A flexible pressure sensor for monitoring a pulse wave and a method of manufacturing the same

Abstract

The present application relates to a kind of flexible pressure sensor for monitoring pulse wave and its preparation method, first respectively prepare sensitive layer and interdigital electrode, then assemble to obtain the flexible pressure sensor for monitoring pulse wave;The prepared flexible pressure sensor for monitoring pulse wave includes sensitive layer and interdigital electrode, two electrodes of interdigital electrode are connected by wire, the sensitive layer is the polymer elastomer film with rigid convex microstructure array on surface;The rigid convex microstructure array is the convex microstructure array based on conductive metal;The highest sensitivity of the flexible pressure sensor is not less than 9.5kPa ‑1 , response time is not higher than 30ms, and the lower limit of mechanical detection is not higher than 8Pa.The rigid convex microstructure constructed on the surface of flexible sensitive layer has no lag and no damping in response to mechanical stimulation, which can give the pressure sensor high sensitivity, fast response speed and low detection limit performance;The preparation method of the present application is simple, and the production cost is low, which is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of pressure sensor technology, and relates to a flexible pressure sensor for monitoring pulse waves and its preparation method. Background Technology

[0002] Human pulse waves contain a wealth of physiological signals, continuously reflecting the regular changes in hemodynamic parameters such as heart rate, blood oxygen, and blood pressure, thus assessing cardiovascular performance. In traditional Chinese medicine, pulse diagnosis is also an important diagnostic method; however, it relies heavily on subjective judgment based on the experience of practitioners, leading to significant variations in diagnostic results and making objective quantification difficult. The emergence of pulse diagnosis devices has provided conditions for objective and standardized diagnosis in traditional Chinese medicine, but traditional devices are bulky, hindering real-time wearable monitoring and widespread application. Using flexible pressure sensors to collect and analyze human pulse wave signals, converting them into digital signals for quantitative analysis, holds significant promise for wearable, continuous monitoring of cardiovascular diseases. To achieve high-quality monitoring of the weak pulse wave signal, protruding microstructures are typically introduced into flexible pressure sensors to improve their sensitivity. However, traditional flexible sensors are composed of flexible polymer elastomers from the substrate to the microstructure. Due to the viscoelasticity of flexible polymer materials, they exhibit significant damping and hysteresis in response to mechanical stimuli, resulting in a high lower limit of mechanical detection and a slow response speed for flexible pressure sensors. Consequently, they cannot achieve high-resolution, high-quality monitoring of the characteristic peaks contained in the pulse wave signal.

[0003] Therefore, it is of great significance to study a highly sensitive and fast-response flexible pressure sensor that can monitor pulse wave signals and its fabrication method. Summary of the Invention

[0004] The purpose of this invention is to solve the problems mentioned above in the prior art and to provide a flexible pressure sensor for monitoring pulse waves and its preparation method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A flexible pressure sensor for monitoring pulse waves includes a sensitive layer and interdigital electrodes, the two electrodes of which are connected by wires. The sensitive layer is a polymer elastomer film with a rigid array of protruding microstructures on its surface.

[0007] The rigid protrusion microstructure array is a protrusion microstructure array based on conductive metal.

[0008] The maximum sensitivity of the flexible pressure sensor is no less than 9.5 kPa. -1 The response time is no higher than 30ms, and the lower limit of mechanical detection is no higher than 8Pa.

[0009] As a preferred technical solution:

[0010] As described above, in a flexible pressure sensor for monitoring pulse waves, the conductive metal is gold, silver, or copper.

[0011] In the flexible pressure sensor for monitoring pulse waves described above, the thickness of the polymer elastomer film is 0.2–0.5 mm.

[0012] The metal thickness of the interdigital electrode is 100–200 nm; the length of the interdigital electrode is 10–20 mm, the width is 10–20 mm, and the finger width and finger spacing are 0.2–2.0 mm.

