Flexible Electrochemical Glucose Sensor Based on Laser Direct Writing and Its Preparation Method

Abstract

The present invention provides a flexible electrochemical glucose sensor and a preparation method thereof. The sensor has a planar three-electrode structure composed of a working electrode, a reference electrode, and a counter electrode located on the same plane of a polyimide film substrate. The working electrode is composed of a graphene layer and a copper oxide layer coated on at least a part of its surface. The reference electrode is composed of a graphene layer and an Ag / AgCl conductive layer coated on at least a part of its surface. The counter electrode is composed of a graphene layer. The above-mentioned working electrode, reference electrode, and counter electrode are arranged at a prescribed interval from each other, and the Ag / AgCl conductive layer in the reference electrode is arranged opposite to the counter electrode. The sensor of the present invention has the advantages of a wide linear detection range, simple processing and preparation, low production cost, easy mass production, good stability after being bent multiple times, and can be integrated with flexible temperature, pressure, and strain sensors, having broad application prospects in the fields of human health detection, biomedicine, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensor manufacturing, and particularly relates to a flexible electrochemical glucose sensor based on laser direct writing and a preparation method thereof. Background Art

[0002] Data from the International Diabetes Federation (IDF) shows that by 2019, approximately 463 million people globally suffered from diabetes, that is, 9.3% of adults aged 20 - 79 had diabetes, and one in 11 people was a diabetic patient. Blood glucose concentration is one of the important indicators for early detection and treatment of diabetes. Therefore, rapid and accurate detection of glucose concentration has important practical significance. Currently, glucose sensors are mainly divided into enzyme-based sensors and non-enzyme sensors.

[0003] Enzyme-based sensors have high selectivity and good sensitivity to glucose, but such sensors have consumability and irreversibility of the reaction. These devices usually have problems such as signal drift and insufficient precision, and are susceptible to environmental factors (pH or temperature) interference. In addition, the modification method of glucose oxidase is also somewhat complex, resulting in poor repeatability.

[0004] Due to the characteristics of nano-metal materials and the absence of bioactive materials, non-enzyme sensors can have advantages such as a wide linear range, good repeatability, simple preparation, and batch production. Patent Document 1 discloses an electrochemical sensor for detecting glucose, which provides a novel and green construction material NiFe2O4-NiCo-LDH@GO for a glucose electrochemical sensor. This sensor has high sensitivity and is environmentally friendly, but it needs to be modified on a glassy carbon electrode, with low integration, and the synthesis method is complex and costly, which is not conducive to mass production.

[0005] In recent years, the development of flexible electronic devices has been relatively rapid, and flexible and wearable sensors have attracted much attention. Wearable flexible non-enzyme glucose sensors have become an urgent need for people. Patent Document 2 discloses a non-enzyme glucose electrochemical sensor based on a flexible Ni-P paper electrode, its preparation method and application. By constructing the Ni-P paper-based electrode, the flexibility and catalytic activity of the detection electrode are increased, thereby improving the detection sensitivity. However, the preparation of this sensing material is still relatively complex and the integration is not high.

[0006] Prior Art Documents

[0007] Patent Document 1: Invention Patent Application No. 201910162139.9

[0008] Patent Document 2: Invention Patent Application No. 201910989455.3 Summary of the Invention

[0009] The object of the present invention is to address the above problems in the prior art, and to provide a flexible electrochemical glucose sensor based on laser direct writing and a preparation method thereof. The obtained glucose sensor can have a wide linear detection range, simple processing and preparation, low production cost, good stability after being bent multiple times, good repeatability, and is easy to mass-produce.

[0010] The present invention includes the following technical solutions [1] to

[10] .

[0011] [1] A flexible electrochemical glucose sensor, comprising a planar three-electrode composed of a working electrode, a reference electrode, and a counter electrode located on the same plane of a polyimide film substrate.

[0012] The above-mentioned working electrode is composed of a graphene layer and a copper oxide layer coated on at least a part of its surface.

