MICROFLUIDICS VALVE

Abstract

A microfluidics valve comprises at least two substrates (1) between which there is at least a microchannel (5). It additionally comprises at least a barrier (4) of a meltable material, placed in the microchannel. The valve further comprises at least an optical heater (6) placed in correspondence with the barrier (4) and at least a section of one of the substrates (1), in correspondence with the optical heater (6), is transparent. The optical heater is a colored line that, when is illuminated with a light source, is heated and releases the heat to the barrier (4) thus melting the part of it that is closer to the line.

Claims

1. Microfluidics valve which comprises: at least two substrates (1) between which at least a microchannel (5) is formed; and at least a barrier (4) of a meltable material, placed in the microchannel (5), blocking said microchannel (5); characterized in that: it comprises at least an optical heater (6) configured to melt the barrier (4) and which is placed in the longitudinal direction of the microchannel (5) projecting from both sides of the barrier (4); at least a section of one of the substrates (1) is transparent.

2. Microfluidics valve according to claim 1 characterized in that the optical heater (6) is placed in one of the substrates (1) and is facing the barrier (4).

3. Microfluidics valve according to claim 2 characterized in that the optical heater (6) is in contact with the barrier (4).

4. Microfluidics valve according to claim 1 characterized in that the optical heater (6) is a feature made of a photothermal material that can absorb light energy in a range of frequencies.

5. Microfluidics valve according to claim 1 characterized in that the optical heater (6) is a printed dark colored line placed in one of the substrates (1).

6. Microfluidics valve according to claim 1 characterized in that one of the substrates comprises at least a hole (3) in correspondence with the microchannel (5) and facing the optical heater (6).

7. Microfluidics valve according to claim 1 characterized in that it comprises a first optical heater (6) placed in the microchannel (5) in correspondence with the barrier (4) and at least an additional optical heater (9) placed in one side of the first optical heater (6).

8. Microfluidics valve according to claim 7 characterized in that it comprises two additional optical heaters (9) placed each at one side of the first optical heater (6).

9. Microfluidics valve according to claim 7 characterized in that the additional optical heaters (9) do not project out of the barrier (4) at any point.

10. Microfluidics valve according to claim 7 characterized in that the first optical heater and the additional optical heaters are photothermal colored features of different colors.

11. Microfluidics valve according to claim 7 characterized in that the first optical heater (6) and the additional optical heaters (9) are colored features of complementary colors.

12. Microfluidics valve according to claim 7 characterized in that the first optical heater (6) is a magenta line and the additional optical heaters (9) are cyan lines.

13. Microfluidics valve according to claim 1 characterized in that the meltable material is wax.

Description

DESCRIPTION OF THE DRAWINGS

[0042] To complement the description being made and in order to aid towards a better understanding of the characteristics of the invention, in accordance with a preferred example of practical embodiment thereof, a set of drawings is attached as an integral part of said description wherein, with illustrative and non-limiting character, the following has been represented:

[0043] FIG. 1a.Shows a perspective view of an embodiment of the microfluidic wax valve.

[0044] FIG. 1b.Shows the microfluidic valve of FIG. 1a with the barrier of meltable material.

[0045] FIG. 1c.Shows a section view of the microfluidics valve of FIG. 1b.

[0046] FIG. 2a.Shows a perspective view of another embodiment of the microfluidics valve.

[0047] FIG. 2b.Shows an exploded view of the microfluidics valve of FIG. 2a.

[0048] FIG. 3.Shows the operation of the microfluidics valve when it is being opened.

[0049] FIG. 4.Shows the operation of the microfluidics valve when it is being closed.

[0050] FIG. 5a.Shows a perspective view of a different embodiment of the microfluidics valve.

[0051] FIG. 5b.Shows the microfluidic valve of FIG. 5a with the barrier of meltable material.

[0052] FIG. 5c.Shows a section view of the microfluidics valve of FIG. 5b.

[0053] FIG. 6a-6b.Shows the opening process of the microfluidics valve of the embodiment of FIGS. 5a-c.

[0054] FIGS. 7a-7c.Shows the closing process of the microfluidics valve of the embodiments of FIGS. 5a-5c.

[0055] FIG. 8.Shows a microfluidic chip comprising five valves.

[0056] FIGS. 9a-f.Show an schematic representation of a microfluidic chip operation during a bead-based immunoassay.

PREFERRED EMBODIMENT OF THE INVENTION

[0057] Following is a description, with the help of FIGS. 1 to 9, of some examples of embodiments of the present invention.

[0058] In FIG. 1a it is shown a perspective view of a microfluidics valve according to one embodiment of the invention. In said embodiment the valve comprises two substrates (1) between which at least a microchannel (5) is formed. The substrates (1) can be joined by an adhesive (2).

[0059] The valve also comprises at least an optical heater (6) as shown in said figure. In order to allow the heating of the optical heater (6), at least a section of one of the substrates (1) is transparent.