[0013] As described above, in a flexible pressure sensor for monitoring pulse waves, the protrusions in the rigid protrusion microstructure array are hemispherical in shape, with a diameter of 0.1 to 1.0 mm (below 0.1 mm, it is difficult to achieve with existing additive manufacturing technology; above 1.0 mm, the protrusion microstructure size is too large and cannot play a role in enhancing sensitivity), and the distance between the centers of two adjacent hemispherical protrusions is 0.15 to 1.5 mm.

[0014] The present invention also provides a flexible pressure sensor for monitoring pulse waves, wherein the sensitive layer and the interdigital electrodes are first prepared separately, and then assembled to obtain the flexible pressure sensor for monitoring pulse waves.

[0015] The rigid protruding microstructure array on the surface of the sensitive layer is prepared by additive manufacturing technology. Due to the limitations of the microstructure preparation method, the existing technology mainly prepares microstructures indirectly through template method. It can only use flexible polymer materials to indirectly form microstructures from fixed templates, and cannot realize the indirect formation of microstructures from templates by rigid metal materials. However, the emergence of additive manufacturing technology has created conditions for rigid metal materials to form protruding microstructures. This invention uses additive manufacturing technology to directly prepare rigid metal materials into protruding microstructures, thereby endowing the pressure sensor with high sensitivity, fast response speed and low mechanical detection limit.

[0016] As a preferred technical solution:

[0017] The specific preparation steps of the method described above are as follows:

[0018] (1) A layer of polymer elastomer precursor liquid or elastic polymer solution is uniformly coated on a flat mold, the mold is placed in an oven and cured completely, and the film is peeled off to obtain a polymer elastomer film.

[0019] (2) The sensitive layer is obtained by constructing a raised microstructure array based on conductive metal paste on the surface of a polymer elastomer film using additive manufacturing technology, and then heating and curing it to form a rigid raised microstructure array based on conductive metal.

[0020] (3) First, the polymer film is ultrasonically cleaned in acetone, ethanol and deionized water in sequence. After drying, the surface of the polymer film is subjected to plasma treatment. Then, a mask with an interdigitated structure is placed on the polymer film. Then, a metal conductive material is deposited on the polymer film. Finally, the mask is removed to obtain the interdigitated electrode.

[0021] (4) The side of the sensitive layer with a rigid protrusion microstructure array prepared in step (2) is brought into contact with the electrode surface of the interdigital electrode prepared in step (3), and the device is encapsulated with adhesive to protect it from external environmental influences, thereby obtaining the flexible pressure sensor for monitoring pulse waves.

[0022] As described above, in step (1), the polymer elastomer precursor is a polydimethylsiloxane precursor, the mass ratio of the basic component to the curing agent in the polydimethylsiloxane precursor is 10:1, and the elastic polymer solution is a thermoplastic polyurethane solution or a hydrogenated styrene-butadiene block copolymer solution.

[0023] When coating with polymer elastomer precursor liquid, the curing temperature is 70-120℃ and the time is 60-180 minutes;

[0024] When coating with an elastic polymer solution, the curing temperature is 50–80°C and the curing time is 12–24 hours.

[0025] As described above, the additive manufacturing technology mentioned in step (2) is pneumatic direct writing technology, ammeter inkjet printing technology or electrospinning technology;

[0026] In step (2), the curing temperature is 70-100℃ and the time is 60-120 minutes.

[0027] As described above, the polymer film in step (3) is made of polyimide, polyethylene terephthalate, or polydimethylsiloxane.

[0028] The ultrasonic cleaning time is 0.1–0.5 hours;

[0029] The plasma treatment time is 10–30 minutes;

[0030] The metallic conductive material is one or more of gold, silver, and copper;

[0031] The deposition method of the metallic conductive material is one or more of vacuum evaporation, magnetron sputtering, and screen printing;

[0032] In the method described above, the adhesive in step (4) is one or more of polydimethylsiloxane precursor liquid, polyimide insulating tape, and polyurethane medical tape;

[0033] The two electrodes of the interdigital electrode are connected by a wire and fixed with conductive adhesive;

[0034] The conductor is made of copper wire or copper foil, and the conductive adhesive is made of conductive silver paste or conductive carbon paste.