[0013] The above-mentioned reference electrode is composed of a graphene layer and an Ag / AgCl conductive layer coated on at least a part of its surface.

[0014] The above-mentioned counter electrode is composed of a graphene layer.

[0015] The above-mentioned working electrode, the above-mentioned reference electrode, and the above-mentioned counter electrode are arranged at a specified interval from each other, and the Ag / AgCl conductive layer in the above-mentioned reference electrode is arranged opposite to the above-mentioned counter electrode.

[0016] [2] The flexible electrochemical glucose sensor according to [1], wherein each graphene layer in the above-mentioned working electrode, the above-mentioned reference electrode, and the above-mentioned counter electrode is formed by laser ablation of the surface of the polyimide film substrate.

[0017] [3] The flexible electrochemical glucose sensor according to [2], wherein laser ablation is performed using a laser engraving machine at a power of 3000 - 5000 mW and a scanning speed of 5000 - 6000 mm / min.

[0018] [4] The flexible electrochemical glucose sensor according to [1], wherein the copper oxide layer in the above-mentioned working electrode is a layer formed by nano copper oxide particles with a particle size of 30 - 500 nm.

[0019] [5] The flexible electrochemical glucose sensor according to [1], wherein the above-mentioned working electrode, the above-mentioned reference electrode, and the above-mentioned counter electrode are arranged at a distance of 0.1 - 10 mm from each other.

[0020] [6] A preparation method of a flexible electrochemical glucose sensor, comprising the following steps:

[0021] (1) Prepare a planar polyimide film, and irradiate the surface of the above polyimide film with an ultraviolet ozone cleaner to improve surface hydrophilicity;

[0022] (2) Uniformly disperse copper nitrate in ethylene glycol, perform water bath heating to obtain a solution containing copper nitrate hydroxide, cool the solution to room temperature, add a small amount of formic acid and ultrasonically vibrate it, then take a small amount of the solution and coat it on the above polyimide film to form a uniform thin film;

[0023] (3) Use a laser engraver to scan the area coated with the above solution, reduce the copper nitrate hydroxide in the above solution to copper, and form a copper-containing layer;

[0024] (4) Then, use a laser engraver to ablate three regions including the copper-containing layer that are spaced apart by a specified interval from each other, ablate the surface of the polyimide film in this region to form a graphene layer, melt the copper in the above copper-containing layer to form nano-copper particles, and further ozone oxidize the nano-copper particles to form a copper oxide layer. The working electrode is composed of parts with a graphene layer and a copper oxide layer;

[0025] (5) Use one of the two graphene layers other than the above working electrode as a reference electrode, and the other as a counter electrode, and form an Ag / AgCl conductive layer on the part of the above reference electrode opposite to the above counter electrode.

[0026] [7] The preparation method of the flexible electrochemical glucose sensor as described in [6], wherein, in step (2), copper nitrate and ethylene glycol are uniformly mixed at a mass ratio of 1:1, and the mixed solution is heated in a water bath at 80-100 °C for 10-40 minutes to obtain a solution containing copper nitrate hydroxide. The solution is cooled to room temperature, a small amount of formic acid is added and ultrasonically vibrated to obtain a solution for coating.

[0027] [8] The preparation method of the flexible electrochemical glucose sensor as described in [6], wherein, in step (4), the power of the above laser engraver is 3000-5000 mW, the scanning speed is 5000-6000 mm / minute, and the copper in the above copper-containing layer is ablated into nano-copper particles with a size of 30-500 nm.

[0028] [9] The preparation method of the flexible electrochemical glucose sensor as described in [6], wherein, in step (5), the above reference electrode is formed by coating conductive silver paste on the graphene layer and adding 0.1-0.5 M ferric chloride solution dropwise on the conductive silver paste for chlorination to form the above Ag / AgCl conductive layer.

[0029]

[10] The preparation method of the flexible electrochemical glucose sensor as described in [6], wherein, in step (1), a UV ozone cleaning machine with UV light sources of wavelengths 185 and 254 nm is used, and the polyimide film substrate is placed at a distance of 1 - 5 cm from the UV light source and irradiated for 5 - 20 minutes.

