Microfluidic system

Abstract

The invention relates to a microfluidic system (1000) comprising a microchannel (21), a pump (30) connected to the microchannel (21), the pump being configured for driving a fluid containing magnetic particles (31) along the microchannel (21), at least one capture device (100) comprising a magnetic element (101) configured to generate a magnetic field having a fixed range of action, the magnetic element (101) comprises a magnetisable tip (11) and a magnet (12), at least one actuator (50a, 50b) configured to move the magnetic element (101) relative to the microchannel (21), the capture device (100) being configured to assume two positions: a first position, a second position, a third position, and a fourth position, wherein the microchannels (21) are contained within the range of action of the magnetic field and the magnetic particles (31) are captured, and a second position wherein the microchannels (21) are outside the range of action of the magnetic field and the magnetic particles (31) are free to move.

Description

Technical Field

[0001] This invention relates to a microfluidic system and method, particularly to the magnetic manipulation of magnetic particles and their application in the detection and / or quantification of analytes. Background Technology

[0002] Magnetic particles, or magnetic beads, are a class of nanoparticles whose movement can be manipulated by a magnetic field. A wide range of potential applications have been envisioned, including next-generation sequencing (NGS), polymerase chain reaction (PCR), quantitative polymerase chain reaction (qPCR), droplet digital polymerase chain reaction (ddPCR), protein purification, and immunoassay.

[0003] For example, immunoassays are a powerful technique widely used in clinical research and medical diagnostics for screening disease biomarkers. Their remarkable specificity and sensitivity are attributed to the molecular recognition between antibodies and their targets among a large number of substances in the sample. Most assays are heterogeneous: immune complexes are formed on a solid surface, typically the bottom of a microplate, and unbound molecules are removed by several washing steps prior to detection. However, this form has several drawbacks, among which the low capture area and surface-to-volume ratio are the most critical, as they directly affect the sensitivity of the immunoassay.

[0004] The emergence of magnetic particles as solid supports for biomarker capture has made it possible to overcome these challenges. In fact, magnetic particles exhibit a large specific surface area and significant binding capacity, thus providing better capture efficiency. Furthermore, their superparamagnetism makes them easy to handle, enabling faster execution of many immunoassay separation and washing steps. This large capture area combined with their microfluidic form enables point-of-care platforms for detecting biomarkers with good sensitivity within minutes.

[0005] To manipulate magnetic particles, it is known to use devices that can apply and measure forces to magnetic particles using magnetic field gradients.

[0006] A common setup involves an electromagnet associated with a pointed end. This results in a high field gradient that can be activated around the tip. Any paramagnetic material within this gradient is magnetized and pulled toward the tip. The magnitude of the force depends on the magnetic field strength and the gradient. While the strength can be controlled by the current driving the electromagnet, the gradient depends on the distance between the tip and the electromagnet.

[0007] However, controlling the magnetic field to achieve the desired strength and gradient is highly sensitive and energy-intensive. Furthermore, this solution has been observed to cause problems related to the manipulation of magnetic particles, such as difficulty in capturing all magnetic particles and deformation or breakage of the droplets encapsulating the magnetic particles.

[0008] Therefore, the problem solved by the present invention is to obtain a system with improved magnetic particle manipulation capabilities for performing chemical, biological, physical or biochemical processes, analyses or reactions. Summary of the Invention

[0009] Therefore, the present invention relates to a microfluidic system comprising:

[0010] - At least one microchannel,

[0011] - A pump connected to the at least one microchannel and configured to drive at least one fluid containing at least one magnetic particle along the microchannel.

[0012] - At least one capturing device, comprising:

[0013] A magnetic element configured to generate a magnetic field with a fixed range of action, the magnetic element comprising a magnetizable tip and a magnet, wherein the magnetizable tip comprises a soft magnetic material and the magnet is a permanent magnet configured to generate a continuous magnetic field.

[0014] At least one actuator is configured to move together the magnetizable tip of the magnetic element and the magnet relative to the microchannel.

[0015] The capture device is configured to operate in two positions:

[0016] In a first position, wherein the tip is close to the microchannel, the microchannel being within the range of the magnetic field of the magnetic element, the trapping device is configured to apply a magnetic field to at least one magnetic particle present in at least one microchannel to trap the at least one magnetic particle.

