Sweat collection module and wearable microfluidic device for sweat collection

Abstract

The invention discloses a sweat collecting module for absorbing skin sweat. The sweat collection module comprises a first base film, a hydrophilic laser-induced graphene (LIG) layer prepared on the first base film by using a carbon dioxide laser, and a hydrophobic laser-induced graphene (LIG) microarray prepared by carrying out secondary laser scanning on the hydrophilic laser-induced graphene (LIG) layer. According to the sweat collecting module, efficient and active sweat capturing can be achieved, and the module is of a composite structure subjected to precise patterning design. The super-hydrophobic microarray on the upper layer serves as a physical barrier, sweat is restrained in a specific hydrophilic channel, and disordered spreading and volatilization of the sweat in the collecting cavity are effectively prevented. According to the collaborative design of the hydrophilic substrate and the hydrophobic array, strong capillary force is created, and rapid and efficient capture and enrichment of trace sweat are achieved. The sweat collecting capacity of the substrate is obviously superior to that of a traditional substrate lacking the micro-nano structure design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sweat health monitoring, and particularly relates to a sweat collection module and a wearable microfluidic device for sweat collection. BACKGROUND

[0002] Current wearable microfluidic devices for sweat collection are mainly based on polydimethylsiloxane (PDMS) material and enhance its performance through various strategies. For example, Wang et al. realized the self-driven, droplet collection and transportation of sweat by capillary force through the construction of superhydrophobic inlets and nanofiber-reinforced superhydrophilic microchannels, and integrated impedance and colorimetric analysis for multi-parameter detection. In order to overcome the hindrance of the inherent hydrophobicity of PDMS to sweat collection at low sweat rate, Lu et al. developed a PDMS-polyethylene glycol (PEG) block copolymer composite material, which was prepared by a simple "one-pot" soft lithography technology. The material can significantly reduce the threshold pressure of sweat into the microfluidic channel, thereby more effectively capturing the initial sweat rich in biomarkers.

[0003] However, these technologies and materials still have obvious deficiencies. First, the hydrophobicity of PDMS is a core challenge, although modification methods such as plasma treatment or PEG blending can improve hydrophilicity, but its effect often recovers hydrophobicity over time, lacking long-term stability. Second, the PDMS material itself has non-specific adsorption to small molecule analytes (such as hormones, metabolites), which may interfere with the accuracy of subsequent high-precision analysis (such as mass spectrometry). Third, the improvement of hydrophilicity may exacerbate sweat evaporation due to the increase of wetted area, affecting the reliability of quantitative analysis. In addition, the manufacturing process of most devices relies on complex processes such as 3D printing mold, photolithography and plasma bonding, which faces challenges in cost, scalability and large-scale integration with flexible electronics. Finally, the adaptability of existing systems to static or low sweat secretion rate scenarios is still poor, limiting their daily application in non-athletic populations (such as clinical patients). SUMMARY

[0004] Based on the problems in the prior art, the present application provides a sweat collection module for absorbing skin sweat, which comprises a first base film, a hydrophilic laser-induced graphene (LIG) layer prepared on the first base film using a carbon dioxide laser, and a hydrophobic laser-induced graphene (LIG) microarray prepared by secondary laser scanning on the hydrophilic laser-induced graphene (LIG) layer.

[0005] On the basis of the above scheme, when preparing the hydrophilic laser-induced graphene layer, the power of the carbon dioxide laser is 5.2-6.0 W; when preparing the hydrophobic laser-induced graphene microarray, the power of the carbon dioxide laser is 3.2-4.0 W.

[0006] On the basis of the above scheme, the material of the first base film is a polyimide (PI) film.

[0007] The application also provides a wearable microfluidic device for sweat collection, comprising a sensor for detecting sweat, and further comprising the sweat collection module for absorbing sweat from the skin.

[0008] On the basis of the above scheme, an inlet microchannel module for transporting sweat collected by the sweat collection module to the detection chamber is further included, the inlet microchannel module comprising a second base film, a hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole trapezoid prepared on the second base film using a carbon dioxide laser, and a first through slot arranged at the center of the second base film, with the narrow bottom of the trapezoid being close to the first through slot.

