MICROFLUIDIC DEVICE

Abstract

Microfluidic devices are provided for separating particulates that have a major dimension above a predetermined threshold value from a fluid, the device comprising an inlet, an inlet channel, a curved channel, a separation chamber, a first outlet and a second outlet; the inlet being connected to the inlet channel, the inlet channel is connected to the curved channel, the curved channel is connected to the separation chamber and the separation chamber is connected to the first outlet by a first outlet channel, and the separation chamber is connected to the second outlet by a second outlet channel; the first outlet channel comprises a serpentine portion; wherein the second outlet channel branches from the separation chamber substantially perpendicular to the first outlet channel.

Claims

1. A microfluidic device for separating particulates that have a major dimension above a predetermined threshold value from a fluid, the device comprising an inlet, an inlet channel, a curved channel, a separation chamber, a first outlet and a second outlet; the inlet being connected to the inlet channel, the inlet channel is connected to the curved channel, the curved channel is connected to the separation chamber and the separation chamber is connected to the first outlet by a first outlet channel, and the separation chamber is connected to the second outlet by a second outlet channel; the first outlet channel comprises a sinusoidal/serpentine portion; wherein the second outlet channel branches from the separation chamber substantially perpendicular to the first outlet channel; the curved channel having an angle of curvature of 150 to 270 degrees; wherein the aspect ratio of the inlet channel is from 10 to 20, the aspect ratio of the curved channel is from 5 to 10, the aspect ratio of first outlet channel is from 1.5 to 6, and the aspect ratio of the second outlet channel is from 15 to 25 such that, during use, fluid flows from the inlet, to the first outlet and the second outlet via the inlet channel, the curved channel, the separation chamber and the first outlet channel and the second outlet channel respectively; wherein particulates within the fluid at the inlet that have a major dimension above the predetermined threshold value are substantially focussed into the second outlet and the fluid that is collected at the first outlet is substantially free of particulates that have a major dimension above the predetermined threshold value.

2. The device of claim 1, wherein the width of the inlet channel is from 1.5 to 3 times greater than the width of the curved channel.

3. The device of claim 1, wherein the predetermined threshold value is from 0.01 μm to 500 μm.

4. The device of claim 1, wherein the width or aspect ratio of second outlet channel is at least 3 times the width or aspect ratio of the first outlet channel.

5. The device of claim 1, wherein the second outlet channel comprises a bend or curved portion.

6. The device of claim 1, wherein the depth of the channels of the device are the same or substantially the same.

7. The device of claim 7, wherein the depth of the channels of the device are from 20 μm to 3000 μm.

8. A microfluidic device for separating particulates that have a major dimension above a predetermined threshold value from a fluid, the device comprising a plurality of layers, each layer within the plurality of layers comprising an inlet, an inlet channel, a curved channel, a separation chamber, a first outlet and a second outlet; the inlet is connected to the inlet channel, the inlet channel is connected to the curved channel, the curved channel is connected to the separation chamber and the separation chamber is connected to the first outlet by a first outlet channel, and the separation chamber is connected to the second outlet by a second outlet channel; the first outlet channel comprises a sinusoidal/serpentine portion; wherein the second outlet channel branches from the separation chamber substantially perpendicular to the first outlet channel; the curved channel having an angle of curvature of 150 to 270 degrees; wherein the aspect ratio of the inlet channel is from 10 to 20, the aspect ratio of the curved channel is from 5 to 10, and the aspect ratio of first outlet channel is from 1.5 to 6; the inlet of each layer within the plurality of layers is in fluid communication with a common inlet manifold, the first outlet of each layer within the plurality of layers being in fluid communication with a common first outlet manifold, and the second the inlet of each layer within the plurality of layers being in fluid communication with a common second outlet manifold; such that, during use, fluid flows from the common inlet manifold to the common first outlet manifold and the common second outlet manifold via the inlet, inlet channel, the curved channel, the separation chamber and the first outlet channel and the second outlet channel of each layer within the plurality of layers; wherein for each layer within the plurality of layers particulates within the fluid at the inlet that have a major dimension above the predetermined threshold value are substantially focussed into the second outlet and the fluid that is collected at the first outlet is substantially free of particulates that have a major dimension above the predetermined threshold value.

