A preparation method of an integrated microfluidic nitrite electrochemical sensing patch

Abstract

The preparation method of the integrated microfluidic nitrite electrochemical sensing patch belongs to the technical field of portable sensing devices, and the steps include the preparation of a patterned graphene three-electrode loop, the preparation of an electrochemical sensing patch sensing module, the preparation of an electrochemical sensing patch microfluidic module, and the preparation of an integrated microfluidic electrochemical sensing patch. The present application provides an integrated microfluidic nitrite electrochemical sensing patch, which provides a feasible and general method for the industrialized mass production of integrated sensors at low cost. The preparation method is simple and easy to operate, which reduces the time cost and does not require expensive large-scale instruments. The raw materials used are extremely cheap. The prepared sensor has high integration and complete functions, and realizes the integration of sample collection and rapid detection.

Description

Technical Field

[0001] This invention belongs to the field of portable sensor technology, specifically relating to a method for preparing an integrated microfluidic nitrite electrochemical sensing patch. Background Technology

[0002] Nitrites are currently widely used as food additives and preservatives, such as in meat, pickles, and dried seafood. However, because nitrites irreversibly convert hemoglobin to methemoglobin, excessive intake can severely impair blood oxygen-carrying capacity, leading to serious illnesses including anemia, lactic acidosis, and blue baby syndrome. Furthermore, under acidic gastric conditions, nitrites can interact with secondary and tertiary amines, leading to the accumulation of endogenous carcinogenic nitrosamines, which can significantly increase the risk of stomach and esophageal cancer. Given the impact of nitrites on human health, monitoring nitrite levels in food is crucial for preventing various diseases, especially cancer. Currently, standard kits based on the Griess reaction or other reported sensing reagents heavily rely on complex sample pretreatment, long processing times, and expensive laboratory equipment, making on-site and real-time measurements difficult. Therefore, developing an easy-to-operate, fast-responding, low-cost, and portable nitrite sensor for on-site detection of nitrites in food is of paramount importance. Summary of the Invention

[0003] The purpose of this invention is to address the above-mentioned situation by providing a method for preparing an integrated microfluidic nitrite electrochemical sensing patch. This method is simple, efficient, low-cost, and suitable for large-scale industrial production.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing an integrated microfluidic nitrite electrochemical sensing patch includes the following steps:

[0006] (1) Preparation of patterned graphene three-electrode circuit: PI film is etched by laser direct writing technology using a carbon dioxide laser cutter. After high temperature carbonization, the PI film forms a patterned graphene-based three-electrode circuit. The PI film is a polyimide film, and the three electrodes are composed of a working electrode, a counter electrode, and a reference electrode.

[0007] (2) Preparation of electrochemical sensing patch sensing module: The prepared hybrid MXene / MWCNTs composite material and cobaltamine are sequentially drop-coated onto the graphene working electrode part obtained in step (1) to obtain the working electrode of the sensing module; Ag / AgCl ink is printed on the graphene reference electrode part to obtain the reference electrode of the sensing module.

[0008] (3) Preparation of electrochemical sensing patch microfluidic module: Double-sided PET tape and PET film are cut by laser cutting machine to obtain patterned microfluidic channels and top cover, and the two are bonded together to obtain electrochemical sensing patch microfluidic module;

[0009] (4) Preparation of integrated microfluidic electrochemical sensing patch: The electrochemical sensing patch sensor module obtained in step (2) is accurately aligned and attached to the adhesive microfluidic module obtained in step (3) to obtain an integrated microfluidic electrochemical sensing patch.

[0010] The preparation process of the hybrid MXene / MWCNTs composite material in step (2) is as follows:

[0011] S21. Add titanium aluminum carbide to a Teflon beaker containing 40% hydrofluoric acid solution and stir continuously in a water bath at 35 ℃ for 10 hours to generate a black suspension.

[0012] S22. Centrifuge the black suspension, wash the solid with deionized water until neutral, and dry it overnight under vacuum at 40 °C to obtain dried MXene-Ti3C2T. X powder;

[0013] S23, Dry MXene-Ti3C2T X The powder was placed in DMSO and stirred for 12 hours. The powder was then centrifuged and washed to remove the DMSO.

[0014] S24. Disperse the product in deionized water, sonicate for 5 hours, centrifuge, and freeze-dry to obtain MXene-Ti3C2T. X Nanosheets;

[0015] S25, MXene-Ti3C2T X Multi-walled carbon nanotubes (MWCNTs) were dispersed in deionized water in DMF, resulting in MXene-Ti3C2T. X The MXene / MWCNTs composite material was obtained by mixing the MXene and MWCNTs in a mass ratio of 5:3, followed by ultrasonic treatment and freeze-drying.

