APPARATUS FOR SORTING MICROFLUIDIC PARTICLES

Abstract

A consumable cartridge for a particle sorter system, the consumable cartridge comprising: an inlet for receiving a particle-containing fluid; a microfluidic chip comprising: an input channel in fluidic connection with the inlet; and a particle sorter junction in fluidic connection with the input channel and comprising an output positive channel and an output negative channel; and first and second outlets in fluidic connection with the output positive channel and the output negative channel respectively, for discharging the fluid from the consumable cartridge, such that at least one enclosed fluidic path is provided in the consumable cartridge between the inlet and the first and second outlets.

Claims

1. A consumable cartridge for a particle sorter system, the consumable cartridge comprising: an inlet for receiving a particle-containing fluid; and a microfluidic chip comprising: an input channel in fluidic connection with the inlet; and a particle sorter junction in fluidic connection with the input channel and comprising an output positive channel and an output negative channel; and first and second outlets in fluidic connection with the output positive channel and the output negative channel respectively, for discharging the fluid from the consumable cartridge, such that at least one enclosed fluidic path is provided in the consumable cartridge between the inlet and the first and second outlets.

2. (canceled)

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4. The consumable cartridge according to claim 1, wherein the inlet comprises a syringe connector configured to receive a syringe for supplying the fluid to the consumable cartridge and at least one of the first and second outlets comprises a tubular structure configured for detachable connection with a complementary tubular vessel.

5. The consumable cartridge according to claim 1, wherein the at least one enclosed fluidic path comprises at least one of: a first flexible tube connected between the output positive channel and the first outlet; and a second flexible tube connected between the output negative channel and the second outlet, wherein the first flexible tube or the second flexible tube is deformable to enable unclogging of particles in the particle sorter junction in operation.

6. The consumable cartridge according to claim 1, wherein the microfluidic chip further comprises: a bubble generator, operable to selectively displace the fluid around a particle to be sorted and thereby to create a transient flow of the fluid in the input channel; and a vortex element, configured to cause a vortex in the transient flow in order to direct the particle to be sorted into the output positive channel.

7. The consumable cartridge according to claim 6, wherein the vortex element comprises a protrusion in the input channel, a turn in the input channel, or a recess in the input channel.

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10. The consumable cartridge according to claim 6, wherein the vortex element is located between the bubble generator and the output positive channel

11. The consumable cartridge according to claim 6, wherein the bubble generator comprises a microheater.

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13. The consumable cartridge according to claim 1, further comprising an inertial focuser configured to centralise particles in the fluid along a centre of the input channel.

14. The consumable cartridge according to claim 13, wherein the inertial focuser comprises a serpentine channel.

15. (canceled)

16. The consumable cartridge according to claim 1, further comprising a valve configured to close to prevent the fluid passing through the output positive channel in order to disrupt the flow of the fluid and thereby direct accumulated debris towards the output negative channel.

17. The consumable cartridge according to claim 1, wherein the microfluidic chip comprises a silicon substrate, a resistor layer, a tracks layer, a passivation layer, an anti-cavitation layer, and an optical layer.

18. The consumable cartridge according to claim 1, further comprising a chip mount that supports the microfluidic chip in the consumable cartridge, the chip mount comprising: a first elastomeric seal for sealing the fluidic connection between the inlet and the input channel; and a second elastomeric seal for sealing the respective fluidic connections between the output positive channel, the output negative channel, the first outlet, and the second outlet.

19. The consumable cartridge according to claim 18, wherein the first elastomeric seal or the second elastomeric seal comprises complementary ridges and grooves.

20. The consumable cartridge according to claim 18, comprising a locating feature for positioning the chip mount on an instrument of the particle sorter system.

21. (canceled)

22. The consumable cartridge according to claim 18, wherein the chip mount comprises an optical window for optical analysis of particles flowing through the microfluidic chip in operation.

23. The consumable cartridge according to claim 18, wherein the chip mount comprises an electrical connector for electrically connecting the microfluidic chip with the instrument.