[0035] The principle of this invention is as follows:

[0036] Existing flexible pressure sensors are constructed with microstructures and sensitive layers made of flexible polymer elastomers. Due to the viscoelasticity of these materials, they exhibit significant damping and hysteresis in response to mechanical stimuli. This significant damping and hysteresis absorbs external force, converting it into energy from polymer chain movement, thus weakening the response to external stimuli. Consequently, they cannot detect minute external forces, resulting in a high mechanical detection limit for flexible pressure sensors. Furthermore, this leads to low sensor sensitivity, slow response speed, and an inability to achieve high-resolution, high-quality detection of pulse wave characteristic peaks. This invention takes a different approach by constructing rigid protruding microstructures on the surface of the flexible sensitive layer. These rigid microstructures exhibit no hysteresis and no damping in response to mechanical stimuli, converting all external force into deformation. This endows the pressure sensor with high sensitivity, fast response speed, and a low mechanical detection limit. Moreover, the flexible sensitive layer conformally adheres to the human skin surface, ensuring the sensor's flexible and wearable performance. Therefore, rigid microstructures can improve the sensitivity and response speed of pressure sensors and lower the lower limit of mechanical detection of sensors, while flexible sensitive layers can ensure that sensors conformally adhere to human skin. Thus, under the combined effect of rigid microstructures and flexible sensitive layers (i.e., the effect of "rigidity and flexibility combined"), the sensor can achieve high-resolution, wearable continuous monitoring of the weak mechanical signal of pulse wave signals.

[0037] Beneficial effects:

[0038] (1) The rigid protruding microstructure constructed on the surface of the flexible sensitive layer in this invention has no hysteresis and no damping in response to mechanical stimulation, which can endow the pressure sensor with high sensitivity, fast response speed and low detection limit performance.

[0039] (2) The flexible sensitive layer can conformally adhere to the surface of human skin, giving the sensor flexible wearable properties;

[0040] (3) The “rigid-flexible combination” of rigid microstructure and flexible sensitive layer can enable the sensor to perform high-resolution, wearable continuous monitoring of human pulse wave signals.

[0041] (4) The flexible pressure sensor of the present invention has a simple preparation method, low production cost, and is suitable for large-scale industrial production. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the flexible pressure sensor of the present invention;

[0043] Figure 2 An optical microscope image of the sensitive layer with a rigid microstructure array prepared in Example 1;

[0044] Figure 3 The graph shows the resistance signal change of the flexible pressure sensor prepared in Example 1 under cyclic pressure.

[0045] Figure 4 The radial artery pulse wave signal of the human body was measured by the flexible pressure sensor prepared in Example 1;

[0046] Figure 5 The radial artery pulse wave signal of a human body was measured by the flexible pressure sensor prepared for Comparative Example 1.

[0047] Among them, 1-sensitive layer, 2-rigid protrusion microstructure array, 3-interdigital electrode. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0049] In the embodiments of the present invention, the mass ratio of the basic component to the curing agent in the polydimethylsiloxane precursor liquid is 10:1.

[0050] Example 1

[0051] The specific fabrication steps of a flexible pressure sensor for monitoring pulse waves are as follows:

[0052] (1) A layer of polydimethylsiloxane precursor liquid is uniformly coated on a flat mold. The mold is placed in an oven and cured at 90°C for 3 hours. The film is then peeled off to obtain a polymer elastomer film with a thickness of 0.3 mm.

[0053] (2) A raised microstructure array based on conductive silver paste was constructed on the surface of a polymer elastomer film by pneumatic direct writing technology. After heating and curing at 80°C for 120 minutes, a rigid raised microstructure array based on conductive silver was formed, and a sensitive layer was obtained.

[0054] The rigid protrusion microstructure array produced features hemispherical protrusions with a diameter of 0.5 mm and a center-to-center distance of 1 mm between adjacent hemispherical protrusions. Figure 2 As shown;

[0055] (3) First, the polymer film is ultrasonically cleaned in acetone, ethanol and deionized water for 0.2 h in sequence. After drying, the surface of the polymer film is subjected to plasma treatment for 10 minutes. Then, a mask with an interdigitated structure is placed on the polymer film. Then, the metal conductive material is deposited on the polymer film. Finally, the mask is removed to obtain the interdigitated electrode.