[0016] Preferably, in step (1), the PI film thickness is 100 μm, and the scanning speed is 110 mm / s and the power is 4.0 W during laser direct writing etching.

[0017] Preferably, in step (2), the specific concentrations and amounts of the hybrid MXene / MWCNTs composite material and cobalamin are as follows: 4 mg of hybrid MXene / MWCNTs is dissolved in 1 mL of 0.25% chitosan solution, with a volume of 4 μL; 0.5 mg of cobalamin is dissolved in 1 mL of 0.25% chitosan solution, with a volume of 4 μL.

[0018] Preferably, the centrifugal rotation speed in step S24 is 4000 rpm, and the time is 20 minutes.

[0019] Preferably, in step S25, MXene-Ti3C2T X The concentration of MWCNTs in deionized water was 2 mg / mL, the concentration of MWCNTs in DMF was 3 mg / mL, and the ultrasonic treatment time after mixing was 60 minutes.

[0020] Preferably, the sensor module prepared in step (2) is 14 × 17 mm in size, and the microfluidic module prepared in step (3) is 14 × 12 mm in size. The channel thickness in the microfluidic module is 0.9 mm, and the top cover thickness is 0.05 mm.

[0021] Beneficial effects:

[0022] This invention proposes an integrated microfluidic nitrite electrochemical sensing patch, providing a feasible and universal method for the large-scale, low-cost industrial fabrication of integrated sensors. The fabrication method is simple and easy to implement, reducing time costs, eliminating the need for expensive large-scale instruments, and using extremely inexpensive raw materials. The fabricated sensor exhibits high integration and complete functionality, achieving integrated sample acquisition and rapid detection. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of an integrated microfluidic nitrite electrochemical sensing patch;

[0024] Figure 2 Here is a SEM image of the prepared hybrid MXene / MWCNTs composite material;

[0025] Figure 3 The image shows the XRD pattern of the prepared hybrid MXene / MWCNTs composite material.

[0026] Figure 4 This is a schematic diagram illustrating the fabrication process of the sensing module in an integrated sensing patch.

[0027] Figure 5 This is the fabrication process and schematic diagram of the microfluidic module in an integrated sensing patch;

[0028] Figure 6The prepared microfluidic module was evaluated through numerical simulation, which simulated the distribution of nitrite concentration in the microfluidic reservoir over time.

[0029] Figure 7 The microfluidic module was evaluated through on-chip experiments, and the filling time distribution of the sample in the microfluidic reservoir was actually tested.

[0030] Figure 8 It is the electrochemical It curve and the linear fitting curve of the current value under different nitrite concentrations;

[0031] Figure 9 These are test results for the selectivity, repeatability, and long-term storage stability of an integrated microfluidic nitrite electrochemical sensing patch.

[0032] Figure 10 This is a comparison chart of the analysis of nitrite concentration in actual samples using an integrated microfluidic nitrite electrochemical sensing patch and a standard nitrite detection kit. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0035] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0036] Example 1

[0037] Figure 1 This is a schematic diagram of the integrated microfluidic electrochemical sensing patch capable of rapidly collecting samples and accurately detecting nitrite concentration, as described in this embodiment of the application. Figure 1 As can be seen, the sensing patch consists of two parts: a microfluidic module and a sensing module. The microfluidic module includes a patterned channel and a reservoir made of PET material, and a patterned PET film cap, which has the function of collecting and storing the sample to be tested. The sensing module includes a PI substrate and an electrochemical three-electrode sensor based on graphene-MXene / MWCNTs-cobalamin attached to the surface of the PI substrate, which has the function of rapidly detecting nitrite concentration.

[0038] The production process is as follows:

[0039] (1) Preparation of hybrid MXene / MWCNTs composite material: 2.6 g of titanium aluminum carbide was carefully added to a mixed solution consisting of 16 mL of hydrofluoric acid and 24 mL of deionized water. The mixture was stirred continuously in a water bath at 35 °C for 10 hours to generate a black suspension. The black suspension was centrifuged, and the solid was washed with deionized water until the pH was close to 7. The synthesized MXene-Ti3C2T was then added to the solution. X The MXene-Ti3C2T was dried overnight under vacuum at 40 °C. X The powder was placed in 20 mL of DMSO and stirred for 12 hours. Centrifugation and washing were then continued to remove the DMSO. The product was dispersed in 200 mL of deionized water, sonicated for 5 hours, and then centrifuged at 4000 rpm for 20 minutes. The black slurry was then freeze-dried to obtain MXene-Ti3C2T. X Nanosheets. 50 mg of MXene-Ti3C2T X 30 mg of MWCNTs were dispersed in 25 mL of water and 10 mL of DMF, respectively, under ultrasonic treatment. The mixture was then ultrasonicated for 60 minutes and freeze-dried to obtain hybrid MXene-Ti3C2T. X / MWCNTs composite materials.

