A flexible pressure sensor for human pulse detection and preparation method thereof

Abstract

The present application provides a flexible pressure sensor for human pulse detection and a preparation method thereof. The flexible pressure sensor includes an upper electrode layer, a lower electrode layer, an ion gel layer and a Spacer layer; the ion gel layer is sandwiched between the upper electrode layer and the lower electrode layer, and the ion gel layer includes multiple active layers stacked in sequence; the Spacer layer is arranged between the ion gel layer and the upper electrode layer; each active layer is provided with a pore structure, and the average pore size of the pore structure of the multi-layer active layer is gradiently distributed. The present application achieves graded deformation of the ion gel membrane under different pressures by precisely controlling the pore gradient of the ion gel layer, thereby improving the sensitivity and linearity of the sensor. The present application creatively sets up a combined structure of a Spacer layer + a multi-layer pore gradient ion gel layer, and the synergistic effect of the two can greatly improve the linearity and sensitivity.

Description

Technical Field

[0001] The present application relates to the technical field of pressure sensors, and in particular to a flexible pressure sensor for human pulse detection and a preparation method thereof. Background Art

[0002] With the rapid development of wearable devices and health monitoring technologies, traditional rigid pressure sensors are often unable to meet the needs of dynamic human body monitoring due to their structural limitations. Flexible pressure sensors are becoming increasingly important because they can provide a monitoring method that is more in line with the human body.

[0003] In practical applications, such as health monitoring and human-computer interaction, sensors need to maintain high sensitivity and good linearity over a wide range of pressure changes. Linearity refers to the accuracy of the linear relationship between the sensor output and the input pressure, which is critical for precise measurement and data analysis. Although flexible pressure sensors have made significant progress in improving wearing comfort and compliance, they still face considerable challenges in ensuring the linearity and sensitivity of pressure detection.

[0004] Therefore, it is particularly urgent to develop a flexible pressure sensor that can overcome the above defects. Summary of the invention

[0005] In view of this, the purpose of the present application is to provide a flexible pressure sensor for human pulse detection and a preparation method thereof, so as to at least solve the problems of low linearity and limited sensitivity of flexible pressure sensors in the prior art. The present application creatively sets up a Spacer layer + ion gel layer combination structure, and the synergistic effect of the two can greatly improve the linearity and sensitivity. The present application achieves graded deformation of the ion gel membrane under different pressures by precisely controlling the pore size gradient of the ion gel layer, thereby improving the sensitivity and linearity of the sensor, and is suitable for dynamic monitoring of the human body, such as pulse detection, muscle activity monitoring, etc.

[0006] In the first aspect, the present application provides a flexible pressure sensor for human pulse detection, comprising an upper electrode layer, a lower electrode layer, an ion gel layer and a Spacer layer; the ion gel layer is sandwiched between the upper electrode layer and the lower electrode layer, and the ion gel layer comprises multiple active layers stacked in sequence; the Spacer layer is arranged between the ion gel layer and the upper electrode layer; a pore structure is arranged on each active layer, and the average pore size of the pore structure of the multiple active layers is gradiently distributed.

[0007] In some embodiments, the multi-layer active layer includes a first active layer, a second active layer, and a third active layer.

[0008] In some embodiments, the thickness of the first active layer is 70-120 μm, the thickness of the second active layer is 160-230 μm, and the thickness of the third active layer is 250-350 μm; and / or, the thickness ratio of the first active layer, the second active layer and the third active layer is 0.8-1.1:1.9-2.2:2.8-3.3.

[0009] In some embodiments, the pore density of the porous structure of the first active layer is 75%-85%, the pore density of the porous structure of the second active layer is 65%-75%, and the pore density of the porous structure of the third active layer is 55%-65%.

[0010] In some embodiments, the average pore size of the porous structure of the first active layer is 10-18 μm, the average pore size of the porous structure of the second active layer is 25-32 μm, and the average pore size of the porous structure of the third active layer is 35-42 μm; and / or, the ratio of the average pore sizes of the porous structures of the first active layer, the second active layer, and the third active layer is 12-18:28-32:38-42.

[0011] In some embodiments, the size of the upper electrode layer and the lower electrode layer is 3×3-10×10 mm, the substrate material of the upper electrode layer and the lower electrode layer is PET, and the conductive parts of the upper electrode layer and the lower electrode layer are Ag;

[0012] In some embodiments, the Spacer layer is 3M tape.

