Flexible needle-type biosensor and method of manufacturing the same

Abstract

The application relates to the technical field of biosensors, in particular to a needle-shaped flexible biosensor and a preparation method thereof. The sensor comprises a plurality of working electrode layers formed on a plurality of corresponding first flexible substrates, a reference electrode layer formed on a second flexible substrate, a counter electrode layer, a counter electrode conductive contact layer and a packaging layer. The plurality of first flexible substrates and the second flexible substrate are pressure-bonded to form an electrode array needle body, the electrode array needle body is shaped to form a flexible probe needle, and the plurality of working electrode layers and the reference electrode layer are exposed in layers in a thin needle working area of the electrode array needle body. The application realizes integration of a plurality of mutually electrically isolated detection channels in a single needle body, has a compact structure, can perform multi-parameter detection, has strong stability and reduces implantation trauma.

Description

Technical Field

[0001] This application relates to the field of biosensor technology, and in particular to a needle-type flexible biosensor and its fabrication method. Background Technology

[0002] With the rapid development of biosensor technology, implantable medical devices have shown great potential in health management, disease monitoring, and personalized medicine. Biosensors that continuously monitor physiological indicators are gradually evolving from single-parameter detection to multi-parameter integration, providing more comprehensive and accurate data support for medical and health monitoring. Especially in scenarios such as chronic disease management and exercise physiology assessment, multi-parameter biosensors can provide real-time data on various metabolites, thereby achieving more efficient health management and disease prevention.

[0003] Currently, to meet the needs of multi-parameter detection, the industry commonly adopts the following solutions: First, multiple independent probes are implanted subcutaneously to monitor different analytes in real time; second, a multi-probe array structure is used to achieve simultaneous detection of multiple indicators using multiple sensing probes; third, multiple detection areas are set in the same needle body, and a multi-channel layout is achieved through a partitioned cavity structure. Furthermore, the manufacturing of existing multi-parameter sensors mainly relies on a full-process screen printing process, where conductive and insulating layers are stacked and formed by screen printing, and UV-cured resin or other materials are used for interlayer isolation. For example, invention patent application publication number CN116448849A discloses an implantable multifunctional electrochemical flexible biosensor and its preparation method. This implantable multifunctional electrochemical flexible biosensor includes a sensor body, which is a sheet-like structure. The sensor body includes a polymer base layer, an electrode material layer, a biosensitive membrane, an insulating layer, a bio-restriction membrane, and electrode contacts. The sensor body also includes a three-electrode system. Multiple electrode contacts are integrated on the sheet-like sensor body to form a multi-probe array structure.

[0004] However, the relevant technologies still have significant drawbacks. Using multiple independent probes can lead to wound enlargement, prolonged wound recovery time, and increased risk of rejection. Multi-probe array structures are too large to meet miniaturization requirements (electrode spacing ≥2mm in patent application CN116448849A). Separate cavity structures, due to their excessively large electrode spacing, cannot achieve a highly integrated single-needle multi-channel layout. Furthermore, traditional screen printing processes face problems such as uneven insulation layer thickness and insufficient interfacial bonding when densely arranging multiple channels, resulting in shortened sensor lifespan and decreased detection accuracy (interlayer resistance fluctuation ±15%). Therefore, how to achieve a highly integrated multi-channel electrode layout in a very small single-needle structure while ensuring electrical isolation and long-term stability has become a pressing technical challenge. Summary of the Invention

[0005] In order to integrate multi-channel electrodes in a single-needle structure sensor and ensure the electrical isolation and long-term stability of the sensor, this application provides a needle-type flexible biosensor and its fabrication method.

[0006] On the one hand, a needle-shaped flexible biosensor is provided, which adopts the following technical solution.

[0007] A needle-shaped flexible biosensor, comprising:

[0008] Multiple working electrode layers are formed on corresponding multiple first flexible substrates;

[0009] A reference electrode layer is formed on a second flexible substrate; wherein, a plurality of the first flexible substrates and the second flexible substrate are hot-pressed together to form an integral electrode array needle body, and the plurality of working electrode layers and the reference electrode layer have different lengths in the fine needle working area of ​​the electrode array needle body;

[0010] The electrode layer is formed on the back side of the electrode array needle body;

[0011] An encapsulation layer is formed on the surface of the electrode array needle body, exposing the fine needle working area and contact area of ​​the electrode array needle body; the electrode array needle body is shaped to form a flexible probe, and the flexible probe exposes multiple working electrode layers and reference electrode layers in layers in the fine needle working area of ​​the electrode array needle body.

[0012] By adopting the above technical solution, multiple working electrode layers and reference electrode layers are pressed together to form a single needle body structure, and the working areas of the fine needle are exposed in layers to form an integrated stacked soft needle structure. At the same time, a counter electrode layer and an encapsulation layer with through holes on the back are set, which realizes the integration of multiple electrically isolated detection channels in a single needle body. The structure is compact, capable of multi-parameter detection, has strong stability, and reduces implantation trauma.

[0013] Optionally, the Young's modulus of the first flexible substrate (11) and the second flexible substrate (12) is between 0.5-2 GPa, and the pressing temperature of the hot pressing process is 120±15℃; an insulating structure is provided between the first flexible substrate and the second flexible substrate, including a polyimide buffer layer or a fluoroplastic isolation film; the nanoscale roughness (Ra) of the first flexible substrate (11) is 50-100nm, the contact angle of the hydrophilic coating is <30°, and it has a gradient porosity structure.

[0014] By adopting the above technical solution, the Young's modulus of the first flexible substrate and the second flexible substrate is set at 0.5-2 GPa, and the pressing temperature of the hot pressing process is 120±15℃. This facilitates the formation of a high-performance integral electrode array needle body from multiple first flexible substrates and second flexible substrates during the hot pressing process. The insulating structure containing a polyimide buffer layer or a fluoroplastic separator between multiple first flexible substrates and second flexible substrates further ensures electrical isolation between different electrode layers in the stacked structure, prevents signal crosstalk, and improves the accuracy and stability of detection. Setting the nanoscale roughness of the first flexible substrate to 50-100 nm, the contact angle of the hydrophilic coating to <30°, and giving it a gradient porosity structure helps improve the surface properties of the first flexible substrate, better adapting it to the working electrode layer and related processes.

