A full-green degradable flexible laser-induced graphene glucose detection chip matched with sweat detection

Abstract

This invention discloses a fully green, biodegradable, flexible laser-induced graphene glucose detection chip for sweat detection, belonging to the field of electrochemical glucose biosensor / detection chip technology. This invention uses LIG as a three-dimensional electrode and Ag / AgCl as a reference electrode. Through electroactivation and electrodeposition treatment of the electrode materials, simultaneous incubation in a glucose oxidase-bovine serum albumin mixed solution and chitosan solution, and rational control of various operational parameters, the resulting laser-induced graphene glucose detection chip possesses advantages such as being fully green, low-cost, rapid in preparation, non-invasive, highly sensitive, and flexible.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical glucose biosensor / detection chip technology, and particularly relates to a fully green, biodegradable, flexible laser-induced graphene glucose detection chip that is compatible with sweat detection. Background Technology

[0002] Current electrochemical biosensors for glucose are mostly invasive, involving finger-prick blood sampling, all of which are painful for patients with diseases like diabetes. Electrochemical biosensors that detect physiological glucose levels in the human body by measuring glucose in sweat have great potential and value. Continuous collection and monitoring of human sweat relies on wearable devices, a requirement that necessitates flexible sensors.

[0003] Existing flexible electrochemical biosensors based on polyimide (PI) substrates (direct LIG molding) struggle to address substrate wrinkling issues, resulting in uneven surfaces on the substrate and electrodes after processing. This hinders the wearable application of electrochemical sensors. Furthermore, polyimide materials require extremely harsh degradation conditions, such as high temperatures and strong alkalis, leading to serious long-term environmental damage. While electrochemical biosensors based on polydimethylsiloxane (PDMS) substrates offer flexibility, they are difficult to biodegrade, have longer fabrication cycles, and the use of metallic coatings on PMDS surfaces results in high costs. Therefore, there is a high demand in the field for glucose electrochemical biosensors that are entirely green, low-cost, rapidly fabricated, non-invasive, highly sensitive, and flexible. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a fully green, biodegradable, flexible laser-induced graphene glucose detection chip that is compatible with sweat detection. This chip has the advantages of being fully green, low cost, rapid preparation, non-invasive, highly sensitive, and flexible.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a fully green, biodegradable, flexible laser-induced graphene glucose detection chip includes the following steps:

[0007] (1) Laser printing was performed on the polyimide substrate to obtain a laser-induced graphene electrode. Molten polycaprolactone was poured onto the laser-induced graphene electrode and hot-pressed. The electrode was then cooled to room temperature to obtain the formed polycaprolactone-laser-induced graphene electrode.

[0008] (2) The Ag / AgCl reference electrode mask was fixed on the surface of the polycaprolactone-laser-induced graphene electrode, air-dried and formed, and thermoplastic polyurethane film was hot-stamped outside the three-electrode area. After the operation was completed, it was cooled to room temperature and encapsulated to obtain the polycaprolactone-laser-induced graphene three-electrode.

[0009] (3) The polycaprolactone-laser-induced graphene three-electrode was immersed in sodium phosphate solution for electroactivation treatment. After activation, it was immersed in brilliant cresol blue solution for electrodeposition treatment. After electrodeposition treatment, the electrode surface was rinsed with ultrapure water to obtain the polycaprolactone-laser-induced graphene-polybrilliant cresol blue working electrode.

[0010] (4) A glucose oxidase-bovine serum albumin mixed solution was dropped onto the surface of the polycaprolactone-laser-induced graphene-polybaccharide blue working electrode and incubated at room temperature. After incubation, chitosan solution was dropped onto the electrode surface, dried overnight, and washed to obtain the polycaprolactone-laser-induced graphene-polybaccharide blue-glucose oxidase glucose detection chip, which is a fully green and biodegradable flexible laser-induced graphene glucose detection chip.