[0013] In a second aspect, the present application provides a method for preparing a flexible pressure sensor for human pulse detection, the method for preparing a flexible pressure sensor for human pulse detection comprising the following steps:

[0014] S1. Dissolve PVDF-HFP in acetone, add [EMIM] [TFSI] and stir to mix;

[0015] S2, adding water during stirring;

[0016] S3, after fully stirring for 1-2 hours, pouring into a mold, and drying at 60-80° C. for more than 12 hours to prepare an active layer;

[0017] S4, repeating steps S1-S3 to obtain the remaining active layers, wherein multiple active layers are stacked up and down in sequence to form an ion gel layer; wherein the average pore size of the pore structure of the multiple active layers is distributed in a gradient manner;

[0018] S5, preparing an upper electrode layer and a lower electrode layer;

[0019] S6. The upper electrode layer, the lower electrode layer and the ion gel layer are integrally encapsulated by a spacer layer to obtain a final product.

[0020] In some embodiments, in S1, the mass ratio of PVDF-HFP to acetone is 1:8-10; and / or, in S1, the mass ratio of PVDF-HFP to [EMIM][TFSI] is 1:1-3.

[0021] In some embodiments, the multilayer active layer prepared in S4 includes a first active layer, a second active layer and a third active layer; when preparing the first active layer, in S2, the mass ratio of water to acetone is 0.8-1.5:16-20; when preparing the second active layer, in S2, the mass ratio of water to acetone is 0.5-1.2:8-10; when preparing the third active layer, in S2, the mass ratio of water to acetone is 1.5-2.5:8-10.

[0022] In some embodiments, in S5, the upper electrode layer and the lower electrode layer are prepared by printing one or a combination of conductive silver paste, graphene, and carbon nanotubes on a PET film; and / or, in S6, 3M tape is used as a spacer layer.

[0023] The beneficial effects that this application can achieve are:

[0024] 1. The Spacer layer serves as a supporting and packaging element, which can fix the ion gel layer and the upper and lower electrodes and separate the ion gel layer from the electrode layer, thereby ensuring that the initial capacitance of the sensor is in a low state and improving the consistency of different sensors.

[0025] 2. The ion gel layer contains a large number of cations and anions. When it comes into contact with the electrode, a double layer is formed at the interface. Under the action of external pressure, the deformation of the ion gel layer causes the contact area between it and the electrode to change, which in turn causes the change in the double layer capacitance, thereby realizing pressure detection. The ion migration characteristics of the ion gel enable it to produce significant capacitance changes when the pressure changes. Therefore, the present application has higher sensitivity than traditional capacitive sensors.

[0026] 3. The ion gel layer of the present application includes multiple active layers stacked in sequence, and adopts a multi-layer and layered microstructure. The layered microstructure refers to the microstructure inside the material, which is arranged in a certain hierarchy to form a composite with specific mechanical properties. This microstructure can be an alternating stack of different material layers, or a porous material layer with different porosities and pore sizes. Layered filling can improve the compressibility of the material by increasing its porous structure. The porous structure allows the material to deform when it is under pressure without being immediately destroyed. This structural feature enables the material to disperse and absorb pressure more effectively when compressed, thereby improving its compressibility.

[0027] 4. This application creatively adopts a multi-layer design to replace a single-layer design. The multi-layer structure can provide more deformation space and energy absorption path. When external force acts on the multi-layer structure, each layer can independently absorb and disperse part of the impact force, thereby reducing the impact on the overall structure. This dispersion and absorption effect can reduce the pressure concentration on a single layer, improve the buffering capacity of the overall structure, and thus improve the linear working range of the flexible pressure sensor.

[0028] 5. The ion gel layer with pore size gradient can provide different mechanical properties. The higher cross-linking density area will form a smaller pore size and provide a higher modulus, while the lower cross-linking density area will form a larger pore size and provide a lower modulus. This gradient structure can achieve different deformations and provide different responses under different pressures, thereby improving the sensitivity and linearity of the sensor. By controlling the cross-linking density of the ion gel layer, the present application can achieve precise control of the change in sensor capacitance and further improve linearity and sensitivity.

[0029] 6. The present application creatively sets up a combined structure of a Spacer layer + a multi-layer pore size gradient ion gel layer, and the synergistic effect of the two can greatly improve the linearity and sensitivity.