[0040] The prepared materials were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. See details below. Figure 2 and Figure 3 .Depend on Figure 2 It can be seen that the long tubular MWCNTs successfully connected the discrete MXene-Ti3C2T X Nanosheets. (From) Figure 3 It is known that MXene-Ti3C2T X The XRD spectrum of / MWCNTs showed a characteristic peak of MWCNTs at 25.9°, confirming the hybridization of MXene-Ti3C2T X Formation of / MWCNTs composite materials.

[0041] (2) Preparation of working electrode modification layer solution: Dissolve 20 μL of formic acid in 10 mL of deionized water, then add 0.025 g of chitosan powder, and stir magnetically at 60 °C to fully dissolve the chitosan to obtain a 0.25% chitosan solution. Dissolve 20 mg of hybrid MXene / MWCNTs composite material ultrasonically in 5 mL of the above 0.25% chitosan solution to obtain the MXene / MWCNTs working electrode modification solution. Dissolve 2.5 mg of cobalamin in 5 mL of the above 0.25% chitosan solution to obtain the cobalamin working electrode modification solution.

[0042] (3) Use CorelDRAW software to design electrode patterns.

[0043] (4) Cut a piece of commercial PI film with dimensions of 14 mm × 17 mm × 100 μm, clean the commercial PI film with deionized water and ethanol in sequence, and then dry it with nitrogen.

[0044] (5) Fabrication of sensing modules: such as Figure 4 As shown in the schematic diagram, the commercial PI film from step (4) was first etched using a carbon dioxide laser cutter at a scanning speed of 110 mm / s and a power of 4.0 W to obtain a PI substrate with an attached graphene loop electrode. Commercial Ag / AgCl ink was then printed onto the graphene reference electrode. 4 μL of the MXene / MWCNTs working electrode modification solution prepared in step (2) was then drop-coated onto the graphene working electrode and dried at room temperature. 4 μL of the cobaltamine working electrode modification solution prepared in step (2) was then drop-coated onto the graphene-MXene / MWCNTs working electrode and dried at room temperature. This resulted in the fabrication of an integrated microfluidic nitrite electrochemical sensing patch sensing module.

[0045] (6) Fabrication of microfluidic modules: such as Figure 5 As shown in the schematic diagram, a commercial PET film with dimensions of 14.0 mm × 12.0 mm × 0.05 mm was cut using a CO2 laser cutter to create a patterned PET film with two 1.0 mm diameter circular holes, serving as the top cover of the microfluidic reservoir. These two holes act as the inlet and outlet for the sample to be tested. Similarly, a PET film with double-sided adhesive tape was cut using a CO2 laser cutter to create a microfluidic channel with a cylindrical reservoir chamber of 8.0 mm diameter, measuring 14.0 mm × 12.0 mm × 0.9 mm. Finally, the patterned PET film top cover and the adhesive microfluidic reservoir chamber were assembled sequentially to obtain an integrated microfluidic nitrite electrochemical sensing patch microfluidic module.

[0046] The performance of the fabricated microfluidic module was evaluated through numerical simulation and on-chip experiments. See details below. Figure 6 and Figure 7 .Depend on Figure 6 It can be seen that when the inlet flow rate is 50 μL·s -1 At that time, the entire sample introduction time of the microfluidic module was approximately 1.0 second, during which the solution concentration changed from 0 to 50 μM. Figure 7 It can be seen that the microfluidic module can effectively collect and store nitrite standard solutions containing blue dye, with a high time resolution, which is in good agreement with the numerical simulation predictions mentioned above.

[0047] (7) Assemble the sensing module prepared in step (5) and the microfluidic module prepared in step (6) to obtain a complete integrated microfluidic nitrite electrochemical sensing patch.

[0048] (8) The steady-state current-nitrite concentration standard curve was determined using the integrated microfluidic nitrite electrochemical sensing patch prepared in step (7). Figure 8 It can be seen that the steady-state current has a good linear relationship with the nitrite concentration, and the corresponding linear equation is I (μA) = 10.533C. nitrite (mM) + 9.110 (R 2 The nitrite concentration range is 0.01-20 mM (> 0.99). Calculations show that the detection limit of this electrochemical sensing patch is 4.22 μM, and the sensitivity is 10.533 μA / mM, easily covering the nitrite level range in food safety standards.

[0049] (9) The integrated microfluidic nitrite electrochemical sensing patch prepared in step (7) was used to test its anti-interference ability, repeatability, and long-term storage stability. Figure 9 It was found that, apart from the nitrite signal, no significant interference signal was detected in the sensing patch; sensing patches manufactured in different batches also exhibited similar responses; when stored at 4 °C, the performance of the sensing patch could be maintained for at least 21 days, with the steady-state current remaining above 90%. These findings demonstrate that the prepared integrated microfluidic nitrite electrochemical sensing patch possesses superior anti-interference capabilities, repeatability, and long-term storage stability.