[0030] Advantages of the Invention

[0031] According to the present invention, a flexible electrochemical glucose sensor based on laser direct writing can be provided, which has a wide linear detection range, is simple to process and prepare, has a low production cost, and has good stability after being bent multiple times. According to the preparation method of the present invention, the above-mentioned electrochemical glucose sensor can be produced at low cost, has good repeatability and is easy to mass-produce. Description of the Drawings

[0032] Figure 1 is a schematic diagram of a flexible electrochemical glucose sensor according to an embodiment of the present invention.

[0033] Figure 2 is an SEM photograph of the working electrode in the flexible electrochemical glucose sensor of the embodiment of the present invention.

[0034] Figure 3 is an EDS photograph of the working electrode in the flexible electrochemical glucose sensor of the embodiment of the present invention, where Figure 3-1 shows a photograph of the working electrode area at high magnification, Figure 3-2 shows the Cu element distribution in the working electrode area at high magnification, Figure 3-3 shows the O element distribution in the working electrode area at high magnification.

[0035] Figure 4 is an X-ray photoelectron spectroscopy (XPS) diagram of Cu before and after copper oxidation in the working electrode of the flexible electrochemical glucose sensor of the embodiment of the present invention 2p .

[0036] Figure 5-1 is a current-time response curve for glucose concentration test detection using the flexible electrochemical glucose sensor of the embodiment, Figure 5-2 showing the glucose calibration curve of the sensor.

[0037] Figure 6 is a current response change curve of the flexible electrochemical glucose sensor of the embodiment under cyclic bending conditions. Detailed Embodiments

[0038] The following describes the technical features of the present invention in conjunction with preferred embodiments, which are intended to illustrate the present invention rather than limit it.

[0039] It should be understood that those skilled in the art can make various obvious modifications, variations, equivalent substitutions based on the embodiments and examples shown below, and on the premise of non - contradiction, the technical features in the following described different embodiments can be arbitrarily combined, and all of these fall within the protection scope of the present invention.

[0040] 〔Flexible Electrochemical Glucose Sensor〕

[0041] The flexible electrochemical glucose sensor of the present invention is a sensor prepared by a laser direct writing method, also referred to as "laser - direct - writing - based flexible electrochemical glucose sensor" in this article, or simply referred to as "the sensor of the present invention" hereinafter. The following is a reference Figure 1 to illustrate the sensor of the present invention. Figure 1 Schematic diagram showing a flexible electrochemical glucose sensor according to an embodiment of the present invention.

[0042] The flexible electrochemical glucose sensor of the present invention includes a planar three - electrode. As Figure 1 shown, the planar three - electrode is formed on the same plane of a polyimide film substrate and is composed of a working electrode 1, a reference electrode 2, and a counter electrode 3.

[0043] The working electrode 1 is composed of a graphene layer and a copper oxide layer coated on at least a part of its surface. In a preferred embodiment, the graphene layer is formed by laser ablation of the surface of the polyimide film substrate. In a preferred embodiment, at least 80% of the surface of the graphene layer is covered with the copper oxide layer, and more preferably the entire surface of the graphene layer is covered with the copper oxide layer. In a preferred embodiment, the copper oxide layer is a layer formed by nano - copper oxide particles with a particle size of 30 - 500 nm, more preferably the nano - copper oxide particles are 100 - 500 nm, and further preferably 300 - 500 nm.

[0044] The reference electrode 2 is composed of a graphene layer and an Ag / AgCl conductive layer coated on at least a part of its surface. The reference electrode 2 is arranged at a prescribed interval from the working electrode 1. In a preferred embodiment, the graphene layer in the reference electrode 2 is formed by laser ablation of the surface of the polyimide film substrate. In a preferred embodiment, at least 50% of the surface of the graphene layer in the reference electrode is coated with the Ag / AgCl conductive layer, preferably at least 80% of the surface of the graphene layer is coated with the Ag / AgCl conductive layer, and particularly preferably the Ag / AgCl conductive layer is coated at one end of the reference electrode 2 opposite to the counter electrode.

