Microstructure electrode flexible electrochemical sensor

Abstract

The invention discloses a micro-structure electrode flexible electrochemical sensor which comprises a flexible electrode substrate with a hemispherical array and three surface electrodes (a working electrode, a counter electrode and a reference electrode). The working electrode comprises a protruding metal array and a through hole array, protruding metal corresponds to the hemisphere array of the substrate, and the through hole array penetrates through the substrate. According to the sensor, the reaction area is increased through the three-dimensional structure, electron transfer is promoted, oxygen supply is guaranteed through the through hole array, the mechanical stability is enhanced through the flexible substrate and the structural design, and the sensor is suitable for wearable equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of health monitoring and relates to a microstructure electrode flexible electrochemical sensor suitable for wearable devices. Background Art

[0002] With the rapid development of wearable health monitoring technology, chemical sensors have shown significant application value in the field of health monitoring. These include body fluid sensors (for detecting metabolites such as blood glucose and lactate in sweat and tissue fluid) and gas sensors (for monitoring ethanol, NH3, and other substances in respiratory gas). While traditional rigid electrochemical sensors offer good detection performance, their brittle substrate materials are unable to adapt to complex curved surfaces and dynamic deformation scenarios, severely limiting their application in emerging fields such as wearable devices. In recent years, with the rapid development of flexible electronics technology, flexible electrochemical sensors have garnered widespread attention.

[0003] However, existing technologies still face the following key challenges, which seriously restrict their reliable application in dynamic wearable scenarios:

[0004] Traditional flexible sensors mostly use planar electrode structures, which have a limited effective reaction area and result in insufficient detection sensitivity. Although the sensing performance can be improved by modifying with nanomaterials (such as graphene and precious metal particles), the strategy of increasing the effective reaction area and thus synergistically enhancing the sensing performance through electrode structure design remains to be studied. In addition, the two-dimensional characteristics of planar electrodes make it difficult to achieve local electric field enhancement effects, which limits further improvements in electron transfer rates.

[0005] The catalytic reaction process of oxidase-based electrochemical sensors typically relies on oxygen as an electron acceptor, and their catalytic efficiency is significantly correlated with oxygen supply. However, when the sensor is attached to the skin surface, the semi-enclosed environment and the limited oxygen diffusion capacity of traditional planar electrodes severely restrict the enzyme's oxygen access, resulting in a significant decrease in the enzyme's catalytic performance. This leads to a significant deviation in the detection signal from the current-concentration relationship established under standard laboratory conditions. This problem is particularly prominent during long-term continuous monitoring, seriously reducing data reliability.

[0006] Wearable devices must maintain stable performance under dynamic deformation. While existing flexible substrates have a certain degree of ductility, when rigid metal electrodes are integrated into the planar structure, bending or stretching can easily cause electrode delamination or disconnection failures due to interfacial stress mismatch.

[0007] Therefore, there is an urgent need for a non-invasive, highly robust flexible sensor design that can simultaneously achieve high sensitivity, reliable oxygen supply and mechanical stability in a dynamic wearable environment, and promote the practical application of wearable health monitoring technology. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a flexible electrochemical sensor with a microstructure electrode.

[0009] The present invention is implemented as follows: a microstructure electrode flexible electrochemical sensor includes a flexible electrode substrate with a hemispherical array and three electrodes arranged on the surface of the flexible electrode substrate; wherein the three electrodes include a working electrode, a counter electrode, and a reference electrode; the working electrode is a circular structure, which includes a protruding metal array and a through-hole array.

[0010] Preferably, the raised metal array is located on the hemispherical array of the flexible electrode substrate, and includes a central raised metal and n raised metal rings with different radii centered on the central raised metal.

[0011] Preferably, each raised metal ring comprises a plurality of raised metals.

[0012] Preferably, adjacent protruding metals in the protruding metal array are connected by metal.

[0013] Preferably, the raised metal is a hemispherical structure.

[0014] Preferably, the protruding metal is sputtered on the surface of the flexible electrode substrate by a magnetron sputtering method.

[0015] Preferably, the through hole array includes n+1 through hole rings arranged on the central raised metal and the periphery of each raised metal ring.

[0016] Preferably, each through-hole ring includes a plurality of periodically distributed micro through-holes, and the micro through-holes penetrate the flexible electrode substrate.

[0017] Preferably, the counter electrode and the reference electrode form an arc with the central raised metal as the center, and there is a gap between them; the working electrode is surrounded by the working electrode and the reference electrode, and there is a gap between it and both the counter electrode and the reference electrode.

[0018] Preferably, the flexible electrode substrate is one of polyimide (PI), polydimethylsiloxane (PDMS), and polyethylene terephthalate (PET).