[0056] The polymer film is made of polyimide; the conductive metal is silver; and the conductive metal is deposited by vacuum evaporation.

[0057] The metal thickness of the fabricated interdigitated electrode is 120 nm; the length of the interdigitated electrode is 15 mm, the width is 15 mm, and the finger width and finger spacing are 0.5 mm.

[0058] (4) The side of the sensitive layer with a rigid protrusion microstructure array prepared in step (2) is brought into contact with the electrode surface of the interdigital electrode prepared in step (3), and the device is encapsulated with adhesive to protect it from external environmental influences, thus obtaining a flexible pressure sensor for monitoring pulse waves.

[0059] The adhesive is a polydimethylsiloxane precursor solution; the two electrodes of the interdigitated electrode are connected by copper wire and fixed with conductive silver paste.

[0060] The fabricated flexible pressure sensor for monitoring pulse waves, such as Figure 1 As shown, it includes a sensitive layer 1 and interdigitated electrodes 3. The sensitive layer is a polymer elastomer film with a rigid protrusion microstructure array 2 on its surface. The rigid protrusion microstructure array is a protrusion microstructure array based on conductive silver.

[0061] The sensing performance of a flexible pressure sensor used for pulse wave monitoring can be obtained by measuring the change in resistance signal under pressure using a digital source meter. The highest sensitivity of this flexible pressure sensor for pulse wave monitoring is 24.2 kPa. -1 With a response time of 13ms and a mechanical detection limit of 3.5Pa, this flexible pressure sensor for monitoring pulse waves exhibits high sensitivity, fast response speed, and a low mechanical detection limit. Furthermore, the resistance signal change of this flexible pressure sensor for monitoring pulse waves under cyclic pressure shows excellent stability and repeatability; its resistance signal change under 20Pa cyclic pressure is as follows: Figure 3 As shown.

[0062] like Figure 4 As shown, the flexible pressure sensor used to monitor pulse waves is attached to the radial artery in the wrist, which can monitor the characteristic peaks contained in the human pulse wave signal at high resolution.

[0063] Comparative Example 1

[0064] A flexible pressure sensor, the specific steps of which are basically the same as in embodiment 1, the difference being that the sensitive layer is prepared by uniformly coating a layer of polydimethylsiloxane precursor liquid on a mold with a hemispherical groove array, heating and curing, peeling off the film to obtain an elastomer film with a flexible hemispherical protrusion microstructure array, and evaporating a layer of conductive silver on the surface of the elastomer film to obtain the sensitive layer; the thickness of the elastomer film is 0.3 mm, the diameter of the hemispherical protrusion is 0.5 mm, the distance between the centers of two adjacent hemispherical protrusions is 1.0 mm, and the thickness of the conductive silver is 100 nm.

[0065] The highest sensitivity of the fabricated flexible pressure sensor is 1.15 kPa. -1 The response time is 180ms, and the lower limit of mechanical detection is 45Pa. For example... Figure 5 As shown, when this flexible pressure sensor is attached to the radial artery in the wrist, it can only roughly measure the pulse beat and cannot measure the characteristic peaks contained in the pulse wave signal at high resolution.

[0066] Comparing Example 1 with Comparative Example 1, it can be seen that constructing a rigid microstructure on the surface of the flexible sensitive layer results in a response to mechanical stimuli without hysteresis or damping, which can endow the flexible pressure sensor with high sensitivity, fast response, and low detection limit performance, enabling high-resolution monitoring of pulse wave signals.

[0067] Example 2

[0068] The specific fabrication steps of a flexible pressure sensor for monitoring pulse waves are as follows:

[0069] (1) A layer of polydimethylsiloxane precursor liquid is uniformly coated on a flat mold. The mold is placed in an oven and cured at 120°C for 1 hour. The film is then peeled off to obtain a polymer elastomer film with a thickness of 0.2 mm.

[0070] (2) A raised microstructure array based on conductive gold paste was constructed on the surface of a polymer elastomer film by means of an ammeter inkjet printing technology. After heating and curing at 70°C for 100 minutes, a rigid raised microstructure array based on conductive gold was formed, and a sensitive layer was obtained.