[0009] On the basis of the above scheme, a sweat inlet module and a sweat collection chamber module for collecting sweat collected by the sweat collection module are sequentially arranged between the sweat collection module and the inlet microchannel module.

[0010] On the basis of the above scheme, a first through hole is arranged in the middle of the hydrophilic laser-induced graphene (LIG) layer of the sweat collection module, the sweat inlet module comprises a third base film, and the third base film is provided with a second through hole corresponding to the first through hole; the sweat collection chamber module comprises a fourth base film, and the fourth base film is provided with a third through hole corresponding to the second through hole, and the middle of the fourth base film is provided with a second through slot in communication with the third through hole.

[0011] On the basis of the above scheme, an outlet microchannel module for outputting the detected sweat from the detection chamber and a sweat outlet module for forming a sweat outflow channel arranged between the inlet microchannel module and the outlet microchannel module are arranged between the inlet microchannel module and the sensor.

[0012] On the basis of the above scheme, the sweat outlet module comprises a fifth base film, and the fifth base film is provided with a V-shaped channel penetrating up and down, and the middle of the fifth base film is provided with a third through slot in communication with the V-shaped channel. The outlet microchannel module comprises a sixth base film, a second hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole trapezoid prepared on the sixth base film using a carbon dioxide laser, and a fourth through slot arranged at the center of the sixth base film. One side of the wide bottom of the second hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole trapezoid is close to the fourth through slot. The V-shaped channel provides a space channel for the discharge of sweat.

[0013] In the above scheme, when preparing the hydrophilic laser-induced graphene (LIG) microarray and the second hydrophilic laser-induced graphene (LIG) microarray, the power of the carbon dioxide laser is 5.2-6.0 W.

[0014] The sweat collection module of the present application can realize efficient active sweat capture, and the module is a composite structure designed with precision patterning. The upper super-hydrophobic microarray acts as a physical barrier to confine the sweat in specific hydrophilic channels, effectively preventing the disordered spreading and evaporation of sweat in the collection cavity. The synergistic design of "hydrophilic substrate + hydrophobic array" creates strong capillary force, realizing rapid and efficient capture and enrichment of micro-sweat. Its sweat collection capacity is significantly better than that of traditional substrates lacking such micro-nano structure design.

[0015] The overall trapezoidal hydrophilic laser-induced graphene (LIG) microarray of the present application can generate asymmetric wetting dynamics, thereby driving the one-way transmission of fluid to the detection chamber. In addition, when inclined at 45°, the overall trapezoidal hydrophilic laser-induced graphene (LIG) microarray of the present application exhibits effective anti-backflow ability by maintaining one-way transmission of fluid under the action of gravity.

[0016] The arrangement of the overall trapezoidal hydrophilic laser-induced graphene (LIG) microarray in the wearable microfluidic device for sweat collection of the present application has a precise gradient density change, which means that the spatial distribution of the microstructure gradually changes from the inlet to the outlet of the channel, thereby forming an asymmetric surface energy potential field. This gradient density design generates an unbalanced capillary force (i.e. Laplace pressure difference) at the front and back ends of the droplet. This pressure difference acts as a driving force to autonomously and directionally push the sweat from the sweat collection module (inlet) to the detection chamber (outlet) without any external power source. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a schematic diagram of the structure of the sweat collection module in Example 1 of the present application; Figure 2 FIG. 2 is a scanning electron microscope image of laser-induced graphene prepared using different powers in Example 1 of the present application; Figure 3 FIG. 3 is a performance test diagram of laser-induced graphene prepared using two powers in Example 1 of the present application; Figure 4 FIG. 4 is a contact angle change diagram of laser-induced graphene prepared using different powers in Example 1 of the present application; Figure 5 FIG. 5 is a schematic diagram of the structure of the wearable microfluidic device in Example 2 of the present application; Figure 6Structure diagram of an inlet microchannel module in a wearable microfluidic device of embodiment 2 of the present application; Figure 7 Relative mobility of different material and structure inlet microchannel modules in embodiment 2 of the present application; Figure 8 Comparison of directional transport capacity of different structure arrays; Figure 9 Comparison of backflow prevention capacity of different structure arrays under a 45° inclination condition; Figure 10 Schematic diagram of sweat flow in a wearable microfluidic device of embodiment 2 of the present application. DETAILED DESCRIPTION