[0019] Preferably, the electrochemical sensor is suitable for use on a wearable device.

[0020] The beneficial effects of the present invention include at least:

[0021] 1. This invention constructs a concentrically arranged array of metal protrusions on the working electrode surface. Each protrusion is hemispherical, creating a three-dimensional surface through an optimized lattice arrangement. By regulating the electrode's reactive area through geometric morphology, enzyme loading sites and electron transfer channels are increased. The hemispherical curvature also induces a localized electric field enhancement effect, further accelerating electron transfer and improving sensitivity.

[0022] 2. The present invention provides an array of through-holes in the central raised metal and the periphery of the raised metal ring. The through-holes penetrate the flexible substrate, forming a low-resistance vertical transmission path, ensuring efficient oxygen diffusion from the back of the substrate to the electrode surface. The gaps between the raised metal rings and the through-holes form a multi-level mass transfer network, precisely controlling oxygen distribution on a ring-by-ring basis. By ensuring uniform oxygen flux across each ring, this approach addresses the oxygen deficiency associated with the semi-enclosed environment of wearable devices placed against the skin.

[0023] 3. The present invention adopts a flexible substrate and combines the mechanical buffer design of the raised metal array to disperse the stress through the hemispherical gap during deformation, thereby avoiding electrode breakage or delamination.

[0024] In summary, the present invention, through the collaborative innovation of geometric morphology and mass transfer channels, breaks through the bottlenecks of traditional flexible sensors in terms of sensitivity, linear range, and environmental adaptability, providing a high-precision, high-reliability solution for wearable health monitoring devices. In addition, the present invention is not only applicable to oxidase-based body fluid and respiratory gas physiological indicator sensing, but can also be expanded to the detection of other biomarkers, humidity sensing (based on the regulation of electrolyte humidity response of through-hole structure) and radiation-induced electrochemical signal conversion (radiation-sensitive materials loaded on hemispherical arrays), providing a universal technical solution for the next generation of wearable sensing systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A schematic structural diagram of a microstructure electrode sensor provided by an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of a top view of the working electrode provided in an embodiment of the present invention;

[0028] Figure 3 Schematic diagram of the side structure of the working electrode;

[0029] Figure 4These are the cyclic voltammetry test results of the microstructured Pt electrode and the traditional planar Pt electrode sensor provided by the embodiments of the present invention.

[0030] Markings in the figure: 1, working electrode; 1-1, raised metal array; 1-1-1, central raised metal; 1-1-2, each raised metal ring; 1-2, through-hole array; 2, counter electrode; 3, reference electrode; 4, first lead electrode; 5, second lead electrode; 6, third lead electrode. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0032] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0033] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0034] See attached Figure 1 This embodiment provides a microstructure electrode flexible electrochemical sensor, including a flexible electrode substrate having a hemispherical array, and three electrodes arranged on the surface of the flexible electrode substrate.

[0035] As an example, the flexible electrode substrate is one of polyimide (PI), polydimethylsiloxane (PDMS), and polyethylene terephthalate (PET).

[0036] Specifically, the three electrodes include a working electrode 1 , a counter electrode 2 , and a reference electrode 3 .

[0037] See attached Figure 2-3 , the working electrode 1 is a circular structure, which includes a protruding metal array 1-1 and a through-hole array 1-2;

[0038] The raised metal array 1-1 is located on the hemispherical array of the flexible electrode substrate and includes a central raised metal 1-1-1 and n (n ≥ 2, for example, 7 in this embodiment) raised metal rings of different radii centered around the central raised metal 1-1-1. Each raised metal ring includes multiple raised metals. Adjacent raised metals in the raised metal array 1-1 are connected by metal.

[0039] As an example, the raised metal is a hemispherical structure, for example, the diameter of the hemisphere is 200 microns and the height is 100 microns.

[0040] As an example, the protruding metal is sputtered on the surface of the flexible electrode substrate by a magnetron sputtering method.

[0041] The through hole array 1-2 includes n+1 through hole rings arranged on the central raised metal 1-1-1 and the periphery of each raised metal ring 1-1-2; each through hole ring includes a plurality of periodically distributed micro through holes, which penetrate the flexible electrode substrate.

[0042] As an example, the diameter of the micro-through holes is 10 microns, and the distance between adjacent micro-through holes on the same through hole ring is 30 microns, in order to ensure sufficient oxygen supply when the flexible enzyme-based sensor is attached to the skin for use.

[0043] The counter electrode 2 and the reference electrode 3 form an arc with the central raised metal 1-1-1 as the center, and there is a gap between the two; the working electrode 1 is surrounded by the working electrode 1 and the reference electrode 3, and there is a gap between it and the counter electrode 2 and the reference electrode 3.