[0011] Further, in step (1), the laser printing parameters are: power 10-30%, speed 10-80mm / s, engraving density 100-300 Row / cm; the hot pressing treatment refers to pressing down a 120℃ hot press table for 10-20 seconds.

[0012] Furthermore, in step (2), the air-drying temperature is 40°C and the time is 20 minutes.

[0013] Further, in step (3), the electroactivation treatment is performed by 10 cycles of cyclic voltammetry at a voltage of -0.6-1.0V; the electrodeposition treatment is performed by 23 cycles of cyclic voltammetry at a voltage of -0.6-1.0V.

[0014] Further, in step (4), the amount of glucose oxidase-bovine serum albumin mixed solution added is 1-10 μL, the concentration of glucose oxidase is 10-40 mg / mL, and the concentration of bovine serum albumin is 5-20 mg / mL.

[0015] Further, in step (4), the amount of chitosan solution added is 1-10 μL, the concentration is 0.001-0.1 M, and the volume fraction of acetic acid is 0.5-5 wt%.

[0016] The present invention also provides a fully green, biodegradable, flexible laser-induced graphene glucose detection chip prepared using the above-described preparation method.

[0017] The present invention also provides an application of the all-green biodegradable flexible laser-induced graphene glucose detection chip in sweat detection.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] This invention, while ensuring detection performance, utilizes fully green and biodegradable materials, natural product mediators, and three-dimensional laser-induced graphene electrodes to fabricate a glucose detection chip. This chip boasts advantages such as being green / biodegradable, flexible, highly sensitive, and having a low detection limit, promoting the development of green, non-invasive, and flexible glucose detection chips, as well as their application in wearable sweat detection. Specifically, LIG, as a three-dimensional electrode, possesses a high specific surface area, thus providing numerous attachment sites for signal molecules, fundamentally improving the chip's sensitivity. PBCB, a naturally occurring mediator, can transfer electrons and reduce overpotential within the chip, while maintaining the chip's green characteristics during mediator modification. Based on the selective effect of GOx, the chip can specifically detect glucose. BSA can resist electrode contamination and, during incubation, reduce the adsorption of interfering substances on the electrode surface and improve the incubation effect of GOx, maintaining incubation stability. Chitosan acts as an encapsulator, allowing GOx to be more stably fixed on the surface of the chip's working electrode, increasing the chip's operational stability. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 A schematic diagram of PCL-LIG chip fabrication;

[0022] Figure 2 This is a schematic diagram of the working electrode structure of the PCL-LIG-PBCB-GOx glucose detection chip;

[0023] Figure 3 The results of cyclic voltammetry characterization of the PCL-LIG-PBCB-GOx glucose detection chip;

[0024] Figure 4 The results of chronoamperometric characterization of the PCL-LIG-PBCB-GOx glucose detection chip;

[0025] Figure 5 Operating curve for glucose detection using the PCL-LIG-PBCB-GOx glucose detection chip;

[0026] Figure 6Interference resistance test for PCL-LIG-PBCB-GOxd glucose detection chip. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0033] The raw materials used in the following embodiments of the present invention are as follows:

[0034]

[0035] This invention provides a method for preparing a fully green, biodegradable, flexible laser-induced graphene glucose detection chip, comprising the following steps:

[0036] (1) A LaserBox D1 laser engraving machine was used to laser print polyimide substrates (PI, carbon content above 50%, theoretically, the carbon structure of high-carbon substrates will be more dense and have better conductivity after laser ablation into graphene). The laser printing processing parameters were adjusted as follows: power 10-30%, speed 10-80 mm / s, and engraving density 100-300 Row / cm. The electrode pattern was imported to process the PI substrate to obtain patterned electrochemical three electrodes (i.e., laser-induced graphene electrodes, LIG). The preferred processing parameters were: power 19%, speed 30 mm / s, and engraving density 300 Row / cm.

