Fluid analysis system including an acoustic wave generating component

Abstract

The invention relates to a fluid analysis system comprising: A microfluidic component (1) incorporating a main microfluidic circuit (10) and having a front face (12) and a rear face (13); A measurement / analysis component (2) mounted on the front face (12) of the microfluidic component (1) and comprising at least one measuring element (21) capable of being mechanically stimulated by acoustic waves; An acoustic wave generator component; The acoustic wave generator component being mounted on the rear face (13) of the microfluidic component (1). Figure to be published with the abbreviation: Figure 2A

Description

Title of the invention: Fluid analysis system including an acoustic wave generating component Technical field of the invention

[0001] The present invention relates to a system for analyzing a fluid. State of the art

[0002] With reference to [Fig. 1], in the field of fluidic analysis, it is known to connect a measurement / analysis component 2 to a microfluidic component 1 (also called a microfluidic interposer, in the sense that it accommodates the measurement / analysis component 2). The microfluidic component 1 is often made of a transparent polymer material and integrates a main microfluidic circuit 10 formed of microfluidic channels in which a fluid to be analyzed itself or carrying particles to be analyzed circulates. The measurement / analysis component 2 comprises a microfluidic measurement circuit 20 connected to the main microfluidic circuit of the microfluidic component and a measurement member 21 capable of being mechanically stimulated by acoustic waves. This type of measurement / analysis component is very often produced in the form of a MEMS ("Micro-ElectroMechanical System") or NEMS ("Nano-ElectroMechanical System") chip.

[0003] To generate the acoustic waves, it is conventional to use an actuation system. Several types of actuation systems can be envisaged, operating in particular by capacitive coupling or by piezoelectric actuation. Piezoelectric actuation is achieved by using a piezoelectric element manufactured in the form of a ceramic. The actuation element is then called a piezoceramic element 3.

[0004] To couple the measurement / analysis component 2 with the microfluidic component 1, it is necessary: - Carry out the fluidic connection between the main microfluidic circuit 10 and the measuring microfluidic circuit 20 in order to be able to ensure the transfer of fluid; - Make the electrical connections of the measurement / analysis component 2 in order to read the generated electrical signal; - Carry out mechanical actuation of the measuring organ 21 of the measuring / analysis component 2;

[0005] In the case where it is desired to connect the measurement / analysis component 2 to the microfluidic component 1, the rear face 23 of the measurement / analysis component 2 is dedicated to the fluidic connection, while its front face 22 is dedicated to the connection electrical. As shown in [Fig.l], to actuate the measurement / analysis component 2, the piezoceramic element 3 is conventionally placed in direct contact with the measurement / analysis component 2 by mounting it on its front face 22.

[0006] However, in this configuration, the piezoceramic element 3 which is opaque prevents direct visualization of the areas of interest inside the fluid circuits during the experiment, and also greatly complicates the handling and connection of the chip, in particular for making the electrical connections.

[0007] There is therefore a need to obtain an analysis system including a microfluidic component and a measurement / analysis component actuated by acoustic waves which - Provides visualization of fluid circuits integrated into components; - Avoids any risk of short circuit between the electrical connection wires connecting to the measurement / analysis component and the acoustic wave generating component when it is, for example, made of piezoceramic; - Avoids any risk of damage to the electrical connection wires; Description of the invention

[0008] This aim is achieved by a fluid analysis system comprising: - A microfluidic component integrating a main microfluidic circuit and comprising a front face and a rear face, - A measurement / analysis component mounted on the front face of the microfluidic component and which comprises at least one measurement member capable of being mechanically stimulated by acoustic waves, - A component generating acoustic waves, - Characterized in that the acoustic wave generating component is mounted on the rear face of the microfluidic component.

[0009] According to a particular feature, the measurement / analysis component is a MEMS / NEMS type resonator comprising a microfluidic measurement circuit connected to the main microfluidic circuit of the microfluidic component.

[0010] According to another feature, the acoustic wave generating component is a piezoelectric component.

[0011] According to another feature, the piezoelectric component is a piezoceramic element.

[0012] According to another feature, the piezoceramic element has a two-dimensional footprint forming a projected surface in which the measurement / analysis component is inscribed.

[0013] According to another feature, the measurement / analysis component is centered on the projected surface of the piezoceramic element.

[0014] According to a particular embodiment, the system comprises several juxtaposed measuring members, actuated by a single component generating acoustic waves.

[0015] According to another feature, the microfluidic component is made of a polymer material.