[0030] 7. The sensor of the present application has high sensitivity, can accurately capture weak physiological signals, has high linearity, and has excellent signal accuracy and predictability. The sensor of the present application can still work normally in 13,000 tests, far exceeding the 7,000 repeatability tests of current wearable sensors. The sensor capacitance value of the present application can reach 300nf, and has high anti-interference performance.

[0031] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 An exploded perspective view of a flexible pressure sensor for human pulse detection according to Embodiment 1 of the present application is shown;

[0034] Figure 2 An exploded front view of a flexible pressure sensor for human pulse detection according to Embodiment 1 of the present application is shown;

[0035] Figure 3 A performance test diagram of a flexible pressure sensor for human pulse detection according to Example 1 of the present application is shown;

[0036] Figure 4 A detailed view of the aperture of the hole structure of the flexible pressure sensor for human pulse detection according to Example 1 of the present application is shown.

[0037] Description of reference numerals:

[0038] 1. Upper electrode layer; 2. Spacer layer; 3. First active layer; 31. Hole structure of the first active layer; 4. Second active layer; 41. Hole structure of the second active layer; 5. Third active layer; 51. Hole structure of the third active layer; 6. Lower electrode layer. DETAILED DESCRIPTION

[0039] The term "comprising" in the specification and claims of the present application and the drawings is synonymous with "including", "containing" or "characterized by", and is inclusive or open-ended, and does not exclude additional undescribed elements or method steps. "Comprising" is a technical term used in the claim language, meaning that the elements are present, but other elements may also be added and still form a structure or method within the scope of the claim.

[0040] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance. The term "about" in this application means to include a small change (up to + / -10%) from the stated value.

[0041] In the first aspect, the present application provides a flexible pressure sensor for human pulse detection, comprising an upper electrode layer, a lower electrode layer, an ion gel layer and a Spacer layer; the ion gel layer is sandwiched between the upper electrode layer and the lower electrode layer, and the ion gel layer comprises multiple active layers stacked in sequence; the Spacer layer is arranged between the ion gel layer and the upper electrode layer; each active layer is provided with a pore structure, and the average pore size of the pore structure of the multiple active layers is distributed in a gradient. The present application creatively sets up a combined structure of a Spacer layer + an ion gel layer, and the synergistic effect of the two can greatly improve linearity and sensitivity.

[0042] In some embodiments, the multilayer active layer includes a first active layer, a second active layer, and a third active layer. In the present application, there is no particular restriction on the number of layers of the multilayer active layer, preferably three layers but not limited thereto, and can be two layers, four layers or even more, but not a single layer. The layered and filled microstructure of the present application can improve the compressibility of the ion electron layer. And the multilayer design can buffer the applied pressure better than the single-layer design, so this strategy can be used to improve the linear working range of the flexible pressure sensor.

[0043] The design of multiple ion gel layers can increase the total capacitance of the sensor, thereby improving its responsiveness to pressure changes. Each ion gel layer will generate an electrical signal under pressure, and the multi-layer structure can superimpose these signals, thereby improving the overall sensitivity and linearity. The multi-layer structure requires precise inter-layer alignment to ensure that each ion gel layer can be evenly compressed and generate consistent electrical signals.

[0044] In some embodiments, the thickness of the first active layer is 70-120 μm, and the thickness of the first active layer is preferably 100 μm, but not limited thereto, and can be 70 μm, 80 μm, 90 μm, 110 μm, 120 μm, and any value therebetween. The thickness of the second active layer is 160-230 μm, and the thickness of the second active layer is preferably 200 μm, but not limited thereto, and can be 160 μm, 170 μm, 180 μm, 190 μm, 210 μm, 220 μm, 230 μm, and any value therebetween. The thickness of the third active layer is 250-350 μm, and the thickness of the third active layer is preferably 300 μm, but not limited thereto, and can be 250 μm, 270 μm, 330 μm, 350 μm, and any value therebetween.

[0045] In some embodiments, the thickness ratio of the first active layer, the second active layer and the third active layer is 0.8-1.1:1.9-2.2:2.8-3.3, and the thickness ratio of the first active layer, the second active layer and the third active layer is preferably 1:2:3, but is not limited thereto, and can be any value therebetween. By optimizing the thickness of the active layer, the sensitivity of the response to pressure can be improved while ensuring the stability of the sensor. A thinner active layer can produce a larger deformation, thereby bringing about a larger capacitance change and improving the sensitivity of the sensor; however, an active layer that is too thin is prone to electrical breakdown, which can damage the performance of the device. Therefore, it is necessary to determine the optimal film thickness during the preparation process. For a multi-layer active layer, a reasonable setting of the thickness ratio between the layers can further optimize the performance of the sensor, such as broadening the detection range and increasing the response speed.