[0045] The counter electrode 3 is composed of a graphene layer. The counter electrode 3 is arranged at a prescribed interval from the working electrode 1 and the reference electrode. In a preferred embodiment, the graphene layer in the counter electrode 3 is formed by laser ablation of the surface of the polyimide film substrate.

[0046] In some preferred embodiments, each graphene layer in the working electrode 1, the reference electrode 2, and the counter electrode 3 is formed by laser ablation of the surface of a polyimide film substrate, and the working electrode 1, the reference electrode 2, and the counter electrode 3 are arranged at a prescribed interval from each other, and the Ag / AgCl conductive layer in the reference electrode is arranged opposite to the counter electrode.

[0047] In some preferred embodiments, the graphene layer is formed by laser ablation of the surface of a polyimide film substrate using a laser engraver at a power of 3000 - 5000 mW and a scanning speed of 5000 - 6000 mm / min. The power is more preferably 4000 - 5000 mW. For example, it can be 4000 mW, 4200 mW, 4500 mW, 4700 mW, 5000 mW, or any value between these values; the scanning speed is more preferably 5200 - 6000 mm / min. For example, it can be 5200 mm / min, 5400 mm / min, 5600 mm / min, 5800 mm / min, 6000 mm / min, or any value between these values. In a preferred embodiment, the power during laser ablation is 4200 mW and the scanning speed is 6000 mm / min.

[0048] In the present invention, the working electrode 1, the reference electrode 2, and the counter electrode 3 are arranged at a prescribed interval from each other, and the Ag / AgCl conductive layer in the reference electrode 2 is arranged opposite to the counter electrode 3. There is no particular limitation on the interval distance between the electrodes as long as the three electrodes are arranged closely, the reference electrode 2 and the counter electrode 3 are as close as possible to the working electrode 1 and surround the working electrode 1, and they are not electrically connected to each other. In some preferred embodiments, the working electrode 1, the reference electrode 2, and the counter electrode 3 are arranged at an interval of 0.1 - 10 mm from each other, more preferably at an interval of 0.5 - 5 mm from each other, and further preferably at an interval of 1 - 3 mm from each other.

[0049] The flexible electrochemical glucose sensor of the present invention can exhibit a wide detection range, and shows quantified bending stability and good repeatability in the cyclic bending test due to its specific planar three - electrode structure and specific composition of each electrode. In the sensor of the present invention, the synergistic effect of graphene and copper oxide nanoparticles enhances the glucose detection ability of the sensor, providing a good basis for manufacturing a flexible electrochemical glucose sensor. In addition, the flexible electrochemical glucose sensor of the present invention has a simple structure, low production cost, and is easy to mass - produce.

[0050] 〔Preparation method of flexible electrochemical glucose sensor〕

[0051] The following refers to Figure 1Describe the preparation method of the flexible electrochemical glucose sensor of the present invention (hereinafter also referred to as "the preparation method of the sensor of the present invention").

[0052] The preparation method of the flexible electrochemical glucose sensor of the present invention comprises the following steps (1) to (5).

[0053] Step (1)

[0054] Prepare a planar polyimide film, and irradiate the surface of the polyimide film using an ultraviolet ozone cleaner to improve the surface hydrophilicity.

[0055] In some preferred embodiments, the polyimide film can be wiped with organic solvents such as ethanol and acetone in advance before irradiation using an ultraviolet ozone cleaner to clean the surface.

[0056] In some preferred embodiments, an ultraviolet ozone cleaner with ultraviolet light wavelengths of 185 and 254 nm is used, the polyimide film substrate is placed 1 - 5 cm away from the ultraviolet light source, more preferably 2 - 5 cm, for example, it can be 2, 3, 4, 5 cm, or any value between these values, and the irradiation time is 5 - 20 minutes, more preferably 5 - 10 minutes, for example, it can be 5, 6, 7, 8, 9, 10 minutes, or any value between these values.