[0016] According to another feature, the microfluidic component is made of Cyclo-Olefin Copolymer or Polymethyl Methacrylate.

[0017] According to another feature, the system comprises an electronic control card on which the acoustic wave generating component is mounted.

[0018] According to another feature, the system comprises an electronic measurement card mounted on the front face of the microfluidic component, carrying a reading unit and electrical contacts connecting said reading unit to the measurement / analysis component.

[0019] It should be noted that the architecture of the system is such that the three components are in physical contact with each other, forming a stack.

[0020] The measurement / analysis component and the acoustic wave generating component are therefore arranged on either side of the microfluidic component, which does not prevent the transmission of acoustic waves through the microfluidic component, even though the latter is often made of a polymer-type material (COC or PMMA for example), a material which would nevertheless be capable of attenuating the transmission of acoustic waves and which incorporates a fluidic network. Brief description of the figures

[0021] Other characteristics and advantages will appear in the detailed description in conjunction with the appended figures listed below: - [Fig.l] represents an architecture of a fluid analysis system in accordance with the state of the art; - Figures 2A and 2B represent an architecture of a fluid analysis system according to the invention, respectively seen in section and in top view by transparency; - [Fig.3] represents a system according to an embodiment variant with several oscillators with common actuation; - [Fig.4] represents a diagram showing the frequency response of the oscillation amplitude of an SNR type measurement / analysis component in different stacking configurations; - [Fig.5] represents a diagram showing the mass detection limit obtained as a function of the integration time, by measuring the Allan variance for different actuation architectures; - [Fig.6] shows an example of mounting the piezoceramic element used in the system of the invention;

[0022] Detailed description of at least one embodiment

[0023] The system of the invention is intended for the analysis of a fluid or particles carried by the fluid using microfluidics. As a reminder, microfluidics consists of manipulating fluids in very small volumes (typically from pL to pL) in a controlled manner. This manipulation is carried out in a microfluidic component.

[0024] Thanks to the system of the invention, it is for example possible to characterize at least one property (for example the mass, the volume, the density) of a particle. By particle, we mean for example a biological particle such as a cell, exosome, virus, bacteria, etc. By particle, we also mean a particle of inorganic type such as for example a particle of Gold, Polystyrene, Silica, etc.

[0025] For the remainder of the description, we define an orthonormal reference frame (X, Y, Z) in order to materialize the three dimensions. Microfluidic component

[0026] [Fig.2A] and [Fig.2B]

[0027] The microfluidic component 1 can also be called a microfluidic chip, microfluidic card, microfluidic interposer or microfluidic cartridge. It is thus in the form of a support that is generally flat or not very thick in the height direction (along the Z axis) with respect to its two other dimensions. It can be composed of an assembly of several layers sealed together. Advantageously, it has a rectangular shape in its two dimensions X and Y and has a constant thickness along Z.

[0028] The microfluidic component 1 is defined with a so-called front face 12 and a so-called rear face 13, opposite the front face and separated from it by the thickness of the microfluidic component. The two front and rear faces each extend along the two axes X and Y and are advantageously planar, perpendicular to the Z axis.

[0029] The microfluidic component 1 comprises a microfluidic circuit called the main microfluidic circuit 10 integrated into its thickness. This main microfluidic circuit 10 may have microfluidic channels of a few micrometers, for example having a square cross-section. In a non-limiting manner, the main microfluidic circuit 10 may also comprise fluidic pumps, fluidic valves, reservoirs or other fluidic elements (not shown) making it possible to circulate the fluid in the main microfluidic circuit 10.

[0030] The microfluidic component 1 may in particular integrate a deformable membrane (type "Ecoflex") forming one of the layers of the microfluidic component 1, this membrane being deployable to perform a function of a fluidic element such as for example pumping, valve, etc.

[0031] The microfluidic component 1 can be manufactured from several types of materials, mainly of the polymer type such as for example COC (Cyclo-Olefin Copolymer) or PMMA (Polymethyl Methacrylate). Measurement / Analysis Component

[0032] [Fig.2A] and [Fig.2B]

[0033] The measurement / analysis system of the invention also comprises a measurement / analysis component 2 mounted on the microfluidic component 1. In other words, the measurement / analysis component 2 is fixed on the microfluidic component 1, on its front face 12, and comes into physical contact against this front face 12. The contact can be made by direct contact, or advantageously via one or more joints pierced at the fluid access points and a mechanical clamping system to ensure sealing. Alternatively, glue can be used as a localized bonding interface between the measurement / analysis component 2 and on the microfluidic component 1, with the exception of the fluid access areas so as not to obstruct them.