[0018] Embodiment 1 As shown in Figure 2 A sweat collection module for absorbing skin sweat, the sweat collection module comprising a first base film 1-1, a hydrophilic laser-induced graphene (LIG) layer 1-2 prepared on the first base film 1-1 using a carbon dioxide laser, and a hydrophobic laser-induced graphene (LIG) microarray 1-3 prepared on the hydrophilic laser-induced graphene (LIG) layer 1-2 by secondary laser scanning.

[0019] Figure 2 In the embodiment, the hydrophilic laser-induced graphene (LIG) layer 1-2 is several, and is uniformly distributed on the outer periphery of the first base film 1-1.

[0020] Specifically, it is a common technical means to obtain LIG with different characteristics using different laser scanning powers. The power is converted from the laser intensity, and when the laser intensity is 100%, the power is 40 W. The laser intensity needs to be adjusted according to different powers during preparation.

[0021] When preparing the hydrophilic LIG layer, the power used is 5.2-6.0 W (preferably 6 W), and when preparing the hydrophobic LIG microarray, the power used is 3.2-4.0 W (preferably 3.2 W), and the scanning speed is 10%.

[0022] As a preferred scheme, the material of the first base film 1-1 is a polyimide (PI) film; and the hydrophilic laser-induced graphene (LIG) layer is circular as a whole.

[0023] The sweat collection module of the present application is composed of a hydrophilic laser-induced graphene substrate and a super-hydrophobic laser-induced graphene microarray, and realizes rapid sweat absorption and effective collection through capillary action.

[0024] The laser-induced graphene prepared by carbon dioxide lasers with different powers was tested for performance using a scanning electron microscope and an optical contact angle measuring instrument, and the results are shown inFigures 2-4 As shown, Figure 2 The results show that hydrophilicity / hydrophobicity tests on laser-induced graphene (LIG) prepared at different powers reveal a relatively regular surface morphology at lower powers (3.2-4.0 W), evolving into a more porous and irregular structure at medium powers (5.2-6.0 W), and finally forming a loose and diverse structure at higher powers (≥6.4 W). This morphological evolution is directly related to changes in wettability, such as... Figure 4 As shown, with the increase of laser power, the contact angle exhibits a characteristic trend of first decreasing and then increasing. Figure 3 As shown, the optimal hydrophilicity (minimum contact angle 17.3°) obtained at 6.0 W, combined with the superhydrophobicity (contact angle 119.9°) obtained at lower power (3.2 W), forms a precisely controlled wetting pattern.

[0025] The sweat collection module of this invention enables highly efficient and active sweat capture. This module is a precisely patterned composite structure. Its substrate is a hydrophilic LIG circular region fabricated with high laser power (5.2-6.0 W), which exhibits strong capillary adsorption of sweat. On this hydrophilic substrate, a superhydrophobic LIG microarray is constructed using a secondary laser scan (using lower power 3.2-4.0 W). These microarrays act as "islands," restricting the lateral diffusion of sweat. When sweat is secreted from the skin, the hydrophilic LIG substrate rapidly adsorbs and locks it in. The upper superhydrophobic microarray acts as a physical barrier, confining the sweat within specific hydrophilic channels, effectively preventing disordered spread and evaporation of sweat within the collection chamber. This synergistic design of "hydrophilic substrate + hydrophobic array" creates powerful capillary forces, enabling rapid and efficient capture and enrichment of minute amounts of sweat. Its sweat collection capacity is significantly superior to traditional substrates lacking this micro / nanostructure design.

[0026] Example 2 like Figure 5 and Figure 6 As shown, the present invention provides a wearable microfluidic device for sweat collection, including a sensor 7 for detecting sweat, characterized in that it further includes a sweat collection module 1 for absorbing sweat from the skin, as described in Example 1.

