A microneedle array electrode with insulating film and preparation method thereof

Abstract

The present invention is applicable to the field of bioelectric signal monitoring technology and provides a microneedle array electrode with an insulating film, comprising: multiple groups of microneedle matrices arranged on a microneedle array base, and the multiple groups of microneedle matrices are conductive to each other; an insulating film, wherein the insulating film covers the surface of the microneedle matrices. The present invention is an insulating film microneedle array electrode, which can effectively shield unstable external signal noise caused by epidermal sweat or the stratum corneum itself by isolating the skin epidermis and the skin stratum corneum from contact with the microneedle conductive area. On the other hand, it can avoid the interference of epidermal sebum membrane, keratinocytes and intercellular lipid noise on signal transmission, realize the precise collection and transmission of electrical signals of active cells in the epidermis, and avoid interference caused by external interference signals from the skin on the bioelectric signal itself and the conduction of the bioelectric signal.

Description

Technical Field

[0001] The present invention relates to the technical field of bioelectric signal monitoring, in particular to a microneedle array electrode with an insulating film and a preparation method thereof. Background Art

[0002] Biosignals help us understand human pathological and physiological conditions and have crucial applications in home healthcare and health management, including electrocardiogram (ECG) signals, electromyogram (EMG) signals, and electroencephalogram (EEG) signals. Currently, the mainstream method for extracting biosignals is through wet electrodes or metal dry electrodes. However, wet electrodes require skin preparation and application of conductive gel during use, making it difficult to quickly and easily acquire signals. Metal dry electrodes are subject to interference from the skin's stratum corneum, resulting in poor signal accuracy. Microneedle array electrodes can overcome the problems of conductive paste drying out, skin allergies, poor flexibility, and unstable signal quality during long-term testing associated with wet electrodes. They can also overcome the problem of metal dry electrodes being subject to interference from the skin's stratum corneum. Microneedle array electrodes are generally 50-400 μm in length and can penetrate the skin's stratum corneum to the distribution of living cells at the lower end of the epidermis. They collect and transmit bioelectrical signals by conducting electrical signals from living cells. Furthermore, because the microneedle array electrodes pierce the stratum corneum but do not reach the dermis or subcutaneous tissue, they do not cause pain or bleeding. The top layer of the skin epidermis is the stratum corneum, which is mostly composed of necrotic cells. It is a poor conductor of electricity and has a certain impedance to low-voltage current.

[0003] In actual biosignal collection, existing microneedle array electrodes are subject to unstable signal noise interference due to the contact between the skin and the electrodes, which is affected by factors such as skin deformation and hair movement. In particular, when sweat glands secrete sweat, the microneedle array electrodes and the skin's outer surface generate significant stratum corneum noise, affecting the accuracy of bioelectrical signal collection and transmission. Therefore, in response to this situation, there is an urgent need to provide a microneedle array electrode with an insulating film and a preparation method to overcome the shortcomings of current practical applications. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a microneedle array electrode with an insulating film and a preparation method thereof, aiming to solve the following problem: in actual biological signal collection, the existing microneedle array electrode is in contact with the skin on the body surface and is affected by factors such as skin deformation and hair movement on the skin surface, resulting in unstable signal noise interference. In particular, when the skin sweat glands secrete sweat, the microneedle array electrode and the outer surface of the skin will generate large stratum corneum noise, affecting the accuracy of bioelectric signal collection and transmission, and therefore it is difficult to be widely used.

[0005] The embodiment of the present invention is implemented as follows: a microneedle array electrode with an insulating film, wherein the microneedle array electrode with an insulating film comprises:

[0006] Multiple groups of microneedle matrices are arranged on a microneedle array substrate, and the multiple groups of microneedle matrices are interconnected;

[0007] An insulating film is covered on the surface of the microneedle substrate.

[0008] A method for preparing a microneedle array electrode with an insulating film, the method comprising the following steps:

[0009] Step 1: Prepare microneedle array;

[0010] Step 2: Prepare an insulating structure on the microneedle array in step 1 to obtain a microneedle array electrode with an insulating film.

