Zanthoxylum nitidum micro-fluidic chip and preparation method thereof

Abstract

The invention discloses a two-sided micro-fluidic chip and a preparation method thereof, and belongs to the field of sweat sensing. The microfluidic chip is divided into a skin attaching layer, a microfluidic channel layer and a top layer from bottom to top, the microfluidic channel layer comprises a main flow channel and a plurality of cavities, the main flow channel is encircled to form a circular or elliptical semi-closed ring structure with an opening, the central area is provided with a cavity as a liquid inlet, and the main flow channel is also sequentially connected and communicated with the plurality of cavities on the outer side of the semi-closed ring structure; an arrow-shaped explosion valve is arranged between any two adjacent sweat storage pools; and the arrow points are consistent with the liquid flowing direction. The interior of the chip becomes hydrophilic through chemical reagent treatment, and the exterior of the chip still keeps hydrophobic. According to the invention, an explosion valve structure is introduced, and meanwhile, hydrophilicity is designed, so that sequential filling of liquid in the chip is realized. And under the influence of the explosion pressure, the explosion valve structure can block the circulation of the liquid in the flow channel until the previous flow channel and the liquid storage tank are completely filled, so that the mixing of samples in different time periods is avoided.

Description

Technical Field

[0001] The invention relates to a Janus microfluidic chip for collecting sweat and a preparation method thereof, and belongs to the field of sweat sensing. Background Art

[0002] Microfluidic chips can be used in the field of sweat sensing. Microfluidic technology is used to collect and store sweat, and electrochemical sensing or Raman detection is used to measure physiological indicators in sweat, thereby achieving sweat sensing. This sweat collection method has significant advantages in the field of sweat sensing. First, the sample volume required is very small, and the required sweat volume can be as low as microliters or even nanoliters. In addition, the chip is small in size and light in weight, making it easy to integrate into wearable devices.

[0003] The commonly used material for microfluidic chips is polydimethylsiloxane (PDMS), which has many advantages such as excellent biocompatibility, thermal stability and flexibility, and has great advantages in the field of sweat collection. However, since the PDMS material itself has strong hydrophobicity, the liquid to be tested needs external force to be pumped into the chip, which greatly reduces the collection efficiency and makes it impossible to make the chip wearable. At the same time, the liquid flows randomly inside the chip, and it is impossible to distinguish samples collected at different time periods. These problems limit the practicality of microfluidic chips for sweat collection. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a microfluidic chip and a preparation method thereof, to solve the problem that in a microfluidic chip used for sweat collection and detection, the liquid cannot flow into the chip autonomously due to the hydrophobicity of the PMDS material itself, and to use a "burst valve" structure to achieve sequential flow of samples inside the chip.

[0005] One of the present inventions is implemented as follows: a microfluidic chip based on PDMS material, which is divided into a skin-attaching layer, a microfluidic channel layer, and a top layer from bottom to top; a microfluidic channel structure exists in the microfluidic channel layer, which includes: a main channel, multiple cavities, and the cavities are hole structures that are transparent from top to bottom; the main channel is surrounded by a semi-closed ring structure such as a circle or an ellipse with an opening, wherein a cavity is provided in the central area of ​​the semi-closed ring structure as a liquid inlet, and the main channel is also connected and communicated with multiple cavities outside the semi-closed ring structure in sequence, and the multiple cavities outside the semi-closed ring structure constitute a sweat storage pool for storing sweat, and an arrow-shaped structural channel "explosion valve" is provided on the main channel between any two adjacent sweat storage pools; the arrow points in the same direction as the liquid flow direction. The liquid inlet is connected and communicated with the starting end of the main channel, and the connection and communication adopts a microchannel connection and communication.

[0006] A micropore array area that is transparent from top to bottom is provided in the center of the skin-contacting layer. The micropores are used to transport sweat. The micropore array area corresponds to the liquid inlet of the microfluidic channel layer from top to bottom, and together they constitute the liquid inlet of the chip; the cavity at the end of the main channel also serves as the liquid outlet; the top layer is used to seal the chip, and the top layer is provided with a plurality of micropore array areas, each micropore array area corresponds to the area of ​​the cavity of the aforementioned microfluidic channel layer, and the micropores of the micropore array are used to balance the internal and external air pressures; wherein the inside of the chip becomes hydrophilic after being treated with chemical reagents, while the outside of the chip still maintains the hydrophobicity of the PDMS material; further, the chemical reagent treatment to become hydrophilic refers to the use of PVA treatment to become hydrophilic.