[0046] In some embodiments, the pore density of the pore structure of the first active layer is 75%-85%, and the pore density of the pore structure of the first active layer is preferably 80%, but it is not limited thereto, and it can be 75%, 85% and any value therebetween. The pore density of the pore structure of the second active layer is 65%-75%, and the pore density of the pore structure of the second active layer is preferably 70%, but it is not limited thereto, and it can be 65%, 75% and any value therebetween. The pore density of the pore structure of the third active layer is 55%-65%, and the pore density of the pore structure of the third active layer is preferably 60%, but it is not limited thereto, and it can be 55%, 65% and any value therebetween. Reasonable setting of the pore density of the pore structure can significantly improve the sensitivity and measurement range of the sensor. By increasing the pore density, the contact area of ​​the conductive material can be increased, thereby enhancing the sensing performance of the sensor, enabling it to detect small pressure changes more accurately. At the same time, a reasonable pore density design also helps to improve the stability and durability of the sensor.

[0047] In some embodiments, the average pore size of the pore structure of the first active layer is 10-18 μm, which can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm and any value therebetween. Preferably, the average pore size of the pore structure of the first active layer is 15 μm.

[0048] The average pore size of the pore structure of the second active layer is 25-32 μm, which can be 25 μm, 27 μm, 30 μm, 32 μm and any value therebetween. Preferably, the average pore size of the pore structure of the second active layer is 30 μm.

[0049] The average pore size of the pore structure of the third active layer is 35-42 μm, which can be 35 μm, 37 μm, 40 μm, 42 μm and any value therebetween. Preferably, the average pore size of the pore structure of the third active layer is 40 μm.

[0050] The ratio of the average pore size of the porous structure of the first active layer, the second active layer and the third active layer is 12-18:28-32:38-42. The ratio of the average pore size of the porous structure of the first active layer, the second active layer and the third active layer is preferably 15:30:40, but is not limited thereto and can be any value therebetween. The ion gel layer with a pore size gradient can provide different mechanical properties, such as a higher cross-linking density area will form a smaller pore size and provide a higher modulus, while a lower cross-linking density area will form a larger pore size and provide a lower modulus. This gradient structure can provide different responses under different pressures, thereby improving the sensitivity and linearity of the sensor.

[0051] It should be noted that the average pore size of each layer of porous structure refers to the average pore size of all single holes and composite holes in each layer. The reason for the appearance of composite holes is that each single hole in each layer is not strictly independently distributed, and there are also cases where multiple single holes are combined together to form composite holes with larger pore sizes. In addition, the method for measuring the pore size in this application is to measure the diameter of the hole under an electron microscope. If the hole is a regular circle, the diameter of the circle is the pore size. When the hole cross section is an irregular shape, the pore size is represented by an equivalent circle diameter, which is the diameter of a circle with the same area as the irregular hole cross section.

[0052] The benefit of the gradient structure design is that it provides continuous sensitivity across the entire pressure range. The small pore structure provides high sensitivity at high pressures, while the large pore structure provides high sensitivity at low pressures. The medium pore structure provides a transition between the two, ensuring high sensitivity and linear response across the entire pressure range.

[0053] The arrangement from small pores to medium pores to large pores can increase the compressibility of the material. This design allows all parts of the sensor to effectively respond to pressure changes in different pressure ranges. The small pore structure provides support under high pressure, while the large pore structure allows more deformation under low pressure, thus providing sensitive response over the entire pressure range.

[0054] The sequence from small pores to medium pores and then to large pores ensures that the sensor can respond effectively at different pressure stages. The small pore structure responds first under high pressure, and as the pressure increases, the medium and large pore structures gradually participate in the response, which ensures that the sensor can maintain high sensitivity and stability over the entire pressure range.

[0055] The gradient structure design of small-pore membrane, medium-pore membrane and large-pore membrane not only improves the compressibility and sensitivity of the ion-type flexible pressure sensor, but also ensures stable and linear response over the entire pressure range. This design utilizes the response characteristics of different pore structures at different pressure stages to achieve high-precision detection of pressure changes.

[0056] In some embodiments, the size of the upper electrode layer and the lower electrode layer is 3×3-10×10 mm, preferably 5×5 mm. The substrate material of the upper electrode layer and the lower electrode layer is PET, the conductive part of the upper electrode layer and the lower electrode layer is Ag, and / or the spacer layer is 3M tape.