[0044] The raised metal array 1-1 in the working electrode 1 is formed with the central raised metal 1-1-1 as the first circle, and the raised metal rings 1-1-2 are increased in sequence, for a total of n circles. By constructing a raised metal array 1-1 based on a concentric circle arrangement, a hierarchical calculation method is used to accurately characterize the radial non-uniform arrangement characteristics, and the size of each circle of raised metal (such as hemispherical radius, number), the radial spacing between adjacent circles, etc. are controlled to control the gas mass transfer efficiency of each circle. The present invention fully considers the unique geometric characteristics and mass transfer characteristics of the concentric circle arrangement through circle-by-circle calculation, and can more accurately predict the oxygen transmission performance of the sensor.

[0045] The hemispherical radius r of the kth raised metal k Calculation:

[0046] r k =kp

[0047] Where P is the radial spacing;

[0048] The number of raised metals per circle is determined by the circumference length N kand radial spacing to ensure uniform distribution, see below:

[0049]

[0050] Local porosity It reflects the proportion of gas channels in each circle and is a key parameter affecting mass transfer efficiency:

[0051]

[0052] Where D is the diameter of the hemisphere;

[0053] By adjusting the size of the raised metal and the radial spacing between adjacent circles, the flow resistance R of the raised metal array of the working electrode can be adjusted. h,k , the flow resistance is used to characterize the resistance of gas passing through the protruding metal array;

[0054]

[0055] Among them, k k is the permeability, which describes the ventilation capacity of the porous medium; D h,k is the hydraulic diameter, which comprehensively reflects the characteristic size of the flow channel; A k is the cross-sectional area of the flow channel, which determines the effective space for gas to pass through;

[0056] By adjusting the through-hole size and substrate thickness, the through-hole array flow resistance R can be adjusted. p,k , which is used to describe the resistance of gas when passing through a vertical channel;

[0057]

[0058] Where d is the through-hole diameter; t is the substrate thickness; μ is the air dynamic viscosity (15.1×10 -6 Pa·s); M k is the number of through holes in the kth circle;

[0059] The flow resistance R of the raised metal array h,k and the through-hole array flow resistance R p,k Parallel connection to form total flow R t,k ;

[0060]

[0061] According to the total flow resistance R t,k , and then establish the quantitative relationship between concentration gradient and transmission resistance, that is, the oxygen flux J O2,k ;

[0062]

[0063] Among them C atmis the atmospheric oxygen concentration (8.7 mol / m 3 );C k is the oxygen concentration at the interface of the kth circle;

[0064] Interface oxygen concentration J O2,k Iterative solution of enzyme kinetic equations;

[0065]

[0066] Where V max is the maximum reaction rate of the enzyme; K m is the Michaelis constant;

[0067] According to the obtained oxygen concentration J at each circle interface O2,k , the total oxygen flux is obtained by accumulating

[0068]

[0069] This invention forms a multi-stage mass transfer network through the gaps between each ring and the through-holes within the raised metal rings. This allows for precise control of oxygen distribution through a ring-by-ring flow resistance model. By iteratively solving the interfacial oxygen concentration equation for enzyme kinetics, this method ensures uniform oxygen flux across each ring, enabling the enzyme to maintain comparable catalytic kinetic properties in the wearable environment to those tested in vitro. This addresses the oxygen depletion associated with the semi-enclosed environment of wearable devices placed against the skin.

[0070] This embodiment also provides a method for preparing a flexible electrochemical sensor with a microstructured electrode. The wearable sensor needs to conform to the dynamic deformation of the skin, and the present invention uses PI as the flexible substrate material. The specific steps are as follows:

[0071] A reverse mold with a structure opposite to the flexible electrode substrate with a hemispherical array (i.e., a hemispherical groove array) was prepared using a 3D printing device with a precision of 10 microns. A fiberglass release agent was sprayed on the mold surface and waited for it to completely evaporate.

[0072] The flexible electrode substrate material is cast and cured in a temperature gradient to obtain a flexible electrode substrate with a hemispherical array. For example, the electrode substrate has a length of 11 mm, a width of 10 mm, and a thickness of 200 microns.

[0073] For example, the temperature gradient curing conditions are: heating at 80°C for 30 minutes, heating at 120°C for 15 minutes, heating at 150°C for 15 minutes, heating at 180°C for 15 minutes, heating at 210°C for 15 minutes, heating at 230°C for 15 minutes, and heating at 250°C for 10 minutes.