[0015] Optionally, the working electrode layer includes a working electrode, a working electrode conductive line, and a working electrode contact, wherein the working electrode is connected to the working electrode contact through the working electrode conductive line; the reference electrode layer includes a reference electrode, a reference conductive line, and a reference electrode contact, wherein the reference electrode is connected to the reference electrode contact through the reference conductive line.

[0016] By adopting the above technical solution, the specific composition of the working electrode layer and the reference electrode layer is clarified, including the electrode for sensing and detection, the conductive line for signal transmission, and the contact for external connection, which ensures the realization of the basic electrochemical detection function of the sensor and the effective extraction of the signal.

[0017] Optionally, the plurality of working electrodes and the reference electrode are exposed in layers in the fine needle working area of ​​the electrode array needle body, and the plurality of working electrode contacts and the reference electrode contacts are arranged alternately in the contact area of ​​the electrode array needle body, with a first dividing gap between the working electrode contacts.

[0018] By adopting the above technical solution, the layered exposure structure of the fine needle working area is conducive to the simultaneous detection of different substances by multiple working electrodes in a limited space; the staggered arrangement and clear demarcation of the contact area facilitates the independent and reliable connection of each electrode to the external circuit, reducing the connection difficulty and short circuit risk.

[0019] Optionally, the electrode array needle body has a through hole for the counter electrode, and a conductive contact layer for the counter electrode is formed on the front side of the electrode array needle body. The conductive contact layer for the counter electrode is connected to the counter electrode layer through the through hole for the counter electrode, and a second dividing notch is provided between the conductive contact layer for the counter electrode and the reference electrode contact. The counter electrode layer includes a counter electrode and a counter electrode conductive line, and the conductive contact layer for the counter electrode is connected to the counter electrode conductive line through the through hole for the counter electrode.

[0020] By adopting the above technical solution, a counter electrode layer is set on the back side and brought out using vias and conductive contact layers on the front side, forming a complete three-electrode detection system that ensures the integrity of the electrochemical reaction circuit.

[0021] Optionally, the encapsulation layer includes a front encapsulation layer covering the front side of the electrode array needle body and a back encapsulation layer covering the back side of the electrode array needle body. In the working area of ​​the fine needle, the front encapsulation layer exposes multiple working electrodes and the reference electrode, and the back encapsulation layer exposes the counter electrode. In the contact area, the front encapsulation layer exposes multiple working electrode contacts, the reference electrode contacts, and the conductive contact layer of the counter electrode. The back encapsulation layer covers the conductive lines of the counter electrode and the through-hole of the counter electrode. The needle-type flexible biosensor has a microfluidic channel disposed between the first flexible substrate and the front encapsulation layer, and has a trapezoidal cross-section.

[0022] By employing the above technical solution, the encapsulation layer precisely exposes the electrode sensing area required for operation and the contact area required for external connections, while protecting the rest, ensuring the sensor's functionality, stability, and durability in the working environment. A trapezoidal microfluidic channel is provided between the first flexible substrate and the front encapsulation layer, which facilitates fluid flow and distribution, improving sensor performance.

[0023] On the other hand, a method for fabricating a needle-shaped flexible biosensor is also provided, which adopts the following technical solution.

[0024] A method for fabricating a needle-shaped flexible biosensor includes the following steps:

[0025] S1. Corresponding working electrode layers are fabricated on multiple first flexible substrates;

[0026] S2. Prepare a reference electrode layer on the second flexible substrate;

[0027] S3. Multiple first flexible substrates and second flexible substrates are hot-pressed together to form an integral electrode array needle body, wherein multiple working electrode layers and reference electrode layers have different lengths in the fine needle working area of ​​the electrode array needle body;

[0028] S4. Prepare a counter electrode layer on the back side of the electrode array needle body;

[0029] S6. An encapsulation layer is formed on the surface of the electrode array needle body, the encapsulation layer covers the surface of the electrode array needle body, and exposes the fine needle working area and contact area of ​​the electrode array needle body;

[0030] S7. The electrode array needle body is cut and shaped to form a flexible probe. The flexible probe exposes multiple working electrode layers and reference electrode layers in layers in the fine needle working area of ​​the electrode array needle body.

[0031] By adopting the above technical solution, the electrode layers are prepared in layers and then pressed together, which avoids the deformation problem that may be caused by multiple high-temperature curing on the same substrate. This improves the process stability and yield of multilayer flexible device manufacturing and enables precise control of the exposure length of each electrode layer in the fine needle working area. Finally, a flexible probe with a layered exposure structure is formed by cutting.

[0032] Optionally, an insulating structure may be provided between the plurality of first flexible substrates and second flexible substrates prior to step S3.

[0033] By adopting the above technical solution, an insulating structure is set up before pressing to ensure reliable electrical isolation between different electrode layers during the subsequent pressing process, which provides a guarantee for the preparation of multi-channel sensors with low crosstalk and high stability.

[0034] Optionally, in step S1, the working electrode layer includes a working electrode, a working electrode conductive line, and a working electrode contact, wherein the working electrode is connected to the working electrode contact through the working electrode conductive line; in step S2, the reference electrode layer includes a reference electrode, a reference conductive line, and a reference electrode contact, wherein the reference electrode is connected to the reference electrode contact through the reference conductive line; in step S3, multiple working electrodes and the reference electrode are exposed in layers in the fine needle working area of ​​the electrode array needle body, and multiple working electrode contacts and the reference electrode contacts are arranged alternately in the contact area of ​​the electrode array needle body. The working electrode contacts have a first dividing gap; the counter electrode layer in step S4 includes a counter electrode and a counter electrode conductive line, and a counter electrode via is also formed in the electrode array needle body; between step S4 and step S6, step S5 is also included, which includes preparing a counter electrode conductive contact layer on the front side of the electrode array needle body, the counter electrode conductive contact layer is connected to the counter electrode layer through the counter electrode via, the counter electrode conductive contact layer and the reference electrode contact have a second dividing gap, and the counter electrode conductive contact in step S5 is connected to the counter electrode conductive line through the counter electrode via.

[0035] By adopting the above technical solution, the correct formation and connection of each key functional part of the sensor (working electrode, reference electrode, counter electrode and its wires and contacts) are ensured through specific preparation steps. The layered exposure of the fine needle working area and the staggered arrangement of the contact area are achieved through pressing, which ensures the integrity and functionality of the final sensor structure.