[0017] ▄ Second position, wherein the tip is away from the at least one microchannel, the microchannel being outside the range of the magnetic field of the magnetic element, such that at least one magnetic particle present in the microchannel moves freely in the at least one fluid.

[0018] "Outside the effective range" refers to a distance large enough to reduce the magnetic field and magnetic field gradient to a value that, within an experimentally compatible timeframe, no longer allows the magnetic particles to displace. In practice, for example, this would correspond to a distance between the magnetizable tip and the microchannel that is at least 10 times, preferably 20 times, or even 50 times, the lateral dimension or radius of the microchannel. In some other embodiments, this may also correspond to a distance between the magnetizable tip and the microchannel that is at least 10 times, preferably 20 times, or even 50 times, the radius of the tip.

[0019] In other words, the present invention relates to a microfluidic system in which a magnetic element is used to capture magnetic particles, and said magnetic element consists of two parts: a magnet capable of generating a magnetic field and a magnetizable tip. The magnetizable tip can generate an induced magnetic field by its close proximity to the magnet. Therefore, the invention relies on close contact between the magnet and the magnetizable tip to obtain a precision tool capable of selectively capturing magnetic particles without disturbing the rest of the system. The invention also relies on the fact that at least one actuator is used to move the magnet and the tip as a whole. This allows for improved magnetic particle manipulation by reducing the risk of droplet deformation or breakage.

[0020] The magnetizable tip contains a soft magnetic material, and the magnets are permanent magnets configured to generate a continuous magnetic field. Because they are in direct and permanent contact and move together, the magnetic elements generate a controlled magnetic field in a undisturbed manner. The magnetic particles can then be controlled efficiently and reliably because they can effectively aggregate as the magnetic elements move toward the microfluidic microchannel and can be reliably released as they move away from the microfluidic microchannel.

[0021] Therefore, the magnetic element does not require a power source to generate a magnetic field. The magnetic field applied to the microchannel is modulated simply by approaching or withdrawing the magnetic element. This is a mechanically simpler way to control the magnetic field compared to solutions that use activatable magnetic elements such as electromagnets, which require precise control of the input current to obtain the desired gradient and magnetic field.

[0022] According to one embodiment, at least one actuator is configured to move a magnetic element relative to the microchannel using a translational motion transverse to an axis of at least one microchannel. However, in some other preferred embodiments, the motion may be a rotational motion. Preferably, the rotation is not in the plane containing the microchannel.

[0023] Lateral motion is a one-dimensional motion that is very easy to implement in microfluidic systems. Simple and economical devices can be used, such as screw-based or hydraulically based devices.

[0024] According to a preferred embodiment, at least one actuator includes a housing and a piston rod within the housing, the piston rod being configured to move along the length of the housing, and wherein a magnetic element is attached to the piston rod.

[0025] In practice, the magnet includes a first surface and a second surface opposite to the first surface, the first surface being attached to the piston rod, and the second surface being attached to the attachment surface of the magnetizable tip. Preferably, the profile of the second surface of the magnet is at least as large as the profile of the attachment surface of the magnetizable tip.

[0026] Advantageously, the system includes two parallel actuators, a first actuator and a second actuator, with magnetic elements attached to a first piston rod of the first actuator and a second piston rod of the second actuator. The two actuators allow for stabilization of the capture device while providing greater flexibility and control over the position of the magnetizable tip.

[0027] As previously described, the trapping device is configured to employ at least two positions. According to one embodiment, in the first position, the tip contacts at least one microchannel. In practice, the closer the tip is to the microchannel wall, the higher the efficiency of magnetic particle trapping.

[0028] Another object of the present invention is to generate a magnetic field at a magnetizable tip with values ​​from 100 mT to 10000 mT and a gradient from 100 T / m to 10000 T / m. These values ​​can be optimized according to the fluid type, the nature of the biological target to be captured, and the type of magnetic particles.

[0029] Therefore, based on these values, in the second position, the tip is located within a distance of 5.5 mm to 7 mm, preferably 6 mm to 6.4 mm, from at least one microchannel. In the second position, the magnetic particles move freely, and interference with the microfluidic flow is minimized.