[0057] In a second aspect, the present application provides a method for preparing a flexible pressure sensor for human pulse detection, the method for preparing a flexible pressure sensor for human pulse detection comprising the following steps:

[0058] S1. Dissolve PVDF-HFP in acetone, add [EMIM] [TFSI] and stir to mix;

[0059] S2, adding water during stirring;

[0060] S3, after fully stirring for 1-2 hours, pouring into a mold, and drying at 60-80° C. for more than 12 hours to prepare an active layer;

[0061] S4, repeating steps S1-S3 to obtain the remaining active layers, wherein multiple active layers are stacked up and down in sequence to form an ion gel layer; wherein the average pore size of the pore structure of the multiple active layers is distributed in a gradient manner;

[0062] S5, preparing an upper electrode layer and a lower electrode layer;

[0063] S6. The upper electrode layer, the lower electrode layer and the ion gel layer are integrally encapsulated by a spacer layer to obtain a final product.

[0064] The present application has no particular restrictions on the stirring and mixing method and specific conditions, and the appropriate stirring speed and stirring time can be selected according to the specific situation.

[0065] In some embodiments, in S1, the mass ratio of PVDF-HFP to acetone is 1:8-10, preferably 1:9, but is not limited thereto and can be any value therebetween.

[0066] In some embodiments, in S1, the mass ratio of PVDF-HFP to [EMIM][TFSI] is 1:1-3, preferably 1:2, but is not limited thereto and can be any value therebetween.

[0067] In some embodiments, the multilayer active layer prepared in S4 includes a first active layer, a second active layer and a third active layer; when preparing the first active layer, in S2, the mass ratio of water to acetone is 0.8-1.5:16-20, preferably 1:18, but not limited thereto, and can be any value therebetween; when preparing the second active layer, in S2, the mass ratio of water to acetone is 0.5-1.2:8-10, preferably 1:9, but not limited thereto, and can be any value therebetween. When preparing the third active layer, in S2, the mass ratio of water to acetone is 1.5-2.5:8-10, preferably 2:9, but not limited thereto, and can be any value therebetween. The mixing ratio of water and acetone during the preparation process determines the size of the pore size. Too little water will result in a pore size that is too small and no effect will be shown. Excessive water will cause the pore size to erode the film, and the consistency of the film will deteriorate and the durability will decrease. The present application achieves precise control of the capacitance change of the sensor and further improves linearity and sensitivity by reasonably setting the mass ratio of water and acetone and controlling the cross-linking density of the ion gel layer.

[0068] In some embodiments, in S5, the upper electrode layer and the lower electrode layer are prepared by printing one or a combination of conductive silver paste, graphene, and carbon nanotubes on the PET film.

[0069] In some embodiments, in S6, 3M tape is used as the Spacer layer. 3M tape performs well in adhesion, which is very important for ensuring the stability and long-term performance of the Spacer layer during the packaging process. 3M tape will not produce residue, contamination or static electricity when removed, nor will it damage the substrate, which is very important for maintaining the cleanliness and integrity of the packaging components. However, it should be noted that 3M tape is preferred as the Spacer layer, but it is not limited to this. There are other brands of tapes on the market that may provide similar performance characteristics, but the specific performance may vary. According to different application requirements and cost considerations, other alternative materials can also be considered as long as they have similar properties to 3M tape.

[0070] The preparation method of the invention has simple steps, convenient operation and control, stable quality, high production efficiency, low production cost, and can be applied to large-scale industrial production.

[0071] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0072] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0073] Example 1

[0074] S1. Dissolve PVDF-HFP in acetone, add [EMIM] [TFSI] and stir to mix;

[0075] The mass ratio of PVDF-HFP, acetone, and [EMIM] [TFSI] is 1:9:2.

[0076] S2, adding water during stirring;

[0077] S3, after being fully stirred for 2 hours, pouring into a mold, and drying at 70° C. for 12 hours to prepare an active layer;

[0078] S4, repeating steps S1-S3 to obtain the remaining active layers, wherein multiple active layers are stacked up and down in sequence to form an ion gel layer; wherein the average pore size of the pore structure of the multiple active layers is distributed in a gradient manner;

[0079] Among them, the prepared multi-layer active layer includes a first active layer, a second active layer and a third active layer; when preparing the first active layer, in S2, the mass ratio of water to acetone is 1:18; when preparing the second active layer, in S2, the mass ratio of water to acetone is 1:9; when preparing the third active layer, in S2, the mass ratio of water to acetone is 2:9.