[0036] Optionally, in step S6, the encapsulation layer includes a front encapsulation layer covering the front side of the electrode array needle body and a back encapsulation layer covering the back side of the electrode array needle body. In the fine needle working area, the front encapsulation layer exposes a plurality of working electrodes and the reference electrode, and the back encapsulation layer exposes the counter electrode. In the contact area, the front encapsulation layer exposes a plurality of working electrode contacts, the reference electrode contacts, and the conductive contact layer of the counter electrode. The back encapsulation layer covers the conductive line of the counter electrode and the through-hole of the counter electrode.

[0037] By adopting the above technical solution, and by precisely controlling the range of the encapsulation layer, it is ensured that the sensing functional area of ​​the fine needle working area and the external connection area of ​​the contact area can be accurately exposed, while other areas are effectively protected, thus ensuring that the sensor can perform electrochemical detection normally and reliably connect to external devices.

[0038] In summary, this application includes at least one of the following beneficial technical effects:

[0039] 1. Multiple working electrode layers and reference electrode layers are pressed together to form a single needle body structure, and the working areas of the fine needle are exposed in layers to form an integrated stacked soft needle structure. At the same time, a counter electrode layer and an encapsulation layer with through holes on the back are set, which realizes the integration of multiple electrically isolated detection channels in a single needle body. The structure is compact, can perform multi-parameter detection, and reduces implantation trauma.

[0040] 2. The layered exposure structure of the fine needle working area is conducive to the simultaneous detection of different substances by multiple working electrodes within a limited space of the stacked soft needle structure; the staggered arrangement of the contact area facilitates the independent and reliable connection of each electrode to the external circuit, reducing the connection difficulty and short circuit risk.

[0041] 3. By preparing electrode layers in layers and then pressing them together, the deformation problem that may be caused by repeated high-temperature curing on the same substrate is avoided. The soft needle structure is stacked in the layered exposed fine needle working area. Even if deformation occurs, the multiple working electrode layers, the reference electrode layer and the counter electrode will not touch each other. This improves the process stability and yield of multilayer flexible device manufacturing and enables precise control of the exposure length of each electrode layer in the fine needle working area. Finally, a flexible probe with a layered exposure structure is formed by cutting. Attached Figure Description

[0042] Figure 1 This is a front view of the needle-type flexible biosensor according to an embodiment of this application;

[0043] Figure 2 This is a rear view of the needle-type flexible biosensor according to an embodiment of this application;

[0044] Figure 3 It is along Figure 1 Sectional view of line AA in the middle;

[0045] Figure 4 This is a schematic flowchart of the main steps of the fabrication method of the needle-type flexible biosensor according to an embodiment of this application;

[0046] Figure 5 It is execution Figure 4 The main view of the structure after the main step S1 ((A) is the blood glucose working electrode layer formed on the first flexible substrate, (B) is the uric acid working electrode layer formed on the first flexible substrate, and (C) is the lactic acid working electrode layer formed on the first flexible substrate).

[0047] Figure 6 It is execution Figure 4 The main view of the structure after the main step S2;

[0048] Figure 7 It is execution Figure 4 The arrangement relationship between the multiple first flexible substrates and the second flexible substrates in the main step S3;

[0049] Figure 8 It is execution Figure 4 The schematic diagram of the hot pressing process in the main step S3 is as follows: (A) printing hot-press adhesive on the first flexible substrate and the second flexible substrate; (B) arranging multiple first flexible substrates and second flexible substrates after the hot-press adhesive is printed; (C) hot-pressing multiple first flexible substrates and second flexible substrates so that the hot-press adhesive penetrates into the fiber structure of the first flexible substrates and second flexible substrates, and the multiple first flexible substrates and second flexible substrates form an integral structure.

[0050] Figure 9 It is execution Figure 4 A front perspective view of the structure after the main step S3 in the process;

[0051] Figure 10 It is execution Figure 4 Rear view of the structure after main step S4;

[0052] Figure 11 It is execution Figure 4 Front perspective view of the structure after main step S5;

[0053] Figure 12 It is execution Figure 4 The structural diagram after the main step S6 ((A) is the front perspective view, (B) is the rear view).

[0054] Explanation of reference numerals in the attached figures: 11, First flexible substrate; 12, Second flexible substrate; 13, Hot-pressed layer; 20, Working electrode layer; 21, Blood glucose working electrode layer; 21a, Blood glucose working electrode; 21b, Conductive circuit of blood glucose working electrode; 21c, Contact of blood glucose working electrode; 22, Uric acid working electrode layer; 22a, Uric acid working electrode; 22b, Conductive circuit of uric acid working electrode; 22c, Uric acid working electrode contact; 23, Lactic acid working electrode layer; 23a, Lactic acid working electrode; 23b 1. Lactic acid working electrode conductive circuit; 23c. Lactic acid working electrode contact; 24. Hollowed-out window; 30. Reference electrode layer; 40. Electrode array needle body; 41. Fine needle working area; 42. Contact area; 50. Counter electrode layer; 51. Counter electrode; 52. Counter electrode conductive circuit; 53. Counter electrode via; 54. Counter electrode conductive contact layer; 61. Front encapsulation layer; 62. Back encapsulation layer; 63. Boundary line; 70. Flexible probe; 71. First boundary notch; 72. Second boundary notch. Detailed Implementation

[0055] The following is in conjunction with the accompanying drawings. Figures 1 to 12 This application will be described in further detail.

[0056] This application discloses a needle-type flexible sensor.

[0057] Figure 1 This is a front view of the needle-type flexible biosensor according to an embodiment of this application. Figure 2 This is a rear view of the needle-type flexible biosensor according to an embodiment of this application. Figure 3 It is along Figure 1 Cross-sectional view along line AA. (Refer to...) Figures 1-3 The needle-shaped flexible biosensor includes multiple working electrode layers 20, a reference electrode layer 30, a counter electrode layer 50, and an encapsulation layer.

[0058] Multiple working electrode layers 20 are formed on corresponding multiple first flexible substrates 11. The thickness of the first flexible substrate 11 can be 0.01-0.1 mm, and the material of the first flexible substrate 11 can be one of polyethylene terephthalate (PET), polyimide (PI), and polyurethane (PU). The Young's modulus of the first flexible substrate 11 is between 0.5-2 GPa. The nanoscale roughness (Ra) of the first flexible substrate 11 is 50-100 nm, the contact angle of the hydrophilic coating of the first flexible substrate 11 is <30°, and the first flexible substrate 11 has a gradient porosity structure with a pore size gradient of 5-20 μm.

[0059] The working electrode layer 20 can be one of the blood glucose working electrode layer 21, the uric acid working electrode layer 22, and the lactic acid working electrode layer 23.