[0057] Step (2)

[0058] Disperse copper nitrate evenly in ethylene glycol, perform water bath heating to obtain a solution containing copper hydroxide nitrate (Cu(OH)(NO3)), cool the solution to room temperature, add a small amount of formic acid and ultrasonically vibrate, then take a small amount of the solution and coat it on the polyimide film to form a uniform thin film shape.

[0059] In some preferred embodiments, copper nitrate and ethylene glycol are uniformly mixed at a mass ratio of 1:1. In some preferred embodiments, the water bath heating is carried out in a water bath at 80 - 100 °C for 10 - 40 minutes, preferably in a water bath at 100 °C for 30 - 40 minutes.

[0060] There is no particular limitation on the method for coating the above solution, and methods such as spin coating, spraying, and bar coating can be used, with spin coating being preferred.

[0061] Step (3)

[0062] Use a laser engraver to scan the area coated with the above solution to reduce copper hydroxide nitrate in the above solution to copper, forming a copper-containing layer.

[0063] After forming the copper-containing layer, it can be rinsed with deionized water more than 3 times and dried.

[0064] In some preferred embodiments, when using a laser engraver for scanning, the irradiation power can be set to 3000 - 5000 mW, more preferably 4000 - 5000 mW. For example, it can be 4000 mW, 4200 mW, 4500 mW, 4700 mW, 5000 mW, or any value between these values; the scanning speed can be set to 5000 - 6000 mm / minute, more preferably 5200 - 6000 mm / minute. For example, it can be 5200 mm / minute, 5400 mm / minute, 5600 mm / minute, 5800 mm / minute, 6000 mm / minute, or any value between these values.

[0065] Step (4)

[0066] Next, use a laser engraver to ablate three regions including the copper-containing layer that are spaced apart by a specified distance from each other, ablate the surface of the polyimide film in this region to form a graphene layer, melt the copper in the copper-containing layer to form nano copper particles, and further subject the nano copper particles to ozone oxidation to form a copper oxide layer. The working electrode 1 is composed of a part having a graphene layer and a copper oxide layer.

[0067] In some preferred embodiments, the power of the laser engraver is 3000 - 5000 mW and the scanning speed is 5000 - 6000 mm / minute. In a preferred embodiment, the power of the laser engraver is 4000 - 5000 mW and the scanning speed is 6000 mm / minute. By using a laser engraver for laser ablation, the copper in the copper-containing layer can be melted into nano copper particles with a size of 30 - 500 nm, preferably forming nano copper particles with a size of 100 - 500 nm, and more preferably 300 - 500 nm. By sintering copper on the graphene surface, the electron transport ability of the sensor can be greatly improved.

[0068] It should be noted that during the above laser ablation process, by controlling the laser irradiation conditions, only the copper-containing layer and the surface of the polyimide film are ablated. That is, only the surface part of the polyimide film is ablated to form a graphene layer, and the part outside its surface is still a flexible polyimide film.

[0069] In some preferred embodiments, further use an ultraviolet ozone cleaning machine preheated for 10 minutes to oxidize the nano copper particles in an ozone environment for 10 - 600 seconds, preferably 100 - 500 seconds. The ultraviolet ozone cleaning machine can decompose the oxygen in the air into ozone and oxidize the nano copper ions into nano copper oxide particles.

[0070] Step (5)

[0071] One of the two graphene layers other than the working electrode is used as the reference electrode 2, and the other is used as the counter electrode 3. An Ag / AgCl conductive layer is formed on the part of the reference electrode 2 opposite to the counter electrode 3.

[0072] In some preferred embodiments, the reference electrode 2 is formed with the above Ag / AgCl conductive layer by coating a conductive silver paste on its graphene layer and adding 0.1 - 0.5 M ferric chloride solution dropwise onto the conductive silver paste for chlorination.