[0080] S5. Preparing an upper electrode layer and a lower electrode layer:

[0081] The size of the upper electrode layer and the lower electrode layer is 5×5 mm, the base material of the upper electrode layer and the lower electrode layer is PET, and the conductive parts of the upper electrode layer and the lower electrode layer are Ag.

[0082] S6. Use 3M tape as a Spacer layer, and use the Spacer layer to package the upper electrode layer, the lower electrode layer and the ion gel layer as a whole to obtain the final product.

[0083] like Figure 1 and Figure 2 As shown, according to the preparation method provided in Example 1, a flexible pressure sensor for human pulse detection is prepared, comprising an upper electrode layer 1, a lower electrode layer 6, an ion gel layer and a Spacer layer 2; the ion gel layer is sandwiched between the upper electrode layer 1 and the lower electrode layer 6, and the ion gel layer comprises a first active layer 3, a second active layer 4 and a third active layer 5 stacked in sequence; the Spacer layer 2 is arranged between the ion gel layer and the upper electrode layer 1; a pore structure is arranged on each active layer, and the average pore size of the pore structure of the multiple active layers is gradiently distributed.

[0084] The thickness of the first active layer 3 is 100 μm, the thickness of the second active layer 4 is 200 μm, and the thickness of the third active layer 5 is 300 μm; the thickness ratio of the first active layer 3, the second active layer 4 and the third active layer 5 is 1:2:3.

[0085] The pore density of the pore structure 31 of the first active layer is 80%, the pore density of the pore structure 41 of the second active layer is 70%, and the pore density of the pore structure 51 of the third active layer is 60%.

[0086] like Figure 4As shown, the average pore size of the porous structure 31 of the first active layer is about 15 μm, the average pore size of the porous structure 41 of the second active layer is about 30 μm, and the average pore size of the porous structure 51 of the third active layer is about 40 μm; the ratio of the average pore sizes of the porous structures of the first active layer, the second active layer and the third active layer is about 15:30:40.

[0087] The performance test of the flexible pressure sensor for human pulse detection obtained in Example 1 was carried out, and the results are as follows: Figure 3 The present application achieves graded deformation of the ion gel membrane under different pressures by precisely controlling the pore size gradient of the ion gel layer, thereby improving the sensitivity and linearity of the sensor, enabling it to accurately capture weak physiological signals of the human body, such as pulse waveforms, muscle activity, etc., which is of great value for health monitoring and disease diagnosis.

[0088] Example 2

[0089] S1. Dissolve PVDF-HFP in acetone, add [EMIM] [TFSI] and stir to mix;

[0090] The mass ratio of PVDF-HFP, acetone, and [EMIM] [TFSI] is 1:9:2.

[0091] S2, adding water during stirring;

[0092] S3, after being fully stirred for 1 hour, pouring into a mold, and drying at 70° C. for 12 hours to prepare an active layer;

[0093] S4, repeating steps S1-S3 to obtain the remaining active layers, wherein multiple active layers are stacked up and down in sequence to form an ion gel layer; wherein the average pore size of the pore structure of the multiple active layers is distributed in a gradient manner;

[0094] The prepared multilayer active layer includes a first active layer and a second active layer; when preparing the first active layer, in S2, the mass ratio of water to acetone is 1:18; when preparing the second active layer, in S2, the mass ratio of water to acetone is 1:9;

[0095] S5. Preparing an upper electrode layer and a lower electrode layer:

[0096] The size of the upper electrode layer and the lower electrode layer is 5×5 mm, the base material of the upper electrode layer and the lower electrode layer is PET, and the conductive parts of the upper electrode layer and the lower electrode layer are Ag.

[0097] S6. Use 3M tape as a Spacer layer, and use the Spacer layer to package the upper electrode layer, the lower electrode layer and the ion gel layer as a whole to obtain the final product.

[0098] The thickness of the first active layer is 100 μm, and the thickness of the second active layer is 200 μm; the thickness ratio of the first active layer to the second active layer is 1:2.

[0099] The pore density of the porous structure of the first active layer is 80%, and the pore density of the porous structure of the second active layer is 70%.