[0007] Furthermore, the diameter of the micropore array region of the skin-applying layer is 3 mm, the micropore spacing in the micropore array is 200 μm, and the micropore diameter is 82.5 μm.

[0008] Furthermore, the top layer is used to seal the chip, and the top layer is provided with a plurality of micropore array areas, each micropore array area corresponds to a cavity area outside the semi-closed ring structure of the cavity microfluidic channel layer, and the micropore array is used to balance the internal and external air pressures. The spacing between adjacent micropores of the micropore array of the top layer is 400 μm, and the micropore diameter is 30 μm.

[0009] Furthermore, the width of the main channel is 200 μm, and there is an arrow-shaped "bursting valve" structure in the main channel, and the arrow points in the same direction as the liquid flow. The starting width of the arrow-shaped "bursting valve" structure is 600 μm, and the ending width is consistent with the width of the main channel, both of which are 200 μm. The angles between the starting and ending points and the main channel are 90° and 135° respectively.

[0010] Furthermore, the thickness of the skin-applying layer, the internal flow channel layer, and the top layer are all 200 μm, and the chip diameter is 30 mm. The second aspect of the present invention is achieved as follows: A method for preparing a microfluidic chip based on a Janus structure, specifically comprising the following steps:

[0011] (1) stirring the PDMS precursor and the crosslinking agent for 30 min; applying the mixed solution evenly on the chip template and the cover template, respectively, and thermally curing at 90° C. for 2 h;

[0012] The cured films are removed from the two templates respectively to obtain a PDMS chip body with a microfluidic channel structure and a skin-attaching layer, wherein the chip body correspondingly includes a top layer and a microfluidic channel layer;

[0013] (2) using a high-power laser to prepare an array of air holes in all cavities except the liquid inlet on the top layer of the PDMS chip body;

[0014] At a position of the skin-applying layer corresponding to the liquid inlet, a micropore array corresponding to the liquid inlet is prepared by using a high-power laser;

[0015] (3) bonding the chip body and the skin-attaching layer by oxygen plasma treatment to obtain a microfluidic chip;

[0016] (4) The interior of the microfluidic chip is hydrophilized by growing a PVA hydrophilic coating inside the chip, thereby forming a Janus structure.

[0017] Furthermore, step (2) using a laser to prepare a microwell array on the PDMS chip material is specifically as follows: using a microscope to focus the laser spot to a micrometer level, and irradiating the surface of the PDMS material to prepare microwells, and using a displacement platform and control software to achieve the preparation of the microwell array;

[0018] Furthermore, the step (3) of bonding the microfluidic chip with oxygen plasma specifically comprises: placing the chip body and the skin-attaching layer into the chamber of a plasma etcher, evacuating the chamber after sealing, and processing for 120 seconds, and then taking them out and quickly assembling them to form a strong chemical bond;

[0019] Furthermore, the step (4) of growing a PVA hydrophilic coating inside the chip is specifically as follows: after bonding is completed, due to the oxygen plasma treatment, the chip is in a hydrophilic state for a short period of time, at which time a PVA colloidal aqueous solution is dripped into the chip from the liquid inlet, and the PVA solution residue on the outside of the chip is cleaned off, and after being placed in an oven for thermal curing, a hydrophilic coating is formed inside the chip, and at the same time, the PDMS outside the chip returns to a hydrophobic state, thereby forming a two-sided structure in which the inside of the chip is hydrophilic and the outside of the chip is hydrophobic.

