Micro-needle electroosmosis blood glucose sensor and preparation method thereof

Abstract

The invention discloses a microneedle electroosmosis blood glucose sensor and a preparation method thereof.The sensor comprises a sensor substrate layer, a micro-fluidic channel layer, an electroosmosis microneedle array and a detection electrode, the sensor substrate layer, the micro-fluidic channel layer and the electroosmosis microneedle array are sequentially stacked, the electroosmosis microneedle array comprises a plurality of electroosmosis microneedles, and the detection electrode is arranged between the plurality of electroosmosis microneedles. The electroosmosis microneedle comprises a microneedle substrate, an electroosmosis cathode layer, an electroosmosis anode layer and a needle hole; each pinhole comprises a first part penetrating through the electroosmosis cathode layer and the microneedle substrate and a second part penetrating through the electroosmosis anode layer; a plurality of micro-fluidic channels are arranged on the micro-fluidic channel layer, the first ends of the micro-fluidic channels are communicated with the corresponding pinholes, and the second ends of the micro-fluidic channels are communicated with the reference electrode, the working electrode and the counter electrode of the detection electrode. A large amount of tissue fluid glucose can be rapidly extracted under small voltage, the electroosmosis efficiency is improved, meanwhile, the correlation between the concentration of glucose in extracted liquid and the concentration of blood glucose can be increased, and the accuracy of the sensor is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of minimally invasive continuous blood glucose monitoring, and in particular relates to a microneedle electroosmotic blood glucose sensor and a preparation method thereof. Background Art

[0002] Nowadays, due to many people's bad eating habits, lifestyles, genes and other influencing factors, the number of diabetes patients is increasing day by day, and is gradually becoming younger. Diabetes seriously affects people's physical and mental health, and there is no cure. Therefore, patients need to undergo continuous and real-time blood sugar testing to more effectively prevent the disease.

[0003] The blood sugar detection methods currently under study are divided into invasive, minimally invasive, and non-invasive methods according to the degree of trauma to the human body. Minimally invasive blood sugar detection is mainly based on semi-implanted microneedle technology. This method has a high accuracy in detecting glucose content, but the main problem is that the needle tip penetrates deep into the human body, which makes it easy for harmful ions on the device to enter the human body and easily cause infection. Especially for implantable technology, the substances modified on the electrode can easily enter the human body with the flowing tissue fluid and blood, resulting in reduced device performance. There is still a strong sense of pain during implantation. Completely painless blood sugar detection technology is still what people expect.

[0004] Traditional sweat sensors use non-invasive technology to detect glucose in sweat. The correlation between sweat glucose concentration and blood glucose concentration is low, and the detection accuracy is low. In non-invasive technology, the interstitial fluid has a relatively high glucose content and has a clear correlation with blood glucose. The existing non-invasive blood glucose detection technology is mainly an integration of a three-electrode system and an electroosmotic electrode system. This technology is completely non-invasive to the skin. It is based on the principle of reverse ion electroosmosis and uses an electric field to extract glucose from tissue fluid. In the traditional non-invasive reverse ion electroosmosis process, in order to achieve a non-invasive effect and avoid irritating the skin, the applied electroosmotic voltage is generally very small. At the same time, the skin tissue is not traumatized, and no skin microchannels are generated to assist the precipitation of substances in the tissue fluid. There is a large resistance to electroosmotic extraction, resulting in a very low electroosmotic efficiency and a small amount of precipitated glucose. Therefore, the detection accuracy and sensitivity of the sensor are low. If the electroosmotic efficiency of the tissue fluid is to be increased, the method of increasing the electroosmotic voltage is generally adopted, which will produce obvious current irritation to the skin and cause discomfort.

[0005] An existing porous microneedle such as Figure 1As shown in the figure, polyethylene glycol (10kDa) is used as a porogen, and a porous microneedle structure is used to collect tissue fluid. The tissue fluid in the body is adsorbed by the micropores on the microneedle due to capillary action, and enters the microneedle through the microneedle channel, and then reacts with the working electrode. This technology forms microchannels on the surface of human skin through invasive stimulation. The skin resistance of tissue fluid precipitation is much smaller than that of non-invasive technology. If it is integrated with an electroosmotic electrode, the required electroosmotic voltage will be smaller, and the electroosmotic efficiency can be improved. However, the micropores of this technology are very easy to cause blockage when transporting macromolecular substances. After a period of use, the sensor generally has a problem of low response ability, which affects the detection accuracy.