[0060] The blood glucose working electrode layer 21 can be formed on the first flexible substrate 11 using a screen printing process. The blood glucose working electrode layer 21 includes a blood glucose working electrode 21a, a blood glucose working electrode conductive line 21b, and a blood glucose working electrode contact 21c. The blood glucose working electrode 21a has a sensing area, which can be made of composite materials such as carbon, platinum-carbon, or carbon nanotubes, for electrochemical detection of blood glucose. The blood glucose working electrode conductive line 21b is formed using carbon paste printing for electrical signal transmission. The blood glucose working electrode contact 21c is formed using carbon material printing for connection to external circuits.

[0061] The uric acid working electrode layer 22 can be formed on the first flexible substrate 11 by screen printing. The uric acid working electrode layer 22 includes a uric acid working electrode 22a, a uric acid working electrode conductive line 22b, and a uric acid working electrode contact 22c. The uric acid working electrode 22a has a sensing area, which can be formed by mixing carbon-based conductive materials with functionalized fillers (such as carbon, platinum carbon, carbon nanotubes, etc.) for electrochemical reaction detection of uric acid. The uric acid working electrode conductive line 22b is formed by printing with carbon paste material for electrical signal transmission. The uric acid working electrode contact 22c is formed by printing with carbon material for connection to external circuitry.

[0062] The lactic acid working electrode layer 23 can be formed on the first flexible substrate 11 using a screen printing process. The lactic acid working electrode layer 23 includes a lactic acid working electrode 23a, a lactic acid working electrode conductive line 23b, and a lactic acid working electrode contact 23c. The lactic acid working electrode 23a has a sensing area, which can be made of composite materials such as carbon, platinum-carbon, or carbon nanotubes. The lactic acid working electrode conductive line 23b is formed using carbon paste material printing and is used for electrical signal transmission. The lactic acid working electrode contact 23c is formed using carbon material printing and is used for connection to external circuits.

[0063] The reference electrode layer 30 is formed on the second flexible substrate 12. Multiple first flexible substrates 11 and second flexible substrates 12 are hot-pressed together to form an integral electrode array needle body 40. Multiple working electrode layers 20 and the reference electrode layer 30 have different lengths in the fine needle working area 41 of the electrode array needle body 40. The hot-pressing process uses a pressing temperature of 120±15℃.

[0064] The thickness of the second flexible substrate 12 can be 0.01-0.1 mm, and the material of the second flexible substrate 12 can be one of polyethylene terephthalate (PET), polyimide (PI), or polyurethane (PU). The Young's modulus of the second flexible substrate 12 is between 0.5-2 GPa. The reference electrode layer 30 can be formed on the second flexible substrate 12 by screen printing. The reference electrode layer 30 includes a reference electrode 31, a reference electrode conductive line 32, and a reference electrode contact 33. The material of the reference electrode 31 can be silver, silver chloride, etc., which can enhance the stability and selectivity of the reference electrode 31. The reference electrode conductive line 32 is formed by carbon material printing and is used for electrical signal transmission. The reference electrode contact 33 is formed by carbon material printing and is used for connection with external circuits.

[0065] An insulating structure (not shown in the figure) is provided between multiple first flexible substrates 11 and second flexible substrates 12. The insulating structure may be a polyimide buffer layer or a fluoroplastic separator film. The thickness of the polyimide buffer layer may be 0.05 mm, and the thickness of the fluoroplastic separator film may be 0.02 mm. The blood glucose working electrode 21a, the uric acid working electrode 22a, the lactic acid working electrode 23a, and the reference electrode 31 are exposed in layers in the fine needle working area 41 of the electrode array needle body 40. The blood glucose working electrode contact 21c, the uric acid working electrode contact 22c, the lactic acid working electrode contact 23c, and the reference electrode contact 33 are arranged alternately in the contact area 42 of the electrode array needle body 40, and there is a first dividing notch 71 between the blood glucose working electrode contact 21c and the uric acid working electrode contact 22c, and between the uric acid working electrode contact 22c and the lactic acid working electrode contact 23c, to ensure electrical isolation between each working area.

[0066] The counter electrode layer 50 is formed on the back side of the electrode array needle body 40, and a counter electrode via 53 is provided in the electrode array needle body 40. The counter electrode layer 50 includes a counter electrode 51 and a counter electrode conductive line 52. The counter electrode 51 and the counter electrode conductive line 52 are formed on the back side of the electrode array needle body 40 by screen printing. The material of the counter electrode 51 and the counter electrode conductive line 52 can be pure carbon. The counter electrode via 53 is formed in the electrode array needle body 40 by laser engraving to facilitate subsequent connection with the front side of the electrode array needle body 40, providing an electrical connection for the counter electrode 51.

[0067] The conductive contact layer 54 of the counter electrode is formed on the front side of the electrode array needle body 40, and the conductive contact layer 54 of the counter electrode is connected to the counter electrode layer 50 through the counter electrode via 53. The conductive contact layer 54 of the counter electrode is formed on the front side of the electrode array needle body 40 by screen printing, and the material of the conductive contact layer 54 of the counter electrode is carbon. The conductive contact layer 54 of the counter electrode covers the counter electrode via 53. During the printing process, the conductive carbon ink covers the surface of the counter electrode via 53, so that the conductive contact layer 54 of the counter electrode is located on the front side of the electrode array needle body 40. The conductive contact layer 54 of the counter electrode can conduct with the conductive line 52 of the counter electrode located on the back side of the electrode array needle body 40 and is electrically connected to the counter electrode 51. There is a second dividing notch 72 between the conductive contact layer 54 of the counter electrode and the reference electrode contact 33 to ensure electrical isolation between the working areas. In addition, the needle insertion operation in the fine needle working area 41 will produce sliding linkage. The first dividing notch 71 and the second dividing notch 72 are positioned on both sides of the contact area 42, which can prevent the sliding of each electrode contact.