[0027] Based on the above technical scheme, the wearable microfluidic device for sweat collection in the embodiment further comprises an inlet microchannel module 2 for transporting the sweat collected by the sweat collection module 1 to the detection chamber, the inlet microchannel module 2 comprises a second base film 2-1, a hydrophilic laser-induced graphene (LIG) microarray 2-2 in the shape of a whole trapezoid prepared on the second base film 2-1 by using a carbon dioxide laser, and a first through groove 2-3 arranged at the center of the second base film 2-1, and the narrow bottom of the trapezoid is close to the first through groove 2-3.

[0028] Specifically, when the hydrophilic laser-induced graphene (LIG) microarray 2-2 is prepared, the power used is 5.2-6.0 W, and the scanning speed is 8%.

[0029] The inlet microchannel module 2 of the present application uses a hydrophilic laser-induced graphene (LIG) microarray 2-2 in the shape of a whole trapezoid, which drives the fluid to unidirectionally transport to the detection chamber by constructing an asymmetric wetting dynamics channel, and the narrow bottom of the trapezoid is close to the first through groove 2-3.

[0030] Fluid flow test: The hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole trapezoid (preparation power 6 W), the ordinary PI substrate and the hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole uniform rectangle (preparation power 6 W) are respectively placed horizontally on a glass plate, 100 μL of deionized water is respectively added to the middle of each, and a camera is used to continuously capture for 4 s, the relative migration rate of the liquid drops in the ST microchannel under different array density compositions is calculated by comparing the moving distance of the water drops within 4 s, so as to verify the directional transport capacity of the ST microchannel under different array density compositions.

[0031] The test results are shown in Figure 7 , Figure 8 and Figure 9 (Fig., Plane represents the ordinary PI substrate, Uniform represents the hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole uniform rectangle, and Gradient represents the hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole trapezoid.

[0032] The hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole trapezoid (preparation power 6 W), the ordinary PI substrate and the hydrophilic laser-induced graphene (LIG) microarray in the shape of a whole uniform rectangle (preparation power 6 W) are respectively placed on a 45° inclined glass plate, 100 μL of black ink is respectively added to the top of each, and a camera is used to continuously capture for 16 s, and the flow of the liquid drops in different time periods is observed to verify the ability of the ST microchannel with different array densities to prevent fluid backflow under the condition of being inclined by 45°.

[0033] FromFigure 8 The results show that the trapezoidal hydrophilic laser-induced graphene (LIG) microarray of this invention can generate asymmetric wetting dynamics, thereby driving unidirectional fluid transport to the detection chamber. Its performance surpasses that of ordinary PI substrates and uniformly rectangular hydrophilic laser-induced graphene (LIG) microarrays. Figure 8 The results show that when tilted at 45°, the trapezoidal hydrophilic laser-induced graphene (LIG) microarray of this invention maintains unidirectional fluid transport under gravity, exhibiting effective backflow prevention capability. Therefore, the trapezoidal hydrophilic laser-induced graphene (LIG) microarray of this invention not only achieves unidirectional fluid transport but also possesses a certain degree of backflow prevention capability.

[0034] Sensor 7 is an existing sensor that can be used to monitor electrolytes, glucose, cortisol, etc. in sweat, and can also detect vitamin C. Further details will not be provided here.

[0035] Between the sweat collection module 1 and the inlet microchannel module 2, there are sequentially arranged a sweat inlet module 3 and a sweat collection chamber module 4 for collecting the sweat collected by the sweat collection module 1.

[0036] Specifically, the hydrophilic laser-induced graphene (LIG) layer 1-1 of the sweat collection module 1 has a through-hole 1-4 in the middle. The sweat inlet module 3 includes a third base film 3-1, on which a second through-hole 3-2 corresponding to the first through-hole 1-4 is provided. The sweat collection chamber module 4 includes a fourth base film 4-1, on which a third through-hole 4-2 corresponding to the second through-hole 3-2 is provided. A second through-groove 4-3 communicating with the third through-hole 4-2 is opened in the middle of the fourth base film 4-1.