[0006] The existing minimally invasive intra-needle sensing technology has a long and hard needle tip, which will cause discomfort to the user, and the microneedle needs to be complexly modified to form a working electrode that can directly detect glucose. The modifications on the needle tip surface are easily lost with the flowing tissue fluid and blood. After a period of use, the sensor's responsiveness will be greatly reduced. At the same time, harmful substances on the detection electrode can easily enter the human body and cause infection. The existing minimally invasive extra-needle sensing technology generally uses a microporous structure to collect tissue fluid, relying on capillary, diffusion, and osmosis to transport the tissue fluid to the surface of the working electrode. However, at the same time, many macromolecular proteins and other substances will enter the micropores with the tissue fluid, which can easily cause blockage, thereby reducing the service life and sensitivity of the sensor. Summary of the invention

[0007] In order to solve the above problems existing in the prior art, the present invention provides a microneedle electroosmotic blood glucose sensor and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0008] One aspect of the present invention provides a microneedle electroosmotic blood glucose sensor, comprising a sensor substrate layer, a microfluidic channel layer, an electroosmotic microneedle array and a detection electrode, wherein:

[0009] The sensor substrate layer, the microfluidic channel layer and the electroosmotic microneedle array are stacked in sequence, the electroosmotic microneedle array comprises a plurality of electroosmotic microneedles arranged regularly, the electroosmotic microneedles comprise a microneedle substrate, an electroosmotic cathode layer, an electroosmotic anode layer and pinholes, the electroosmotic cathode layer, the microneedle substrate and the electroosmotic anode layer are stacked in sequence;

[0010] The pinhole comprises a first part and a second part which are coaxial and connected, the first part passes through the electroosmotic cathode layer and the microneedle substrate, the second part passes through the electroosmotic anode layer, and the diameter of the first part is smaller than the diameter of the second part;

[0011] A plurality of microfluidic channels are arranged on the microfluidic channel layer, the detection electrodes include a reference electrode, a working electrode and a counter electrode, the first ends of the plurality of microfluidic channels are connected to the corresponding pinholes, and the second ends of the microfluidic channels are connected to the reference electrode, the working electrode and the counter electrode.

[0012] In one embodiment of the present invention, the diameter of the first portion of the pinhole is 0.1-0.5 mm, the diameter of the second portion is 0.25-0.7 mm; the length of the second portion of the pinhole is 0.5-1 mm.

[0013] In one embodiment of the present invention, the microneedle substrate is a flexible PI film with a thickness of 75 to 125 μm, and the electroosmotic cathode layer includes 10 to 30 nm of chromium and 100 to 250 nm of platinum stacked.

[0014] In one embodiment of the present invention, the electroosmosis anode layer is conical, including a first surface, a second surface and a first arcuate side extending from the first surface to the second surface, and the second part of the pinhole extends from the center of the first surface to the center of the second surface.

[0015] In one embodiment of the present invention, the microneedle electroosmotic blood glucose sensor comprises an electroosmotic region and a detection region, wherein:

[0016] The electroosmotic microneedles are all arranged in the electroosmotic area, and the detection electrodes are arranged in the detection area;

[0017] The detection area includes a sensor substrate layer, a microfluidic channel layer and a microneedle substrate arranged from bottom to top, and the reference electrode, the working electrode and the counter electrode are spaced between the microfluidic channel layer and the microneedle substrate.

[0018] In one embodiment of the present invention, the electroosmotic microneedle further comprises a microneedle support structure, the microneedle support structure comprises a third surface and a fourth surface and a second arc-shaped side surface extending from the third surface to the fourth surface, and the electroosmotic anode layer is formed on the second arc-shaped side surface of the microneedle support structure;

[0019] The first portion of the pinholes penetrates the electroosmotic cathode layer and the microneedle substrate, and the second portion penetrates the microneedle supporting structure.

[0020] In one embodiment of the present invention, the microneedle supporting structure is made of resin.

[0021] Another aspect of the present invention provides a method for preparing a microneedle electroosmotic blood glucose sensor, the method comprising:

[0022] Selecting a microneedle substrate and depositing metal in the electroosmotic region on the microneedle substrate to form an electroosmotic cathode layer, and forming a detection electrode in the electrode region;

[0023] Punching holes on the microneedle substrate and the electroosmotic cathode layer to form a first portion of the pinhole;

[0024] An electroosmotic anode layer of a preset shape is printed on the second surface of the microneedle substrate by 3D printing technology, wherein the electroosmotic anode layer includes a second portion coaxial with the first portion of the pinhole;

[0025] A microfluidic channel layer with multiple microfluidic channels is prepared, and one side with the microfluidic channels is attached to the electroosmotic cathode layer and the detection electrode, and the other side is fixed on the surface of the sensor substrate.

[0026] In one embodiment of the present invention, a microfluidic channel layer having a plurality of microfluidic channels is prepared, and one side having the microfluidic channels is attached to the electroosmotic cathode layer and the detection electrode, and the other side is fixed to the surface of the sensor substrate, comprising:

[0027] A microfluidic channel layer having a plurality of microfluidic channels is prepared using polydimethylsiloxane material by soft lithography, 3D printing or injection molding, wherein the diameter of the microfluidic channel is close to the diameter of the first part of the pinhole;

[0028] Modifying the polydimethylsiloxane material by plasma treatment or ultraviolet radiation treatment, so that the microfluidic channel becomes a hydrophilic channel;

[0029] The side of the microfluidic channel layer with the microfluidic channel is applied to the electroosmotic cathode layer and the detection electrode after position alignment, and then the side of the microfluidic channel layer without the microfluidic channel is fixed to the surface of the sensor substrate by reactive ion etching.