[0020] The method for using a microfluidic chip of the present invention is characterized in that a skin-adhering layer is attached to the skin surface, sweat at a first moment enters from a liquid inlet and is then introduced into a first sweat storage pool corresponding to a main channel, when the first sweat storage pool is full, sweat enters into a corresponding second sweat storage pool at a second moment, when the second sweat storage pool is full, sweat enters into a corresponding third sweat storage pool at a third moment, and so on and so forth until the last sweat storage pool, i.e., a liquid outlet, is filled or the sweat enters into a certain sweat storage pool in the middle and stops as required; due to the existence of a "bursting valve" structure, sweat in the sweat storage pool cannot flow at will, thereby avoiding mixing of samples in different time periods.

[0021] The advantages of the present invention are as follows: a microfluidic chip and a preparation method thereof can be applied to the collection and detection of human sweat. The difference in hydrophilicity between the inner and outer sides of the microporous array at the liquid inlet of the chip is obtained by growing a PVA hydrophilic coating. This difference in two-sidedness produces a one-way conduction effect of the liquid, that is, the liquid spontaneously moves from the hydrophobic outer side of the microporous array to the hydrophilic inner side, and the liquid is prohibited from overflowing to the hydrophobic outer side without external force, which effectively improves the collection efficiency of the microfluidic chip for body surface sweat;

[0022] In addition, the present invention introduces a "bursting valve" structure based on conventional microfluidic technology, and realizes the sequential filling of liquid inside the chip through bursting pressure. Under the influence of bursting pressure, the "bursting valve" structure will hinder the flow of liquid in the flow channel until the previous flow channel and liquid reservoir are filled, so that the collected sweat is filled into each liquid reservoir in sequence, avoiding the mixing of samples in different time periods. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0024] Figure 1 Schematic diagram of the structure of the microfluidic chip according to an embodiment of the present invention.

[0025] Figure 2 Schematic diagram of the structure of the microfluidic channel of an embodiment of the present invention.

[0026] Figure 3 The figure is a flowchart of the steps of an embodiment of the present invention.

[0027] Figure 4 This is a diagram showing the effect of the Janus structure in an embodiment of the present invention.

[0028] Figure 5 This is a diagram showing the effect of the "bursting valve" structure in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] See also Figure 1 and Figure 2As shown in the figure, the microfluidic chip of the present invention is formed by bonding three layers of PDMS film, and its structure includes: from bottom to top, it is divided into a skin-applying layer, a microfluidic channel layer, and a top layer, the chip diameter is 30mm, and the thickness of the skin-applying layer, the internal channel layer, and the top layer is 200μm. The inside of the chip becomes hydrophilic after being treated with chemical reagents, while the outside of the chip still maintains the hydrophobicity of the PDMS material; there is a micropore array area for transporting sweat in the central area of ​​the skin-applying layer, the diameter of the area is 3mm, the spacing between the micropore arrays is 200μm, and the diameter of the micropores is 82.5μm; there is a microfluidic channel structure in the microfluidic channel layer, which includes: a main channel, a plurality of cavities connected to the main channel, wherein the cavity located in the central area is connected to the aforementioned The microporous array of the skin-friendly layer together constitutes the liquid inlet of the chip, and the remaining cavities serve as sweat storage pools for storing sweat, and the cavity at the end of the flow channel also serves as the liquid outlet; the width of the main channel is 200μm, and there is an arrow-shaped "burst valve" structure in the main channel, and the arrow points in the same direction as the liquid flow. The starting width of the arrow-shaped "burst valve" structure is 600μm, and the ending width is consistent with the width of the main channel, both of which are 200μm, and the angles between the starting and the end and the main channel are 90° and 135° respectively; the top layer is used to seal the chip, and the top layer corresponds to the area of ​​the cavity of the aforementioned microfluidic channel layer, and there is a microporous array for balancing the internal and external air pressures, the microporous array spacing is 400μm, and the microporous diameter is 30μm.

[0030] like Figure 3 As shown, the method for preparing the microfluidic chip of the present invention specifically comprises the following steps:

[0031] Prepare PDMS gel and apply it on the mold, and obtain the microfluidic chip body (microfluidic channel layer and top layer) and the skin-attaching layer after thermal curing;

[0032] In each cavity of the chip body, a microhole array for balancing the internal and external air pressure is prepared by laser processing;

[0033] In the central area of ​​the skin-contacting layer, a micropore array for transporting sweat is prepared by laser processing;

[0034] Bonding the chip body and the skin-attaching layer by oxygen plasma treatment to obtain a microfluidic chip;

[0035] The inside of the microfluidic chip is hydrophilized by growing a PVA hydrophilic coating inside the chip, thereby forming a Janus structure.

