An integrated dual-channel optical fiber and capillary reflective microfluidic sensing device

Abstract

The utility model discloses a kind of integrated double-channel optical fiber and capillary's reflective micro-flow sensing device, including double-channel optical fiber, two microchannels being independently arranged in double-channel optical fiber, one end of first quartz capillary is fused with single-mode optical fiber and forms the first reflecting surface of light, the other end is fused with the input end of two microchannels of double-channel optical fiber and forms the second reflecting surface of light, and first quartz capillary is communicated with two microchannels, the output end of double-channel optical fiber is misaligned with second quartz capillary and is fused, so that two microchannels of double-channel optical fiber become liquid inlet channel and liquid outlet channel respectively, and second quartz capillary is used for liquid inlet.The utility model sets liquid inlet and liquid outlet on two independent microchannels respectively, and is communicated by quartz capillary inside, forms a physically separated U-shaped micro-flow path, greatly facilitates the injection and replacement of liquid;It improves the accuracy and repeatability of detection.

Description

Technical Field

[0001] This utility model relates to the field of fiber optic sensing and microfluidics technology, specifically to a reflective microfluidic sensing device integrating a dual-channel optical fiber and a quartz capillary. Background Technology

[0002] Microfluidics technology, with its advantages of high efficiency and low power consumption, is widely used in biochemical analysis, while fiber optic sensors possess characteristics such as resistance to electromagnetic interference and high sensitivity. Combining the two to form microfluidic sensor probes is currently a research hotspot. However, existing fiber optic microfluidic sensor structures still face significant challenges in design and application. For example, some structures that fabricate microcavities on the fiber end face suffer from slow liquid diffusion, sluggish response, and difficulty in cleaning the cavity. Another approach using photonic crystal fibers, while achieving photo-liquid interaction, has an interior composed of dense micron-sized pores, resulting in extremely high flow resistance, requiring high-pressure drive, and the complex microporous structure makes cleaning extremely difficult. Furthermore, most existing solutions employ a symmetrical axial flow path design, where the liquid inlet and outlet are located at the axial ends of the fiber. This structure causes the fiber pigtail used for optical signal transmission to become spatially entangled with the fluid conduit, which is extremely inconvenient in actual installation, especially when integrated into compact spaces such as microfluidic chips, and is prone to mutual interference. Therefore, there is an urgent need in the field for a new type of sensing device that can achieve low flow resistance and fast response microfluidic detection, while having a compact structure with spatial separation between the optical interface and the fluid interface. Utility Model Content

[0003] This invention addresses at least one of the aforementioned problems in the prior art by disclosing a reflective microfluidic sensing device integrating a dual-channel optical fiber and a capillary. The inlet and outlet are respectively located on two independent microchannels and connected internally by a quartz capillary, forming a physically separated U-shaped microfluidic path. This greatly facilitates liquid injection and replacement. Due to the unobstructed and directional flow path, the liquid to be tested can be easily pushed in from the inlet by subsequent samples or cleaning fluid and directly discharged from the outlet, effectively avoiding sample residue and cross-contamination within the sensing cavity, thus improving the accuracy and repeatability of the detection.

[0004] This utility model is achieved through the following technical solution: This invention first provides a reflective microcurrent sensing device integrating a dual-channel optical fiber and a capillary tube. The device includes a dual-channel optical fiber with two independent microchannels running through it along the axial direction. One end of a first quartz capillary tube is fused to a single-mode optical fiber to form a first light-reflecting surface, and the other end is fused to the input ends of both microchannels of the dual-channel optical fiber to form a second light-reflecting surface. The first quartz capillary tube is connected to both microchannels. The output end of the dual-channel optical fiber is fused to the second quartz capillary tube in a staggered manner, so that the two microchannels of the dual-channel optical fiber become a liquid inlet channel and a liquid outlet channel, respectively. The second quartz capillary tube is used for liquid inlet, and the single-mode optical fiber is used to connect to an optical modem.

[0005] As a further solution, the two microchannels are designated as a first microchannel and a second microchannel. One end of the second quartz capillary is fused to the output end of the second microchannel and is offset from the first microchannel, so that the second microchannel becomes the liquid inlet channel and the first microchannel becomes the liquid outlet channel.