[0030] Another aspect of the present invention provides another method for preparing a microneedle electroosmotic blood glucose sensor, the method comprising:

[0031] Selecting a microneedle substrate and depositing metal in the electroosmotic region on the microneedle substrate to form an electroosmotic cathode layer, and forming a detection electrode in the electrode region;

[0032] Punching holes on the microneedle substrate and the electroosmotic cathode layer to form a first portion of the pinhole;

[0033] A microneedle support structure of a preset shape is printed on the second surface of the electroosmotic substrate by 3D printing technology, wherein the microneedle support structure includes a second portion coaxial with the first portion of the pinhole;

[0034] Depositing metal on the surface of the microneedle support structure to form an electroosmotic anode layer;

[0035] A microfluidic channel layer having multiple microfluidic channels is prepared, and the side of the microfluidic channel layer having the microfluidic channels is applied to the electroosmotic cathode layer and the detection electrode, and the side without the microfluidic channels is fixed to the surface of the sensor substrate.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The microneedle electroosmotic blood glucose sensor of the present invention adopts a method of combining electroosmotic electrodes with electroosmotic microneedles, deposits metal on the upper and lower surfaces of the electroosmotic substrate to form an electroosmotic cathode layer and an electroosmotic anode layer, and arranges a microfluidic channel layer having a microfluidic channel on the electroosmotic cathode layer, and applies a voltage by using the diameter difference between the first part and the second part of the pinhole, so that a longitudinal electric field can be formed on the skin surface, and a counter-ion electroosmosis effect occurs. The electroosmosis process is added on the basis of the microneedle extraction process to synergistically promote the precipitation of glucose in the tissue fluid, so that the present invention can quickly extract a large amount of tissue fluid glucose under a small voltage and improve the electroosmotic efficiency. At the same time, through counter-ion electroosmosis, glucose in the tissue fluid is additionally extracted in sweat, forming a system combining sweat detection with tissue fluid detection, increasing the correlation between the glucose concentration in the extracted liquid and the blood glucose concentration, and improving the accuracy of the sensor. In addition, by adopting microfluidic technology, the microfluidic channel is easy to clean, which can solve the problem of macromolecular substances blocking the sensor channel and effectively prolong the life of the sensor.

[0038] 2. The present invention adopts a method of combining electroosmotic electrodes, microneedle arrays and microfluidic pipelines to extract glucose from tissue fluid through electroosmotic electrodes, and guide the sweat carrying extra glucose to the detection electrode through the capillary effect of the microfluidic pipeline, thereby greatly increasing the glucose content in the sweat drawn out by the microfluidic pipeline, while avoiding the need to add additional conductive liquid to the traditional electroosmotic electrodes. The present invention is of great significance to the development of multimodal sweat biosensors. By adding different types of detection electrodes in the back-end pipeline, the detection of target analytes such as blood glucose, but not limited to blood glucose, can be achieved.

[0039] 3. The present invention uses an electroosmotic microneedle with a length of 0.5mm to 1mm to extract glucose from tissue fluid. It is almost non-invasive when used by users, does not damage nerves, is gentler than traditional minimally invasive methods, and has less stimulation to the human body. The electroosmotic electrode is only wrapped by a layer of metal, has a simple structure, and is separated from the detection electrode, which improves the stability of the sensor system and reduces the risk of infection. The present invention uses an ultra-minimally invasive needle tip, which is simple, low-cost, high in device stability, low risk of infection, and high in device safety. The electroosmotic process is separated from the working electrode, which improves the process flexibility of modifying the working electrode.

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the working principle of an existing minimally invasive porous microneedle blood glucose sensor;

[0042] Figure 2 is a system schematic diagram of a microneedle electroosmotic blood glucose sensor provided by an embodiment of the present invention;

[0043] Figure 3 is a schematic structural diagram of an electroosmotic microneedle provided in an embodiment of the present invention;

[0044] Figure 4 is a schematic structural diagram of another electroosmotic microneedle provided in an embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of a system for extracting glucose from sweat and tissue fluid using electroosmotic microneedles provided in an embodiment of the present invention;

[0046] Figure 6 Schematic diagram of a preparation process of an electroosmotic microneedle provided in an embodiment of the present invention;

[0047] Figure 7 It is a schematic diagram of another preparation process of an electroosmotic microneedle provided in an embodiment of the present invention.

[0048] Description of reference numerals:

[0049] 1-sensor substrate layer; 2-microfluidic channel layer; 21-microfluidic channel; 3-electroosmotic microneedle; 31-microneedle substrate; 32-electroosmotic cathode layer; 33-electroosmotic anode layer; 34-pinhole; 35-microneedle supporting structure; 4-detection electrode. DETAILED DESCRIPTION

[0050] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a microneedle electroosmotic blood glucose sensor and a method for preparing the electroosmotic microneedle thereof proposed in accordance with the present invention are described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0051] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0052] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the statement "including one..." do not exclude the existence of other identical elements in the article or device including the elements.