[0050] (10) The integrated microfluidic nitrite electrochemical sensing patch prepared in step (7) was used to determine the nitrite concentration of actual samples, and compared with a commercial standard nitrite detection kit. Figure 10 It can be seen that in the measurement of nitrite concentration in five kinds of food, the detection results of the invented integrated microfluidic nitrite electrochemical sensing patch and the commercial standard nitrite detection kit were not significantly different, demonstrating the wide applicability and accurate detection capability of the patch.

[0051] It should be understood that the above description is only a specific embodiment of the present invention. For those skilled in the art, improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an integrated microfluidic nitrite electrochemical sensing patch, comprising the following steps: (1) Preparation of patterned graphene three-electrode circuit: PI film is etched by laser direct writing technology using a carbon dioxide laser cutter. After high temperature carbonization, the PI film forms a patterned graphene-based three-electrode circuit. The PI film is a polyimide film, and the three electrodes are composed of a working electrode, a counter electrode, and a reference electrode. (2) Preparation of electrochemical sensing patch sensing module: The prepared hybrid MXene / MWCNTs composite material and cobaltamine are sequentially drop-coated onto the graphene working electrode part obtained in step (1) to obtain the working electrode of the sensing module; Ag / AgCl ink is printed on the graphene reference electrode part to obtain the reference electrode of the sensing module. (3) Preparation of electrochemical sensing patch microfluidic module: Double-sided PET tape and PET film are cut by laser cutting machine to obtain patterned microfluidic channels and top cover, and the two are bonded together to obtain electrochemical sensing patch microfluidic module; (4) Preparation of integrated microfluidic electrochemical sensing patch: The electrochemical sensing patch sensor module obtained in step (2) is accurately aligned and attached to the adhesive microfluidic module obtained in step (3) to obtain an integrated microfluidic electrochemical sensing patch. in, The preparation process of the hybrid MXene / MWCNTs composite material in step (2) is as follows: S21. Add titanium aluminum carbide to a Teflon beaker containing 40% hydrofluoric acid solution and stir continuously in a water bath at 35 ℃ for 10 hours to generate a black suspension. S22. Centrifuge the black suspension, wash the solid with deionized water until neutral, and dry it overnight under vacuum at 40 °C to obtain dried MXene-Ti3C2T. X powder; S23, Dry MXene-Ti3C2T X The powder was placed in DMSO and stirred for 12 hours. The powder was then centrifuged and washed to remove the DMSO. S24. Disperse the product in deionized water, sonicate for 5 hours, centrifuge, and freeze-dry to obtain MXene-Ti3C2T. X Nanosheets; S25, MXene-Ti3C2T X Multi-walled carbon nanotubes (MWCNTs) were dispersed in deionized water in DMF, resulting in MXene-Ti3C2T. X The MXene / MWCNTs composite material was obtained by mixing the MXene and MWCNTs in a mass ratio of 5:3, followed by ultrasonic treatment and freeze-drying.

2. The method for preparing an integrated microfluidic nitrite electrochemical sensing patch according to claim 1, characterized in that, In step (1), the PI film thickness is 100 μm, and the scanning speed is 110 mm / s and the power is 4.0 W during laser direct writing etching.

3. The method for preparing an integrated microfluidic nitrite electrochemical sensing patch according to claim 1, characterized in that, In step (2), the specific concentrations and amounts of the hybrid MXene / MWCNTs composite material and cobalamin are sequentially drop-coated onto the working electrode as follows: 4 mg of hybrid MXene / MWCNTs is dissolved in 1 mL of 0.25% chitosan solution, with a volume of 4 μL; 0.5 mg of cobalamin is dissolved in 1 mL of 0.25% chitosan solution, with a volume of 4 μL.

4. The method for preparing an integrated microfluidic nitrite electrochemical sensing patch according to claim 1, characterized in that, The centrifugal rotation speed in step S24 is 4000 rpm, and the time is 20 minutes.

5. The method for preparing an integrated microfluidic nitrite electrochemical sensing patch according to claim 1, characterized in that, In step S25, MXene-Ti3C2T X The concentration of MWCNTs in deionized water was 2 mg / mL, the concentration of MWCNTs in DMF was 3 mg / mL, and the ultrasonic treatment time after mixing was 60 minutes.

6. The method for preparing an integrated microfluidic nitrite electrochemical sensing patch according to claim 1, characterized in that, The sensor module prepared in step (2) is 14 × 17 mm in size, and the microfluidic module prepared in step (3) is 14 × 12 mm in size. The channel thickness in the microfluidic module is 0.9 mm, and the top cover thickness is 0.05 mm.

Images