[0100] The average pore size of the pore structure of the first active layer is about 15 μm, and the average pore size of the pore structure of the second active layer is about 30 μm; the ratio of the average pore size of the pore structure of the first active layer to that of the second active layer is about 15:30.

[0101] Example 3

[0102] S1. Dissolve PVDF-HFP in acetone, add [EMIM] [TFSI] and stir to mix;

[0103] The mass ratio of PVDF-HFP, acetone, and [EMIM] [TFSI] is 1:9:2.

[0104] S2, adding water during stirring;

[0105] S3, after being fully stirred for 2 hours, pouring into a mold, and drying at 70° C. for 12 hours to prepare an active layer;

[0106] S4, repeating steps S1-S3 to obtain the remaining active layers, wherein multiple active layers are stacked up and down in sequence to form an ion gel layer; wherein the average pore size of the pore structure of the multiple active layers is distributed in a gradient manner;

[0107] The prepared multilayer active layer includes a first active layer, a second active layer, a third active layer and a fourth active layer; when preparing the first active layer, the mass ratio of water to acetone in S2 is 1:18; when preparing the second active layer, the mass ratio of water to acetone in S2 is 1:9; when preparing the third active layer, the mass ratio of water to acetone in S2 is 2:9; when preparing the fourth active layer, the mass ratio of water to acetone in S2 is 3:9;

[0108] S5. Preparing an upper electrode layer and a lower electrode layer:

[0109] The size of the upper electrode layer and the lower electrode layer is 5×5 mm, the substrate material of the upper electrode layer and the lower electrode layer is PET, and the conductive parts of the upper electrode layer and the lower electrode layer are Ag.

[0110] S6. Use 3M tape as a Spacer layer, and use the Spacer layer to package the upper electrode layer, the lower electrode layer and the ion gel layer as a whole to obtain the final product.

[0111] The thickness of the first active layer is 100 μm, the thickness of the second active layer is 200 μm, the thickness of the third active layer is 300 μm, and the thickness of the fourth active layer is 400 μm; the thickness ratio of the first active layer, the second active layer, the third active layer, and the fourth active layer is 1:2:3:4.

[0112] The pore density of the porous structure of the first active layer is 80%, the pore density of the porous structure of the second active layer is 70%, the pore density of the porous structure of the third active layer is 60%, and the pore density of the porous structure of the fourth active layer is 50%.

[0113] The average pore size of the porous structure of the first active layer is about 15μm, the average pore size of the porous structure of the second active layer is about 30μm, the average pore size of the porous structure of the third active layer is about 40μm, and the average pore size of the porous structure of the fourth active layer is about 48μm; the ratio of the average pore size of the porous structure of the first active layer, the second active layer, the third active layer, and the fourth active layer is 15:30:40:48.

[0114] Comparative Example 1

[0115] The method of Example 1 is referred to, except that step S4 is not performed, that is, only one ion gel layer is used. The one ion gel layer here is the first active layer, that is, the second active layer and the third active layer are not provided in Comparative Example 1.

[0116] Comparative Example 2

[0117] The method of Example 1 is referred to, except that in S6, other conventional processes in the prior art are used for packaging, that is, the flexible pressure sensor for human pulse detection prepared in Comparative Example 2 does not have a Spacer layer.

[0118] Comparative Example 3

[0119] The method of Example 1 is referred to, except that the average pore size of the porous structure of the second active layer and the third active layer prepared in S4 is the same as that of the first active layer, that is, the average pore size of the porous structure of the multi-layer active layer is not distributed in a gradient.

[0120] Test Case

[0121] The flexible pressure sensors obtained in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0122] Linearity is an important indicator to describe the static characteristics of the sensor. It characterizes the difference between the actual characteristic curve of the sensor and the ideal characteristic straight line within the full range. Linearity can be measured by nonlinear error, which refers to the percentage of the maximum deviation between the sensor calibration curve and the fitted straight line to the full-scale output under specified conditions.

[0123] The calculation formula of nonlinear error is as follows:

[0124] Nonlinear error = 100% × |Max(Y-Y0)| / (Xmax-Xmin)

[0125] Where Y is the actual output value, Y0 is the theoretical output value, Xmax and Xmin are the upper and lower limits of the range respectively. This formula calculates the percentage of the maximum deviation between the actual output and the theoretical output within the entire range.