[0030] According to one embodiment, at least one actuator is configured to move a magnetic element at a speed of 1 mm / s to 20 mm / s, preferably 2 mm / s to 10 mm / s, and more preferably 4 mm / s to 5 mm / s, most preferably 4.5 mm / s to 5 mm / s. The speed of the actuator for moving the magnetic element can be optimized according to the specific application and the microfluidic environment. This speed is advantageously adapted to allow for precise positioning of the tip relative to the microchannel wall. In practice, if the tip is too far from the microchannel, the magnetic field is not strong enough to accurately capture magnetic particles, while if the tip is too close to the microchannel, it may damage the microchannel or even compromise its integrity by puncturing it.

[0031] According to another aspect, the present invention relates to a method for extracting at least one magnetic particle from at least one droplet of a fluid flowing in at least one microchannel. The method uses the system described above and includes the following steps:

[0032] - Pumping at least one fluid containing at least one magnetic particle into the microchannel, and

[0033] - Switch the capturing device to the first position and capture at least one magnetic particle.

[0034] According to one embodiment, the method further includes:

[0035] - Pump the first fluid into the microchannel.

[0036] - Pump at least one droplet of a second fluid, which is immiscible with the first fluid, into the microchannel. The second fluid contains the at least one magnetic particle.

[0037] - Switch the capture device to a first position and capture at least one magnetic particle present in at least one droplet of the second fluid, and pump at least one droplet of the second fluid out of the microchannel.

[0038] This method allows the generation of droplets encapsulated with magnetic particles, and the use of pumping devices to manipulate the droplets for biological or chemical purposes, such as purifying or extracting biological substances like proteins, DNA, RNA, antibodies, etc. Attached Figure Description

[0039] The invention, and its other objects, details, features, and advantages, will become more apparent from the following detailed explanatory description of embodiments of the invention given as illustrative, purely descriptive, and non-limiting examples, and with reference to the accompanying drawings:

[0040] Figure 1 This is a perspective view of the system according to the first embodiment of the present invention.

[0041] Figure 2 This is a perspective view of the system according to the second embodiment of the present invention.

[0042] Figure 3 It comes from Figure 1 Or a perspective view of the capturing device of type 2.

[0043] Figure 4 This is a block diagram of the method according to the present invention.

[0044] Figure 5 It comes from Figure 4 A schematic diagram of the first step of the method.

[0045] Figure 6 It comes from Figure 4 A schematic diagram of the second step of the method.

[0046] Figure 7 It comes from Figure 4 A schematic diagram of the third step of the method.

[0047] Figure 8 It comes from Figure 4 A diagram illustrating the fourth step of the method, and

[0048] Figure 9 It comes from Figure 4 A diagram illustrating the fifth step of the method. Detailed Implementation

[0049] Microfluidic Systems 1000

[0050] Figure 1 A microfluidic system 1000 is shown, comprising at least one microchannel 21 extending along a longitudinal axis X. The at least one microchannel 21 includes an upper end portion 22 and a lower end portion 23. The upper end portion 22 is connected to a pumping device 30 configured to drive fluids 32, 33 contained in a reservoir 61 along the microchannel 21. At least one of these fluids 32, 33 contains at least one magnetic particle 31. Alternatively, the pumping device 30 may be connected to the lower end portion 23 of the microchannel 21. The microfluidic system 1000 also includes at least one trapping device 100 for generating a magnetic field to trap the magnetic particles 31 within the microchannel 21 and performing a method according to the invention, such as... Figures 4 to 9 As shown.

[0051] Advantageously, the microfluidic system 1000 may include at least a pair of trapping devices 100, which are opposite each other on both sides of at least one microchannel 21 and extend along an axis Y transverse to the axis X, preferably perpendicular to the axis X. The pair of trapping devices 100 may also be referred to as “magnetic tweezers.” Doing so can increase the magnetic field strength, thereby further facilitating the manipulation of the magnetic particles 31.

[0052] Capture device 100

[0053] like Figure 3 As shown, the capturing device 100 includes a magnetic element 101 mounted on at least one actuator 50a, 50b.