24. The consumable cartridge according to claim 18, wherein the chip mount comprises complementary first and second half pieces which are mated together so as to seal around the microfluidic chip.

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46. A particle sorter system comprising: a consumable cartridge comprising: an inlet for receiving a particle-containing fluid; and a microfluidic chip comprising: an input channel in fluidic connection with the inlet and a particle sorter junction in fluidic connection with the input channel and comprising an output positive channel and an output negative channel; and first and second outlets in fluidic connection with the output positive channel and the output negative channel respectively, for discharging the fluid from the consumable cartridge, such that at least one enclosed fluidic path is provided in the consumable cartridge between the inlet and the first and second outlets; and a syringe for providing the particle-containing fluid to the inlet; or an instrument comprising an interface feature for locating the chip mount on the instrument.

47. A particle sorter system comprising: a microfluidic chip comprising: an inertial particle focusser the inertial particle focusser comprising: an asymmetric upstream channel section comprising a plurality of alternating bends, a first set of the bends having a greater radius of curvature in a first direction and a second set of the bends having a smaller radius of curvature in a second, opposite direction; and a symmetric downstream channel section comprising a plurality of alternating bends having an equal radius of curvature in the first and second directions.

48. The particle sorter system according to claim 47, said inertial particle focusser further comprising a hairpin bend channel section located between the asymmetric upstream channel section and the symmetric downstream channel section, such that the asymmetric upstream channel section and the symmetric downstream channel section are arranged generally parallel with each other.

49. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Examples will now be described, by way of example, with reference to the accompanying figures in which:

[0053] FIG. 1A-B shows a consumable cartridge according to the invention;

[0054] FIG. 2A-D shows a chip mount within the consumable cartridge;

[0055] FIG. 3 shows the chip layer structure;

[0056] FIG. 4 A-B shows the chip design;

[0057] FIG. 5 shows an instrument according to the invention;

[0058] FIG. 6 A-C shows an instrument-consumable cartridge interface;

[0059] FIG. 7 A-D shows an optical assembly within the instrument;

[0060] FIG. 8 A-C shows further details of the optics; and

[0061] FIG. 9 shows an electronic control system.

DETAILED DISCUSSION

[0062] A consumable cartridge is shown in FIG. 1A-B. A shell 101 comprises a syringe connector which holds a removable input syringe 102, two removable output centrifuge tubes with vented caps 103, a chip mount 104, and tubing connecting the syringe and output tubes to the chip mount. The shell further comprises finger grips 105, for the user to hold and insert the consumable onto the instrument-consumable cartridge interface. The shell also comprises a sprung section 106 that locates the chip mount within the shell.

[0063] The syringe connector may be a luer adapter, a threaded adapter, or any type of connector that seals a syringe onto a tube.

[0064] The chip mount is shown in FIG. 2 A-D and comprises two moulded plastic halves, which snap together mechanically, via catchments in the moulding 201. Both halves are structured with ribs 202 for increased bending rigidity.

[0065] A first half 203 is designed to mate with the instrument, and provides an optical window 204 along with two sockets 205 for precise location on matching posts on the instrument-consumable cartridge interface, and accommodates a flexible circuit connector 206, which wraps around its edge.

[0066] The second half 207 provides an elastomeric seal 208, which makes a fluidic seal onto the chip 212, and which extends through the body of the second half to seal onto input and output tubing 209. In the elastomeric seal are moulded grooves and ridges 210 which connect the fluid ports in the chip to the input and output tubing. The input port 211 is situated away from the output ports so that it can seal to a higher pressure.