[0071] The rigid protrusion microstructure array has a hemispherical shape with a diameter of 0.15 mm and a center-to-center distance of 0.3 mm between two adjacent hemispherical protrusions.

[0072] (3) First, the polymer film is ultrasonically cleaned in acetone, ethanol and deionized water for 0.4 h in sequence. After drying, the surface of the polymer film is subjected to plasma treatment for 15 minutes. Then, a mask with an interdigitated structure is placed on the polymer film. Then, the metal conductive material is deposited on the polymer film. Finally, the mask is removed to obtain the interdigitated electrode.

[0073] The polymer film is made of polyethylene terephthalate; the conductive metal is gold; and the conductive metal is deposited by magnetron sputtering.

[0074] The metal thickness of the fabricated interdigitated electrode is 120 nm; the length of the interdigitated electrode is 12 mm, the width is 12 mm, and the finger width and finger spacing are 0.2 mm.

[0075] (4) The side of the sensitive layer with a rigid protrusion microstructure array prepared in step (2) is brought into contact with the electrode surface of the interdigital electrode prepared in step (3), and the device is encapsulated with adhesive to protect it from external environmental influences, thus obtaining a flexible pressure sensor for monitoring pulse waves.

[0076] The adhesive is polyimide insulating tape; the two electrodes of the interdigitated electrode are connected by copper foil and fixed with conductive carbon paste.

[0077] The fabricated flexible pressure sensor for monitoring pulse waves, such as Figure 1 As shown, it includes a sensitive layer 1 and interdigitated electrodes 3. The sensitive layer is a polymer elastomer film with a rigid protrusion microstructure array 2 on its surface. The rigid protrusion microstructure array is a protrusion microstructure array based on conductive gold.

[0078] The flexible pressure sensor used to monitor pulse waves has a maximum sensitivity of 35.2 kPa. -1 The response time is 9ms, and the lower limit of mechanical detection is 2.8Pa.

[0079] Example 3

[0080] The specific fabrication steps of a flexible pressure sensor for monitoring pulse waves are as follows:

[0081] (1) A layer of thermoplastic polyurethane solution is uniformly coated on a flat mold. The mold is placed in an oven and cured at 50°C for 24 hours. The film is then peeled off to obtain a polymer elastomer film with a thickness of 0.38 mm.

[0082] (2) A raised microstructure array based on conductive copper paste was constructed on the surface of a polymer elastomer film by electrospinning technology. After heating and curing at 100°C for 80 minutes, a rigid raised microstructure array based on conductive copper was formed, and a sensitive layer was obtained.

[0083] The rigid protrusion microstructure array has a hemispherical shape with a diameter of 0.25 mm and a center-to-center distance of 0.5 mm between two adjacent hemispherical protrusions.

[0084] (3) First, the polymer film is ultrasonically cleaned in acetone, ethanol and deionized water for 0.3h in sequence. After drying, the surface of the polymer film is subjected to plasma treatment for 30 minutes. Then, a mask with an interdigitated structure is placed on the polymer film. Then, the metal conductive material is deposited on the polymer film. Finally, the mask is removed to obtain the interdigitated electrode.

[0085] The polymer film is made of polydimethylsiloxane; the conductive metal is copper; and the conductive metal is deposited by screen printing.

[0086] The metal thickness of the fabricated interdigitated electrode is 160 nm; the length of the interdigitated electrode is 18 mm, the width is 18 mm, and the finger width and finger spacing are 0.8 mm.

[0087] (4) The side of the sensitive layer with a rigid protrusion microstructure array prepared in step (2) is brought into contact with the electrode surface of the interdigital electrode prepared in step (3), and the device is encapsulated with adhesive to protect it from external environmental influences, thus obtaining a flexible pressure sensor for monitoring pulse waves.

[0088] The adhesive is polyurethane medical tape; the two electrodes of the interdigital electrode are connected by copper wire and fixed with conductive silver paste.