[0054] Magnetic Component 101

[0055] like Figure 3 As shown, the magnetic element 101 includes a housing 13 configured to encapsulate a permanent magnet 12 and hold the permanent magnet 12 and the tip 11 together. The permanent magnet 12 may have a parallelepiped shape, with a height of 0.5 cm to 1 cm, typically 0.8 cm, a length of 0.5 cm to 10 cm, typically 4 cm, and a width of 0.1 cm to 1 cm, typically 0.15 cm. The permanent magnet 12 may be made of neodymium iron boron (NdFeB) or samarium cobalt (SmCo) and additionally have a nickel plating (Ni-Cu-Ni). The permanent magnet 12 may be classified as N52, meaning that it resists temperatures up to 80°C without losing its magnetism and has a remanence of 1420 mT to 1470 mT.

[0056] The housing 13 can be made of a rigid material, such as plastic, ceramic, titanium, aluminum, or stainless steel. Alternatively, the housing 13 can be made of an elastic material, such as rubber. The permanent magnet 12 and the tip 11 can be inserted into the housing 13 by deforming the elastic material. The housing 13 can be adapted to the shape of the permanent magnet 12 and the tip 11 using an adjustment device such as a screw. The permanent magnet 12 and the tip 11 can be additionally held together using a fixing device such as glue or welding. Alternatively, the magnet 12 can be an activatable magnet, such as an electromagnet. The magnet can have a thickness of 2 mm to 20 mm, preferably 2 mm to 15 mm, more preferably 2 mm to 10 mm, and even more preferably 5 mm to 10 mm.

[0057] The tip 11 can have various shapes. It can be a conical shape with a circular cross-section. The conical tip 11 according to the invention preferably has a apex angle of less than 45°, more preferably less than 30°, more preferably less than 25°, or alternatively less than 20°. Another type of tip 11 particularly useful in the invention is a blade-shaped tip 11. In this case, the tip 11 may have an acute tip angle only in one direction, i.e., in a plane perpendicular to the blade edge. The blade-shaped tip 11 according to the invention preferably has a tip angle of less than 45°, more preferably less than 30°, more preferably less than 25°, or alternatively less than 20°. The blade-shaped tip has the advantage of being able to act on multiple microchannels simultaneously.

[0058] Another type of tip 11 that is particularly useful in this invention is a tip 11 with a triangular prism shape, comprising a rectangular base and elongated opposing edges, such as... Figure 3 As shown. However, the tip 11 according to the invention can have many different shapes. For example, the three-dimensional shape of the tip 11 can have more complex shapes, involving ellipsoids, circular blades, etc. Furthermore, for reasons of mechanical manufacturing or robustness, the tip 11 according to the invention may be blunt or flat at its end. Generally, it is advantageous for the tip 11 to have a generally decreasing cross-section. The flat or blunt portion may have only a small area compared to the maximum cross-section of the tip 11, typically less than 10% of the maximum cross-section, preferably less than 5% of the maximum cross-section, and more preferably less than 2% of the maximum cross-section.

[0059] The typical dimensions of the tip 11 can vary depending on the application and, in particular, the size of the microchannel 21. The tip 11 can have a total length at least equal to or greater than the thickness of the magnet, more preferably up to twice the magnet thickness, more preferably up to three times, and advantageously up to four times. The tip 11 of the magnetic element 101 can have dimensions comparable to the size of the microchannel 21. For example, the length of the tip 11 can be defined as the distance between the upper end of the tip 11 and the permanent magnet 12. For example, for a microchannel 21 with a lateral dimension of 100µm to 1mm, the tip 11 can have a length of 500µm to 20mm or 200µm to 10mm.

[0060] The tip 11 is preferably made of a soft magnetic material, such as a metal or metal alloy, such as an iron-silicon alloy, a nickel-iron alloy, an iron-cobalt alloy, or a ferrite, so as to exhibit little or no residual magnetism after excitation. These materials have the advantage of being adaptable to a wide variety of tip shapes and providing a greater range of manufacturability compared to permanent magnet tips.