[0011] Compared with the prior art, the beneficial effects of the embodiments of the present invention are as follows: the present invention is an insulating thin film microneedle array electrode, which can effectively shield the unstable external signal noise caused by epidermal sweat or the stratum corneum itself by isolating the skin epidermis and the skin stratum corneum from contact with the microneedle conductive area. On the other hand, it can avoid the interference of epidermal sebum membrane, keratinocytes and intercellular lipid noise on signal transmission, realize the precise collection and transmission of electrical signals of active cells in the epidermis, and avoid interference caused by external interference signals of the skin to the bioelectric signal itself and the conduction of bioelectric signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the structure of the conductive microneedle body in an embodiment of the present invention.

[0013] Figure 2 A schematic structural diagram of a microneedle array electrode with an insulating film provided in an embodiment of the present invention.

[0014] Figure 3 Schematic diagram of coating an insulating film layer on the surface of a microneedle in an embodiment of the present invention.

[0015] Figure 4 Schematic diagram of applying a protective layer on the upper end of a microneedle needle in an embodiment of the present invention.

[0016] Figure 5 Schematic diagram of coating a protective layer on the bottom of a microneedle tip coated with an insulating film layer according to an embodiment of the present invention.

[0017] Figure 6 for Figure 1 Schematic diagram of the side structure.

[0018] Figure 7 for Figure 2 Schematic diagram of the side structure.

[0019] Figure 8 for Figure 3Schematic diagram of the side structure.

[0020] Figure 9 for Figure 4 Schematic diagram of the side structure.

[0021] Figure 10 for Figure 5 Schematic diagram of the side structure.

[0022] In the accompanying drawings: 1-microneedle substrate, 2-insulating film, 3-protective layer. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0025] See also Figures 1-10 An embodiment of the present invention provides a microneedle array electrode with an insulating film, wherein the microneedle array electrode with an insulating film comprises:

[0026] A plurality of groups of microneedle matrices 1 are arranged on a microneedle array substrate, and the plurality of groups of microneedle matrices 1 are electrically connected to each other;

[0027] an insulating film 2, wherein the insulating film 2 covers the surface of the microneedle substrate 1; and

[0028] The protective layer 3 is provided on the microneedle substrate 1 and includes a mask protective layer and an etching protective layer.

[0029] In an embodiment of the present invention, a microneedle array is formed by arranging multiple groups of microneedle matrices 1 on a microneedle array substrate. The insulating film 2 isolates the contact between the microneedle array electrodes and the surface skin, thereby reducing the influence of surface skin signal interference without affecting the extraction of bioelectric signals from the microneedle needle tips, and ultimately significantly improving the accuracy of the extracted biosignals. The insulating film 2 covers 10-95% of the total height of the microneedles at the lower end of the microneedle matrix 1 and the bottom of the microneedle matrix 1, and the aspect ratio of the microneedle electrodes is 1.0-2.5.

[0030] In one embodiment of the present invention, see Figure 2 The insulating film 2 is made of a high-insulating oxide.

[0031] In this embodiment, the highly insulating oxide is such as aluminum oxide, silicon oxide, etc.

[0032] In one embodiment of the present invention, see Figure 2 The insulating film 2 is made of insulating polymer.

[0033] In this embodiment, the insulating polymer is such as parylene.

[0034] In one embodiment of the present invention, see Figure 2 The thickness of the insulating film 2 is 0.01-20 μm.

[0035] In one embodiment of the present invention, see Figure 1 The microneedle substrate 1 is made of single crystal silicon.

[0036] In this embodiment, the microneedle substrate 1 can also be made of materials such as metal or high molecular polymer.

[0037] In one embodiment of the present invention, see Figure 1 The microneedle array substrate is made of at least one material selected from the group consisting of stainless steel, copper, gold, tungsten, platinum, silver, iron, silicon, silver chloride, a flexible material, and a flexible material doped with conductive particles.

[0038] A method for preparing a microneedle array electrode with an insulating film, the method comprising the following steps:

[0039] Step 1: Prepare microneedle array;

[0040] Step 2: Prepare an insulating structure on the microneedle array in step 1 to obtain a microneedle array electrode with an insulating film.

[0041] In one embodiment of the present invention, in step 1, the method for preparing the microneedle array comprises:

[0042] Step 1.1: Fabricate a silicon-based microneedle array using a wet etching method. A 1.0-2.0 mm thick silicon wafer is selected as the microneedle substrate 1 of the microneedle array. A 100-500 nm thick silicon oxide layer is used as a masking layer for the counter electrode. An anisotropic cycle is performed using the Bosch process. C4F8 gas is introduced at a flow rate of approximately 50-90 mL / min for etching for 5-10 seconds. SF6 gas is introduced at a flow rate of approximately 100-150 mL / min for passivation for 2-9 seconds. The etching ratio of silicon to silicon oxide is greater than 300:1, and the etching depth to width is greater than 100:1. C4F8 gas is introduced at a flow rate of approximately 10-80 mL / min for etching for 10-20 seconds.