[0006] As a further option, the cross-section of the first microchannel and the second microchannel can be any one of a circle, a semicircle, or an ellipse.

[0007] As a further option, the first microchannel and the second microchannel are set up in parallel.

[0008] As a further embodiment, the first microchannel and the second microchannel are set at an angle, with the first microchannel tilted downward from the input end to the output end, with a tilt angle ranging from 3° to 10°, and the second microchannel tilted upward from the input end to the output end, with a tilt angle ranging from 3° to 10°.

[0009] As a further option, the open end of the second quartz capillary is connected to a rubber hose as an inlet, and the rubber hose is connected to a needle controlled by a microfluidic pump.

[0010] As a further option, the single-mode fiber is a standard single-mode fiber with an outer diameter of 125 micrometers and an inner diameter of 9 micrometers.

[0011] As a further embodiment, the first quartz capillary has an outer diameter of 125 micrometers, an inner diameter of 75 micrometers, and a length of 120-180 micrometers.

[0012] As a further embodiment, the second quartz capillary has an outer diameter of 60 micrometers, an inner diameter of 45 micrometers, and a length of 120-180 micrometers.

[0013] As a further embodiment, the dual-channel optical fiber has a length of 5-6 cm, an outer diameter of 125 micrometers, and an inner diameter of 35-45 micrometers for each microchannel.

[0014] The features and beneficial effects of this utility model are as follows: (1) This utility model defines an independent liquid inlet channel and a liquid outlet channel by staggered welding. The liquid inlet and liquid outlet are respectively set on two independent microchannels and connected by the inside of the quartz capillary, forming a physically separated U-shaped microflow path, which greatly facilitates the injection and replacement of liquid. Since the flow path is unobstructed and the direction is clear, the liquid to be tested can be easily pushed in from the liquid inlet by the subsequent sample or cleaning liquid and discharged directly from the liquid outlet, effectively avoiding the residue and cross-contamination of the sample in the sensing cavity, and improving the accuracy and repeatability of the detection.

[0015] (2) The present invention has a simple structure and can complete all the splicing steps by using an optical fiber fusion splicer. It has good process repeatability and is suitable for mass production.

[0016] (3) The length of the dual-channel optical fiber set in this utility model is 5-6 cm, the outer diameter is 125 micrometers, and the diameter of each microchannel inside is 35-45 micrometers. The outer diameter is consistent with that of the single-mode optical fiber and the first quartz capillary and the second quartz capillary. The use of a 5-6 cm long dual-channel optical fiber can completely lose the light signal transmitted through the second reflective surface 5, avoiding the occurrence of a third reflection. The microchannel diameter is controlled at 35-45 micrometers, so that the liquid to be tested can flow through with low flow resistance. At the same time, it avoids the microchannel diameter being too large, causing the fiber core to be too thin and difficult to cause a second reflection. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the sensing device described in an embodiment of the present utility model; Figure 2 This is a schematic diagram showing the connection of the single-mode optical fiber, quartz capillary, and dual-channel optical fiber according to an embodiment of the present invention. Figure 3 This is a schematic diagram of a dual-channel optical fiber according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a dual-channel optical fiber according to another embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the working principle of the sensing device described in an embodiment of this utility model.

[0019] Explanation of reference numerals in the attached figures: 1. Single-mode optical fiber; 2. First quartz capillary; 3. Dual-channel optical fiber; 31. First microchannel; 32. Second microchannel; 4. First reflecting surface; 5. Second reflecting surface; 6. Second quartz capillary; 7. Liquid inlet; 8. Liquid outlet; 9. Waste liquid pool; A. Optical signal entry and reflection path; B. Flow path of the liquid to be tested. Detailed Implementation

[0020] To facilitate understanding of this utility model, a more comprehensive description of this utility model will be provided below, along with embodiments of this utility model, but this does not limit the scope of this utility model.