[0074] In order to solve the problem of skin hypoxia, a through-hole array 1-2 was constructed on the PI substrate. That is, the hemispherical array area of the flexible electrode substrate with a hemispherical array was punched by femtosecond laser to prepare a through-hole array 1-2. The through-holes had a diameter of 10 μm and were distributed in concentric rings (with a spacing of 200 μm between each ring and a total of 8 rings). The spacing between adjacent through-holes was 30 μm ( Figure 2 By optimizing the laser energy and scanning speed, the through-hole sidewalls are ensured to be smooth and the gas flow resistance is reduced.

[0075] Then, a two-step magnetron sputtering is performed to achieve sputtering of a working electrode 1 made of, for example, platinum in the hemispherical array area. For example, the working electrode 1 is a circle with a diameter of 4 mm, and the raised metal of its raised metal array 1-1 is a hemispherical structure with a diameter of 200 microns and a height of 100 microns. There are 8 layers of structure (including the central raised metal 1-1-1) in the raised metal array 1-1. The three-dimensional microstructure design of the raised metal array 1-1 enables the actual effective surface area of the electrode to reach 17.93 mm 2 , which is 1.428 times that of the planar electrode. The increased electrode reaction area will directly improve the sensitivity of the sensor. At the same time, a through hole array 1-2 is arranged around the convex metal array 1-1. The prepared working electrode 1 is as shown in FIG. Figure 2 and Figure 3 shown.

[0076] The counter electrode 2, for example, made of platinum, and the reference electrode 3, for example, made of silver, are sputtered on the periphery of the working electrode 1 through a mask. The reference electrode 3 and the counter electrode 2 are concentric ring segments. The prepared microstructure electrode sensor is as follows Figure 1 shown.

[0077] The working electrode 1 , the counter electrode 2 and the reference electrode 3 are connected to the first lead electrode 4 , the second lead electrode 5 and the third lead electrode 6 respectively.

[0078] The above sensor was tested: the potential range was set to -0.2V~0.7V, the scan rate was set to 50mV / s, and the cyclic voltammetry (CV) was used to investigate the microstructure electrode sensor and the planar electrode sensor in the presence of 5mM [Fe(CN)6] 3- / 4- Electrochemical performance in 0.1 M KCl solution.

[0079] like Figure 4 As shown, the redox peak of the microstructured electrode sensor is significantly higher than that of the planar electrode sensor, with the redox peak intensity being 1.32 times that of the planar electrode sensor. These results demonstrate that the hemispherical array structure design significantly enhances the electrochemical response of the sensor. Subsequent electrode material modification can further enhance the sensor's electrochemical sensing performance.

[0080] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A microstructured electrode flexible electrochemical sensor, characterized in that: The electrochemical sensor comprises a flexible electrode substrate having a hemispherical array, and three electrodes arranged on the surface of the flexible electrode substrate; wherein the three electrodes comprise a working electrode (1), a counter electrode (2), and a reference electrode (3); the working electrode (1) is a circular structure, comprising a protruding metal array (1-1) and a through-hole array (1-2).

2. The electrochemical sensor according to claim 1, characterized in that The raised metal array (1-1) is correspondingly located on the hemispherical array of the flexible electrode substrate, and comprises a central raised metal (1-1-1) and n raised metal rings with different radii with the central raised metal (1-1-1) as the center.

3. The electrochemical sensor according to claim 2, characterized in that Each raised metal ring includes a plurality of raised metals.

4. The electrochemical sensor according to claim 2 or 3, characterized in that Adjacent protruding metals in the protruding metal array (1-1) are connected by metal.

5. The electrochemical sensor according to claim 3, characterized in that The raised metal is a hemispherical structure.

6. The electrochemical sensor according to claim 3 or 5, characterized in that The protruding metal is sputtered on the surface of the flexible electrode substrate by a magnetron sputtering method.

7. The electrochemical sensor according to claim 1, characterized in that The through hole array (1-2) comprises n+1 through hole rings arranged on the central raised metal (1-1-1) and the periphery of each raised metal ring (1-1-2), and each through hole ring comprises a plurality of periodically distributed micro through holes.

8. The electrochemical sensor according to claim 1, characterized in that The counter electrode (2) and the reference electrode (3) form an arc with the central raised metal (1-1-1) as the center, and there is a gap between the two; the working electrode (1) is surrounded by the working electrode (1) and the reference electrode (3), and there is a gap between the counter electrode (2) and the reference electrode (3).

9. The electrochemical sensor according to claim 1, characterized in that: The flexible electrode substrate is one of polyimide, polydimethylsiloxane and polyethylene terephthalate.

10. The electrochemical sensor according to claim 1, characterized in that: The electrochemical sensor is suitable for use in wearable devices.

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