[0067] The chip layer structure is shown in FIG. 3, not to scale, and comprises: a silicon substrate 301, with a thermally deposited layer of silicon dioxide 311, in which through-vias are etched to make the input and output ports 302. A trench layer 303 is etched on the front of the substrate, to accommodate thin film layers. A resistor layer 304 of titanium is deposited in the trench, followed by a track layer 305 of gold or aluminium. The track layer also provides electrical connection pads on the edge of the chip, and an optical mirror feature in the sorter region. A passivation layer 306 of silicon nitride is deposited on top of the electrical features via chemical vapour deposition. An adhesion layer 307 of chromium is deposited on top of the passivation layer. An anti-cavitation layer 308 of tantalum, tantalum nitride or tantalum aluminium nitride is deposited on top of the passivation layer, specifically above the actuator. Finally a second glass layer 309, with microfluidic channels 310 etched in one face, is anodically bonded to the silicon substrate. The microfluidic channels in the glass may be made by deep reactive ion etching or by several other available techniques for patterning glass. The surfaces of the microfluidic channels may be polished to preserve optical and imaging quality by thermal, chemical or laser polishing techniques.

[0068] The chip design is shown in FIG. 4 A-B and comprises an input port 401, an output positive port 402, and an output negative port 403. From the input port is connected an inertial particle focusser 404, or another microfluidic particle focusing device. The focusser is connected to the sorter device (shown in FIG. 4 detail inset), which comprises an input channel 410, a microheater 405, which is protected by anti-cavitation and passivation layers from the solution, a vortex-creating edge 406, and a junction where the channel splits into positive 407 and negative 408 output channels. A mirror layer 409 is deposited on the silicon substrate under the channel to aid imaging. Conductive tracks 411 and contact pads 412 are provided. The channels widths are chosen such that the centre streamline is biased towards the negative output channel, and particles thus flow to the negative output unless actively sorted. A typical split of output flows are 60%:40% in favour of the negative output, and an example set of dimensions is below.

[0069] In an example, such as is shown in FIG. 4A, the inertial particle focusser 404 comprises several channel sections. The first section is an asymmetric serpentine channel, comprising alternating bends: a low-curvature bend in one direction followed by a high-curvature bend in the opposite direction, these bends being repeated several times. The second section is a symmetric serpentine channel comprising alternating bends: a bend in one direction followed by a bend in the opposite direction; both bends of equal curvature, these bends being repeated several times. Between the two sections is a hairpin bend, which allows the wrapping of the inertial focusser into a shorter overall length. The purpose of including an asymmetric serpentine section upstream is that the particle focussing effect proceeds within a relatively short device length. The purpose of including a symmetric serpentine section downstream, is that the accuracy of the particle focussing effect is improved relative to the asymmetric serpentine alone, and the particle position at the exit does not depend on size or density of the particle. It will be understood that the described inertial particle focusser is suitable for use not only in the microfluidic chip described herein, but also more generally in microfluidic particle sorters.

[0070] Thus the consumable comprises enclosed input and output vessels that can be connected and disconnected to a cartridge comprising a single-junction sorter chip, mounting components and tubing.

[0071] An instrument is shown in FIG. 5, showing a case 501 housing optics and electronics, with a door 502 on the front, providing laser safety interlocking and access to the instrument-consumable cartridge interface 503.

[0072] The instrument-cartridge interface is shown in FIG. 6A-C; details are including with and without the consumable cartridge mounted (601 and 602). FIG. 6A-C shows mounting surface 603 and posts 604, which mate with and precisely locate the consumable cartridge. The mounting surface is supported by a motorized 3-axis XYZ translation stage, which is able to move the consumable cartridge such that the input channel is precisely located at the focus of the laser beams. A hole 605 provides input of light from the instrument and collection of scattered and fluorescently emitted light output. A sprung electrical connector 606 makes contact with the flexible circuit connector on the consumable cartridge. A syringe driver 607 makes contact with the syringe which is received by the consumable cartridge.

[0073] The finger grips 105 on the shell are connected to the chip mount only via flexible mechanical linkages between the outside of the shell and the chip mount. Thus, on insertion of the consumable to the instrument-consumable cartridge interface, the location of the chip is determined by the mating of the sockets 205 with the matching posts 604.