[0021] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0022] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0023] A reflective microcurrent sensing device integrating dual-channel optical fiber and capillary, such as Figures 1 to 5As shown, the optical fiber includes a dual-channel fiber 3. The dual-channel fiber 3 has two independent microchannels that run through it along the axis. One end of the first quartz capillary 2 is fused to the single-mode fiber 1 to form a first light reflecting surface 4. The other end is fused to the input ends of both microchannels of the dual-channel fiber 3 to form a second light reflecting surface 5. The first quartz capillary 2 is connected to both microchannels. The output end of the dual-channel fiber 3 is fused to the second quartz capillary 6 in a staggered manner. The second quartz capillary 6 is used for liquid inlet, so that the two microchannels of the dual-channel fiber 3 become the liquid inlet channel and the liquid outlet channel, respectively. The single-mode fiber 1 is used to connect to the optical modem.

[0024] In one embodiment, the dual-channel optical fiber 3 has an independent first microchannel 31 and a second microchannel 32. One end of the second quartz capillary 6 is fused to the output end of the second microchannel 32 and is offset from the first microchannel 31 to avoid interference with the liquid outlet 8 of the first microchannel 31. The other end of the second quartz capillary 6 serves as the liquid inlet 7, making the second microchannel 32 the liquid inlet channel and the first microchannel 31 the liquid outlet channel. The output end is the liquid outlet 8, which is used to connect with the waste liquid pool 9. This structure physically defines independent liquid inlet and liquid outlet channels, which are connected internally through the second quartz capillary 6, forming a physically separated U-shaped microfluidic path, which greatly facilitates the injection and replacement of liquid.

[0025] In one embodiment, the open end of the second quartz capillary 6 is connected to a rubber hose as an inlet 7, and the rubber hose is connected to a syringe controlled by a microfluidic pump for adding liquid.

[0026] In some embodiments, the single-mode fiber 1 is a standard single-mode fiber with an outer diameter of 125 micrometers and an inner diameter of 9 micrometers. This ensures seamless compatibility of the sensor with the vast majority of commercial fiber optic connectors, fusion splicers, and system equipment, greatly reducing integration barriers and costs. Simultaneously, single-mode transmission produces clear and stable interference patterns, which is fundamental to achieving high-precision sensing.

[0027] In some embodiments, the outer diameter of the first quartz capillary 2 is 125 micrometers, the inner diameter is 75 micrometers, and the length is 120-180 micrometers, preferably 150 micrometers. The outer diameter of the first quartz capillary 2 is perfectly matched with the outer diameter of the single-mode fiber 1. The 75-micrometer inner diameter ensures that the light beam with a certain divergence angle emitted from the single-mode fiber will never touch the inner wall when passing through this capillary, thereby avoiding light energy loss and stray reflection. The 150-micrometer length design can minimize the divergence loss of the light beam in the air, while also facilitating precise operation and alignment in a fusion splicer.

[0028] In some embodiments, the second quartz capillary 6 has an outer diameter of 60 micrometers, an inner diameter of 45 micrometers, and a length of 120-180 micrometers, preferably 150 micrometers. The inner diameter of 45 micrometers is very close to the microchannel diameter of the dual-channel optical fiber 3. This size ensures a smooth flow path transition when liquid flows from the capillary into the microchannel, avoiding the risk of flow disturbance or blockage caused by abrupt size changes. The outer diameter of 60 micrometers ensures that the capillary can perfectly avoid the second microchannel while fusing with the first microchannel, preventing blockage of the liquid outlet.

[0029] In some embodiments, the dual-channel optical fiber 3 has a length of 5-6 cm, an outer diameter of 125 micrometers, and a diameter of 35-45 micrometers for each internal microchannel. The outer diameter is consistent with that of the single-mode optical fiber 1, the first quartz capillary 2, and the second quartz capillary 6. Using a 5-6 cm long dual-channel optical fiber allows for complete loss of the light signal transmitted through the second reflecting surface 5, avoiding a third reflection. Controlling the microchannel diameter to 35-45 micrometers allows the liquid to flow through with low flow resistance, while preventing the fiber core from becoming too thin and difficult to reflect a second time due to an excessively large microchannel diameter.

[0030] In some embodiments, the cross-section of the first microchannel 31 and the second microchannel 32 is any one of a circle, a semicircle, or an ellipse.

[0031] In some embodiments, the first microchannel 31 and the second microchannel 32 are arranged in parallel.