[0061] Advantageously, the trapping device 100 is configured to generate a magnetic field strength of 100 mT to 10000 mT, preferably 100 mT to 500 mT, or 500 mT to 1000 mT, or 1000 mT to 10000 mT, more preferably 1000 mT to 5000 mT, or 5000 mT to 10000 mT, along a longitudinal axis of the microchannel 21 of 10 T / m to 10000 T / m, preferably 10 T / m to 100 T / m, or 100 T / m to 500 T / m, or 500 T / m to 1000 T / m, or 1000 T / m to 5000 T / m, or 5000 T / m to 10000 T / m.

[0062] Actuators 50a, 50b

[0063] At least one actuator 50a, 50b is preferably a linear actuator configured to move the magnetic element 101 along the Y direction. The at least one actuator 50a, 50b may be a screw-driven linear actuator having a rotating threaded rod that causes a nut to move along the thread, resulting in linear motion. Alternatively, it may be a belt-driven linear actuator, using a belt driven by a motor to generate linear motion. As another example, it may be a rack and pinion linear actuator, using gears meshing with a rack to generate linear motion. It may also be a pneumatic linear actuator, using compressed air to transmit linear motion. The air is typically controlled by a valve that opens and closes to allow air to move the piston back and forth. Alternatively, it may be a hydraulic linear actuator, using a fluid (typically oil) to generate linear motion. The fluid is controlled by a valve that opens and closes to allow fluid to move the piston back and forth. Furthermore, it may be a piezoelectric linear actuator, using a piezoelectric element to generate linear motion. When a voltage is applied to the element, it changes shape, causing linear motion. Finally, it can be an electromechanical linear actuator, which uses a combination of electrical and mechanical components to produce linear motion. The most common type is the stepper motor-driven linear actuator.

[0064] Typically, at least one actuator 50a, 50b includes a movable element that moves in the Y direction, such as... Figure 3 The piston rod 51 or nut shown is to which the magnetic element 100 is attached by screws, adhesives, welding, rivets, bolts, clamps, or a combination thereof. The movable element can be configured to move relative to the fixed element. This fixed element can be a hollow cylinder or a housing 52, such as... Figure 3 As shown. In one specific embodiment, magnet 12 has a first surface attached to piston rod 51, for example, via a threaded connection, while the attachment surface of magnetizable tip 11 is in direct and permanent contact with a second surface of magnet 12, and is attached thereto, for example, by adhesive, magnetism, or any other means. The second surface of magnet 12 has at least the same profile and dimensions as the attachment surface of magnetizable tip 11. In another embodiment, magnet 12 is attached to piston rod 51 by press fit or heat shrink fit, while magnetizable tip 11 is attached to magnet by adhesive or mechanical fasteners. The specific attachment method may depend on the specific materials used for the actuator and magnetic element, as well as the required connection strength and durability. Attaching magnetizable tip to magnet allows for better control of the magnetic field when the movable element translates the magnetic element from a proximal position to a distant position and from a distant position to a proximal position. More precisely, it eliminates magnetophores in the capillary through magnet recoil. Another advantage is that the magnitude of the magnetic field force can be modulated by adjusting the distance between the tip and the microchannel.

[0065] At least one actuator 50a, 50b should be capable of moving the magnetic element 100 at a controlled and consistent speed. This speed will depend on the specific application and requirements of the system 1000. Preferably, the displacement speed of the magnetic element 100 is from 1 mm / s to 20 mm / s, more preferably from 2 mm / s to 10 mm / s, more preferably from 4 mm / s to 5 mm / s, and even more preferably from 4.5 mm / s to 5 mm / s.

[0066] The length by which the magnetic element 100 can be displaced depends on the design of the microfluidic system 1000. Preferably, the piston stroke is 8 to 12 mm. However, the expected displacement may be 0 mm to 7 mm, preferably 0 mm to 6.4 mm. Advantageously, at least one actuator 50a, 50b is chosen because of its micron-level precision, repeatability, and durability. At least one actuator 50a, 50b should be able to move the magnetic element to the desired position with high precision and accuracy, and should be able to repeat this process multiple times without significant wear or degradation.

[0067] For example, at least one actuator 50a, 50b may have repeatability of ±0.1 mm, a maximum speed of 25 mm / s, a maximum force of 22 N, a counter-driving force of 12 N, and a mechanical backlash of 0.2 mm.