[0037] (2) Polycaprolactone (PCL) is heated to 120°C until it is completely melted into a liquid state, resulting in liquid polycaprolactone (i.e., liquid PCL). Polycaprolactone can also be replaced with polymers such as polylactic acid (PLA), polyvinyl alcohol (PVA), butylene adipate, or butylene terephthalate (PBAT).

[0038] (3) Take a portion of PCL liquid and place it on the LIG surface. Press down the 120℃ hot press table to immerse the PCL liquid into the LIG three-dimensional network structure. Press it fully for 10-20 seconds, take out the PCL-LIG and cool it. After cooling to room temperature, the formed PCL-LIG is obtained. Cut it to a suitable size to prepare for subsequent preparation steps.

[0039] (4) Fix the Ag / AgCl reference electrode mask at a suitable position on the PCL-LIG surface, apply Ag / AgCl liquid slurry to the exposed area of ​​the mask, transfer it to a 40℃ oven, heat and air dry for 20 minutes, and dry and shape it.

[0040] (5) Take out the PCL-LIG chip with Ag / AgCl electrodes, attach double conductive Cu tape (or fix copper wires with conductive silver paste, etc.) to the end of the conductive line outside the three-electrode area, and hot stamp the thermoplastic polyurethane (TPU) film outside the three-electrode area. Briefly heat (heating temperature is 120℃, time is 10s) to make TPU adhere to the PCL substrate and LIG material. After the operation is completed, cool to room temperature and wait for the shape to be set and encapsulated to obtain polycaprolactone-laser induced graphene three-electrode (i.e. PCL-LIG three-electrode).

[0041] (6) Immerse the surface of the PCL-LIG three electrodes in sodium phosphate (Cl-free) - In a solution environment, the working electrode was electroactivated by performing cyclic voltammetry (CV) scans for 10 cycles (20 segments) using a Shanghai Huachen electrochemical workstation CHI660E with the voltage set to -0.6-1.0V.

[0042] (7) After activation, immerse the three electrodes in a 2mM brilliant cresol blue (BCB) solution environment (sodium phosphate system, without Cl). - A cyclic voltammetric scan was performed with a voltage of -0.6 to 1.0 V for 23 cycles. The BCB monomer polymerized on the surface of the working electrode in the potential range of 0.8 to 0.9 V to form polybright cresol blue (PBCB), which was deposited on the surface of the working electrode and acted as a redox mediator for subsequent glucose detection, thus obtaining the polycaprolactone-laser-induced graphene-polybright cresol blue working electrode (i.e., PCL-LIG-PBCB working electrode).

[0043] (8) After deposition is complete, rinse the device surface repeatedly with ultrapure water to remove residual BCB solution.

[0044] (9) Add glucose oxidase (GOx)-bovine serum albumin (BSA) mixed solution (GOx concentration range 10-40 mg / mL, BSA concentration range 5-20 mg / mL, drop volume 1-10 μL, solution environment PBS buffer) to the surface of PCL-LIG-PBCB working electrode, and incubate at room temperature for 4 h.

[0045] (10) Add chitosan solution (acetic acid volume fraction 0.5-5%, concentration range 0.001-0.1M, drop volume 1-10μL, solution environment PBS buffer) to the surface of the working electrode and dry overnight for 12h.

[0046] (11) After incubation, ultrapure water was gently flowed over the electrode surface to clean the deposits on the electrode surface. The electrode was then dried at room temperature to obtain the polycaprolactone-laser-induced graphene-polybaccharide blue-glucose oxidase glucose detection chip (i.e., PCL-LIG-PBCB-GOx glucose detection chip).

[0047] The following embodiments are further illustrations of the technical solution of the present invention.

[0048] Example 1

[0049] A method for preparing a fully green, biodegradable, flexible laser-induced graphene glucose detection chip includes the following steps:

[0050] (1) The polyimide substrate was processed using a LaserBox D1 laser engraving machine. The processing parameters were adjusted as follows: power 19%, speed 30 mm / s, and engraving density 300 Row / cm. The electrode pattern was imported to process the PI substrate to obtain a patterned electrochemical three-electrode (i.e., laser-induced graphene electrode, LIG).