[0037] Specifically, the thickness of the sweat inlet module 3 and the sweat collection chamber module 4 is 3-5mm. The function of the third through hole 4-2 is to provide a spatial channel for the delivery of sweat in the inlet microchannel module 2.

[0038] An outlet microchannel module 6 for outputting detected sweat into the detection chamber is provided between the inlet microchannel module 2 and the sensor 7, and a sweat outlet module 5 for forming a sweat outflow channel is provided between the inlet microchannel module 2 and the outlet microchannel module 6.

[0039] Specifically, the sweat outlet module 5 includes a fifth base membrane 5-1, on which a V-shaped channel 5-2 is provided that runs vertically through, and a third through groove 5-3 that communicates with the V-shaped channel 5-2 is opened in the middle of the fifth base membrane 5-1. Specifically, the outlet microchannel module 6 includes a sixth base film 6-1, a second hydrophilic laser-induced graphene (LIG) microarray 6-2 with an overall trapezoidal shape fabricated on the sixth base film 6-1 using a carbon dioxide laser, and a fourth through groove 6-3 disposed in the center of the sixth base film 6-1. The wide bottom side of the second hydrophilic laser-induced graphene (LIG) microarray 6-2 is close to the fourth through groove 6-3. The V-shaped channel 5-2 provides a spatial channel for the excretion of sweat.

[0040] Specifically, when preparing the second hydrophilic laser-induced graphene (LIG) microarray 6-2, the power used was 5.2-6.0 W and the scanning speed was 8%.

[0041] Specifically, the thickness of the sweat outlet module 5 and the outlet microchannel module 6 is 3-5mm.

[0042] Specifically, the first base film 1-1, the second base film 2-1, the third base film 3-1, the fourth base film 4-1, the fifth base film 5-1, and the sixth base film 6-1 are all polyimide (PI) films. The detection chamber is surrounded vertically by the sweat inlet module 3 and the sensor 7, and circumferentially by the second through groove 4-3, the first through groove 2-3, the third through groove 5-3, and the fourth through groove 6-3.

[0043] The present invention features a trapezoidal arrangement of hydrophilic laser-induced graphene (LIG) microarrays with a precise gradient density variation. This means that the spatial distribution of the microstructures gradually changes from the inlet to the outlet of the channel, thereby creating an asymmetric surface potential field. This gradient density design generates an unbalanced capillary force (i.e., a Laplace pressure difference) at the front and rear ends of the droplet. This pressure difference acts as a driving force, autonomously and directionally propelling sweat from the sweat collection module 1 (inlet) to the detection chamber (outlet) without any external power source.

[0044] Tilt the entire system at 45° to simulate the posture changes during human movement. The trapezoidal hydrophilic laser-induced graphene (LIG) microarray channels still maintain unidirectional sweat flow, effectively overcoming the effects of gravity and preventing the backflow of transported sweat to the collection end. This characteristic is crucial, ensuring the timing accuracy and stability of the sensing signal and avoiding concentration interference caused by the mixing of sweat secreted at different times. Its unidirectional perfusion performance far surpasses that of flat PI substrates or uniformly structured rectangular microchannels.

[0045] The wearable microfluidic device for sweat collection of the present invention comprises a system assembly in which a sweat collection module 1 and an inlet microchannel module 2 are three-dimensionally integrated in the form of a multilayer PI substrate. The sweat collection module 1 is directly connected to the inlet of the inlet microchannel module 2, while the outlet of the inlet microchannel module 2 is precisely pointed towards the detection chamber.