[0068] Multiple actuators 50a, 50b can be used to move the magnetic element 101 in a precise and controlled manner. The positioning and coordination of at least one actuator 50a, 50b can be achieved using a control system and frame to hold at least one actuator 50a, 50b on a plane and control the alignment, balance, and simultaneity of the actuators 50a, 50b.

[0069] Microchannel 21

[0070] The term microchannel 21 refers to any tubular reservoir or conduit, such as a rigid or flexible tube. The microchannels 21 according to the invention are preferably one-dimensional, for example, they have a width, thickness and length, and the length is much greater than the width and thickness, at least 10 times, and typically 100 times or more.

[0071] The microchannels 21 according to the invention are advantageously cylindrical or parallelepiped, but they can also have more complex shapes, involving wedges, protrusions, grooves, microstructures, or any features that may be interesting in microfluidics.

[0072] As a general feature, the microchannels 21 of the present invention have a sub-millimeter cross-section, that is, they have a cross-section of less than 1 mm² over at least a portion of their length, particularly over at least a portion of their length facing the magnetically activatable element, particularly over at least 50% of their length, or at least one cross-sectional dimension of less than 500 µm.

[0073] In various preferred embodiments, the cross-section of the microchannel 21 according to the invention is 100µm² to 5mm², preferably 500µm² to 4µm², and even more preferably 10000µm² to 1mm².

[0074] The microfluidic system 1000 according to the present invention includes at least one microchannel 21, and may include multiple microchannels 21-23, such as... Figure 2 As shown. Microchannels 21-23 can be spaced 0.5 to 2 cm apart. In some other embodiments, microchannels 21-23 can be arranged with an inter-channel distance of 100 µm to 0.5 cm. The microchannels 21-23 can be completely linear or branched into a network. Microchannels 21-23 may include branches, such as side branches or cross branches. Preferably, the branching regions along the microchannels 21-23 are located away from the region facing the activatable magnetic element.

[0075] The microchannels 21-23 defined according to the present invention can be advantageously fabricated by photolithography or "soft lithography".

[0076] The system 1000 of the present invention also includes means for generating droplets in a microchannel, including a pump 30.

[0077] Pump 30

[0078] Pump 30 can be connected to one or both ends of microchannel 21. Advantageously, pump 30 is connected to the upper end 22 of microchannel 21, while the lower end 23 of microchannel 21 can be inserted into a fluid reservoir for pumping.

[0079] Pump 30 may be a push-pull pump, configured to inject and draw fluid into and out of at least one microchannel 21.

[0080] Pump 30 may include a pressure controller and / or a flow controller, which can be connected to an external pressure source configured to provide pressure up to 1 bar. Advantageously, pump 30 includes a pressure sensor and / or a flow sensor configured to measure pressure applied within at least one microchannel 21. The pressure sensor and / or flow sensor allows for pressure and / or flow regulation. The flow controller can regulate the flow rate with a stability of 0.005% within 40 ms.

[0081] Advantageously, pump 30 can communicate with a processor, such as a tablet or computer, that includes a human-machine interface. A user can request pressure and / or flow values ​​through the human-machine interface. Pump 30 can be configured to send pressure and / or flow values ​​measured by pressure and / or flow sensors to the processor. The processor is then configured to control the pressure controller and / or flow controller to achieve the requested pressure and / or flow rate.

[0082] Droplet generation

[0083] System 1000 may include means for forming droplets 24 based on at least two immiscible fluids in at least one microchannel 21. Various means for transporting sequences of droplets 24 in microchannel 21 are known in the art. For example, they may relate to flow focusing devices, T-junctions, or two-phase micropipettes, or combinations thereof.

[0084] Because of this, and combined with the overall one-dimensional nature of the microchannel, the present invention can transport a variety of samples or reagents in droplet form by the simple flow or pressure of the surrounding fluid.

[0085] The first fluid 33 can be an organic phase, comprising oil selected from fluorinated oils, silicone oils, vegetable oils, mineral oils, hydrocarbon oils, and surfactants such as PEG-di-Krytox fluorinated surfactants, perfluorooctyl alcohol, perfluorodecanol, and perfluoropolyether derivatives, including perfluoropolyether-polyethylene glycol triblock copolymers, Span 80, AbilEM90, monoolein, oleic acid, and n-butanol. The second fluid 32 can be an aqueous phase, comprising at least one cell culture medium, drug solution, antibody solution, cell suspension, or phase suspension (phospholipids, Triton-X-100, SDS, Pluronic, Tween 20 / 80).