[0053] Embodiment 1

[0054] See also Figure 2 and Figure 3 , Figure 2 is a system schematic diagram of a microneedle electroosmotic blood glucose sensor provided by an embodiment of the present invention, Figure 3 Schematic diagram of the structure of an electroosmotic microneedle provided by an embodiment of the present invention. The microneedle electroosmotic blood glucose sensor comprises a sensor substrate layer 1, a microfluidic channel layer 2, an electroosmotic microneedle array and a detection electrode 4, wherein the sensor substrate layer 1, the microfluidic channel layer 2 and the electroosmotic microneedle array are stacked in sequence, the electroosmotic microneedle array comprises a plurality of regularly arranged electroosmotic microneedles 3, the electroosmotic microneedles 3 comprise a microneedle substrate 31, an electroosmotic cathode layer 32, an electroosmotic anode layer 33 and a pinhole 34, the electroosmotic cathode layer 32, the microneedle substrate 31 and the electroosmotic anode layer 33 are stacked in sequence; the pinhole 34 comprises a first part which is coaxial and connected and a second part, the first part penetrates the electroosmotic cathode layer 32 and the microneedle substrate 31, and the second part penetrates the electroosmotic anode layer 33, the diameter of the first part is smaller than the diameter of the second part, that is, the diameter of the pinhole 34 increases slightly when passing through the electroosmotic anode layer 33; a plurality of microfluidic channels 21 are arranged on the microfluidic channel layer 2, the detection electrode 4 includes a reference electrode, a working electrode and a counter electrode, the first ends of the plurality of microfluidic channels 21 are connected to the corresponding pinholes 34, and the second ends of the microfluidic channels 21 are connected to the reference electrode, the working electrode and the counter electrode. The microfluidic channel 21 of this embodiment is a groove of a preset shape opened on a surface of the microfluidic channel layer 2 and the electroosmotic cathode layer 32, and the diameter of the microfluidic channel 21 is approximately equal to the diameter of the first part of the pinhole 34.

[0055] In this embodiment, the material of the sensor substrate layer 1 is preferably a flexible PI film, which is easy to wear. The size of the sensor substrate layer 1 can be 15*30mm, and the thickness can be 75-125μm; the microneedle substrate 31 can be a flexible PI film with a thickness of 75-125μm, and the electroosmotic cathode layer 32 includes 10-30nm chromium and 100-250nm platinum stacked. Preferably, the thickness of the microneedle substrate 31 is 100μm, and the electroosmotic cathode layer 32 includes 25nm chromium and 125nm platinum stacked.

[0056] The diameter of the first part of the pinhole 34 is 0.1-0.5 mm, and the diameter of the second part is 0.25-0.7 mm; the length of the second part of the pinhole 34 is 0.5-1 mm. In other words, the diameter of the part that penetrates the electroosmotic cathode layer 32 and the microneedle substrate 31 is 0.1-0.5 mm, the diameter of the part that penetrates the electroosmotic anode layer 33 is 0.25-0.7 mm, and the thickness of the electroosmotic anode layer 33 at the maximum thickness is 0.5-1 mm.

[0057] Furthermore, if Figure 3 As shown, the electroosmosis anode layer 33 of this embodiment is conical (microneedle shape), including a first surface, a second surface and a first arc-shaped side extending from the first surface to the second surface, and the second part of the pinhole 34 extends from the center of the first surface to the center of the second surface.

[0058] The microneedle electroosmotic blood glucose sensor includes an electroosmotic region and a detection region, wherein the electroosmotic microneedles 3 are all arranged in the electroosmotic region, and the detection electrode 4 is arranged in the detection region; the detection region includes a sensor substrate layer 1, a microfluidic channel layer 2 and a microneedle substrate 31 arranged from bottom to top, and the reference electrode, the working electrode and the counter electrode are arranged between the microfluidic channel layer 2 and the microneedle substrate 31, and are all connected to the microfluidic channel. Figure 1 As shown, the electroosmotic microneedle array of the present invention includes 16 electroosmotic microneedles, which are evenly distributed, and the overall size of the electroosmotic area is 15mm*15mm. The interval between adjacent pinholes is 3mm-4mm.

[0059] That is to say, the sensor substrate layer 1, the microfluidic channel layer 2 and the microneedle substrate 31 are laid in the entire electroosmosis area and the detection area, while the electroosmosis cathode layer 32 and the electroosmosis anode layer 33 are only laid in the electroosmosis area, and are separated from the reference electrode, working electrode and counter electrode in the detection area.

[0060] During use, the reference electrode, the working electrode and the counter electrode are connected to an external electrochemical detector, the electroosmotic anode layer 33 and the electroosmotic cathode layer 32 are connected to the anode and cathode of a constant voltage power supply respectively, and the side with the electroosmotic microneedle is attached to the skin. The electroosmotic area integrates several electroosmotic microneedles with special structures. The length of the electroosmotic microneedle is generally 0.5-1 mm, which is ultra-minimally invasive to the human body and does not cause irritation. The metals deposited on the upper and lower surfaces of the microneedle substrate 31 of the electroosmotic microneedle 3 serve as the electroosmotic cathode layer 32 and the electroosmotic anode layer 33 respectively. A small voltage is applied to the two layers of metal using a constant voltage power supply to form an electric field in a direction perpendicular to the microneedle substrate. The glucose in the tissue fluid moves to the electroosmotic cathode layer 32 together with the sodium ions, thereby achieving the effect of tissue fluid precipitation out of the body under the action of the electric field. With the assistance of the electric field, the pinhole 34 and the microfluidic channel 21, a large amount of tissue fluid glucose can be quickly extracted. All electroosmotic microneedles are connected by microfluidic channels, so that the sweat and the tissue fluid glucose it carries are gathered to the working electrode surface of the detection electrode. There is only the transported tissue fluid on the surface of the detection electrode, and the working environment is stable. The probability of the modified object falling off or harmful substances entering the human body is extremely small. The working electrode can adopt enzyme or non-enzyme modification process according to needs, and the process flexibility is very high.

