Micropillar-based microfluidic system for measuring viscosity with optical readout

Abstract

The invention relates to a microfluidic system based on micropillars (1) that measure the viscosity with optical readout and allows viscosity measurement to be performed faster, at low cost and in a compact volume.

Description

[0001] MICROPILLAR-BASED MICROFLUIDIC SYSTEM FOR MEASURING VISCOSITY WITH OPTICAL READOUT

[0002] Technical Field

[0003] The invention relates to a micropillar-based microfluidic system that measures viscosity with optical readout and allows viscosity measurement to be performed faster, at low cost and in a compact volume.

[0004] Prior Art

[0005] Measurement of changes in viscosity is particularly critical in diagnostic techniques based on biological fluids such as cerebral, amniotic and blood. Recently, microfluidic chips have played a role in realizing viscosity measurement quickly, cost-effectively and in a compact volume.

[0006] Microfluidic chips enable pressure-based viscosity measurements (obtaining viscosity using data from two pressure sensors placed at different locations) [1-5], flow rate based [6,7], surface tension based [8,9], comparator principle based (viscosity measurement based on the intersection interface formed by different liquids in a microchannel) [10,17], and droplet-based (based on the measurement of viscosity based on drop size and inter-drop spacing using droplet formation techniques) [18-22] as [18-22],

[0007] With the advancement of microfabrication technology, cantilever and micropillarbased viscosity measuring devices have been developed. Unlike the previous technique, viscosity can be obtained by looking at the static (amount of bending) and dynamic (frequency of oscillation) properties of these movable (micropillar and cantilever) structures.

[0008] The disadvantages of these systems available in the art are that they require a large volume of liquid, errors in the measurement of high viscosity values, bubbles formed at the boundary of two different liquids (for comparator-based devices) make measurement difficult, and the use of highly moving or oscillating parts (lever-based viscosity measurement devices).

[0009] In the patent document numbered US10071359B2, which is in the known state of the art, the production and manipulation of high-speed microfluidic droplets is mentioned. In the document, due to the small distances in the aspect ratio of the pillars, if light is coupled to only one pillar, unwanted coupling to the neighboring pillar occurs.

[0010] In the patent document numbered US2005195394A1, which is in the known state of the art, an optical sensing device for biochemically analyzing samples of microfluidic chips such as DNA chips or protein chips is mentioned.

[0011] In the patent document numbered US2021268497A1 in the known state of the art, a microfluidic thromboelastometry device is mentioned.

[0012] In the patent document numbered WO2021097085 A2, which is in the known state of the art, a microfluidic device and the usage areas of this device are mentioned.

[0013] When the existing works in the art are examined, it has been necessary to develop a microfluidic system based on a micropillar that measures viscosity with optical readout and allows viscosity measurement to be performed faster, at low cost and in a compact volume in order to eliminate the disadvantages mentioned above.

[0014] Aims of the Invention

[0015] The object of the present invention is the development of a microfluidic system based on a micropillar array that measures viscosity with optical readout and allows viscosity measurement to be performed faster, at low cost and in a compact volume.

[0016] Another object of the present invention is the development of a micropillar-based microfluidic system capable of compactly measuring viscosity using a single optical detector (photodetector) without the use of a camera. Another object of the present invention is to develop a microfluidic system based on a micropillar-based microfluidic chip that can measure viscosity more precisely and with better accuracy by looking at a microfluidic chip from the side rather than from above, in alternative applications where a camera is used.

[0017] Another aim of the present invention is to develop a micropillar-based microfluidic system that can perform measurements much faster and with high noise tolerance by using signal processing techniques on images obtained by looking at the camera from the side, which is used in alternative applications.

[0018] Detailed Description of the Invention

[0019] A micropillar-based microfluidic system realized to achieve the object of the present invention is shown in the attached figures.

[0020] These figures are;

[0021] Figure 1: Schematic view of the inventive system.

[0022] Figure 2: Schematic view of the inventive system in an alternative embodiment.

[0023] Figure 3: Schematic view of the inventive system in an alternative embodiment, where the light is sent to the microfluidic chip by the micropillar.

[0024] Figure 4: Schematic view of an alternative embodiment of the system according to the invention, in which the light is sent to the microfluidic chip from the chip part in a multiple way (light is mapped to each micropillar) using a lens array.

[0025] Figure 5: Schematic view of an alternative embodiment of the system according to the invention, where multiplexing is realized by using a diffraction grating.

[0026] Figure 6: Schematic view of an alternative embodiment of the system according to the invention, where the light is transmitted by the chip and multiplexed by the lens array, using a fiber optic cable array placed inside the chip and aligned with each micropillar. Figure 7: Schematic view of an alternative embodiment of the system according to the invention, where a side view is taken by the camera.

[0027] Figure 8a: Schematic view of the pattern obtained by the camera in an alternative embodiment of the inventive system.

[0028] Figure 8b: Schematic view of the Fourier Transform pattern of the pattern obtained by the camera in an alternative embodiment of the inventive system.

[0029] The parts in the figures are individually numbered and the corresponding numbers are given below.