9. (canceled)

10. The device of claim 8, wherein the width of the first outlet channel varies from the separation chamber to the first outlet.

11. The device of claim 10, wherein the first outlet channel comprises a flared portion and the width of the flared portion increases from the separation chamber to the end of the flared portion closest to the first outlet.

12. The device of claim 11, wherein the flared portion extends part of the way along the first outlet channel such that the width of the remainder of the first outlet channel is constant.

13. The device of claim 11, wherein the flared portion corresponds to a portion of the serpentine portion of the first outlet channel.

14. A method of use of a device according to claim 1, the method comprising the steps: providing a fluid comprising a target population of particles; driving the fluid into the inlet of the device or the inlet of the common inlet manifold of the device at a first rate of flow; and collecting the fluid from the first and second outlets of the device or each layer within the plurality of layers, wherein the fluid from the second outlet of the or each layer comprises the target population of particles, and fluid from the first outlet is substantially devoid of the target population of particles.

15. A system for removing populations of particles from a fluid comprising a plurality of devices according to claim 1, the first outlet of a first device is in fluid communication with the inlet of a subsequent second device, wherein the channels of the first device are dimensioned to focus particles of a first range of diameters into the second outlet of the first device, and the channels of the second device are dimensioned to focus particles of a second range of diameters into the second outlet of the second device, such that fluid comprising populations of particles with diameters within the first and/or second range of diameters may be sequentially removed from the fluid as the fluid passes through the plurality of devices.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0091] Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings.

[0092] FIG. 1: A microfluidic device according to an embodiment;

[0093] FIG. 2: A zoomed in view of the portion of a device according to an embodiment indicated by the dotted circle in FIG. 1;

[0094] FIG. 3: A photograph of a device comprising a stack of microchannels according to an embodiment with a first and second manifold coupled to the first and second outlets of each microchannel, and an inlet manifold coupled to the inlets of each microchannel;

[0095] FIG. 4: An example common inlet manifold that may be used with the device comprising a stack of microchannels showing the flow rate through the common inlet manifold; and

[0096] FIG. 5: Chart showing efficacy of a stack of 750 devices according to an embodiment to filter Scenedesmus quadricyada from a sample of a period of time, where the dotted chart shows % recovery and the dashed chart shows the time of operation for that recovery in 15 minute intervals.

DETAILED DESCRIPTION

[0097] While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

[0098] To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

[0099] In order to demonstrate the efficacy of the device, the following experiments were carried out.

Example 1—Single Flow Channel

[0100] Test samples were used containing a variety of algal species to determine the percentage of biomass that could be removed from the sample. This experiment was called a “dewatering” experiment.

[0101] A device as shown in FIG. 1 and FIG. 2 was used to process the test samples. The device 1 comprises an inlet 2, a linear inlet channel 4 (acting as an inlet channel), a curved channel 6, a separation chamber 8, a first outlet channel 10, a first outlet 12, a second outlet channel 14 and a second outlet 16.

[0102] During use, fluid flows from the inlet 2 to the first outlet 12 via the inlet channel 4, the curved channel 6, the separation chamber 8, and the first outlet channel 10 or to the second outlet 16 via the inlet channel 4, the curved channel 6, the separation chamber 8, and the second outlet channel 14.

[0103] All channels have a depth of 60 μm.

[0104] The inlet channel 4 has a width of 0.92 mm and an aspect ratio of 15.33. The curved channel 6 has a width of 0.52 mm, an aspect ratio of 8.67 and an angle of curvature 24 of 180°. Accordingly, there is a discontinuity 18 where the inlet channel 4 and the curved channel 6 connect.

[0105] The first outlet channel 10 has an initial width of 0.24 mm (aspect ratio of 4), increasing in a flared portion 20 to a width of 0.51 mm (aspect ratio of 8.5). The second outlet channel has a width of 1.2 mm and an aspect ratio of 20.

[0106] The first outlet channel has a sinusoidal portion 22.

[0107] Fluid from each test sample was put into a reservoir at the inlet of the device. The fluid was the pumped into the inlet at a rate of 6 mL/min. The fluid was collected at the first outlet (“permeate”) and at the second outlet (“retentate”). The optical density of the initial test samples, the retentate and the permeate where measured using a photo-spectrometer and the results are provided in Table 1 below.