[0060] Furthermore, as shown in FIG. 1b, the valve of the invention also comprises at least a barrier (4) of meltable material, placed in the microchannel (5), blocking said microchannel (5). As can be seen in the figure the optical heater (6) is placed in the longitudinal direction of the microchannel (5) and, in said direction, projects from both sides of the barrier (4).

[0061] In FIG. 1c it is shown a section view of the microfluidics valve. The section has been made in correspondence with the microchannel (5) so the microchannel (5) and the barrier (4) blocking said microchannel (4) are appreciated. The direction of the fluid through the valve has also been represented with arrows.

[0062] By actuating the optical heaters (6) corresponding to predetermined microchannels (5) the barriers (4) of said microchannels (5) are partially melted and tunnels (11) are opened to allow the fluid to pass through them. To actuate the optical heaters (6) an external light is focused on them. In this way the optical heaters (6) are heated and they transfer the heat to the meltable material of the barrier (4) which is contact with said optical heaters (6). In FIGS. 6b and 7a the tunnel (11) formed in the barrier (4) placed in the microchannel (5) can be appreciated.

[0063] In the embodiments shown in the figures, the optical heater (6) is a colored line. The light used to actuate the optical heaters (6) has to be of a color complementary to the color of the optical heater (6). That is, if the optical heater (6) absorbs most of the light power at a particular range of frequencies, the light source has to have enough optical power at the same range of frequencies to assure the correct functioning of the valve.

[0064] In the embodiment shown in FIGS. 1a-1c the microfluidics valve comprises at least a hole (3) in correspondence with the microchannel (5) and facing the optical heater (6).

[0065] This embodiment of FIGS. 1a-1c allows easily placing the barrier (4) of meltable material on its correct position. In valves of the state of the art the meltable material had to be melted and then introduced into the microchannel and displaced until its final position. These solutions of the state of the art need a lot of time for the manufacture, part of the barrier can be finally placed in a position which is not the correct final position, lot of resources are need to place the barrier (it has to be melt, pressure has to be applied to displace it, etc.) and external tools have to be used.

[0066] Also, this embodiment comprising the hole (3) cannot be used in the solutions of the state of the art because, in those valves the meltable material barrier (4) blocking the microchannel (5) is totally melted for the passing the fluids through the microchannel (5). In those cases, when melting the barrier, the meltable material forming the barrier (4) would exit through the hole (3) and it would be impossible to send the material back to the microchannel (5) to close the valve when needed, or to avoid the scape of liquid through the hole (3). In an embodiment of the invention the meltable material is wax.

[0067] In the present invention, when the optical heater (6) is actuated, only a small part of the barrier (4) is heated (only the part in contact with the optical heater (6)) so only a tunnel (11) of a smaller section than the microchannel (5) is opened for the passage of the fluid.

[0068] In an embodiment of the invention, the valve is to be installed between a first volume at initially higher pressure and a second volume at initially lower pressure in order to use said pressure during the opening of the valve to displace the melted barrier.

[0069] In FIGS. 2a and 2b another embodiment of the invention is shown. In this case the valve comprises two substrates (1) with a wax layer (7) placed between them.

[0070] In the example of FIG. 2b, the valve structure comprises a 500 m-length barrier (4) located in a microchannel (5) at the entrance of a chamber. The line printed on the substrate, which in an embodiment of the invention is black, is the optical heater (6) and is positioned perpendicular to the barrier (4) extending on both sides of the valve structure. This valve is designed for opening when a pressure difference is applied across the barrier (4) and for closing when there is no pressure. Both opening and closing of the valve occurred when the meltable material (for example wax) of the barrier (4) is melted using the heat released by the printed line upon light source (8) irradiation.

[0071] As represented in FIG. 3, the operation of the valve when it is being opened comprises a step of irradiating the optical heater (6) with a light source (8). In the first part of the figure a closed valve has been represented. It can be appreciated how the microchannel (5) of the valve is blocked with a barrier (4). Said barrier (4) is, in turn, placed in correspondence with the optical heater (6). As can be seen in the second part of the figure, when the light source (8) is applied and the optical heater (6) melts the barrier (4) which, in this case, is ejected to the interior of the chamber thus creating a tunnel (11) in the barrier (4) through which the fluid can pass.

[0072] In FIG. 4 it is represented the operation of the valve when it is being closed. In this case the original situation of the valve is with the barrier (4) having a tunnel. In the second part of the figure it can be seen how, when the optical heater (6) is activated again, the meltable material (for example wax) returns to its original position in the microchannel (5) and blocks it. Once the optical heater (6) is turned off, the meltable material (for example wax) solidifies and the valve remains permanently closed.

[0073] Performance of the microfluidics valves in an exemplary embodiment of the invention is characterized in both air and water under different experimental conditions. In both cases a minimum pressure drop of 3 kPa is required for a successful valve opening. The valve exhibits reversible open-close behavior for up to 30 actuation cycles in air (50 kPa) and 15 in water (25 kPa).

[0074] In FIGS. 5a-c it is represented another embodiment of the invention. In this case, the microfluidics valve is designed to be used in applications requiring closure of the valve while there is a fluid flow through it, and therefore pressure difference across it.