[0034] The measurement / analysis component 2 comprises a microfluidic circuit called measurement 20 which is fluidically connected to the main microfluidic circuit 10 when the measurement / analysis component 2 is mounted on the front face 12 of the microfluidic component 1.

[0035] The measurement / analysis component 2 is for example a mechanical oscillator.

[0036] The measurement / analysis component 2 thus comprises a measurement member 21 capable of being mechanically excited by acoustic waves. This measurement member 21 may consist of a beam capable of being set into vibration when it is excited.

[0037] For example, the mechanical oscillator may be a SMR / SNR type resonator (for "Suspended MicroChannel Resonator" and "Suspended Nanochannel Resonator") used for example for weighing nano or microparticles (inorganic or biological).

[0038] A mechanical resonator 1 (SMR or SNR) comprises at least one fixed part, and a suspended part, forming the measuring member 21, connected to the fixed part and capable of vibrating when it is excited. It also comprises the microfluidic measuring circuit 20 integrated into its suspended part, this microfluidic circuit comprising at least one fluidic channel hollowed out inside its suspended part, covered with sealed walls on the four faces (top, bottom, laterally) and intended to be used to inject a fluid into it in which are for example placed one or more particles to be characterized.

[0039] The suspended part is excited by external means, at the resonance frequency or at a frequency of a higher natural mode. In this type of resonator, the vibration is generally carried out out of plane, but alternatively it can be generated in the plane, or even in torsion.

[0040] The measurement / analysis component 2 is advantageously in the form of a right prism, for example a parallelepiped (a chip in electronic language). It is mounted in a suitable housing made on the front face of the microfluidic component 1.

[0041] The measurement / analysis component 2 may comprise electrical contacts to which a reading unit is connected, responsible for reading the electrical signals generated by the measurement / analysis component when it is excited. The reading unit may be produced on an electronic card 5 (PCB - "Printed Circuit Board" - visible [Fig.2B] in top view), the electrical contacts of the measurement / analysis component 2 being connected to electrical pads of the reading unit assembled on the card 5, for example via electrical connection wires. This electronic card 5 may be a dedicated electronic card, separate from that used for controlling the piezoceramic element 3.

[0042] The measuring member 21 of the measuring / analysis component 2 is capable of being excited using acoustic waves, created by an acoustic wave generating component. Acoustic wave generating component

[0043] [Fig.2A] and [Fig.2B]

[0044] The acoustic wave generating component is a piezoelectric component. It is advantageously produced in the form of a piezoceramic element 3. It could also be a SAW (for "Surface Acoustic Wave") or PMUT (for "Piezoelectric Micromachined Ultrasonic Transducer") type device.

[0045] The acoustic wave generating component has electrical connections for receiving electrical control pulses and is thus configured to generate the desired acoustic waves.

[0046] The piezoceramic element 3 is for example in the form of a rectangular plate comprising electrical contact tabs.

[0047] In [Fig.2B], the piezoceramic element 3 is shown in transparency. It should be understood that it is positioned under the microfluidic component 1.

[0048] A control unit is associated with the piezoceramic element 3. It is for example produced on an electronic card 4 mounted on the rear face of the piezoceramic element 3. Stacking components

[0049] [Fig.2A] and [Fig.2B]

[0050] According to the invention, the system is configured so as to form a stack along the Z axis. In this stack, we have: - The microfluidic component 1 which has its rear face 13 and its front face 12; - The measuring / analysis component 2 mounted on the front face 12 of the microfluidic component 1, so as to come into contact with it. The microfluidic measuring circuit 20 is fluidically connected to the main microfluidic circuit 10 of the microfluidic component 1; - The acoustic wave generating component, for example formed from the piezoceramic element 3, mounted on the rear face 13 of the microfluidic component 1

[0051] The system may also include the electronic card 4 having a front face on which the piezoceramic element 3 is welded and the electronic card 5 dedicated to reading the signals emanating from the measurement / analysis component 2.

[0052] Advantageously, the acoustic wave generating component has a footprint in the two dimensions X and Y forming a projected surface along the Z axis. The measurement / analysis component 2 also has a footprint in the two dimensions X and Y, the surface of which is included in the projected surface of the acoustic wave generating component.

[0053] Also advantageously, the measurement / analysis component 2 is centered relative to the acoustic wave generating component and has a size along the X and Y dimensions smaller than that of the acoustic wave generating component. Special achievement

[0054] [Fig.2A], [Fig.2B] and [Fig.6].