[0073] As the conductive silver paste, there is no particular limitation, and a conductive silver paste with a volume resistivity of 20 mΩ / mm 2 or less can be used. Preferably, the volume resistivity is 10 mΩ / mm 2 or less, and more preferably 5 mΩ / mm 2 or less.

[0074] The flexible electrochemical glucose sensor prepared by the preparation method of the present invention has planar three electrodes formed on the same plane of the polyimide film substrate, namely the working electrode 1, the reference electrode 2, and the counter electrode 3. The three electrodes are arranged closely, and the reference electrode 2 and the counter electrode 3 are as close as possible to the working electrode 1 and surround the working electrode 1, and they just need not conduct with each other. In some preferred embodiments, in the obtained sensor, the working electrode 1, the reference electrode 2, and the counter electrode 3 are arranged at a distance of 0.1 - 10 mm from each other, more preferably at a distance of 0.5 - 5 mm from each other, and further preferably at a distance of 1 - 3 mm from each other.

[0075] According to the preparation method of the flexible electrochemical glucose sensor of the present invention, the above-mentioned electrochemical glucose sensor can be produced at low cost, has good repeatability, is easy to mass-produce, and the obtained electrochemical glucose sensor has a wide linear detection range and still has good stability after being bent multiple times.

[0076] Examples

[0077] The following further illustrates the composition and advantages of the present invention through examples, but it should be understood that the following examples are only illustrative of the implementation of the present invention and are not intended to limit the protection scope of the present invention.

[0078] (Preparation of Flexible Electrochemical Glucose Sensor)

[0079] Prepare a polyimide film with a thickness of 0.125 mm, and wipe and clean the surface with ethanol. Use an ultraviolet ozone cleaning machine with ultraviolet light sources of wavelengths 185 and 254 nm to irradiate the polyimide substrate, with the polyimide film substrate at a distance of 2 cm from the ultraviolet light source and irradiating for 10 minutes, thereby generating active groups on the substrate surface and improving the surface hydrophilicity.

[0080] Add 2.5 g of copper nitrate and 2.5 g of ethylene glycol into a beaker, and stir the mixed solution of copper nitrate and ethylene glycol on a magnetic stirrer until the copper nitrate is evenly dispersed in the ethylene glycol. Heat the obtained mixed solution in a water bath at 100 °C for 30 minutes until the solution changes from dark blue to dark green and a large amount of light yellow gas (NO2) is generated. Quickly take out the mixed solution and cool it at room temperature to obtain a solution containing copper hydroxide nitrate (Cu(OH)(NO3)). After the solution is cooled to room temperature, add 15 μL of formic acid, stir quickly, and then perform ultrasonic oscillation for 5 minutes. Take a small amount of the mixed solution and coat it on a polyimide film, and spin-coat it with a spin coater to make the solution form a uniform thin film on the film.

[0081] Use a laser engraving machine to irradiate and scan the area coated with the above solution at a power of 4200 mW and a scanning speed of 6000 mm / minute to reduce the copper hydroxide nitrate in the solution to copper, forming a copper-containing layer (a circular copper film with a diameter of about 7.5 mm). Then rinse it 3 times with deionized water and dry it.

[0082] Then use a laser engraving machine to ablate three regions including the copper-containing layer and spaced about 1 mm apart from each other at a power of 4200 mW and a scanning speed of 6000 mm / minute (refer to Figure 1 ), ablate the surface of the polyimide film in this region to form a graphene layer, and melt the copper in the copper-containing layer. Observe the melted copper layer with a scanning electron microscope, and it can be observed that the sintered copper particles have a particle size of about 50 - 200 nm and uniformly cover the surface of the graphene (as shown in Figure 2 ). Then, use an ultraviolet ozone cleaning machine preheated for 10 minutes to oxidize the nano copper particles in an ozone environment for 300 seconds. The ultraviolet ozone cleaning machine can decompose the oxygen in the air into ozone and oxidize the nano copper ions into nano copper oxide particles, thereby forming a copper oxide layer. Take the part with the graphene layer and the copper oxide layer as the working electrode of the sensor of the present invention (1 in Figure 1 ).