[0068] The encapsulation layer is formed on the surface of the electrode array needle body 40, exposing the fine needle working area 41 and contact area 42 of the electrode array needle body 40. The electrode array needle body 40 is formed into a flexible probe 70, which exposes multiple working electrode layers 20 and reference electrode layers 30 in layers within the fine needle working area 41 of the electrode array needle body 40. The encapsulation layer includes a front encapsulation layer 61 covering the front side of the electrode array needle body 40 and a back encapsulation layer 62 covering the back side of the electrode array needle body 40. The front encapsulation layer 61 exposes the blood glucose working electrode 21a, the uric acid working electrode 22a, the lactic acid working electrode 23a, and the reference electrode 31 in the fine needle working area 41. The contact area 42 exposes the blood glucose working electrode contact 21c, the uric acid working electrode contact 22c, the lactic acid working electrode contact 23c, the reference electrode contact 33, the counter electrode conductive contact layer 54, and the area where a first boundary notch 71 and a second boundary notch 72 are predetermined. The back encapsulation layer 62 exposes the counter electrode 51 in the fine needle working area 41. A microfluidic channel is provided between the first flexible substrate 11 and the front encapsulation layer 61. The cross-section of the microfluidic channel is trapezoidal, wherein the length of the trapezoidal base can be 100 μm, and the length of the trapezoidal opening can be 50 μm.

[0069] Experimental verification and comparison between the needle-type flexible biosensor of this application embodiment and flexible biosensors in related technologies revealed the following: The electrode impedance of the flexible biosensors in related technologies is 5.8±1.2kΩ, the crosstalk rate is ≥12%, the bending fatigue life is less than 200 cycles, and the retention time in vivo is less than 30 days. In contrast, the needle-type flexible biosensor of this application embodiment has an electrode impedance of 2.1±0.3kΩ, a crosstalk rate ≤5%, a bending fatigue life greater than 500 cycles, and a retention time in vivo exceeding 90 days. Therefore, compared to related technologies, the needle-type flexible biosensor of this application embodiment shows significant optimization and improvement in electrode impedance, crosstalk rate, bending fatigue life, and in vivo retention time.

[0070] The implementation principle of a needle-type flexible biosensor in this application embodiment is as follows: multiple working electrode layers 20 and reference electrode layers 30 are pressed together to form a single needle structure, and the working area 41 of the fine needle is exposed in layers. At the same time, a counter electrode layer 50 with a counter electrode through hole 53 connected on the back and a back encapsulation layer 62 covering the conductive line 52 of the counter electrode are provided. This realizes the integration of multiple electrically isolated detection channels in a single needle body. The structure is compact, capable of multi-parameter detection, has strong stability, and reduces implantation trauma.

[0071] This application also discloses a method for fabricating a needle-shaped flexible biosensor.

[0072] Figure 4 This is a schematic flowchart of the main steps in a method for fabricating a needle-shaped flexible biosensor according to an embodiment of this application. (Refer to...) Figure 4 The method includes the following main steps:

[0073] S1. Corresponding working electrode layers 20 are prepared on multiple first flexible substrates 11.

[0074] S2. Prepare a reference electrode layer 30 on the second flexible substrate 12.

[0075] S3. Multiple first flexible substrates 11 and second flexible substrates 12 are hot-pressed together to form an integral electrode array needle body 40. Multiple working electrode layers 20 and reference electrode layers 30 have different lengths in the fine needle working area 41 of the electrode array needle body 40.

[0076] S4. A counter electrode layer 50 is prepared on the back side of the electrode array needle body 40, and a counter electrode via 53 is formed in the electrode array needle body 40.

[0077] S5. A conductive contact layer 54 for the counter electrode is prepared on the front side of the electrode array needle body 40. The conductive contact layer 54 for the counter electrode is connected to the counter electrode layer 50 through the counter electrode via 53.

[0078] S6. An encapsulation layer is formed on the surface of the electrode array needle body 40, the encapsulation layer covers the surface of the electrode array needle body 40, and exposes the fine needle working area 41 and contact area 42 of the electrode array needle body 40.

[0079] S7. The electrode array needle body 40 is cut and shaped to form a flexible probe 70. The flexible probe 70 exposes multiple working electrode layers 20 and reference electrode layers 30 in layers in the fine needle working area 41 of the electrode array needle body 40.

[0080] The main steps of this method are explained in detail below.

[0081] In the main step S1, corresponding working electrode layers 20 are prepared on multiple first flexible substrates 11. Figure 5 It is execution Figure 4 The main view of the structure after main step S1 ((A) is the blood glucose working electrode layer 21 formed on the first flexible substrate 11, (B) is the uric acid working electrode layer 22 formed on the first flexible substrate 11, and (C) is the lactic acid working electrode layer 23 formed on the first flexible substrate 11). (Refer to...) Figure 5 A blood glucose working electrode layer 21 can be prepared on one of the first flexible substrates 11, a uric acid working electrode layer 22 can be prepared on another of the first flexible substrates 11, and a lactic acid working electrode layer 23 can be prepared on another of the first flexible substrates 11.

[0082] The thickness of the first flexible substrate 11 can be 0.01-0.1 mm, and the material of the first flexible substrate 11 can be one of polyethylene terephthalate (PET), polyimide (PI), and polyurethane (PU). The blood glucose working electrode layer 21 can be formed on the first flexible substrate 11 by screen printing. The blood glucose working electrode layer 21 includes a blood glucose working electrode 21a, a blood glucose working electrode conductive line 21b, and a blood glucose working electrode contact 21c. The blood glucose working electrode 21a has a sensing area, which can be made of composite materials such as carbon, platinum carbon, and carbon nanotubes, for electrochemical response detection of blood glucose. The blood glucose working electrode conductive line 21b is formed by printing with carbon paste material for electrical signal transmission. The blood glucose working electrode contact 21c is formed by printing with carbon material for connection with external circuits.

[0083] The uric acid working electrode layer 22 can be formed on another first flexible substrate 11 by screen printing. The uric acid working electrode layer 22 includes a uric acid working electrode 22a, a uric acid working electrode conductive line 22b, and a uric acid working electrode contact 22c. The uric acid working electrode 22a has a sensing area, which can be made of a mixture of carbon-based conductive material and functionalized filler (such as carbon, platinum carbon, carbon nanotubes, etc.) for electrochemical reaction detection of uric acid. The uric acid working electrode conductive line 22b is formed by printing with carbon paste material for electrical signal transmission. The uric acid working electrode contact 22c is formed by printing with carbon material for connection with external circuits. The uric acid working electrode layer 22 has a hollow window 24 laser-engraved in the fine needle working area 41 to expose the blood glucose working electrode 21a during subsequent hot pressing and bonding, ensuring that the functional areas between channels do not interfere with each other.