[0043] Step 1.2: A metal conductive layer is deposited on the surface of the microneedle array using a magnetron sputtering method to make the surface of the microneedle array conductive. The silicon-based microneedle array is preheated to 40-70°C, and then Ar gas is introduced to adjust the pressure to 1-5 Pa. A radio frequency (RF) plasma cleaning process with a power of 100 W is performed for about 3-7 minutes. The single-sided multiplex coating process is then performed, and the pressure of the reaction chamber is controlled to 0.1-0.05 Pa, the carrier speed is 30-50 r / min, the bias voltage is approximately 30-60 V, and the sputtering target is Pt. The process is repeated three times, with a cooling time of 5-10 minutes between each coating pass. Finally, Ar gas (400 sccm) is introduced to cool the array for 10-15 minutes before removing the finished product from the coating chamber.

[0044] In this embodiment, the etching process must strictly control the etching time and ensure that the etching height is less than the height of the silicon wafer; and ensure that the microneedles in the array will not separate during the etching process; this embodiment takes the sputtering of the platinum conductive film layer as an example.

[0045] In one embodiment of the present invention, in step 2, the method for preparing the insulating structure includes:

[0046] An insulating coating is sputtered or plated on the surface of the microneedle array, and the insulating coating on the upper end of the needle tip is etched away by laser processing to obtain a microneedle array electrode with an insulating film.

[0047] In this embodiment, the specific steps of the thin film laser etching method are as follows: first, a 2-7 μm thick aluminum oxide insulating coating is continuously deposited on the microneedle array electrode by electrochemical plating or other methods. Next, an array of a mask template with a concentric circle pattern is designed for laser etching, and 5-90% of the total height of the microneedle on the microneedle tip is set as a mask-free protection area. Then, the substrate is placed in the effective working area of ​​the laser engraving machine, and the laser etching voltage is set to 2000-3000V, the etching time is 0.5-2s, and the substrate is laser processed with reference to the laser etching mask template pattern. Since the melting point and lattice of the insulating material and the metal material are different and the etching time is short, the mask thin film laser etching method will etch away the insulating part of the microneedle tip but retain the conductive part, and finally obtain a microneedle array electrode with an insulating thin film.

[0048] In one embodiment of the present invention, in step 2, the method for preparing the insulating structure includes:

[0049] 5-90% of the total height of the microneedle tip is protected by masking, an insulating coating is sputtered or plated on the microneedle substrate 1, and the mask protection layer is cleaned to obtain a microneedle array electrode with an insulating film.

[0050] In this embodiment, the specific steps of this method are: first, designing a photolithography mask pattern with the microneedle array needle tip as the center of the concentric circle and a concentric circle diameter of 20-300 μm, then applying 2-10 μm thick photoresist on the microneedle needle tip surface, exposing and developing the upper part of the microneedle needle tip through the photolithography mask pattern for 5-10 minutes, obtaining a microneedle array electrode with a mask protective layer coated on the upper part of the microneedle needle tip, and then continuously depositing a 2-7 μm thick polyparaxylene layer on the microneedle array electrode by physical vapor deposition as an insulating coating for the microneedle, finally preparing a photoresist cleaning solution, mixing 10% concentration hydrogen peroxide and 98% concentration sulfuric acid in a ratio of 1:2, and placing the microneedle inverted in the container of the cleaning solution, thereby removing the insulating coating photoresist on the surface of the microneedle needle tip to obtain a microneedle array electrode with an insulating film.

[0051] In one embodiment of the present invention, in step 2, the method for preparing the insulating structure includes:

[0052] An insulating coating is sputtered or plated on the surface of the microneedle array, and an etching protection layer is plated on the microneedle substrate 1 and 10-95% of the total height of the microneedles below the microneedle tips by spin coating for protection. Then, the microneedle array is etched as a whole to expose the conductive area on the upper part of the microneedle tips.