[0083] Figure 3 shows the EDS photo of the working electrode in the flexible electrochemical glucose sensor of the present invention, where Figure 3-1 shows the photo of the working electrode region at high magnification, Figure 3-2 shows the Cu element distribution in the working electrode region at high magnification, Figure 3-3 shows the O element distribution in the working electrode region at high magnification. It can be seen in Figure 3-3 that the oxygen element is distributed in a granular shape, which matches the previous two figures. It can be inferred that the copper particles become copper oxide nanoparticles after oxidation.

[0084] Figure 4 shows the Cu before and after copper oxidation in the working electrode of the sensor of the present invention 2pX-ray photoelectron spectroscopy (XPS) shows that the Cu peak shifts to the right and a satellite peak unique to divalent copper appears, indicating that the copper particles are oxidized to copper oxide.

[0085] One of the two graphene layers other than the working electrode is used as a reference electrode ( Figure 1 2 in Figure 1 ), and the other is used as a counter electrode ( 2 3 in

[0086] (Electrochemical performance test)

[0087] The prepared flexible electrochemical glucose sensor is electrochemically tested using an electrochemical workstation CHI-660E. An electrode with a copper oxide nanoparticle coverage area of π×7.5 mm 2 is used as the working electrode, the electrode coated with an Ag / AgCl conductive layer is used as the reference electrode, and the remaining electrode is used as the counter electrode.

[0088] Using the chronoamperometry method, a constant voltage of 0.55 V is applied to test the electrochemical performance of the flexible electrochemical glucose sensor. All subsequent tests are measured at a constant voltage of 0.55 V. The sensor is placed in 50 mL of 0.1 M sodium hydroxide solution, and 10 μM glucose solution is added 6 times, 20 μM glucose solution is added 7 times, 100 μM glucose solution is added 8 times, and 500 μM glucose solution is added 14 times. It can be observed that each time the glucose solution is added, the current will increase accordingly (as Figure 5-1 shown).

[0089] Figure 5-2 shows the glucose calibration curve of the sensor, indicating that the sensor of the present invention has a wide detection range. The sensitivity of the sensor is 0.81229 mA*mM -1 *cm -2 (R 2 = 0.98) in the glucose concentration range of 10 μM to 1.5 mM, and 0.10915 mA*mM -1 *cm -2 (R 2 = 0.94) in the glucose concentration range of 3 mM to 8 mM.

[0090] (Cyclic bending stability test)

[0091] The cyclic bending test was carried out on the flexible electrochemical glucose sensor of the present invention. After multiple sets of cyclic bending of the sensor, the current response in a 0.1 M sodium hydroxide solution containing 2 mM glucose was measured.

[0092] The sensor was clamped to a tensile machine and compressed by 1 cm to bend the sensor. Four groups of bending were carried out, with 50, 100, 200, and 300 bends respectively. After each group of bending, the current response of the sensor in a 0.1 M sodium hydroxide solution containing 2 mM glucose was observed. The test results are as Figure 6 shown. The sensor could still maintain a 74.1% current response after 300 bends, indicating that the sensor has good cyclic bending stability.

[0093] Finally, it should be understood that the above descriptions of the embodiments and examples are illustrative in all aspects and do not constitute a limitation to the present invention. Those of ordinary skill in the art can make various improvements without creative labor within the scope of the spirit of the present invention. The scope of the present invention is represented by the claims, rather than the above embodiments or examples. In addition, the scope of the present invention includes all changes within the meaning and scope equivalent to the claims.

[0094] Industrial applicability

[0095] The flexible electrochemical glucose sensor of the present invention has a wide linear detection range, is simple to process and prepare, has a low production cost, has good stability after multiple bends, and the synergistic effect of graphene and copper oxide nanoparticles enhances the detection ability of the sensor for glucose, providing a good foundation for manufacturing flexible electrochemical glucose sensors. The sensor of the present invention can be integrated with flexible temperature, pressure, and strain sensors, and has broad application prospects in the fields of human health detection, biomedicine, etc.