[0032] In other embodiments, the first microchannel 31 and the second microchannel 32 are arranged at an angle, and the first microchannel 31 is inclined downward from the input end to the output end with an inclination angle ranging from 3° to 10°, and the second microchannel 32 is inclined upward from the input end to the output end with an inclination angle ranging from 3° to 10°, so that the liquid to be tested can flow through with low flow resistance, while avoiding the liquid from stagnating due to the small inner diameter of the channel, and facilitating the liquid to enter from the inlet 7 and then be discharged from the outlet 8 under gravity, so as to be completely drained.

[0033] The fusion splice between the single-mode optical fiber 1 and the first quartz capillary tube 2 is an aligned fusion splice, the fusion splice between the first quartz capillary tube 1 and the dual-channel optical fiber 3 is an aligned fusion splice, and the fusion splice between the second quartz capillary tube 6 and the dual-channel optical fiber 3 is an misaligned fusion splice.

[0034] A method for fabricating a reflective microcurrent sensing device integrating dual-channel optical fiber and capillary: 1) Cut a quartz capillary tube with a length of about 150 micrometers, an outer diameter of 125 micrometers and an inner diameter of 75 micrometers as the first quartz capillary tube 2. Cut a quartz capillary tube with a length of about 150 micrometers, an outer diameter of 60 micrometers and an inner diameter of 45 micrometers as the second quartz capillary tube 6. Cut a dual-channel optical fiber 3 with a length of about 5 centimeters, an outer diameter of 125 micrometers and two internal microchannels with a diameter of 35~45 micrometers.

[0035] 2) On the fiber optic fusion splicer, align and fusion the end face of the single-mode fiber 1 with one end of the first quartz capillary tube 2; then, align and fusion the other end of the first quartz capillary tube 2 with the first end of the dual-channel fiber 3.

[0036] 3) Fusion splice one end of the second quartz capillary 6 to the second end of the dual-channel optical fiber 3. This step is a critical misaligned fusion splice: the position needs to be adjusted in the horizontal direction so that the second quartz capillary 6 is only connected to the opening of the second microchannel 32 of the dual-channel optical fiber, while completely avoiding the opening of the first microchannel 31, and the other end of the second quartz capillary 6 remains open.

[0037] 4) The end of the first microchannel of the dual-channel optical fiber 3 serves as the liquid outlet 8, directly connected to the waste liquid tank 9. The open end of the second quartz capillary 6 is connected to a rubber hose as the liquid inlet 7, and the rubber hose is connected to the needle tube controlled by the microfluidic pump. At this point, the reflective microfluidic sensing device is complete.

[0038] The method of using a reflective microcurrent sensing device integrating dual-channel optical fiber and capillary is as follows: a single-mode optical fiber 1 is connected to an optical modem, and then the liquid to be tested is introduced from the inlet 7. The liquid flows sequentially through the second quartz capillary 7, the second microchannel 32 of the dual-channel optical fiber 3, and then flows horizontally through the hollow core of the first quartz capillary 2 inside the dual-channel optical fiber 3. After that, it flows through the first microchannel 31 of the dual-channel optical fiber 3 and finally flows out from the outlet 8 and into the waste liquid pool 9.

[0039] Working principle of a reflective microcurrent sensing device integrating dual-channel optical fiber and capillary: Incident light A is transmitted through single-mode fiber 1. After reaching the first reflecting surface 4, incident light A is split into two parts: for ease of understanding, we will refer to them as partial light A1 and partial light A2. Partial light A1 is immediately reflected back, while partial light A2 is transmitted into the cavity of the first quartz capillary 2 and continues to propagate to the right to the second reflecting surface 5. After reaching the second reflecting surface, partial light A2 is split into two parts again: partial light A21 and partial light A22. Partial light A21 is reflected back and propagates to the left through the cavity of the first quartz capillary 2. Partial light A22 is transmitted into the dual-channel fiber 3. However, this part of the light will experience a large loss during transmission in the 5-6 cm long dual-channel fiber 3, and will not undergo a third reflection to generate interference signals. The portion of light A21 reflected back by the second reflecting surface 5 passes through the cavity of the first quartz capillary 2 and reaches the first reflecting surface 4, where it undergoes partial reflection and transmission again… This process continues many times, generating a series of reflected beams with gradually decreasing intensity. The portion of light A211 transmitted through the first reflecting surface 4 and the portion of light A1 reflected by the first reflecting surface 4 propagate in the single-mode fiber 1, but there is an optical path difference between them. When these two beams are finally received by the optical modem, they meet and superimpose, forming an interference spectrum. When the liquid to be tested enters from the inlet 7, flows through the second quartz capillary 6, and then through the second microchannel 32 of the dual-channel fiber 3 into the cavity of the first quartz capillary 2, the change in the refractive index of the medium within the cavity of the first quartz capillary 2 causes a phase change in the interference spectrum, manifested as a wavelength shift in the interference valley. By using an external controller to monitor the amount of this shift in the interference spectrum in real time, high-sensitivity, real-time detection of the liquid's refractive index is achieved.