[0089] The fabricated flexible pressure sensor for monitoring pulse waves, such as Figure 1 As shown, it includes a sensitive layer 1 and interdigitated electrodes 3. The sensitive layer is a polymer elastomer film with a rigid protrusion microstructure array 2 on its surface. The rigid protrusion microstructure array is a protrusion microstructure array based on conductive copper.

[0090] The flexible pressure sensor used to monitor pulse waves has a maximum sensitivity of 19.6 kPa. -1 The response time is 16ms, and the lower limit of mechanical detection is 5.7Pa.

[0091] Example 4

[0092] The specific fabrication steps of a flexible pressure sensor for monitoring pulse waves are as follows:

[0093] (1) A layer of thermoplastic polyurethane solution is uniformly coated on a flat mold. The mold is placed in an oven and cured at 60°C for 20 hours. The film is then peeled off to obtain a polymer elastomer film with a thickness of 0.4 mm.

[0094] (2) A raised microstructure array based on conductive silver paste was constructed on the surface of a polymer elastomer film by pneumatic direct writing technology. After heating and curing at 90°C for 90 minutes, a rigid raised microstructure array based on conductive silver was formed, and a sensitive layer was obtained.

[0095] The rigid protrusion microstructure array has hemispherical protrusions with a diameter of 0.8 mm and a center-to-center distance of 1.6 mm between two adjacent hemispherical protrusions.

[0096] (3) First, the polymer film is ultrasonically cleaned in acetone, ethanol and deionized water for 0.5 h in sequence. After drying, the surface of the polymer film is subjected to plasma treatment for 10 minutes. Then, a mask with an interdigitated structure is placed on the polymer film. Then, the metal conductive material is deposited on the polymer film. Finally, the mask is removed to obtain the interdigitated electrode.

[0097] The polymer film is made of polyimide; the conductive metal is gold; and the conductive metal is deposited by vacuum evaporation.

[0098] The metal thickness of the fabricated interdigitated electrode is 200 nm; the length of the interdigitated electrode is 20 mm, the width is 20 mm, and the finger width and finger spacing are 1.6 mm.

[0099] (4) The side of the sensitive layer with a rigid protrusion microstructure array prepared in step (2) is brought into contact with the electrode surface of the interdigital electrode prepared in step (3), and the device is encapsulated with adhesive to protect it from external environmental influences, thus obtaining a flexible pressure sensor for monitoring pulse waves.

[0100] The adhesive is a polydimethylsiloxane precursor solution; the two electrodes of the interdigitated electrode are connected by copper foil and fixed with conductive carbon paste.

[0101] The fabricated flexible pressure sensor for monitoring pulse waves, such as Figure 1 As shown, it includes a sensitive layer 1 and interdigitated electrodes 3. The sensitive layer is a polymer elastomer film with a rigid protrusion microstructure array 2 on its surface. The rigid protrusion microstructure array is a protrusion microstructure array based on conductive silver.

[0102] The flexible pressure sensor used to monitor pulse waves has a maximum sensitivity of 9.5 kPa. -1 The response time is 26ms, and the lower limit of mechanical detection is 7.6Pa.

[0103] Example 5

[0104] The specific fabrication steps of a flexible pressure sensor for monitoring pulse waves are as follows:

[0105] (1) A layer of hydrogenated styrene-butadiene block copolymer solution was uniformly coated on a flat mold. The mold was placed in an oven and cured at 70°C for 16 hours. The film was then peeled off to obtain a polymer elastomer film with a thickness of 0.35 mm.

[0106] (2) A raised microstructure array based on conductive gold paste was constructed on the surface of a polymer elastomer film by means of ammeter inkjet printing technology. After heating and curing at 80°C for 80 minutes, a rigid raised microstructure array based on conductive gold was formed, and a sensitive layer was obtained.

[0107] The rigid protrusion microstructure array has a hemispherical shape with a diameter of 0.7 mm and a center-to-center distance of 1.4 mm between two adjacent hemispherical protrusions.

[0108] (3) First, the polymer film is ultrasonically cleaned in acetone, ethanol and deionized water for 0.1 h in sequence. After drying, the surface of the polymer film is subjected to plasma treatment for 25 minutes. Then, a mask with an interdigitated structure is placed on the polymer film. Then, the metal conductive material is deposited on the polymer film. Finally, the mask is removed to obtain the interdigitated electrode.