[0084] The lactic acid working electrode layer 23 can be formed on another first flexible substrate 11 by screen printing. The lactic acid working electrode layer 23 includes a lactic acid working electrode 23a, a lactic acid working electrode conductive line 23b, and a lactic acid working electrode contact 23c. The lactic acid working electrode 23a has a sensing area, which can be made of composite materials such as carbon, platinum carbon, or carbon nanotubes. The lactic acid working electrode conductive line 23b is formed by printing with carbon paste material and is used for electrical signal transmission. The lactic acid working electrode contact 23c is formed by printing with carbon material and is used for connection with external circuits. The uric acid working electrode layer 22 has a hollow window 24 in the fine needle working area 41 by laser engraving, which is used to expose the blood glucose working electrode 21a and the uric acid working electrode 22a during subsequent hot pressing and bonding, so as to realize single needle multi-channel collaborative output.

[0085] Figure 6 It is execution Figure 4 The main view of the structure after main step S2. (Refer to...) Figure 6In main step S2, a reference electrode layer 30 is prepared on a second flexible substrate 12. The thickness of the second flexible substrate 12 can be 0.01-0.1 mm, and the material of the second flexible substrate 12 can be one of polyethylene terephthalate (PET), polyimide (PI), or polyurethane (PU). The reference electrode layer 30 can be formed on the second flexible substrate 12 by screen printing. The reference electrode layer 30 includes a reference electrode 31, a reference electrode conductive line 32, and a reference electrode contact 33. The material of the reference electrode 31 can be silver, silver chloride, etc., which can enhance the stability and selectivity of the reference electrode 31. The reference electrode conductive line 32 is formed by carbon material printing and is used for electrical signal transmission. The reference electrode contact 33 is formed by carbon material printing and is used for connection with external circuits. The reference electrode layer 30 has a hollow window 24 laser-engraved in the fine needle working area 41 to expose the blood glucose working electrode 21a, the uric acid working electrode 22a and the lactic acid working electrode 23a during subsequent hot pressing and bonding, so as to ensure that the functional areas of each detection channel do not interfere with each other.

[0086] Figure 7 It is execution Figure 4 The arrangement relationship between the multiple first flexible substrates and the second flexible substrates in the main step S3. Figure 8 It is execution Figure 4 The schematic diagram of the hot pressing process of the main step S3 is as follows: (A) printing hot pressing adhesive on the first flexible substrate and the second flexible substrate; (B) stacking multiple first flexible substrates and second flexible substrates after printing hot pressing adhesive; (C) hot pressing multiple first flexible substrates and second flexible substrates so that the hot pressing adhesive penetrates into the fiber structure of the first flexible substrate and the second flexible substrate, and multiple first flexible substrates and second flexible substrates form an integral structure. Figure 9 It is execution Figure 4 A front perspective view of the structure after main step S3. (Refer to...) Figures 7-9 In the main step S3, multiple first flexible substrates 11 and second flexible substrates 12 are thermally pressed together to form an integral electrode array needle body 40. Multiple working electrode layers 20 and reference electrode layers 30 have different lengths in the fine needle working area 41 of the electrode array needle body 40.

[0087] Before step S3, an insulating structure is provided between the plurality of first flexible substrates 11 and second flexible substrates 12. The insulating structure can be a polyimide film or a fluoroplastic film, and its thickness can be adjusted according to actual needs. This insulating structure effectively prevents short circuits between the first flexible substrate 11 and the second flexible substrate 12, improving the overall reliability of the structure. Furthermore, the insulating structure also acts as a buffer, reducing the impact of the external environment on the electrode layer and further improving detection performance.

[0088] Then, the previously prepared blood glucose working electrode layer 21, uric acid working electrode layer 22, lactic acid working electrode layer 23 and reference electrode layer 30 are stacked together and fused into a whole electrode array needle body 40 by hot pressing. During the hot-pressing process, hot-pressing adhesive is first printed on the back of the first flexible substrate 11 on which the uric acid working electrode layer 22 is formed, the first flexible substrate 11 on which the lactic acid working electrode layer 23 is formed, and the second flexible substrate 12 on which the reference electrode layer 30 is formed to form a hot-pressing layer 13. After printing the hot-pressing adhesive, multiple first flexible substrates 11 and second flexible substrates 12 are stacked, so that the blood glucose working electrode layer 21, the uric acid working electrode layer 22, the lactic acid working electrode layer 23 and the reference electrode layer 30 are stacked in a specific order to ensure precise alignment of the fine needle working area 41. Then, the different layers of materials are bonded by hot-pressing technology, so that the hot-pressing adhesive in the hot-pressing layer 13 penetrates into the fiber structure of the first flexible substrate 11 and the second flexible substrate 12 under certain temperature and pressure, forming a strong bond and forming an integral electrode array needle body 40. The blood glucose working electrode 21a, the uric acid working electrode 22a, the lactic acid working electrode 23a, and the reference electrode 31 are exposed in layers in the fine needle working area 41 of the electrode array needle body 40, and the blood glucose working electrode contact 21c, the uric acid working electrode contact 22c, the lactic acid working electrode contact 23c, and the reference electrode contact 33 are arranged alternately in the contact area of ​​the electrode array needle body 40.

[0089] The hot-pressing process can be applied at temperatures ranging from 100°C to 160°C, ensuring thorough bonding of the materials and preventing degradation due to overheating. The application time can range from 30 to 180 seconds, adjusted based on the material thickness and required bond strength. The application pressure can be from 0.5 MPa to 3 MPa to ensure tight bonding between layers, reducing interlayer bubbles and voids, and ensuring the overall electrical performance and stability of the electrode. During hot pressing, it is crucial to ensure complete bonding of the insulation structure between layers, preventing interlayer bubbles, cracks, or delamination, thus guaranteeing electrical stability during long-term use.

[0090] Figure 10It is execution Figure 4 The rear view of the structure after main step S4. (Refer to...) Figure 10 In main step S4, a counter electrode layer 50 is prepared on the back side of the electrode array needle body 40, and a counter electrode via 53 is formed in the electrode array needle body 40. The counter electrode layer 50 includes a counter electrode 51 and a counter electrode conductive line 52. The counter electrode 51 and the counter electrode conductive line 52 are formed on the back side of the electrode array needle body 40 by screen printing. The material of the counter electrode 51 and the counter electrode conductive line 52 can be pure carbon. Furthermore, the counter electrode via 53 is formed in the electrode array needle body 40 by laser engraving to facilitate subsequent connection with the front side of the electrode array needle body 40, providing an electrical connection for the counter electrode 51.