[0040] In summary, this application utilizes staggered fusion splicing technology to physically define independent inlet and outlet channels. The inlet and outlet are respectively positioned on two independent microchannels and connected internally by a quartz capillary, forming a physically separated U-shaped microfluidic path. This greatly facilitates liquid injection and replacement. Due to the unobstructed and directional flow path, the test liquid can be easily pushed in by subsequent samples or cleaning fluid from the inlet and directly discharged from the outlet, effectively avoiding sample residue and cross-contamination within the sensing cavity, thus improving the accuracy and repeatability of the detection. All splicing steps can be completed using a fiber optic fusion splicer. By controlling the length of the quartz capillary and the splicing parameters, alignment and misalignment can be precisely controlled, resulting in good process repeatability and suitability for batch production.

[0041] It should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A reflective microcurrent sensing device integrating dual-channel optical fiber and capillary, characterized in that: The optical fiber includes a dual-channel fiber. Inside the dual-channel fiber, there are two independent microchannels that run through each other along the axis. One end of the first quartz capillary is fused to the single-mode fiber to form the first light reflecting surface, and the other end is fused to the input ends of both microchannels of the dual-channel fiber to form the second light reflecting surface. The first quartz capillary is connected to both microchannels. The output end of the dual-channel fiber is fused to the second quartz capillary in a staggered manner, so that the two microchannels of the dual-channel fiber become the liquid inlet channel and the liquid outlet channel, respectively. The second quartz capillary is used for liquid inlet, and the single-mode fiber is used to connect to the optical modem.

2. The reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 1, characterized in that: The two microchannels are the first microchannel and the second microchannel. One end of the second quartz capillary is fused to the output end of the second microchannel and is offset from the first microchannel, so that the second microchannel becomes the liquid inlet channel and the first microchannel becomes the liquid outlet channel.

3. The reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 2, characterized in that: The cross-sections of the first and second microchannels can be any one of circular, semi-circular, or elliptical shapes.

4. The reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 2, characterized in that: The first and second microchannels are set in parallel.

5. The reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 2, characterized in that: The first microchannel and the second microchannel are set at an angle, with the first microchannel tilted downward from the input end to the output end, with an tilt angle ranging from 3° to 10°, and the second microchannel tilted upward from the input end to the output end, with an tilt angle ranging from 3° to 10°.

6. The reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 1, characterized in that: The open end of the second quartz capillary is connected to a rubber hose as an inlet, and the rubber hose is connected to a syringe controlled by a microfluidic pump.

7. The reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 1, characterized in that: The single-mode fiber is a standard single-mode fiber with an outer diameter of 125 micrometers and an inner diameter of 9 micrometers.

8. The reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 1, characterized in that: The first quartz capillary has an outer diameter of 125 micrometers, an inner diameter of 75 micrometers, and a length of 120-180 micrometers.

9. The reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 1, characterized in that: The second quartz capillary has an outer diameter of 60 micrometers, an inner diameter of 45 micrometers, and a length of 120-180 micrometers.

10. A reflective microcurrent sensing device integrating dual-channel optical fiber and capillary as described in claim 1, characterized in that: The dual-channel optical fiber is 5-6 cm long, has an outer diameter of 125 micrometers, and an inner diameter of 35-45 micrometers for each microchannel.

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