[0051] (2) Heat polycaprolactone (PCL) to 120°C to completely melt PCL into a liquid state to obtain polycaprolactone liquid (i.e. PCL liquid).

[0052] (3) Take a portion of PCL liquid and place it on the LIG surface. Press down the 120℃ hot press table to immerse the PCL liquid into the LIG three-dimensional network structure. Press it fully for 10-20 seconds, take out the PCL-LIG and cool it. After cooling to room temperature, the formed PCL-LIG is obtained. Cut it to a suitable size (specific size: 17mm long × 23mm wide) to prepare for subsequent preparation steps.

[0053] (4) Fix the Ag / AgCl reference electrode mask at a suitable position on the PCL-LIG surface, apply Ag / AgCl liquid slurry to the exposed area of ​​the mask, transfer it to a 40℃ oven, heat and air dry for 20 minutes, and dry and shape it.

[0054] (5) Remove the PCL-LIG chip with Ag / AgCl electrodes and attach double-sided conductive copper tape (or use conductive silver paste to fix copper wires, etc.) to the ends of the conductive lines connected to the three electrodes. After the thermoplastic polyurethane (TPU) film is hot-stamped outside the three electrode area (heating temperature is 120℃, time is 10s), cool to room temperature, and complete the encapsulation to obtain the polycaprolactone-laser-induced graphene three electrodes (i.e., PCL-LIG three electrodes).

[0055] (6) The surface of the PCL-LIG three electrodes was immersed in a sodium phosphate solution (specifically, PB buffer, which is prepared by sodium dihydrogen phosphate and disodium hydrogen phosphate, with an anion concentration of 0.1M, pH 7.0, and no Cl-). The working electrodes were electroactivated by cyclic voltammetry (CV) scans for 10 cycles (20 segments) using a Shanghai Huachen electrochemical workstation CHI660E with the voltage set to -0.6-1.0V.

[0056] (7) After activation, immerse the three electrodes in a 2mM brilliant cresol blue (BCB) solution environment (sodium phosphate system, without Cl). - The voltage was set to -0.6-1.0V and cyclic voltammetry was performed for 23 cycles to obtain the polycaprolactone-laser-induced graphene-polybaccharide blue working electrode (i.e., PCL-LIG-PBCB working electrode).

[0057] (8) After deposition is complete, rinse the device surface repeatedly with ultrapure water to remove residual BCB solution.

[0058] (9) Add glucose oxidase (GOx)-bovine serum albumin (BSA) mixed solution (GOx concentration range 20 mg / mL, BSA concentration range 10 mg / mL, drop volume 5 μL, solution environment PBS buffer) to the surface of PCL-LIG-PBCB working electrode, and incubate at room temperature for 4 h.

[0059] (10) Add chitosan solution (acetic acid volume fraction 1%, concentration range 0.01M, drop volume 4μL, solution environment PBS buffer) to the working electrode surface and let it dry overnight for 12h.

[0060] (11) After incubation, ultrapure water was gently flowed over the electrode surface to clean the deposits on the electrode surface. The electrode was then dried at room temperature to obtain the polycaprolactone-laser-induced graphene-polybaccharide blue-glucose oxidase glucose detection chip (i.e., PCL-LIG-PBCB-GOx glucose detection chip).

[0061] Figure 1 This is a schematic diagram of the PCL-LIG chip fabrication process, where PCL represents polycaprolactone, LIG ​​represents laser-induced graphene, Ag / AgCl represents silver / silver chloride, AE represents auxiliary electrode, WE represents working electrode, RE represents reference electrode, TPU represents thermoplastic polyurethane elastomer rubber, and Cu represents copper.