[0091] Figure 11 It is execution Figure 4 A front perspective view of the structure after main step S5. (Refer to...) Figure 11 In main step S5, a conductive contact layer 54 for the counter electrode is formed on the front side of the electrode array needle body 40. The conductive contact layer 54 is connected to the counter electrode layer 50 through the counter electrode via 53. The conductive contact layer 54 is formed on the front side of the electrode array needle body 40 using a screen printing process, and the material of the conductive contact layer 54 is carbon. The conductive contact layer 54 covers the counter electrode via 53. During the printing process, the conductive carbon ink covers the surface of the counter electrode via 53, making the conductive contact layer 54 on the front side of the electrode array needle body 40 conductive on the front side of the electrode array needle body 40 conductive on the back side of the electrode array needle body 40 conductive on the counter electrode 51.

[0092] Figure 12 It is execution Figure 4 The structural diagram after main step S6 ((A) is a front perspective view, (B) is a rear view). See reference. Figure 12In main step S6, an encapsulation layer is formed on the surface of the electrode array needle body 40. The encapsulation layer covers the surface of the electrode array needle body 40 and exposes the fine needle working area 41 and contact area 42 of the electrode array needle body 40. The encapsulation layer includes a front encapsulation layer 61 covering the front side of the electrode array needle body 40 and a back encapsulation layer 62 covering the back side of the electrode array needle body 40. The front encapsulation layer 61 exposes the blood glucose working electrode 21a, the uric acid working electrode 22a, the lactic acid working electrode 23a, the reference electrode 31, and the area where the first boundary notch 71 and the second boundary notch 72 are to be formed in the fine needle working area 41. The contact area 42 exposes the blood glucose working electrode contact 21c, the uric acid working electrode contact 22c, the lactic acid working electrode contact 23c, the reference electrode contact 33, and the counter electrode conductive contact layer 54. The back encapsulation layer 62 exposes the counter electrode 51 in the fine needle working area 41.

[0093] The encapsulation layer can be made of UV-insulating material, formed on the surface of the electrode array needle body 40 by screen printing. This material has good insulation and stability, ensuring electrical isolation between electrodes and enhancing the long-term stability of the sensor, thus preventing interference or damage from the external environment. The dividing line 63 of the encapsulation layer is used to separate the fine needle working area 41 inside the insert from the external connection area, ensuring the stability of the data transmission path.

[0094] Figure 1 This is a front view of the needle-type flexible biosensor according to an embodiment of this application. Figure 2 This is a rear view of the needle-type flexible biosensor according to an embodiment of this application. Figure 3 It is along Figure 1 Cross-sectional view along line AA. (Refer to...) Figures 1-3 In main step S7, the electrode array needle body 40 is cut and shaped to form a flexible probe 70, thus completing the fabrication of the needle-type flexible biosensor. The flexible probe 70 exposes multiple working electrode layers 20 and reference electrode layers 30 in layers within the fine needle working area 41 of the electrode array needle body 40.

[0095] The electrode array needle body 40 can be precisely cut using laser engraving technology to ensure a clear division of the shape and functional areas of the needle-shaped flexible biosensor. During the engraving process, laser engraving technology is used to precisely cut the packaged electrode array needle body 40 to create the required shape and size, ensuring the integrity of the contact area 42. Laser engraving not only cuts out the sensor's shape but also creates a clear first boundary notch 71 between the blood glucose working electrode contact 21c and the uric acid working electrode contact 22c, and between the uric acid working electrode contact 22c and the lactic acid working electrode contact 23c. A clear second boundary notch 72 is also created between the reference electrode contact 33 and the counter electrode conductive contact layer 54, thus delineating the external electrode working area and the implantation area in the human body, ensuring clear functionality for each area. After engraving, it is ensured that the implantation area in the human body is connected to the external electrode working area, while maintaining complete electrical isolation between the functional areas to ensure smooth signal transmission and avoid cross-interference.

[0096] The implementation principle of the needle-type flexible biosensor fabrication method in this application embodiment is as follows: by preparing electrode layers in layers and then pressing them together, the deformation problem that may be caused by multiple high-temperature curing on the same substrate is avoided, the process stability and yield of multilayer flexible device manufacturing are improved, and the exposure length of each electrode layer in the fine needle working area 41 can be precisely controlled. Finally, a flexible probe 70 with a layered exposure structure is formed by cutting.

[0097] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A needle-shaped flexible biosensor, characterized in that, include: Multiple working electrode layers (20) are formed on corresponding multiple first flexible substrates (11); A reference electrode layer (30) is formed on a second flexible substrate (12); wherein, a plurality of first flexible substrates (11) and second flexible substrates (12) are pressed together to form an integral electrode array needle body (40), and the plurality of working electrode layers (20) and the reference electrode layer (30) have different lengths in the fine needle working area (41) of the electrode array needle body (40); the Young's modulus of the first flexible substrate (11) and the second flexible substrate (12) is between 0.5-2 GPa, and the pressing temperature of the hot pressing process is 120±15℃; an insulating structure is provided between the plurality of first flexible substrates (11) and the second flexible substrate (12), including a polyimide buffer layer or a fluoroplastic isolation film; the nanoscale roughness (Ra) of the first flexible substrate (11) is 50-100nm, the contact angle of the hydrophilic coating is <30°, and it has a gradient porosity structure; The electrode layer (50) is formed on the back side of the electrode array needle body (40); An encapsulation layer is formed on the surface of the electrode array needle body (40) and exposes the fine needle working area (41) and contact area (42) of the electrode array needle body (40); the electrode array needle body (40) is formed into a flexible probe (70), and the flexible probe (70) exposes multiple working electrode layers (20) and reference electrode layers (30) in layers in the fine needle working area (41) of the electrode array needle body (40), so that the multiple working electrode layers (20) and reference electrode layers (30) form a three-dimensional layered exposure structure to integrate multiple electrically isolated detection channels in a single needle body.

2. The needle-type flexible biosensor according to claim 1, characterized in that, The working electrode layer (20) includes working electrodes (21a, 22a, 23a), working electrode conductive lines (21b, 22b, 23b), and working electrode contacts (21c, 22c, 23c). The working electrodes (21a, 22a, 23a) are connected to the working electrode contacts (21c, 22c, 23c) through the working electrode conductive lines (21b, 22b, 23b). The reference electrode layer (30) includes a reference electrode (31), a reference conductive line (32), and a reference electrode contact (33). The reference electrode (31) is connected to the reference electrode contact (33) through the reference conductive line (32).