[0030] 1. Micropillar

[0031] 2. Microfluidic chip

[0032] 3. Light source

[0033] 4. Beam of light

[0034] 5. Lens

[0035] 6. Reflective prism

[0036] 7. Photo sensor

[0037] 8. Fiber optic cable

[0038] 9. Diffraction grating

[0039] 10. Levels of light

[0040] 11. Camera

[0041] 12. Pattern obtained with the camera

[0042] 13. Micropillar angle axis

[0043] 14. Axis perpendicular to the micropillar angle axis

[0044] 15. Fourier Transform pattern

[0045] 16. Spots

[0046] The invention relates to a microfluidic system based on micropillars (1) that measures viscosity with optical readout and allows viscosity measurement to be performed faster, at low cost and in a compact volume, comprising the parts

[0047] - microfluidic chip (2) containing micropillars (1), - light source that generates the light required for viscosity measurement (3),

[0048] - lens (5) through which the light beam (4) from the light source (3) is transmitted and through which the light can be mapped into the micropillar (1) on the microfluidic chip (2),

[0049] - reflecting prism (6) that directs the light beam (4) passing through the lens (5) to the micropillars (1),

[0050] - a photodetector (7) placed in front of one or more micropillars (1) and enabling the amount of bending to be detected by converting the light intensity of the light beam (4) emerging from the reflecting prism (6) into electric current or voltage.

[0051] In the inventive system, laser or different light sources (LED, sLED etc.) (3) can be matched to illuminate the micropillars (1) on the microfluidic chip (2) from above or below. This may require one or more lenses (5) and reflective prisms (mirrors) (6). Acting as a waveguide, the micropillars (1) bend in response to the fluid viscosity and flow rate applied to the microfluidic chip (2). This bending causes the light emitted from the micropillars (1) to be displaced. The amount of light displacement is detected by one or more photodetectors (7) (or light-sensitive components) to infer the viscosity value of the respective liquid.

[0052] In alternative embodiments of the system according to the invention, laser or other light sources (3) (LED, sLED, etc.) can be sent to illuminate the micropillars (1) on the microfluidic chip (2) from the side. In this case, a camera (11) placed on the opposite side of the illumination will observe the shadow of the micropillars (1). By performing a Fourier Transform on this shadow image, the angles of the micropillars (1) can be precisely determined.

[0053] The microfluidic chip (2) based on the micropillars (1) used in the system is manufactured by microfabrication manufacturing processes, and the liquid delivered into it by means of a syringe pump etc. causes the micropillars (1) to bend in the direction of flow. The aim is to couple the light beam (4) emitted from the light source (3) such as laser, LED or sLED (superluminescent diode) etc. into the micropillars (1).

[0054] This pairing process can be done by using a lens (5) in one micropillar (1) or in more than one micropillar (1).

[0055] In both the lens (5) and the lens (5) array, the coupling can be performed from the bottom or the top surface of the micropillars (1).

[0056] The coupling can be performed directly from a light source (3) into the micropillars

[0057] (I), or it can be performed during the manufacturing process of one or more fiber optic cables (8) into the substrate and aligned with the micropillars (1). In this case, the light must be coupled to the fiber optic cables (8). The light from the fiber optic cables (8) will be processed into the corresponding aligned micropillar (1).

[0058] In an alternative embodiment of the system according to the invention, the light source (3) can be directed to the diffraction grating (9) to multiplex the light beam (4) and map it into each micropillar (1) with a secondary lens (5). Each discrete angle at which the light beam (4) entering the diffraction grating (9) is split is called a light order. Each order can be mapped into a different micropillar (1).

[0059] In the case where the microfluidic chip (2) is illuminated from the side, the camera

[0060] (I I) is used to obtain the shadow pattern of the micropillars (1). Based on the camera pattern (12) showing the shadows of the micropillars (1), the angle axis (13) of the micropillar and the axis perpendicular to this axis (14) can be determined. The camera pattern (12) is the pattern in which the bending of the micropillars (1) will be tracked. From this, a Fourier Transform can be used to calculate the average angle of all or a selected portion of the micropillars (1). Obtaining a clear shadow of the micropillars (1) requires the use of a non-transparent material in the manufacturing of the micropillars (1) and / or mixing it with the main production material.

[0061] Due to the periodic nature of the micropillars (1), the Fourier Transform pattern (15) also consists of periodic and discrete array pattern (16). This array pattern (16) is essentially the Fourier Transform image of the previously described light orders (10). The angle of a line superimposed on the pattern (16) is perpendicular to the angle of the micropillar (1). Hence, the average angle of the micropillar (1) can be obtained.

Claims

CLAIMS1. A micropillar (1) based microfluidic system that measures viscosity with optical readout and allows viscosity measurement to be performed faster, at low cost and in a compact volume, characterized by comprising- a microfluidic chip (2) containing micropillars (1),- a light source (3) that generates the light required for viscosity measurement,- a lens (5) through which the light beam (4) from the light source (3) is transmitted and through which the light can be mapped into the micropillars (1) on the microfluidic chip (2),- a reflecting prism (6) that directs the light beam (4) passing through the lens (5) to the micropillars (1),- a photodetector (7) placed opposite one or more micropillars (1) and enabling the amount of bending to be detected by converting the light intensity of the light beam (4) emerging from the reflective prism (6) into electric current or voltage.

2. A microfluidic system according to claim 1, characterized in that the light source (3) is a laser, LED or sLED (superluminescent diode), etc.

3. A microfluidic system according to claim 1, characterized in that the aspect ratio of the micropillars (1) is > 4.

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