[0053] In this embodiment, the specific steps of this method are as follows: first, a 2-7 μm thick polyparaxylene layer is continuously deposited on the microneedle array electrode by physical vapor deposition, and then a 1-2 μm thick 3-propyl methacrylate layer is plated on the microneedle substrate and 10-95% of the total height of the microneedles below the microneedle tip as a tackifier for the polyparaxylene insulating coating below the needle tip and the polyimide protective layer to enhance the adhesion of the protective layer, and then the spin coating speed is set to 20-100 r / min, and the time is 2-10min, use the spin coating method to cover the 5-10μm thick polyimide layer on the bottom of the microneedle as the etching protection layer of the microneedle, and then use the plasma etching method to etch the unprotected polyparaxylene layer around the upper end of the microneedle. Set the voltage to 200-400V and the time to 7-10min to etch away the polyparaxylene layer on the upper end of the microneedle and part of the polyimide protective layer on the lower end. Finally, use the developer to remove the polyimide layer to obtain a microneedle array electrode with a polyparaxylene insulating coating.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A microneedle array electrode with an insulating film, comprising a plurality of microneedle substrates disposed on a microneedle array substrate, wherein the plurality of microneedle substrates are interconnected, characterized in that: Also includes: an insulating film, wherein the insulating film covers the surface of the microneedle substrate; The method for preparing the microneedle array electrode with an insulating film comprises the following steps: Step 1: Prepare microneedle array; Step 2: preparing an insulating structure on the microneedle array in step 1 to obtain a microneedle array electrode with an insulating film; In step 1, the method for preparing the microneedle array includes: Step 1.1: Fabricate a silicon-based microneedle array using a wet etching method. A 1.0-2.0 mm thick silicon wafer is used as the microneedle substrate of the microneedle array. A 100-500 nm thick silicon oxide layer is used as a masking layer for the counter electrode. Anisotropic cycling is performed using the Bosch process. 50-90 mL / min of C4F8 gas is introduced for etching for 5-10 seconds. 100-150 mL / min of SF6 gas is introduced for passivation for 2-9 seconds. The etching ratio of silicon to silicon oxide is greater than 300:1, and the etching depth to width is greater than 100:

1. 10-80 mL / min of C4F8 gas is introduced for etching for 10-20 seconds. Step 1.2: A metal conductive layer is deposited on the surface of the microneedle array using a magnetron sputtering method to make the surface of the microneedle array conductive. The silicon-based microneedle array is preheated to 40-70°C, and then Ar gas is introduced to adjust the pressure to 1-5 Pa. A radio frequency plasma cleaning process with a power of 100 W is performed for 3-7 minutes. The single-sided multi-layer coating process is performed, and the pressure of the reaction chamber is controlled to 0.1-0.05 Pa, the carrier speed is 30-50 r / min, the bias voltage is 30-60 V, and the sputtering target material is Pt. The process is repeated three times, with a cooling time of 5-10 minutes between each coating. Finally, Ar gas is introduced again, and the finished product is removed from the coating chamber after cooling for 10-15 minutes. In step 2, the method for preparing the insulating structure includes: An insulating coating is sputtered or plated on the surface of the microneedle array, and the insulating coating on the upper end of the needle tip is etched away by laser processing to obtain a microneedle array electrode with an insulating film; In step 2, the method for preparing the insulating structure includes: A mask is applied to protect 5-90% of the total height of the microneedle on the microneedle tip, an insulating coating is sputtered or plated on the microneedle substrate, and the mask protective layer is cleaned to obtain a microneedle array electrode with an insulating film; In step 2, the method for preparing the insulating structure includes: An insulating coating is sputtered or plated on the surface of the microneedle array, and an etching protection layer is plated on the microneedle substrate and 10-95% of the total height of the microneedle below the microneedle tip by spin coating for protection. The microneedle array is then etched as a whole to expose the conductive area above the microneedle tip.

2. The microneedle array electrode with an insulating film according to claim 1, characterized in that: The insulating film is made of high-insulating oxide.

3. The microneedle array electrode with an insulating film according to claim 1, characterized in that: The insulating film is made of insulating polymer.

4. The microneedle array electrode with an insulating film according to claim 1, characterized in that: The thickness of the insulating film is 0.01-20 μm.

5. The microneedle array electrode with an insulating film according to claim 1, characterized in that: The microneedle substrate is made of single crystal silicon.

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