[0055] Experimentally, a first prototype of the system was produced, including a microfluidic component 1, a mechanical oscillator of the SNR type (produced in the form of an SNR chip) mounted on the front face 12 of the microfluidic component 1 to play the role of the measurement / analysis component 2 and a piezoceramic element 3 mounted on the rear face 13 of the microfluidic component 1 and playing the role of the acoustic wave generator component.

[0056] The microfluidic component 1 is in the form of a plate or card made of a plastic polymer of the COC (Cyclo-Olefin Copolymer) or PMMA (Polymethyl Acrylic Methacrylate) type, which is machined using a precision machining machine. The machining of this part is done on both sides: - On the rear side 13 to draw the microfluidic channels of the main microfluidic circuit 10 which will then be closed using an adhesive film (for example of the "MicroAmp" type); - On the front face 12, to create the housings for accommodating the SNR chip and the electronic card 5 for reading the signal from the SNR chip;

[0057] The plastic plate advantageously contains several holes allowing to accommodate screws, on the one hand to ensure the sealed fluidic connection using flexible seals and on the other hand to ensure the maintenance of the piezoceramic element 3 in contact with the rear face 13 of the microfluidic component 1.

[0058] With reference to [Fig.6], two additional parts 30, 31 are for example also machined from COC or PMMA type plastic, and are integrated into the system to maintain the piezoceramic element 3 in physical contact with the rear face 13 of the microfluidic component 1, at the desired location. The piezoceramic element 3 is then sandwiched between these two parts 30, 31, screwed together. The assembly between these two parts in contact notably provides a housing for the electronic card 4 dedicated to the control of the piezoceramic element 3.

[0059] Once the parts have been prepared, it is necessary to ensure the electrical connections allowing the reading of the signal from the SNR chip. To do this, a "wire bonding" step can be carried out, allowing the metal contacts of the SNR chip to be electrically connected to the metal contacts of the electronic reading card 5. The fluidic connection is then established to allow the circulation of fluids inside the microfluidic component 1 and within the SNR chip.

[0060] It is also possible to ensure firm contact between the SNR chip and the microfluidic component 1 using a clamping part (not shown), screwed on either side of the SNR chip, to hold it in place. This part, machined from transparent plastic and possibly containing an observation hole, then does not hinder the viewing of the parts of interest of the MEMS chip. Experimentation

[0061] [Fig.4] and [Fig.5].

[0062] In order to test the proper functioning of the system, the protocol consists of testing the frequency response of the SNR chip when the main microfluidic circuit 10 is filled with air. A frequency sweep is then carried out to determine the resonance frequency of the SNR chip and its quality factor. It can thus be observed that the waves generated by the piezoceramic element are indeed transmitted to the SNR chip through the COC support formed by the microfluidic component 1. However, it should be noted that there is a moderate drop in amplitude (less than an order of magnitude) in the response compared to that obtained when the piezoceramic element is directly mounted on the SNR chip ([Fig.4]).

[0063] This can be explained in three ways: - The transmission of mechanical waves takes place through an additional thickness (that of the microfluidic component), which causes dissipation of the waves and therefore a slight reduction in actuation efficiency. - The microfluidic channels being hollow and unfilled, located directly under the SNR chip, the transmission of mechanical waves is less important. - The mechanical contact between the SNR chip and the microfluidic component is ensured here by a simple double-sided adhesive, which can help to dissipate some of the waves.

[0064] However, the quality factor, performance index, does not appear to be negatively affected by operating the SNR chip through the microfluidic component.

[0065] The SNR chip is then operated in a closed loop (i.e. its resonance frequency is read continuously and the signal applied to the piezoceramic element 3 is constantly updated according to any frequency fluctuations).

[0066] An experiment called "Allan variance" is carried out in order to obtain the average frequency noise of the SNR chip, which is then translated into a mass detection limit. After 10 minutes of acquisition of the frequency noise data, it is then possible to calculate the Allan variance of the SNR chip, a value which makes it possible to obtain an estimate of the lower mass detection limit of the chip, as a function of the integration time of the control loop. This detection limit depends on numerous factors, and in particular on the actuation efficiency of the chip. This experiment is carried out by applying the same actuation voltage to the piezoceramic, for actuation in direct contact with the SNR chip (according to the state of the art - [Fig.l]) and remote actuation through the microfluidic component according to the invention.

[0067] With reference to the diagram in [Fig.5], it can be seen that the Allan variance is similar for all the architectures tested, and a very small modification of the mass detection limit is noted when the SNR chip is actuated through the microfluidic component according to the architecture of the invention.