[0126] Table 1

[0127]

[0128] From the above results, it can be seen that, compared with the comparative example, the present application creatively sets a spacer layer + multi-layer ion gel layer combination structure, and the synergistic effect of the two can greatly improve the linearity and sensitivity. The multi-layer ion gel layer with pore size gradient in the present application can provide different mechanical properties, achieve different deformations and provide different responses under different pressures, thereby greatly improving the sensitivity and linearity of the sensor.

[0129] Furthermore, according to the examples, by adopting the preferred implementation of the present application, the pore size gradient distribution of the ion gel layer with a multilayer structure can be more accurately controlled, and the graded deformation of the ion gel membrane under different pressures can be achieved, further improving the sensitivity and linearity of the sensor.

[0130] The embodiments of the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A flexible pressure sensor for human pulse detection, characterized in that: include: an upper electrode layer and a lower electrode layer; An ion gel layer, the ion gel layer is sandwiched between the upper electrode layer and the lower electrode layer, and the ion gel layer includes multiple active layers stacked in sequence; A Spacer layer, wherein the Spacer layer is disposed between the ion gel layer and the upper electrode layer, and the Spacer layer is used to fix the ion gel layer and the upper electrode layer, and to separate the ion gel layer from the upper electrode layer; Wherein, each active layer is provided with a hole structure, and the average pore diameters of the hole structures of the multiple active layers are distributed in a gradient manner; The multilayer active layer comprises a first active layer, a second active layer and a third active layer; The average pore size of the pore structure of the first active layer is 10-18 μm, the average pore size of the pore structure of the second active layer is 25-32 μm, and the average pore size of the pore structure of the third active layer is 35-42 μm.

2. The flexible pressure sensor for human pulse detection according to claim 1, characterized in that: The thickness of the first active layer is 70-120 μm, the thickness of the second active layer is 160-230 μm, and the thickness of the third active layer is 250-350 μm; and / or, The thickness ratio of the first active layer, the second active layer and the third active layer is 0.8-1.1:1.9-2.2:2.8-3.

3.

3. The flexible pressure sensor for human pulse detection according to claim 1, characterized in that: The pore density of the pore structure of the first active layer is 75%-85%, the pore density of the pore structure of the second active layer is 65%-75%, and the pore density of the pore structure of the third active layer is 55%-65%.

4. The flexible pressure sensor for human pulse detection according to claim 1, characterized in that: The ratio of average pore diameters of the pore structures of the first active layer, the second active layer and the third active layer is 12-18: 28-32: 38-42.

5. The flexible pressure sensor for human pulse detection according to claim 1, characterized in that: The size of the upper electrode layer and the lower electrode layer is 3×3-10×10 mm, the base material of the upper electrode layer and the lower electrode layer is PET, and the conductive parts of the upper electrode layer and the lower electrode layer are Ag; and / or, The Spacer layer is 3M tape.

6. A method for preparing a flexible pressure sensor for human pulse detection, the method for preparing the flexible pressure sensor for human pulse detection as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Dissolve PVDF-HFP in acetone, add [EMIM] [TFSI] and stir to mix; S2, adding water during stirring; S3, after fully stirring for 1-2 hours, pouring into a mold, and drying at 60-80° C. for more than 12 hours to prepare an active layer; S4, repeating steps S1-S3 to obtain the remaining active layers, wherein multiple active layers are stacked up and down in sequence to form an ion gel layer; wherein the average pore size of the pore structure of the multiple active layers is distributed in a gradient manner; S5, preparing an upper electrode layer and a lower electrode layer; S6. The upper electrode layer, the lower electrode layer and the ion gel layer are integrally encapsulated by a spacer layer to obtain a final product.

7. The preparation method according to claim 6, characterized in that: In S1, the mass ratio of PVDF-HFP to acetone was 1:8-10; and / or, In S1, the mass ratio of PVDF-HFP to [EMIM][TFSI] is 1:1-3.

8. The preparation method according to claim 6, characterized in that: In S4, a plurality of active layers are prepared, including a first active layer, a second active layer and a third active layer; when preparing the first active layer, in S2, the mass ratio of water to acetone is 0.8-1.5:16-20; when preparing the second active layer, in S2, the mass ratio of water to acetone is 0.5-1.2:8-10; when preparing the third active layer, in S2, the mass ratio of water to acetone is 1.5-2.5:8-10.

9. The preparation method according to claim 6, characterized in that: In S5, an upper electrode layer and a lower electrode layer are prepared by printing one or a combination of conductive silver paste, graphene, and carbon nanotubes on a PET film; and / or, In S6, 3M tape is used as the spacer layer.

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