[0062] Figure 2 This is a schematic diagram of the PCL-LIG-PBCB-GOx glucose detection chip, where Chitosan represents chitosan, GOx represents glucose oxidase, BSA represents bovine serum albumin, and PBCB represents polybleach blue.

[0063] Figure 3 The results of cyclic voltammetry characterization of the PCL-LIG-PBCB-GOx glucose detection chip were obtained, with a test potential of -0.7V to 0.3V and a scan rate of 50mVs. -1 The test direction was anodic scanning, and the solution environment was standard 1×PBS solution. From Figure 3 As can be seen, the pair of redox peaks appearing near -0.1V proves that PBCB has a modification effect on the surface of the chip's working electrode (consistent with the potential of PBCB); while the pair of redox peaks appearing near -0.3V proves that substances such as glucose oxidase have a modification effect on the surface of the working electrode (appearing with the modification of enzyme substances).

[0064] Figure 4 The results of the chronoamperometric characterization of the PCL-LIG-PBCB-GOx glucose detection chip show that each change in glucose concentration in the solution system produces a significant current response. The solution environment is a standard 1×PBS solution. Figure 4 As can be seen, the chip is highly sensitive to changes in glucose concentration in the solution system, and the response amplitude produced at the same stimulus level (100 μM) remains largely consistent. Furthermore, even at a stimulus concentration of 10 μM, close to the detection limit, the chip still produces a small but noticeable response.

[0065] Figure 5The working curve of the PCL-LIG-PBCB-GOx glucose detection chip for glucose detection was obtained, and the fitting results showed a sensitivity S = 4.499 μM. -1 R 2 =0.995, indicating that the glucose detection chip prepared by the present invention has high sensitivity.

[0066] Figure 6 For the anti-interference test of the PCL-LIG-PBCB-GOxd glucose detection chip, the concentration change of each substance was 0.2mM. The results showed that the chip only produced a significant specific response to glucose, but did not have a specific response to interfering substances such as urea, calcium chloride, and ascorbic acid.

[0067] Comparative Example 1

[0068] Same as Example 1, except that in step (7), brilliant cresol blue is replaced with 1-pyrene butyric acid.

[0069] Comparative Example 2

[0070] Same as Example 1, except that step (6) is removed and the PCL-LIG three electrodes obtained in step (5) are directly subjected to the electrodeposition process in step (7).

[0071] Comparative Example 3

[0072] Same as Example 1, except that step (10) is omitted.

[0073] Comparative Example 4

[0074] Same as in Example 1, except that the order of steps (6) and (7) is reversed, that is, step (7) is performed first, and then step (6) is performed.

[0075] Comparative Example 5

[0076] Same as Example 1, except that in step (9), the concentration of glucose oxidase is 5 mg / mL.

[0077] Application examples

[0078] The conventional blood glucose meter method was used as a control group. The glucose content in sweat was detected by the chips prepared in Example 1 and Comparative Examples 1-5. The results were repeated multiple times and the final average value was taken. The results are shown in Table 1.

[0079] The specific usage method is as follows:

[0080] (1) In vitro detection: To pre-calibrate the glucose detection effect of individual sweat, sweat is dropped onto the surface of the chip electrode, covering the detection area (i.e., the unencapsulated area). An external potentiostat is applied to apply the working potential, and timing current detection is performed. After waiting for about 60 seconds (or longer), the reading on the potentiometer is taken, and the glucose concentration corresponding to the reading current is calculated.

[0081] (2) Wearable detection: This method pre-calibrates the detection effect of individual sweat glucose. A sweat collection device is attached to the skin at the sweating site, and the current is detected and read in real time using a chronoamperometry method. The corresponding glucose concentration is calculated based on the current reading. The measured sweat glucose concentration (scaled down proportionally to blood glucose concentration) is compared with the blood glucose concentration detected by a blood glucose meter, using a sweat glucose / blood glucose concentration ratio of 100 (a relatively representative ratio, although slight differences exist between individuals).