[0061] The microneedle used in the present invention is an extremely fine needle with a length of 0.5 to 1 mm and a diameter of 0.25 to 0.7 mm. Since only the tissue fluid of the superficial skin structure needs to be extracted, it is not necessary to penetrate the skin deeply and the nerves are not injured, so there is no pain. At the same time, only a layer of metal is deposited on the microneedle, the structure is simple, the electroosmosis and the detection electrode work separately, the working environment of the working electrode is stable, and the service life of the sensor is greatly improved. This structure prevents harmful substances from entering the human body and improves the safety of the device. The working electrode can even be modified using enzyme-free technology, which broadens the development direction of the sensor.

[0062] See also Figure 5 , Figure 5The present invention is a schematic diagram of the principle of an electroosmotic microneedle isolating impurities on the skin surface provided by an embodiment of the present invention. The microneedle electroosmotic blood glucose sensor of the present invention adopts a method of combining an electroosmotic electrode with an electroosmotic microneedle, deposits metal on the upper and lower surfaces of the electroosmotic substrate to form an electroosmotic cathode layer and an electroosmotic anode layer, and arranges a microfluidic channel layer having a microfluidic channel on the electroosmotic cathode layer, and applies a voltage by using the diameter difference between the first part and the second part of the pinhole, so that a longitudinal electric field can be formed on the skin surface, and a counter-ion electroosmosis effect occurs. The electroosmotic process is added on the basis of the microneedle extraction process to synergistically promote the precipitation of glucose in the tissue fluid, so that the present invention can quickly extract a large amount of tissue fluid glucose under a small voltage, thereby improving the electroosmotic efficiency. At the same time, through counter-ion electroosmosis, glucose in the tissue fluid is additionally extracted in sweat, forming a system combining sweat detection with tissue fluid detection, increasing the correlation between the glucose concentration in the extracted liquid and the blood glucose concentration, and improving the accuracy of the sensor. In addition, the microfluidic technology is adopted, and the microfluidic channel is easy to clean, which can solve the problem of macromolecular substances blocking the sensor channel and effectively prolong the life of the sensor.

[0063] The present invention adopts a method of combining an electroosmotic electrode, a microneedle array and a microfluidic pipeline, extracts glucose from tissue fluid through the electroosmotic electrode, and guides sweat carrying extra glucose to the detection electrode through the capillary effect of the microfluidic pipeline, greatly increasing the glucose content in the sweat drawn out by the microfluidic pipeline, while avoiding the need to add additional conductive liquid to the traditional electroosmotic electrode. The present invention is of great significance to the development of multimodal sweat biosensors. By adding different types of detection electrodes in the back-end pipeline, the detection of target analytes such as blood sugar, but not limited to blood sugar, can be achieved.

[0064] The present invention adopts electroosmotic microneedles with a length of 0.5mm to 1mm, and utilizes the microneedles to extract glucose from tissue fluid. It is almost non-invasive when used by users, will not damage nerves, is gentler than traditional minimally invasive methods, and has less stimulation to the human body. The electroosmotic electrode is only wrapped by a layer of metal, has a simple structure, and is separated from the detection electrode, which improves the stability of the sensor system and reduces the risk of infection.

[0065] Embodiment 2

[0066] This embodiment provides another electroosmotic microneedle, see Figure 4 The electroosmotic microneedle 3 includes a microneedle substrate 31, an electroosmotic cathode layer 32, an electroosmotic anode layer 33, and a pinhole 34, and also includes a microneedle support structure 35, the microneedle support structure 35 includes a third surface and a fourth surface and a second arc-shaped side surface extending from the third surface to the fourth surface, and the electroosmotic anode layer 33 is formed on the second arc-shaped side surface of the microneedle support structure 35; the first part of the pinhole 34 penetrates the electroosmotic cathode layer 32 and the microneedle substrate 31, and the second part penetrates the microneedle support structure 35. Further, the material of the microneedle support structure 35 is resin.

[0067] That is to say, the difference between the electroosmotic microneedle of this embodiment and the electroosmotic microneedle of Example 1 lies in that it includes a microneedle support structure 35, the structure of which is similar to the shape of the electroosmotic anode layer 33 in Example 1, while the electroosmotic anode layer 33 of this embodiment is a layer of metal covering the second curved side of the microneedle support structure 35.

[0068] The other structures of the electroosmotic microneedle of this embodiment are completely the same as those of the electroosmotic microneedle of the first embodiment, and will not be described again here.

