or 25, wherein each bridge inlet port diameter is in the range of 0. 1m to 0.6mm. A microfluidic network as claimed in any of claims 24 to 26, wherein each bridge compensation port diameter is in the range of 0. 1m to 0.6mm. A microfluidic network as claimed in any of claims 24 to 27, wherein the network further comprises a segmenter for segmenting a large droplet or a stream into droplets and delivering said droplets to the inlet port of the bridge. A microfluidic network as claimed in claim 28, wherein the segmenter comprises a bridge having a chamber with an inlet and an outlet, and a droplet temporarily adheres to the inlet and transfers to the outlet when it becomes unstable. A microfluidic network as claimed in claim 29, wherein the segmenter comprises a chamber, for containing carrier liquid in the space between the inlet and the outlet. A microfluidic network as claimed in any of claims 24 to 30, further comprising a manifold for delivering droplets from a well to a plurality of bridges. A microfluidic network as claimed in claim 31, further comprising an infusion pump for delivering carrier liquid to the manifold. A microfluidic network as claimed in any of claims 24 to 32, wherein the bridges and the draft conduit are arranged in an array and there is a well adjacent each bridge. A microfluidic network as claimed in claim 33, wherein said wells are arranged in a pattern of an assay well plate.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IE2007/0072A IE84902B1 (en) | 2007-02-07 | A microfluidic droplet queuing network |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IEIRELAND07/02/20062006/0077 | |||
IE20060077 | 2006-02-07 | ||
IE20060709 | 2006-09-28 | ||
IE2007/0072A IE84902B1 (en) | 2007-02-07 | A microfluidic droplet queuing network |
Publications (2)
Publication Number | Publication Date |
---|---|
IE20070072A1 IE20070072A1 (en) | 2007-09-19 |
IE84902B1 true IE84902B1 (en) | 2008-06-11 |
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