[0109] The polymer film is made of polyethylene terephthalate; the conductive metal is silver; and the conductive metal is deposited by magnetron sputtering.

[0110] The metal thickness of the fabricated interdigitated electrode is 160 nm; the length of the interdigitated electrode is 15 mm, the width is 15 mm, and the finger width and finger spacing are 1.6 mm.

[0111] (4) The side of the sensitive layer with a rigid protrusion microstructure array prepared in step (2) is brought into contact with the electrode surface of the interdigital electrode prepared in step (3), and the device is encapsulated with adhesive to protect it from external environmental influences, thus obtaining a flexible pressure sensor for monitoring pulse waves.

[0112] The adhesive is polyimide insulating tape; the two electrodes of the interdigitated electrode are connected by copper wire and fixed with conductive silver paste.

[0113] The fabricated flexible pressure sensor for monitoring pulse waves, such as Figure 1 As shown, it includes a sensitive layer 1 and interdigitated electrodes 3. The sensitive layer is a polymer elastomer film with a rigid protrusion microstructure array 2 on its surface. The rigid protrusion microstructure array is a protrusion microstructure array based on conductive gold.

[0114] The flexible pressure sensor used to monitor pulse waves has a maximum sensitivity of 27.2 kPa. -1 The response time is 22ms, and the lower limit of mechanical detection is 5.8Pa.

[0115] Example 6

[0116] The specific fabrication steps of a flexible pressure sensor for monitoring pulse waves are as follows:

[0117] (1) A layer of hydrogenated styrene-butadiene block copolymer solution was uniformly coated on a flat mold. The mold was placed in an oven and cured at 80°C for 12 hours. The film was then peeled off to obtain a polymer elastomer film with a thickness of 0.45 mm.

[0118] (2) A raised microstructure array based on conductive copper paste was constructed on the surface of a polymer elastomer film by electrospinning technology. After heating and curing at 80°C for 60 minutes, a rigid raised microstructure array based on conductive copper was formed, and a sensitive layer was obtained.

[0119] The rigid protrusion microstructure array has a hemispherical shape with a diameter of 0.5 mm and a center-to-center distance of 1.3 mm between two adjacent hemispherical protrusions.

[0120] (3) First, the polymer film is ultrasonically cleaned in acetone, ethanol and deionized water for 0.3h in sequence. After drying, the surface of the polymer film is subjected to plasma treatment for 20 minutes. Then, a mask with an interdigitated structure is placed on the polymer film. Then, the metal conductive material is deposited on the polymer film. Finally, the mask is removed to obtain the interdigitated electrode.

[0121] The polymer film is made of polydimethylsiloxane; the conductive metal is copper; and the conductive metal is deposited by screen printing.

[0122] The metal thickness of the fabricated interdigitated electrode is 160 nm; the length of the interdigitated electrode is 16 mm, the width is 16 mm, and the finger width and finger spacing are 1.1 mm.

[0123] (4) The side of the sensitive layer with a rigid protrusion microstructure array prepared in step (2) is brought into contact with the electrode surface of the interdigital electrode prepared in step (3), and the device is encapsulated with adhesive to protect it from external environmental influences, thus obtaining a flexible pressure sensor for monitoring pulse waves.

[0124] The adhesive is polyurethane medical tape; the two electrodes of the interdigital electrode are connected by copper foil and fixed with conductive carbon paste.

[0125] The fabricated flexible pressure sensor for monitoring pulse waves, such as Figure 1 As shown, it includes a sensitive layer 1 and interdigitated electrodes 3. The sensitive layer is a polymer elastomer film with a rigid protrusion microstructure array 2 on its surface. The rigid protrusion microstructure array is a protrusion microstructure array based on conductive copper.

[0126] The flexible pressure sensor used to monitor pulse waves has a maximum sensitivity of 40.6 kPa. -1 The response time is 11ms, and the lower limit of mechanical detection is 3.7Pa.