[0069] The electroosmotic microneedle of this embodiment is ultra-minimally invasive to the human body and does not cause irritation. By applying a small voltage to the electroosmotic cathode layer and the electroosmotic anode layer, an electric field can be formed in a direction perpendicular to the substrate. With the assistance of the electric field, pinholes and microfluidic channels, a large amount of tissue fluid glucose can be quickly extracted. Each microneedle is connected by a microfluidic channel, and the capillary action can be used to transport sweat and converge it to the working electrode surface of the detection electrode. The sweat carries the tissue fluid glucose additionally extracted by the electroosmotic microneedle. The detection electrode surface only has sweat transported by capillary action. The working environment is stable, and the probability of the modified object falling off or harmful substances entering the human body is extremely small. The working electrode can adopt an enzyme or non-enzyme modification process according to needs, and the process flexibility is very high. In addition, an absorbent sponge can be applied to the end of the microfluidic channel to promote sweat transport and prevent protein accumulation.

[0070] Embodiment 3

[0071] Based on Example 1, this example provides a method for preparing a microneedle electroosmotic blood glucose sensor. Figure 6 As shown, the preparation method comprises:

[0072] S1: Select a microneedle substrate 31 and deposit metal in the electroosmosis region on the microneedle substrate 31 to form an electroosmosis cathode layer 32, and form a detection electrode in the electrode region. The figure only shows the preparation process of the electroosmosis region.

[0073] First, the microneedle substrate 31 is selected. There are many materials to choose from for the microneedle substrate 31. Its main function is to carry the sensor. A flexible PI film with a thickness of 75 to 125 μm can be used for easy wear. An undoped silicon wafer, such as Figure 6 (a) shown.

[0074] Then, a uniform layer of metal Pt is deposited on the upper surface of the microneedle substrate 31 by electron beam melting molding (EBM) as the electro-osmosis cathode layer 32. Preferably, the process can also be adopted to first deposit 10 to 30 nm of chromium (Cr) and then deposit 100 to 250 nm of platinum (Pt), such as Figure 6 (b) as shown.

[0075] S2: drilling holes on the microneedle substrate 31 and the electroosmotic cathode layer 32 to form the first part of the pinhole.

[0076] Specifically, the microneedle substrate 31 and the electroosmotic cathode layer 32 are punched by laser drilling technology to form a first portion of the pinhole penetrating the microneedle substrate 31 and the electroosmotic cathode layer 32, such as Figure 6 It should be noted that, in the actual preparation process, the microneedle substrate 31 and the electroosmotic cathode layer 32 are laid in the entire electroosmotic area. In this step, a predetermined number of pinholes are formed on the microneedle substrate 31 and the electroosmotic cathode layer 32 according to the number and arrangement of the required electroosmotic microneedles. The diameter of the first part of the pinholes is about 0.1 to 0.5 mm, and the pinholes are evenly distributed in the electroosmotic area.

[0077] S3: Printing an electroosmotic anode layer 33 of a preset shape on the second surface of the microneedle substrate 31 by 3D printing technology, wherein the electroosmotic anode layer 33 includes a second portion coaxial with the first portion of the pinhole.

[0078] First, a metal model of the electroosmotic anode layer 33 to be 3D printed is drawn using computer-aided design (CAD) software, including the shape and position of the electroosmotic anode layer 33 of all electroosmotic microneedles. The model is scaled and adjusted according to the actual size required to ensure that the electroosmotic anode layer 33 finally printed has a suitable size. Subsequently, the electroosmotic anode layer 33 of a preset shape is printed on the second surface of the microneedle substrate 31 by 3D printing technology, as shown in FIG. Figure 6 (d) as shown.

[0079] S4: Prepare a microfluidic channel layer 2 having multiple microfluidic channels 21, and apply the side of the microfluidic channel layer 2 having the microfluidic channels 2 to the electroosmotic cathode layer 32 and the detection electrode 4, and fix the side without the microfluidic channels 21 to the surface of the sensor substrate 1.

[0080] Specifically, a microfluidic channel layer 2 having a plurality of microfluidic channels 21 is prepared using polydimethylsiloxane (PDMS) material by soft lithography, 3D printing or injection molding, and the diameter of the microfluidic channel 21 is close to the diameter of the first part of the pinhole 34, such as Figure 6 (e) as shown; the polydimethylsiloxane material is modified by plasma treatment, ultraviolet radiation treatment and the like, so that the microfluidic channel becomes a hydrophilic channel to promote capillary action; the side of the microfluidic channel layer 2 with the microfluidic channel 21 is applied to the electroosmotic cathode layer 32 and the detection electrode 4 after position alignment, and then the side of the microfluidic channel layer 2 without the microfluidic channel 21 is fixed to the surface of the sensor substrate 1 by reactive ion etching (RIE), thereby forming the final microneedle electroosmotic blood glucose sensor, as shown in FIG. Figure 2 shown.

[0081] The present invention adopts an ultra-minimally invasive needle tip, which is simple, low in cost, has high device stability, low infection risk, high device safety, and separates the electroosmosis process from the working electrode, thereby improving the process flexibility of modifying the working electrode.

[0082] Embodiment 4

[0083] Based on Example 2, this example provides another method for preparing a microneedle electroosmotic blood glucose sensor. Figure 7 As shown, the preparation method comprises:

[0084] S1': Select a microneedle substrate 31 and deposit metal in the electroosmosis region on the microneedle substrate 31 to form an electroosmosis cathode layer 32, and form a detection electrode in the electrode region. The figure only shows the preparation process of the electroosmosis region.