Claims

1. A flexible electrochemical glucose sensor, comprising a planar three - electrode structure composed of a working electrode, a reference electrode, and a counter electrode located on the same plane of a polyimide film substrate. The working electrode is composed of a graphene layer and a copper oxide layer coated on at least a part of its surface. The reference electrode is composed of a graphene layer and an Ag / AgCl conductive layer coated on at least a part of its surface. The counter electrode is composed of a graphene layer. The working electrode, the reference electrode, and the counter electrode are arranged at a prescribed interval from each other, and the Ag / AgCl conductive layer in the reference electrode is arranged opposite to the counter electrode. Among them, Each graphene layer in the working electrode, the reference electrode, and the counter electrode is formed by laser ablation of the surface of the polyimide film substrate using a laser engraving machine with a power of 3000 - 5000 mW and a scanning speed of 5000 - 5800 mm / minute.

2. The flexible electrochemical glucose sensor according to claim 1, characterized in that, The copper oxide layer in the working electrode is a layer formed by nano - copper oxide particles with a particle size of 30 - 500 nm.

3. The flexible electrochemical glucose sensor according to claim 1, wherein The working electrode, the reference electrode, and the counter electrode are arranged at a distance of 0.1 - 10 mm from each other.

4. A method for preparing a flexible electrochemical glucose sensor, comprising the following steps: (1) Prepare a planar polyimide film, and irradiate the surface of the polyimide film using an ultraviolet - ozone cleaning machine to improve surface hydrophilicity. (2) Uniformly disperse copper nitrate in ethylene glycol, heat it in a water bath to obtain a solution containing copper nitrate hydroxide, cool the solution to room temperature, add a small amount of formic acid and ultrasonically vibrate it, and then take a small amount of the solution and coat it on the polyimide film to form a uniform thin - film shape. (3) Use a laser engraving machine to scan the area coated with the solution to reduce copper nitrate hydroxide in the solution to copper, forming a copper - containing layer. (4) Then, use a laser engraving machine to ablate three regions including the copper - containing layer at a prescribed interval from each other, ablate the surface of the polyimide film in this region to form a graphene layer, melt the copper in the copper - containing layer to form nano - copper particles, and further ozone - oxidize the nano - copper particles to form a copper oxide layer. The part with the graphene layer and the copper oxide layer constitutes the working electrode. (5) Use one of the two graphene layers other than the working electrode as the reference electrode and the other as the counter electrode, and form an Ag / AgCl conductive layer on the part of the reference electrode opposite to the counter electrode.

5. The preparation method of the flexible electrochemical glucose sensor according to claim 4, characterized in that, In step (2), copper nitrate and ethylene glycol are uniformly mixed at a mass ratio of 1:1, the mixed solution is heated in a water bath at 80 - 100 °C for 10 - 40 minutes to obtain a solution containing copper nitrate hydroxide, the solution is cooled to room temperature, a small amount of formic acid is added and ultrasonically vibrated to obtain a solution for coating.

6. The preparation method of the flexible electrochemical glucose sensor according to claim 4, wherein, In step (4), the power of the laser engraving machine is 3000 - 5000 mW and the scanning speed is 5000 - 6000 mm / minute, and the copper in the copper - containing layer is ablated into nano - copper particles with a size of 30 - 500 nm.

7. The preparation method of the flexible electrochemical glucose sensor according to claim 4, wherein, In step (5), the reference electrode is formed by coating a conductive silver paste on the graphene layer and then dropping a 0.1-0.5 M ferric chloride solution on the conductive silver paste for chlorination to form the Ag / AgCl conductive layer.

8. The preparation method of the flexible electrochemical glucose sensor according to claim 4, characterized in that, In step (1), a UV ozone cleaner with UV light sources having wavelengths of 185 and 254 nm is used, and the polyimide film substrate is placed at a distance of 1-5 cm from the UV light source and irradiated for 5-20 minutes.

Images