[0082] Table 1

[0083]

[0084] Note: Accuracy rate refers to the accuracy of glucose content measurement compared to the control group.

[0085] As shown in Table 1, the chip prepared in Example 1 achieved an accuracy of 95% compared to the blood glucose meter detection method, while the accuracy and sensitivity of Comparative Examples 1-5 were significantly lower than those of the control group. This demonstrates that the glucose detection chip for sweat detection prepared in this invention has high accuracy and high sensitivity.

[0086] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a fully green, biodegradable, flexible laser-induced graphene glucose detection chip, characterized in that, Includes the following steps: (1) Laser printing was performed on the polyimide substrate to obtain a laser-induced graphene electrode. Molten polycaprolactone was poured onto the laser-induced graphene electrode and hot-pressed. The electrode was then cooled to room temperature to obtain the formed polycaprolactone-laser-induced graphene electrode. (2) The Ag / AgCl reference electrode mask was fixed on the surface of the polycaprolactone-laser-induced graphene electrode, air-dried and formed, and thermoplastic polyurethane film was hot-stamped outside the three-electrode area. After the operation was completed, it was cooled to room temperature and encapsulated to obtain the polycaprolactone-laser-induced graphene three-electrode. (3) The polycaprolactone-laser-induced graphene three-electrode was immersed in sodium phosphate solution for electroactivation treatment. After activation, it was immersed in brilliant cresol blue solution for electrodeposition treatment. After electrodeposition treatment, the electrode surface was rinsed with ultrapure water to obtain the polycaprolactone-laser-induced graphene-polybrilliant cresol blue working electrode. (4) A glucose oxidase-bovine serum albumin mixed solution was dropped onto the surface of the polycaprolactone-laser-induced graphene-polybaccharide blue working electrode and incubated at room temperature. After incubation, chitosan solution was dropped onto the electrode surface, dried overnight, and washed to obtain the polycaprolactone-laser-induced graphene-polybaccharide blue-glucose oxidase glucose detection chip, which is a fully green and biodegradable flexible laser-induced graphene glucose detection chip.

2. The method for preparing the all-green, biodegradable, flexible laser-induced graphene glucose detection chip according to claim 1, characterized in that, In step (1), the laser printing parameters are: power 10-30%, speed 10-80mm / s, engraving density 100-300 Row / cm; the hot pressing treatment refers to pressing down a 120℃ hot press table for 10-20 seconds.

3. The method for preparing the all-green, biodegradable, flexible laser-induced graphene glucose detection chip according to claim 1, characterized in that, In step (2), the air-drying temperature is 40°C and the time is 20 minutes.

4. The method for preparing the all-green, biodegradable, flexible laser-induced graphene glucose detection chip according to claim 1, characterized in that, In step (3), the electroactivation treatment is performed by 10 cycles of cyclic voltammetry at a voltage of -0.6 to 1.0 V; the electrodeposition treatment is performed by 23 cycles of cyclic voltammetry at a voltage of -0.6 to 1.0 V.

5. The method for preparing the all-green, biodegradable, flexible laser-induced graphene glucose detection chip according to claim 1, characterized in that, In step (4), the amount of glucose oxidase-bovine serum albumin mixed solution added is 1-10 μL, the concentration of glucose oxidase is 10-40 mg / mL, and the concentration of bovine serum albumin is 5-20 mg / mL.

6. The method for preparing the all-green, biodegradable, flexible laser-induced graphene glucose detection chip according to claim 1, characterized in that, In step (4), the amount of chitosan solution added is 1-10 μL, the concentration is 0.001-0.1 M, and the volume fraction of acetic acid is 0.5-5 wt%.

7. A fully green, biodegradable, flexible laser-induced graphene glucose detection chip prepared by the preparation method according to any one of claims 1-6.

8. The application of the all-green, biodegradable, flexible laser-induced graphene glucose detection chip as described in claim 7 in sweat detection.

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