[0075] As previously described, in cases in which the valve has to be used in applications in which a difference of pressure at both sides of the valve is present, additional optical heaters are needed.

[0076] In this case it is represented a valve which comprises two substrates (1) joined by an adhesive (2). Between the substrates (1) it is formed at least a microchannel (5) and a barrier (4) of a meltable material is placed blocking said microchannel (5), as in the embodiment of FIGS. 1a-c. The valve also comprises a hole (3) in correspondence with the microchannel (5) for the passing of the meltable material for forming the barrier (4) when manufacturing the valve.

[0077] In FIGS. 5a-5c it can be appreciated the essential feature of this embodiment of the invention which is that the microfluidics valve, in this case, comprises a plurality of heaters. In this case, a first optical heater (6) is placed in correspondence with the barrier (4), in longitudinal direction of the barrier (4) and projecting from its sides.

[0078] In this embodiment, there is also at least an additional optical heater (9) placed at one side of the first heater (6). Preferably, as represented in the figures, there are two additional optical heaters (9) which are placed each one at each side of the first heater (6). Said additional optical heaters (9) are contained in the space of the microchannel (5) occupied by the barrier (4), embedded in said barrier (4). That is to say, the additional optical heaters (9) do not project out of the barrier (4) at any point.

[0079] The first optical heater (6) and the additional optical heaters (9) are photothermal colored features which are colored in different colors, complementary colors, that is, absorb light power at different frequency ranges. In an exemplary embodiment of the invention the first optical heater (6) is a magenta line and the additional optical heaters (9) are cyan lines. Those colors have been selected because they adsorb light at different frequencies, the magenta line absorbing green light, that is light of wavelength around 530 nanometers and the cyan line absorbing red light, that is, light of wavelength around 630 nanometers, so it is possible to not actuate the additional optical heaters when actuating the first optical heater and viceversa.

[0080] In this case, to open the valve, since the first optical heater (6) is magenta, a green light (8) is applied in order to heat the first optical heater (6) without heating the additional heaters, as can be seen in FIGS. 6a-b.

[0081] In order to close the valve, an additional light source (10) is used. In this case the additional optical heaters (9) are cyan so the additional light source (10) is red. When the additional light source actuates the optical heaters (9), the meltable material in contact with those additional optical heaters (9) is melted and displaces to the tunnel (11) where it becomes solid, creating again the barrier (4) and blocking the microchannel (5), as can be seen in FIGS. 7a-c.

[0082] This valve notably improves current drawbacks of paraffin wax microvalves in terms of response time, energy consumption, multiple actuation and complexity of the fabrication processes. Furthermore, the microfluidic technology described here is highly promising for mass production of fully-integrated disposable lab-on-a-chip devices.

[0083] FIG. 8 shows a microfluidic chip, comprising five microvalves (V1-V5) as previously described, designed to perform a simple bead-based enzymatic immunoassay. It also comprises two inlets (I) and an outlet (O). The chip is composed by one structured double-sided adhesive layer sandwiched between two transparent polyester films. The bottom transparency film incorporates the printed black ink lines that function as photo-thermal heaters for wax valve actuation. Wax valves are easily fabricated at the desired locations within the microchannels by simple deposition of solid wax on the substrate before the chip assembly followed by heating step. External white LEDs are used as light source for valve actuation. An LED-photodetector pair is used for absorbance measurement in the detection microchannel.

[0084] In an example of embodiment, a negative pressure of 10 kPa is applied at the outlet (O) for valve opening. Valve closing is performed with no pressure applied. The valves can be either partially (and reversibly) or fully (irreversibly) opened, depending on the duration of the actuation light pulse.

[0085] During valve (V1-V5) partial opening, wax in contact with the heated black line is melted and ejected from the barrier (4), thus creating a tunnel. When closing (no pressure applied) the wax around the heater (6) melts and refills the tunnel. Valve V2 to be opened irreversibly requires a channel (5) widening to trap the melt wax.

[0086] A simple immunoassay was performed on-chip following the steps shown in FIGS. 9a-f. Anti-rabbit IgG antibodies labeled with horseradish peroxidase were successfully detected using rabbit IgG functionalized (and BSA blocked) polystyrene microbeads (30 m diameter) and 3,3,5,5-Tetramethylbenzidine (TMB) as enzymatic substrate.

[0087] In FIGS. 9a-f are depicted the following steps of the chip operation: the loading of microbeads (which is made in a microbeads loading port (MLP)) (FIG. 9a), an immunoassay (sample, immunoreagents, and washing solutions injected from inlet I1) (FIG. 9b), microbeads displacement (FIG. 9c), enzymatic substrate injection from inlet I2 (FIG. 9d), enzymatic reaction (FIG. 9e), detection (which is made in a detection point (D)) (FIG. 9f)).

[0088] The size of the tunnel in partially open valves is small enough to allow liquid flow while retaining the microbeads. Fully opened valves (V2) allow the passage of the microbeads. The movement of microbeads enabled performing the enzymatic reaction in a clean channel, which yielded an order of magnitude improvement in the limit of detection.