[0068] In Figures 4 and 5, an architecture is also taken into account in which the piezoceramic element 3 is on the rear face 13 and the system comprises a clamping device to hold the stack in place. Measurement / analysis system

[0069] [Fig.3].

[0070] It is also possible to use the principle of the invention on a complete analysis system in which a single acoustic wave generating component (for example a single piezoceramic element 3) is mounted on the rear face 13 of the same microfluidic component 1 to actuate several oscillators manufactured on the same chip or on several distinct juxtaposed chips 2a, 2b, mounted on the front face 12 of the microfluidic component 1.

[0071] In this configuration, the chip or chips 2a, 2b mounted on the front face 12 of the microfluidic component 1 are arranged so as to be placed in the surface projected from the acoustic wave generating component so that all the oscillators can be actuated by the same piezoceramic element 3.

[0072] It is in fact possible to actuate several oscillators by means of a single piezoceramic element 3, provided that the resonance frequency of each oscillator is sufficiently differentiated from the others, and that their quality factor is sufficiently high so that the actuation of one oscillator does not disturb another juxtaposed oscillator, and that there is no crosstalk between these oscillators, if ever their respective resonance frequency were too close to one another.

[0073] This system has several advantages. It is in fact possible to: - Carry out several analyses in parallel of the same sample, on the same microfluidic component 1; - Test the influence of several treatment conditions on the same sample.

[0074] Furthermore, as already indicated above, the microfluidic component 1 may have a complex architecture with fluidic elements such as pumps, valves, reservoirs, actuable for example by a membrane integrated in the stack of layers of the microfluidic component. This type of architecture is notably described in the publication referenced below: Achard, Y. Fouillet, Quantitative biological assays with on-chip calibration using versatile architecture and collapsible chambers, Sensors and Actuators B: Chemical, Volume 261, 2018, Pages 106-114, ISSN 0925-4005,

[0076] https: / / doi.org / ! 0.1016 / j.snb.2018.01.111.

[0077] The solution of the invention thus makes it possible to remotely actuate a measurement / analysis component 2 sensitive to acoustic waves mounted on the front face 12 of a microfluidic component 1 by bringing into contact, against the rear face 13 of the microfluidic component, a suitable acoustic wave generating component, controlled to emit the acoustic waves. This principle applies even when the microfluidic channels of the main microfluidic circuit 10 are empty.

[0078] By this configuration, it is possible to continue the observation of the main microfluidic circuit, to facilitate the electrical connections of the components and to implement several distinct juxtaposed measurement / analysis chips, mounted on the front face of a single microfluidic component.

Claims

Claims

1. Fluid analysis system comprising: - A microfluidic component (1) integrating a main microfluidic circuit (10) and comprising a front face (12) and a rear face (13), - A measurement / analysis component (2) mounted on the front face (12) of the microfluidic component (1) and which comprises at least one measurement member (21) capable of being mechanically stimulated by acoustic waves, - An acoustic wave generating component, - Characterized in that the acoustic wave generating component is mounted on the rear face (13) of the microfluidic component (1).

2. System according to claim 1, characterized in that the measurement / analysis component (2) is a MEMS / NEMS type resonator comprising a microfluidic measurement circuit (20) connected to the main microfluidic circuit (10) of the microfluidic component (1).

3. System according to claim 1 or 2, characterized in that the acoustic wave generating component is a piezoelectric component.

4. System according to claim 3, characterized in that the piezoelectric component is a piezoceramic element (3).

5. System according to claim 4, characterized in that the piezoceramic element (3) has a two-dimensional footprint forming a projected surface in which the measurement / analysis component (2) is inscribed.

6. System according to claim 5, characterized in that the measuring / analysis component (2) is centered on the projected surface of the piezoceramic element.

7. System according to one of claims 1 to 6, characterized in that it comprises several juxtaposed measuring members, actuable by a single component generating acoustic waves.

8. System according to one of claims 1 to 7, characterized in that the microfluidic component (1) is made of a polymer material.

9. System according to claim 8, characterized in that the component microfluidics (1) is made of Cyclo-Olefin Copolymer or Poly-Methyl Methacrylate.

10. System according to one of claims 1 to 9, characterized in that it comprises an electronic control card (4) on which the acoustic wave generating component is mounted.

11. System according to one of claims 1 to 10, characterized in that it comprises an electronic measurement card (5) mounted on the front face (12) of the microfluidic component, carrying a reading unit and electrical contacts connecting said reading unit to the measurement / analysis component (2).

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