[0085] First, the microneedle substrate 31 is selected. There are many materials to choose from for the microneedle substrate 31. Its main function is to carry the sensor. A flexible PI film with a thickness of 75 to 125 μm can be used for easy wear. An undoped silicon wafer, such as Figure 7 (a) shown.

[0086] Then, a uniform layer of metal Pt is deposited on the upper surface of the microneedle substrate 31 by electron beam melting molding (EBM) as the electro-osmosis cathode layer 32. Preferably, the process can also be adopted to first deposit 10 to 30 nm of chromium (Cr) and then deposit 100 to 250 nm of platinum (Pt), such as Figure 7 (b) as shown.

[0087] S2': drilling holes on the microneedle substrate 31 and the electroosmotic cathode layer 32 to form the first part of the pinhole.

[0088] Specifically, the microneedle substrate 31 and the electroosmotic cathode layer 32 are punched by laser drilling technology to form a first portion of the pinhole penetrating the microneedle substrate 31 and the electroosmotic cathode layer 32, such as Figure 7 It should be noted that, in the actual preparation process, the microneedle substrate 31 and the electroosmotic cathode layer 32 are laid in the entire electroosmotic area. In this step, a predetermined number of through holes are formed on the microneedle substrate 31 and the electroosmotic cathode layer 32 according to the number and arrangement of the required electroosmotic microneedles, and the diameter of the first part of the pinhole is about 0.1 to 0.5 mm.

[0089] S3': A microneedle support structure 35 of a preset shape is formed on the second surface of the electroosmotic substrate 31 by 3D printing technology, and the microneedle support structure 35 includes a second part coaxial with the first part of the pinhole, such as Figure 7 (d) as shown.

[0090] Specifically, the microneedle support structure 35 of all the electroosmotic microneedles is simultaneously printed on the second surface of the electroosmotic substrate 31 using 3D printing technology, and the microneedle support structure 35 is made of resin material.

[0091] In another specific embodiment, the microneedle support structure 35 of a preset shape may be printed first, and then the printed microneedle support structure 35 may be aligned and fixed on the second surface of the electroosmotic substrate 31 by an adhesive.

[0092] S4 ′: depositing metal on the surface of the microneedle support structure 35 to form an electroosmotic anode layer 33 .

[0093] Specifically, an electron beam melting molding (EBM) method is used to deposit a uniform layer of metal Pt on the surface of the microneedle support structure 35 as the electroosmotic anode layer 33, with a thickness of 100 to 200 nm. Figure 7 (e) as shown.

[0094] S5': prepare a microfluidic channel layer 2 having multiple microfluidic channels 21, and apply the side of the microfluidic channel layer 2 having the microfluidic channels 2 to the electroosmotic cathode layer 32 and the detection electrode 4, and fix the side without the microfluidic channels 21 to the surface of the sensor substrate 1.

[0095] Specifically, a microfluidic channel layer 2 having a plurality of microfluidic channels 21 is prepared using polydimethylsiloxane material by soft lithography, 3D printing or injection molding, and the diameter of the microfluidic channel 21 is close to the diameter of the first part of the pinhole 34, such as Figure 7 (f) As shown; the polydimethylsiloxane material is modified by plasma treatment, ultraviolet radiation treatment and other methods to make the microfluidic channel a hydrophilic channel to promote capillary action; the side of the microfluidic channel layer 2 with the microfluidic channel 21 is aligned and applied to the electroosmotic cathode layer 32 and the detection electrode 4, and then the side of the microfluidic channel layer 2 without the microfluidic channel 21 is fixed to the surface of the sensor substrate 1 by reactive ion etching, thereby forming the final microneedle electroosmotic blood glucose sensor.

[0096] In the several embodiments provided by the present invention, it should be understood that the apparatus and method disclosed by the present invention can be implemented in other ways. For example, the apparatus embodiments described above are only illustrative, for example, the division of the modules is only a logical function division, and there may be other division methods in actual implementation, for example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0097] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of hardware plus software functional modules.

[0098] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A microneedle electroosmotic blood glucose sensor, characterized in that: It comprises a sensor substrate layer (1), a microfluidic channel layer (2), an electroosmotic microneedle array and a detection electrode (4), wherein: The sensor substrate layer (1), the microfluidic channel layer (2) and the electroosmotic microneedle array are stacked in sequence, the electroosmotic microneedle array comprises a plurality of electroosmotic microneedles (3) arranged in a regular pattern, the electroosmotic microneedles (3) comprise a microneedle substrate (31), an electroosmotic cathode layer (32), an electroosmotic anode layer (33) and a pinhole (34), and the electroosmotic cathode layer (32), the microneedle substrate (31) and the electroosmotic anode layer (33) are stacked in sequence; The pinhole (34) comprises a first part and a second part which are coaxial and connected, the first part passes through the electroosmosis cathode layer (32) and the microneedle substrate (31), the second part passes through the electroosmosis anode layer (33), and the diameter of the first part is smaller than the diameter of the second part; The microfluidic channel layer (2) is provided with a plurality of microfluidic channels (21); the detection electrode (4) comprises a reference electrode, a working electrode and a counter electrode; the first ends of the plurality of microfluidic channels (21) are connected to the corresponding pinholes (34); and the second ends of the microfluidic channels (21) are connected to the reference electrode, the working electrode and the counter electrode.