3. The needle-type flexible biosensor according to claim 2, characterized in that, Multiple working electrodes (21a, 22a, 23a) and the reference electrode (31) are exposed in layers in the fine needle working area (41) of the electrode array needle body (40), and multiple working electrode contacts (21c, 22c, 23c) and the reference electrode contact (33) are arranged alternately in the contact area (42) of the electrode array needle body (40), and there is a first dividing gap (71) between the working electrode contacts (21c, 22c, 23c).

4. The needle-type flexible biosensor according to claim 2, characterized in that, The electrode array needle body (40) has a through hole (53) for the counter electrode. A conductive contact layer (54) for the counter electrode is formed on the front side of the electrode array needle body (40). The conductive contact layer (54) for the counter electrode is connected to the counter electrode layer (50) through the through hole (53). There is a second dividing gap (72) between the conductive contact layer (54) for the counter electrode and the reference electrode contact (33). The counter electrode layer (50) includes a counter electrode (51) and a counter electrode conductive line (52). The conductive contact layer (54) for the counter electrode is connected to the counter electrode conductive line (52) through the through hole (53).

5. The needle-type flexible biosensor according to claim 4, characterized in that, The encapsulation layer includes a front encapsulation layer (61) covering the front of the electrode array needle body (40) and a back encapsulation layer (62) covering the back of the electrode array needle body (40); in the needle working area (41), the front encapsulation layer (61) exposes a plurality of working electrodes (21a, 22a, 23a) and the reference electrode (31), and the back encapsulation layer (62) exposes the counter electrode (51); in the contact area (42), the front encapsulation layer (61) exposes a plurality of working electrode contacts (21c, 22c, 23c), the reference electrode contact (33) and the counter electrode conductive contact layer (54), and the back encapsulation layer (62) covers the counter electrode conductive line (52) and the counter electrode via (53); the needle-type flexible biosensor has a microfluidic channel disposed between the first flexible substrate (11) and the front encapsulation layer (61), and has a trapezoidal cross-section.

6. A method for fabricating a needle-shaped flexible biosensor, characterized in that, Includes the following steps: S1. Corresponding working electrode layers (20) are prepared on multiple first flexible substrates (11). S2. Prepare a reference electrode layer (30) on the second flexible substrate (12); S3. Multiple first flexible substrates (11) and second flexible substrates (12) are hot-pressed together to form an integral electrode array needle body (40). Multiple working electrode layers (20) and reference electrode layers (30) have different lengths in the fine needle working area (41) of the electrode array needle body (40). The Young's modulus of the first flexible substrate (11) and the second flexible substrate (12) is between 0.5-2 GPa, and the pressing temperature of the hot pressing process is 120±15℃. An insulating structure is provided between the multiple first flexible substrates (11) and the second flexible substrates (12), including a polyimide buffer layer or a fluoroplastic isolation film. The nanoscale roughness (Ra) of the first flexible substrate (11) is 50-100nm, the contact angle of the hydrophilic coating is <30°, and it has a gradient porosity structure. S4. Prepare a counter electrode layer (50) on the back side of the electrode array needle body (40). S6. An encapsulation layer is formed on the surface of the electrode array needle body (40), the encapsulation layer covers the surface of the electrode array needle body (40) and exposes the fine needle working area (41) and contact area (42) of the electrode array needle body (40). S7. The electrode array needle body (40) is cut and shaped to form a flexible probe (70). The flexible probe (70) exposes multiple working electrode layers (20) and reference electrode layers (30) in the fine needle working area (41) of the electrode array needle body (40) in layers, so that the multiple working electrode layers (20) and reference electrode layers (30) form a three-dimensional layered exposure structure to integrate multiple electrically isolated detection channels in a single needle body.

7. The method for fabricating the needle-shaped flexible biosensor according to claim 6, characterized in that, An insulating structure is provided between the plurality of first flexible substrates (11) and second flexible substrates (12) prior to step S3.

8. The method for fabricating the needle-shaped flexible biosensor according to claim 6, characterized in that, In step S1, the working electrode layer (20) includes working electrodes (21a, 22a, 23a), working electrode conductive lines (21b, 22b, 23b), and working electrode contacts (21c, 22c, 23c). The working electrodes (21a, 22a, 23a) are connected to the working electrode contacts (21c, 22c, 23c) through the working electrode conductive lines (21b, 22b, 23b). In step S2, the reference electrode layer (30) includes a reference electrode (31), a reference conductive line (32), and a reference electrode contact (33). The reference electrode (31) is connected to the reference electrode contact (33) through the reference conductive line (32). In step S3, multiple working electrodes (21a, 22a, 23 ... 23a) The reference electrode (31) and the reference electrode (33) are exposed in layers in the fine needle working area (41) of the electrode array needle body (40), and multiple working electrode contacts (21c, 22c, 23c) and the reference electrode contact (33) are arranged alternately in the contact area (42) of the electrode array needle body (40). There is a first dividing gap (71) between 23c); the counter electrode layer (50) in step S4 includes a counter electrode (51) and a counter electrode conductive line (52), and a counter electrode via (53) is also opened in the electrode array needle body (40); between step S4 and step S6, there is also step S5, which includes preparing a counter electrode conductive contact layer (54) on the front side of the electrode array needle body (40), the counter electrode conductive contact layer (54) is connected to the counter electrode layer (50) through the counter electrode via (53), there is a second dividing gap (72) between the counter electrode conductive contact layer (54) and the reference electrode contact (33), and the counter electrode conductive contact layer (54) in step S5 is connected to the counter electrode conductive line (52) through the counter electrode via (53).

9. The method for fabricating the needle-shaped flexible biosensor according to claim 8, characterized in that, In step S6, the encapsulation layer includes a front encapsulation layer (61) covering the front side of the electrode array needle body (40) and a back encapsulation layer (62) covering the back side of the electrode array needle body (40); in the fine needle working area (41), the front encapsulation layer (61) exposes a plurality of working electrodes (21a, 22a, 23a) and the reference electrode (31), and the back encapsulation layer (62) exposes the counter electrode (51); in the contact area (42), the front encapsulation layer (61) exposes a plurality of working electrode contacts (21c, 22c, 23c), the reference electrode contact (33) and the counter electrode conductive contact layer (54), and the back encapsulation layer (62) covers the counter electrode conductive line (52) and the counter electrode via (53).

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