Claims

1. A flexible pressure sensor for monitoring pulse waves, comprising a sensitive layer and interdigital electrodes, wherein the two electrodes of the interdigital electrodes are connected by wires, characterized in that: The sensitive layer is a polymer elastomer film with a rigid array of protruding microstructures on its surface; The rigid protrusion microstructure array is a protrusion microstructure array based on conductive metal; the conductive metal is gold, silver or copper; the protrusions in the rigid protrusion microstructure array are hemispherical in shape, the diameter of the hemisphere is 0.1~1.0mm, and the distance between the centers of two adjacent hemispherical protrusions is 0.15~1.5mm. The maximum sensitivity of the flexible pressure sensor is no less than 9.5 kPa. -1 The response time is no higher than 30ms, and the lower limit of mechanical detection is no higher than 8Pa.

2. A flexible pressure sensor for monitoring pulse waves according to claim 1, characterized in that, The thickness of the polymer elastomer film is 0.2~0.5 mm; The metal thickness of the interdigital electrode is 100~200nm; the length of the interdigital electrode is 10~20mm, the width is 10~20mm, and the finger width and finger spacing are 0.2~2.0mm.

3. A method for preparing a flexible pressure sensor for monitoring pulse waves as described in any one of claims 1 to 2, characterized in that: First, the sensitive layer and the interdigitated electrodes are prepared separately, and then assembled to obtain the flexible pressure sensor for monitoring pulse waves; The array of rigid protruding microstructures on the surface of the sensitive layer is prepared by additive manufacturing technology.

4. The method according to claim 3, characterized in that, The specific preparation steps are as follows: (1) A layer of polymer elastomer precursor liquid or elastic polymer solution is uniformly coated on a flat mold, the mold is placed in an oven and cured completely, and the film is peeled off to obtain a polymer elastomer film; (2) The sensitive layer is obtained by constructing a raised microstructure array based on conductive metal paste on the surface of a polymer elastomer film using additive manufacturing technology, and then heating and curing it to form a rigid raised microstructure array based on conductive metal. (3) First, the polymer film is ultrasonically cleaned in acetone, ethanol and deionized water in sequence. After drying, the surface of the polymer film is subjected to plasma treatment. Then, a mask with an interdigitated structure is placed on the polymer film. Then, a metal conductive material is deposited on the polymer film. Finally, the mask is removed to obtain the interdigitated electrode. (4) The side of the sensitive layer with a rigid protrusion microstructure array prepared in step (2) is brought into contact with the electrode surface of the interdigital electrode prepared in step (3), and encapsulated with adhesive to obtain the flexible pressure sensor for monitoring pulse waves.

5. The method according to claim 4, characterized in that, In step (1), the polymer elastomer precursor is a polydimethylsiloxane precursor, and the elastic polymer solution is a thermoplastic polyurethane solution or a hydrogenated styrene-butadiene block copolymer solution. When coating with polymer elastomer precursor liquid, the curing temperature is 70~120℃ and the time is 60~180 minutes; When coating with an elastic polymer solution, the curing temperature is 50~80℃ and the time is 12~24h.

6. The method according to claim 4, characterized in that, The additive manufacturing technology mentioned in step (2) is pneumatic direct writing technology, ammeter inkjet printing technology or electrospinning technology; In step (2), the curing temperature is 70~100℃ and the time is 60~120 minutes.

7. The method according to claim 4, characterized in that, The polymer film described in step (3) is made of polyimide, polyethylene terephthalate or polydimethylsiloxane; The ultrasonic cleaning time is 0.1~0.5h; The plasma treatment time is 10-30 minutes; The metallic conductive material is one or more of gold, silver, and copper; The deposition method of the metallic conductive material is one or more of vacuum evaporation, magnetron sputtering and screen printing.

8. The method according to claim 4, characterized in that, The adhesive mentioned in step (4) is one or more of polydimethylsiloxane precursor liquid, polyimide insulating tape, and polyurethane medical tape; The two electrodes of the interdigital electrode are connected by a wire and fixed with conductive adhesive; The conductor is made of copper wire or copper foil, and the conductive adhesive is made of conductive silver paste or conductive carbon paste.

Images