[0086] The size of the droplet 24 can vary greatly, from 1 pL to 2 L. However, the present invention can advantageously obtain droplets of a size range that are not easily obtained in the prior art, particularly 10 pL to 500 nL, particularly 10 pL to 100 pL, 100 pL to 1 nL, 1 nL to 10 nL, 10 nL to 100 nL, or 100 nL to 500 nL.

[0087] Magnetic particles

[0088] The magnetic particles 31 are preferably superparamagnetic. The size of the magnetic particles 31 can vary greatly depending on the application. The size of the magnetic particles 31 refers to the maximum size of the magnetic particles 31. In a preferred embodiment, the average size of the magnetic particles 31 is from 0.2 µm to 10 µm, and more preferably from 0.5 µm to 5 µm. Unless otherwise stated, the average size of a set of magnetic particles 31 is the particle size statistical size of D50.

[0089] In another embodiment, the magnetic particles 31 may have different sizes. For example, the first group of magnetic particles 31 has an average size of 1µm to 5µm, and the second group of magnetic particles 31 is mixed with the first group and has a larger average size, preferably 10µm to 50µm, or 50µm to 100µm, or 100µm to 200µm, or 200µm to 500µm.

[0090] Magnetic particles 31 can be functionalized to connect with ligands such as chemical components, drugs, nucleic acids, combinations of nucleic acids and enzymes such as mixtures for DNA amplification, antibodies, fluorescent parts, luminescent parts, dyes, nanoparticles, gold nanoparticles, quantum dots, DNA-intercalating dyes, aptamers, or any species type that may affect cellular metabolism or the properties of colloidal objects according to the invention, particularly their optical properties.

[0091] Method 200

[0092] The microfluidic system 1000 can be used to implement, including Figures 4 to 9 The method involves several steps, as shown.

[0093] like Figure 5 As shown, the first step 201 involves filling the microchannel 21 with a first fluid 33, which may be, for example, an organic phase. The microchannel 21 can be filled using a pump 30 configured in a suction mode, pumping fluid from a first reservoir 61 of the first fluid 33. Once the microchannel 21 is filled, in the second step 202, as... Figure 6 As shown, the first storage tank 61 can be switched to a second storage tank 62 containing a second fluid 32, which may be, for example, an aqueous phase containing magnetic particles 31. In the third step 203, as... Figure 7 As shown, droplets 24 of the second fluid 32 can be pumped into the microchannel 21. In the fourth step 204, as... Figure 8 As shown, pumping can be stopped, and the trapping device 100 can be switched to a first position, where the piston rod of the trapping device 100 extends and the tip 11 contacts the microchannel 21. Therefore, the magnetic particles 31 are acted upon by the magnetic field emitted by the tip 11 and accumulate at the wall of the microchannel 21 where the tip 11 is located. The magnetic field is stronger than the flow inside the microchannel 21, which is why in step 205, as... Figure 9 As shown, droplets 24 of the second fluid 32, no longer containing magnetic particles, can be pumped into the third reservoir 63. In a separate step not shown in the figure, second droplets of the third fluid can be sent to retrieve the magnetic particles 31.

[0094] According to the present invention, the liquid storage tanks 61-63 may be separate liquid storage tanks or contained in a perforated plate.

Claims

1. A microfluidic system (1000) comprising: - at least one microchannel (21-23), - a pump (30) connected to the at least one microchannel (21-23) and configured for driving at least one fluid (32-34) containing at least one magnetic particle (31) along the microchannel (21-23), - at least one capture device (100) comprising: o a magnetic element (101) configured to generate a magnetic field having a fixed range of action, the magnetic element (101) comprising a magnetizable tip (11) and a magnet (12), wherein the magnetizable tip (11) contains a soft magnetic material and the magnet (12) is a permanent magnet configured to generate a persistent magnetic field o at least one actuator (50a, 50b) configured for moving the magnetizable tip and the magnet of the magnetic element (101) together with respect to the microchannel (21-23), the capture device (100) being configured to adopt two positions: ▄ a first position in which the magnetizable tip (11) is close to the microchannel (21-23) contained within the range of action of the magnetic field of the magnetic element (101), the capture device (100) being configured to apply a magnetic field to at least one magnetic particle (31) present in the at least one microchannel (21-23) to capture the at least one magnetic particle (31), and ▄ a second position in which the magnetizable tip (11) is distanced from the at least one microchannel (21-23) outside the range of action of the magnetic field of the magnetic element (101) so that at least one magnetic particle (31) present in the microchannel (21-23) is free to move in the at least one fluid (31-34).