TABLE-US-00001 TABLE 1 The performance of dewatering of single chip technology OD OD OD % of Name of species initial retentate permeate recovery Chlorella vulgaris 0.548 0.5795 0.045 92.23 Tetraselmis suecica 0.6705 0.62 0.077 87.58 Tetraselmis suecica 0.9005 0.917 0.092 89.96 concentrated Dunaliella primolecta 0.5155 0.4425 0.023 94.80 Phaedactylum 1.59 1.665 0.0105 99.36 tricornutum Spirulina maxima 0.734 0.8085 0.114 85.89 Scenedesmus 1.5045 1.608 0.0035 99.78 quadricuada

[0108] The best results of up to 99% of biomass recovery was shown for Phaeodactylum tricornutum and Scenedesmus quadricauda, taking into account that the initial concentration of these both cultures were relatively high (OD=1.5-1.59) in Table 1. The other species dewatering was less efficient with results ranging from 85 to 95%. The less efficient dewatering was for Spirulina maxima, potentially because this culture has specific forms of filament formation.

[0109] In addition, it has been found that the optimum flow rate of fluid through the device is as provided in Table 2.

TABLE-US-00002 TABLE 2 The determined optimal flow rate for devices having a given depth of channel Channel Depth (μm) Optimum Flow rate (mL/min) 50 3.1 60 4.5 75 6.0 90 13.0 180 30.0

[0110] Optimal flow rate was determined to be the maximum flow rate of fluid through the device without a negative impact in particle separation efficacy.

Example 2—Stacked Device

[0111] A stacked device 200 (for example, see FIG. 3) having 750 microchannels operating in parallel was tested to demonstrate that a high volume of fluid can be processed without losing separation efficacy.

[0112] Each microchannel of the stacked device corresponded to a device as described in the first example. The inlet of each microchannel (acting as a layer) was coupled to an inlet manifold 202 (acting as a common inlet manifold). The inlet manifold 202 (see FIG. 4) comprising an inlet 204, a branched portion 206, an open portion 208 and a manifold outlet 210.

[0113] The first outlet of each microchannel was coupled to a first outlet manifold 212 (acting as a common first outlet manifold). The second outlet of each microchannel was coupled to a second outlet manifold 214 (acting as a common second outlet manifold). Each of the first outlet manifold and second outlet manifold had a structure similar to that of the inlet manifold as shown in FIG. 4.

[0114] A test sample containing Scenedesmus quadricuada was pumped into the inlet of the inlet manifold and thereby processed by the device. Particulate contents of the fluid collected by the first outlet manifold and the second outlet manifold was determined by optical density measurements. The separation efficiency of the stacked device 200 is shown in FIG. 5, demonstrating that good separation performance was maintained for at least 4 hours.

[0115] Power consumption was monitored and results indicate an energy requirement of ˜1.25 kWh/m.sup.3 of sample processed. Alternative methods of particle separation from a fluid, such as membrane filtration have an energy consumption of 2.23 kWh/m.sup.3 (Gerardo et al., Journal of Membrane Science 464:86-99, 2014), and centrifugation has an energy consumption typically in the region of 8 kWh/m.sup.3. Accordingly, the stacked device is more energy efficient that alternative devices used for particulate separation.

[0116] This energy efficiency is enabled by increasing the cross-sectional area in dimensions of the device that have been shown to be non-critical. This has the effect of increasing the aspect ratio, which had previously been considered to be damaging to performance. However, it has been shown that the present device is able to successfully separate out particles of a desired dimension from a fluid whilst increasing the aspect ratio of at least some channels to thereby increase the volume of fluid that can be processed in a given time.

[0117] Furthermore, the ability to vary the distance between the first outlet and the second outlet by providing a first outlet channel having a flared portion allows the first and second outlets to be sufficiently separated to spatially allow manifolds to be positioned such that fluid from the first and second outlets of each microchannel in the stacked device can be collected, thereby allowing a plurality of microchannels to process a fluid in parallel, thereby significantly improving the efficiency of the device and allowing a much higher volume of fluid to be processed in a compact device.