[0036] The method of preparing a micropore array on a PDMS material using a laser specifically comprises: focusing a laser spot to a micrometer level using a microscope, and irradiating the laser spot on the surface of the PDMS material to prepare micropores, and using a displacement platform and control software to realize the preparation of the micropore array;

[0037] The method of bonding the microfluidic chip with oxygen plasma is as follows: the chip body and the cover plate are placed in the chamber of a plasma etcher, vacuumized after sealing, and processed for 60 seconds, and two sample films are taken out and quickly assembled to form a strong chemical bond;

[0038] Specifically, the PVA hydrophilic coating is grown inside the chip as follows: after bonding is completed, the chip is in a hydrophilic state for a short period of time due to oxygen plasma treatment, at which time the PVA solution is introduced into the chip, and the PVA solution residue on the outside of the chip is cleaned off, and the chip is placed in an oven for thermal curing, so that a hydrophilic coating is formed inside the chip, and at the same time, the PDMS outside the chip is restored to a hydrophobic state, thereby forming a two-sided structure in which the inside of the chip is hydrophilic and the outside of the chip is hydrophobic;

[0039] The effect of Janus structure on the droplets on the hydrophilic and hydrophobic sides is as follows: Figure 4 As shown, the droplets on the hydrophilic side cannot pass through the Janus microporous membrane, while the droplets on the hydrophobic side pass through the microporous membrane quickly.

[0040] The microfluidic chip has the following effects: Figure 5 As shown, due to the existence of the Janus structure, the liquid spontaneously flows into the chip. As shown in Figures S1 and S2, before the cavity before the "bursting valve" is filled, the liquid cannot pass through the bursting valve; when the previous cavity is filled, the liquid flows through the bursting valve and enters the next cavity, and the above process is repeated until the entire chip is filled.

Claims

1. A two-sided microfluidic chip based on PDMS material, characterized in that: From bottom to top, it is divided into a skin-applying layer, a microfluidic channel layer, and a top layer; the microfluidic channel layer contains a microfluidic channel structure, which includes: a main channel, multiple cavities, and the cavities are hole structures that are transparent from top to bottom; the main channel is surrounded by a semi-closed ring structure such as a circle or an ellipse with an opening, wherein a cavity is provided in the central area of ​​the semi-closed ring structure as a liquid inlet, and the main channel is also connected and communicated with multiple cavities outside the semi-closed ring structure in sequence, and the multiple cavities outside the semi-closed ring structure constitute a sweat storage pool for storing sweat, and an arrow-shaped structural channel "bursting valve" is provided on the main channel between any two adjacent sweat storage pools; the arrow points in the same direction as the liquid flow direction; the liquid inlet is connected and communicated with the starting end of the main channel, and the connection is connected and communicated by a microchannel connection; A microporous array area that is transparent from top to bottom is provided in the center of the skin-applying layer. The micropores are used to transport sweat. The microporous array area corresponds to the liquid inlet of the microfluidic channel layer from top to bottom, and together they constitute the liquid inlet of the chip; the cavity at the end of the main channel also serves as the liquid outlet; the top layer is used to seal the chip, and the top layer is provided with a plurality of microporous array areas, each of which corresponds to the area of ​​the cavity of the aforementioned microfluidic channel layer, and the micropores of the microporous array are used to balance the internal and external air pressures; the inside of the chip becomes hydrophilic after being treated with chemical reagents, while the outside of the chip still maintains the hydrophobicity of the PDMS material.

2. A two-sided microfluidic chip based on PDMS material according to claim 1, characterized in that: The chemical reagent treatment to become hydrophilic refers to the use of PVA treatment to become hydrophilic.