2. The microfluidic system according to claim 1, wherein the actuator (50a, 50b) is configured to move the magnetic element (101) with respect to the microchannel (21-23) using a translational motion transverse to an axis (X) of the at least one microchannel (21-23).

3. The microfluidic system according to any one of claims 1 or 2, wherein the at least one actuator (50a, 50b) comprises a housing (52a, 52b) and a piston rod (51a, 51b) within the housing (52a, 52b), the piston rod (51a, 51b) being configured to move along a length of the housing (52a, 52b), and wherein the magnetic element (101) is attached to the piston rod (51a, 51b).

4. The microfluidic system according to claim 3, wherein the magnet (12) comprises a first surface and a second surface opposite to the first surface, the first surface being attached to the piston rod (51a, 51b) and the second surface being attached to an attachment surface of the magnetizable tip (11).

5. The microfluidic system according to claim 4, wherein the profile of the second surface of the magnet (12) is at least as large as the profile of the attachment surface of the magnetisable tip (11).

6. The microfluidic system according to claims 3 to 5, wherein the system comprises two parallel actuators (50a, 50b), the two parallel actuators comprising a first actuator (50a) and a second actuator (50b), the magnetic element (101) being attached to a first piston rod (51a) of the first actuator (50a) and to a second piston rod (51b) of the second actuator (50b).

7. The microfluidic system according to any one of claims 1 to 6, wherein in the first position, the tip (11) is in contact with the at least one microchannel (21-23).

8. The microfluidic system according to any one of claims 1 to 7, wherein the magnetic field generated at the magnetisable tip (11) has a value of 100 mT to 10000 mT and a gradient of 100 T / m to 10000 T / m.

9. The microfluidic system according to claim 8, wherein the at least one actuator (50a, 50b) is configured to move the magnetic element (101) at a speed of 1 mm / s to 20 mm / s, preferably 2 mm / s to 10 mm / s, preferably 4 mm / s to 5 mm / s, and further preferably 4.5 mm / s to 5 mm / s.

10. The microfluidic system according to claim 8 or 9, wherein in the second position, the tip (11) is located within a distance of 5.5 mm to 7 mm, preferably 6 mm to 6.4 mm, from the at least one microchannel (21-23).

11. A method (200) of extracting at least one magnetic particle (31) from at least one droplet (35) of at least one fluid (32) flowing in at least one microchannel (21-23), the method using a system (1000) according to any one of claims 1 to 10, the method comprising the steps of: - pumping at least one fluid (32) comprising at least one magnetic particle (31) inside the microchannel (21-23), and - switching the capturing device (100) to the first position and capturing the at least one magnetic particle (31).

12. The method according to claim 11, wherein the method further comprises: - pumping a first fluid (33) inside the microchannel (21-23), - pumping at least one droplet (35) of a second fluid (32) inside the microchannel (21-23), the second fluid (32) being immiscible with the first fluid (33), the second fluid (34) comprising the at least one magnetic particle (31), - switching the capturing device (100) to the first position and capturing the at least one magnetic particle (31) present in the at least one droplet (35) of the second fluid (34), and pumping the at least one droplet of the second fluid (32) outside the microchannel (21-23).

13. The method according to claim 12, wherein the method further comprises: - pumping a third fluid (34) inside the microchannel (21-23), the third fluid (34) being immiscible with the second fluid (32), the third fluid (34) comprising the at least one magnetic particle (31), - switching the capturing device (100) to the first position and capturing the at least one magnetic particle (31) present in the at least one droplet (35) of the third fluid (34), and pumping the at least one droplet of the third fluid (34) outside the microchannel (21-23).

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