[0074] An optical assembly is shown in FIG. 7A-D. Two lasers 701 are configured to focus within the input channel of the sorter chip: the laser beam passes through beam shaping lenses 702 and into holes 703 in the optical housing. Four photomultiplier tube (PMT) fluorescence detectors 704 and two photodiode 705 scattering detectors are configured to collect light from one or both of the laser foci. A strobe illumination LED 706 and a camera 707 are configured to image particles within the sorter device. Input and output light travels through an objective lens 708.

[0075] The optical system is configured for reflection imaging, reflected scatter and epifluorescence as follows: after entering the entrance holes 703, each beam passes through a polarizing beam splitter 714, and is combined by dichroic mirror 717 with a slight offset between beams. The beams reflect on dichroic mirror 713 and pass through dichroic mirror 716, from there passing through quarter-wave plate 715. The beams are then focused by objective lens 708 onto two separate spots on the chip 709 upstream of the sorter.

[0076] Collected light passes back through the objective lens 708 through the quarter wave plate 715 and dichroic mirror 716. After that it is split by a dichroic mirror 713, where light of the same wavelength as the lasers is reflected. This light is further split by a dichroic mirror 717 to the wavelength corresponding to each laser. Each reflected beam then enters polarizing beam splitters 714. Here the scattered light whose polarization has been rotated is reflected out of the plane of the drawing. While in the infinity plane 719 it passes through a beam stop, and is then focused by lens 718 onto a scattering detector 705.

[0077] The collected fluorescence light passes through dichroic mirror 717 and is reflected by dichroic mirrors 710 which each split off fluorescent light within a wavelength band. The light from each dichroic mirror is focused by a lens 711 onto the plane 712 of a movable slit. The slit selects from which laser beam focus to pass light through to the PMT 704.

[0078] FIG. 8A-C shows the movable slits and beam stops. The movable slit 801 comprises a slit on a sprung screwed stage, and is situated in focus plane 712. Thus it is able to let one laser focus through and block the other. The beam stops are shown in 803 and 802 and are situated in plane 719 for forward scatter and side scatter respectively.

[0079] Beam stop bar 803 accurately stops the specular reflection of the on-axis beam, thus allowing small-angle scattered light through to the detector. The bar is mounted eccentrically so that the position of the stop may be adjusted.

[0080] Beam stop plate 802 comprises a crescent-shaped orifice or aperture. The plate thus blocks an off-axis beam, and lets through the large-angle scattered light to the detector.

[0081] An electronic control system is shown schematically in FIG. 9. All solid blocks are on the main control board, while dashed blocks are separate. Two photodiodes (PDs) and up to six photomultiplier tubes (PMTs) are connected to and are powered by the PCB. The PMTs have a programmable gain which is set by a DAC. Signals from the PDs and PMTs first go through an analogue front end conditioning their signals for the ADCs, these ADCs pass their readings on to the FPGA. The FPGA carries out signal processing, peak detection, and makes sorting decisions. The FPGA then triggers the microheater, LED, camera, and pinch valve solenoid drivers, which drive the microheater, LED, camera, pinch valve solenoid, respectively. Finally, the FPGA is connected to an external PC via ethernet, sending peak data and receiving settings.

[0082] The external PC is also connected to a USB3 hub on the PCB. This USB hub is connected to, and allows control of, the two lasers and syringe pump via USB. The hub is further connected to two USB to 4×UART converters which allow control of the DAC, stage-positioning motor drivers, microcontroller, and fan controller via serial communications. The microcontroller drivers an LED strip for visual indications to the user, and the fan driver monitors temperature and drives chassis fans.

[0083] It will be understood that the invention has been described in relation to its preferred examples and may be modified in many different ways without departing from the scope of the invention as defined by the accompanying claims.

[0084] In an example, a magnetic stir bar is placed within the syringe, while a rotating magnet or electrically generated rotating magnetic field is placed on the instrument, being configured to rotated the magnetic stir bar within the syringe and mix the sample.