3. A two-sided microfluidic chip based on PDMS material according to claim 1, characterized in that: The diameter of the micropore array area of ​​the skin-attaching layer is 3mm, the micropore spacing in the micropore array is 200μm, and the micropore diameter is 82.5μm; the top layer is used to seal the chip, and the top layer is provided with multiple micropore array areas, each micropore array area corresponds to a cavity area outside the semi-closed ring structure of the cavity microfluidic channel layer, and the micropore array is used to balance the internal and external air pressure. The spacing between adjacent micropores of the micropore array in the top layer is 400μm, and the micropore diameter is 30μm.

4. A two-sided microfluidic chip based on PDMS material according to claim 1, characterized in that: The width of the main channel is 200 μm, and there is an arrow-shaped "bursting valve" structure in the main channel, and the arrow points in the same direction as the liquid flow; the starting width of the arrow-shaped "bursting valve" structure is 600 μm, and the ending width is consistent with the width of the main channel, both of which are 200 μm.

5. A two-sided microfluidic chip based on PDMS material according to claim 1, characterized in that: The angles between the start and end of the main channel are 90° and 135° respectively.

6. A two-sided microfluidic chip based on PDMS material according to claim 1, characterized in that: The thickness of the skin layer, internal flow channel layer and top layer are all 200μm, and the chip diameter is 30mm.

7. A method for preparing a two-sided microfluidic chip based on PDMS material according to any one of claims 1 to 6, characterized in that: The specific steps include: (1) stirring the PDMS precursor and the crosslinking agent for 30 min; applying the mixed solution evenly on the chip template and the cover template, respectively, and thermally curing at 90° C. for 2 h; The cured films are removed from the two templates respectively to obtain a PDMS chip body with a microfluidic channel structure and a skin-attaching layer, wherein the chip body correspondingly includes a top layer and a microfluidic channel layer; (2) using a high-power laser to prepare an array of air holes in all cavities except the liquid inlet on the top layer of the PDMS chip body; At a position of the skin-applying layer corresponding to the liquid inlet, a micropore array corresponding to the liquid inlet is prepared by using a high-power laser; (3) bonding the chip body and the skin-attaching layer by oxygen plasma treatment to obtain a microfluidic chip; (4) The interior of the microfluidic chip is hydrophilized by growing a PVA hydrophilic coating inside the chip, thereby forming a Janus structure.

8. The method according to claim 7, characterized in that Step (2) using a laser to prepare a microwell array on the PDMS chip material is specifically as follows: using a microscope to focus the laser spot to the micrometer level, and irradiating the surface of the PDMS material to prepare microwells, and using a displacement platform and control software to achieve the preparation of the microwell array; The step (3) of bonding the microfluidic chip with oxygen plasma is specifically as follows: the chip body and the skin-attaching layer are placed in the chamber of a plasma etcher, and vacuumized after sealing, and processed for 120 seconds, and then quickly assembled after being taken out to form a strong chemical bond; The step (4) of growing a PVA hydrophilic coating inside the chip is specifically as follows: after bonding is completed, the chip is in a hydrophilic state for a short period of time due to oxygen plasma treatment, at which time a PVA colloidal aqueous solution is dripped into the chip from the liquid inlet, and the PVA solution residue on the outside of the chip is cleaned off. After being placed in an oven for thermal curing, a hydrophilic coating is formed inside the chip, and at the same time, the PDMS outside the chip returns to a hydrophobic state, thereby forming a two-sided structure in which the inside of the chip is hydrophilic and the outside of the chip is hydrophobic.

9. A method for using a two-sided microfluidic chip based on PDMS material according to any one of claims 1 to 6, characterized in that: The skin-attaching layer is attached to the skin surface, and the sweat at the first moment enters from the liquid inlet and is then guided into the first sweat storage pool corresponding to the main channel. When the first sweat storage pool is full, the sweat enters the corresponding second sweat storage pool at the second moment. When the second sweat storage pool is full, the sweat enters the corresponding third sweat storage pool at the third moment, and so on until the last sweat storage pool, i.e. the liquid outlet, is filled or the sweat enters a certain sweat storage pool in the middle and stops as needed. Due to the existence of the "bursting valve" structure, the sweat in the sweat storage pool cannot flow freely, thereby avoiding the mixing of samples in different time periods.

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