2. The microneedle electroosmotic blood glucose sensor according to claim 1, characterized in that: The diameter of the first part of the pinhole (34) is 0.1-0.5 mm, and the diameter of the second part is 0.25-0.7 mm; the length of the second part of the pinhole (34) is 0.5-1 mm.

3. The microneedle electroosmotic blood glucose sensor according to claim 1, characterized in that: The microneedle substrate (31) is a flexible PI film with a thickness of 75 to 125 μm, and the electroosmotic cathode layer (32) comprises 10 to 30 nm of chromium and 100 to 250 nm of platinum which are stacked.

4. The microneedle electroosmotic blood glucose sensor according to claim 1, characterized in that: The electroosmotic anode layer (33) is conical, comprising a first surface, a second surface, and a first arc-shaped side surface extending from the first surface to the second surface, and the second part of the pinhole (34) extends from the center of the first surface to the center of the second surface.

5. The microneedle electroosmotic blood glucose sensor according to claim 1, characterized in that: The microneedle electroosmotic blood glucose sensor comprises an electroosmotic area and a detection area, wherein: The electroosmotic microneedles (3) are all arranged in the electroosmotic area, and the detection electrodes (4) are arranged in the detection area; The detection area comprises a sensor substrate layer (1), a microfluidic channel layer (2) and a microneedle substrate (31) arranged from bottom to top, and the reference electrode, the working electrode and the counter electrode are arranged between the microfluidic channel layer (2) and the microneedle substrate (31).

6. The microneedle electroosmotic blood glucose sensor according to claim 1, characterized in that: The electroosmotic microneedle (3) further comprises a microneedle support structure (35), wherein the microneedle support structure (35) comprises a third surface and a fourth surface and a second arc-shaped side surface extending from the third surface to the fourth surface, and the electroosmotic anode layer (33) is formed on the second arc-shaped side surface of the microneedle support structure (35); The first portion of the pinhole (34) penetrates the electroosmotic cathode layer (32) and the microneedle substrate (31), and the second portion penetrates the microneedle supporting structure (35).

7. The microneedle electroosmotic blood glucose sensor according to claim 6, characterized in that: The material of the microneedle supporting structure (35) is resin.

8. A method for preparing a microneedle electroosmotic blood glucose sensor, characterized in that: For preparing the microneedle electroosmotic blood glucose sensor according to claims 1 to 4, the preparation method comprises: Selecting a microneedle substrate and depositing metal in the electroosmotic region on the microneedle substrate to form an electroosmotic cathode layer, and forming a detection electrode in the electrode region; Punching holes on the microneedle substrate and the electroosmotic cathode layer to form a first portion of the pinhole; An electroosmotic anode layer of a preset shape is printed on the second surface of the microneedle substrate by 3D printing technology, wherein the electroosmotic anode layer includes a second portion coaxial with the first portion of the pinhole; A microfluidic channel layer with multiple microfluidic channels is prepared, and one side with the microfluidic channels is attached to the electroosmotic cathode layer and the detection electrode, and the other side is fixed on the surface of the sensor substrate.

9. The method for preparing the microneedle electroosmotic blood glucose sensor according to claim 8, characterized in that: A microfluidic channel layer having a plurality of microfluidic channels is prepared, and one side having the microfluidic channels is attached to the electroosmotic cathode layer and the detection electrode, and the other side is fixed to the surface of the sensor substrate, comprising: A microfluidic channel layer having a plurality of microfluidic channels is prepared using polydimethylsiloxane material by soft lithography, 3D printing or injection molding, wherein the diameter of the microfluidic channel is close to the diameter of the first part of the pinhole; Modifying the polydimethylsiloxane material by plasma treatment or ultraviolet radiation treatment, so that the microfluidic channel becomes a hydrophilic channel; The side of the microfluidic channel layer with the microfluidic channel is applied to the electroosmotic cathode layer and the detection electrode after position alignment, and then the side of the microfluidic channel layer without the microfluidic channel is fixed to the surface of the sensor substrate by reactive ion etching.

10. A method for preparing a microneedle electroosmotic blood glucose sensor, characterized in that: For preparing the microneedle electroosmotic blood glucose sensor according to claim 5 or 6, the preparation method comprises: Selecting a microneedle substrate and depositing metal in the electroosmotic region on the microneedle substrate to form an electroosmotic cathode layer, and forming a detection electrode in the electrode region; Punching holes on the microneedle substrate and the electroosmotic cathode layer to form a first portion of the pinhole; A microneedle support structure of a preset shape is printed on the second surface of the electroosmotic substrate by 3D printing technology, wherein the microneedle support structure includes a second portion coaxial with the first portion of the pinhole; Depositing metal on the surface of the microneedle support structure to form an electroosmotic anode layer; A microfluidic channel layer having multiple microfluidic channels is prepared, and the side of the microfluidic channel layer having the microfluidic channels is applied to the electroosmotic cathode layer and the detection electrode, and the side without the microfluidic channels is fixed to the surface of the sensor substrate.

Images