[0046] like Figure 10 As shown, in operation, the sweat is first efficiently captured by the sweat collection module 1. Then, the sweat passes through the first through-hole 1-4 and the sweat inlet module 3, entering the third through-hole 4-2 of the sweat collection chamber module 4. The sweat is then directed and continuously transported to the detection chamber by the spontaneous capillary force generated by the trapezoidal hydrophilic laser-induced graphene (LIG) microarray 2-2 on the inlet microchannel module 2. After detection by the sensor 7, the sweat is discharged through the trapezoidal second hydrophilic laser-induced graphene (LIG) microarray 6-2 on the outlet microchannel module 6.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A sweat collection module, characterized in that, The sweat collection module includes a first base film (1-1), a hydrophilic laser-induced graphene (LIG) layer (1-2) prepared on the first base film (1-1) using a carbon dioxide laser, and a hydrophobic laser-induced graphene (LIG) microarray (1-3) prepared by secondary laser scanning on the hydrophilic laser-induced graphene (LIG) layer (1-2).

2. The sweat collection module according to claim 1, characterized in that, When preparing hydrophilic laser-induced graphene layers (1-2), the power of the carbon dioxide laser was 5.2-6.0 W; When preparing hydrophobic laser-induced graphene microarrays (1-3), the power of the carbon dioxide laser is 3.2-4.0 W.

3. The sweat collection module according to claim 1, characterized in that, The material of the first base film (1-1) is a polyimide (PI) film.

4. A wearable microfluidic device for sweat collection, comprising a sensor (7) for detecting sweat, characterized in that, It also includes the sweat collection module (1) according to any one of claims 1-3.

5. The wearable microfluidic device for sweat collection according to claim 4, characterized in that, It also includes an inlet microchannel module (2) for transporting the sweat collected by the sweat collection module (1) to the detection chamber. The inlet microchannel module (2) includes a second base film (2-1) and an integrally trapezoidal hydrophilic laser-induced graphene (LIG) microarray (2-2) prepared on the second base film (2-1) using a carbon dioxide laser. A first through groove (2-3) is provided in the center of the second base film (2-1), and the narrow bottom of the trapezoid is close to the first through groove (2-3).

6. The wearable microfluidic device for sweat collection according to claim 5, characterized in that, Between the sweat collection module (1) and the inlet microchannel module (2), there is a sweat inlet module (3) and a sweat collection chamber module (4) for collecting the sweat collected by the sweat collection module (1).

7. The wearable microfluidic device for sweat collection according to claim 6, characterized in that, The hydrophilic laser-induced graphene (LIG) layer (1-1) of the sweat collection module (1) has a through hole (1-4) in the middle. The sweat inlet module (3) includes a third base membrane (3-1) and a second through hole (3-2) corresponding to the first through hole (1-4) is provided on the third base membrane (3-1). The sweat collection chamber module (4) includes a fourth base membrane (4-1) and a third through hole (4-2) corresponding to the second through hole (3-2) is provided on the fourth base membrane (4-1). A second through groove (4-3) communicating with the third through hole (4-2) is opened in the middle of the fourth base membrane (4-1).

8. The wearable microfluidic device for sweat collection according to claim 6, characterized in that, An outlet microchannel module (6) for outputting detected sweat into the detection chamber is provided between the inlet microchannel module (2) and the sensor (7), and a sweat outlet module (5) for forming a sweat outflow channel is provided between the inlet microchannel module (2) and the outlet microchannel module (6).

9. The wearable microfluidic device for sweat collection according to claim 5, characterized in that, The sweat outlet module (5) includes a fifth base membrane (5-1), on which a V-shaped channel (5-2) runs vertically through is provided, and a third channel (5-3) communicating with the V-shaped channel (5-2) is opened in the middle of the fifth base membrane (5-1). The outlet microchannel module (6) includes a sixth base film (6-1), a second hydrophilic laser-induced graphene (LIG) microarray (6-2) that is integrally trapezoidal and prepared on the sixth base film (6-1) using a carbon dioxide laser, and a fourth through groove (6-3) disposed in the center of the sixth base film (6-1); the wide bottom side of the integrally trapezoidal second hydrophilic laser-induced graphene (LIG) microarray (6-2) is close to the fourth through groove (6-3).

10. The wearable microfluidic device for sweat collection according to claim 9, characterized in that, When preparing the hydrophilic laser-induced graphene (LIG) microarray (2-2) and the second hydrophilic laser-induced graphene (LIG) microarray (6-2), the power of the carbon dioxide laser is 5.2-6.0 W.

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