A flexible micro pressure sensor and its preparation process

Abstract

The present invention discloses a flexible micro-pressure sensor and a preparation process. The flexible micro-pressure sensor is composed of multiple layers of flexible substrates printed with printed circuits. First, the printed circuit and lead heads are printed on the upper surface of the flexible substrate serving as the bottom layer; then a second layer of flexible substrate is covered; the printed circuit and lead heads are printed on the second layer of flexible substrate, and a slope with a certain slope is cut out of the second layer of flexible substrate. The lead heads are printed on the slope and extend to the lead heads of the bottom layer of flexible substrate, so that the upper and lower layers of circuits are connected together; the corresponding number of layers is prepared as needed, and finally a flexible protective layer is covered to complete the preparation of the flexible micro-pressure sensor. The present invention is used in conjunction with a vector network analyzer for measuring the pressure of blood vessels, organs, or arteriovenous fistulas in the medical field. The present invention has a simple preparation process, high detection sensitivity, can realize wireless transmission isolation detection, is easy to use, and has strong practicality.

Description

Technical Field

[0001] The present invention belongs to the field of pressure sensors and relates to a pressure sensor, in particular to a flexible micro pressure sensor and a preparation process. Background Art

[0002] An arteriovenous fistula is a surgical procedure used in hemodialysis treatment. The arteriovenous fistula provides an adequate blood supply, enhancing dialysis treatment. Arteriovenous fistulas have a limited lifespan, and different types of blood vessels (such as those with different diameters) require different surgical procedures. Monitoring the condition of arteriovenous fistulas is crucial, as it can effectively prevent many complications, particularly thrombosis.

[0003] Current blood pressure monitoring methods rely on external devices such as sphygmomanometers to directly measure blood pressure at a specific location on the body. This reflects the overall blood pressure status of the body, but cannot monitor the blood pressure in a specific blood vessel. To better pinpoint the location of blood vessels, accurately measure their physiological indicators, and prevent vascular disease, implantable sensors can be used for monitoring.

[0004] Traditional pressure sensors are made from rigid materials like silicon, which cannot adhere tightly to flexible biological tissue surfaces. This can lead to sensor failure and errors due to bending and deformation of biological structures. Therefore, there is a need for flexible micro-pressure sensors made from novel materials that exhibit bendability, ductility, and biocompatibility to monitor the status of arteriovenous fistulas. Summary of the Invention

[0005] In response to the problems of fistula blockage, slow blood flow, and thrombosis that occur after long-term dialysis of arteriovenous fistulas, the present invention proposes a preparation process for a flexible micro-pressure sensor. The micro-pressure sensor is flexible, has no power supply of its own, and has wireless information transmission capability. It can monitor the pressure changes of arteriovenous fistulas in real time over a long period of time, and then reflect the status of the arteriovenous fistula, thereby effectively preventing complications such as thrombosis and arteriovenous aneurysms after arteriovenous fistula surgery.

[0006] The working principle and specific effects achieved by the flexible passive wireless micro-pressure sensor involved in the present invention in the application of arteriovenous fistula are as follows:

[0007] For arteriovenous fistulas formed during medical surgery, the flexible micro-pressure sensor of this invention can adapt its overall size and shape to the size of the fistula without affecting its functionality. The flexible micro-pressure sensor adheres to the surface of the fistula, and the sensor packaging material used has good biocompatibility.

[0008] The condition of an artificial fistula after long-term vascular dialysis differs significantly from that of a newly mature artificial fistula. Due to the lifespan of an arteriovenous fistula, after long-term dialysis, insufficient blood volume and reduced blood flow can occur in the fistula, leading to thrombosis and reduced contraction of the artificial fistula. A flexible passive wireless micro-pressure sensor attached to the surface of the artificial fistula can monitor minute fluctuations in the fistula. These fluctuations alter the distance between the upper and lower capacitor plates of the pressure sensor, causing a change in capacitance. The sensor converts the physical signal into an electrical signal. An external vector network analyzer then senses the sensor's resonant frequency changes, analyzing the fluctuations in the fistula and enabling real-time monitoring of the fistula's condition. This allows for timely medical attention based on the actual situation, preventing blockage and thrombosis in the arteriovenous fistula.

[0009] The above-mentioned purpose of the present invention is achieved through the following solutions:

[0010] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0011] The present invention provides a flexible micro-pressure sensor, comprising at least two flexible substrates with micro-deformation capabilities and insulation, wherein the multiple flexible substrates are stacked in sequence, a printed circuit and lead heads connected to the printed circuit are provided on the upper surface of each flexible substrate, a flexible protective layer is provided on the topmost printed circuit and lead heads, each printed circuit comprises a capacitor plate located in the middle and an inductor coil surrounding the capacitor plate, and the lead heads on two adjacent layers of flexible substrates are connected by a connecting structure to form an LC circuit for pressure detection.

[0012] Furthermore, in two adjacent layers of flexible substrates, a slope leading to the lead head area of ​​the lower layer is provided on the flexible substrate on the upper layer; the lead heads on the upper flexible substrate are printed on the slope and aligned with and contact the lead heads of the lower flexible substrate, and the upper and lower lead heads contact at the slope to form a connection structure.

[0013] The present invention also provides a process for preparing the flexible micro-pressure sensor, which is characterized by comprising the following steps:

[0014] S1, prepare a corresponding number of flexible substrates according to the number of layers of the micro pressure sensor, and cut inclined surfaces with a certain slope on the flexible substrate except the bottom layer. If the flexible substrate has more than two layers, adjacent inclined surfaces are staggered;

[0015] S2, printing a printed circuit and a lead head on the upper surface of the flexible substrate serving as the bottom layer;

[0016] S3, covering the flexible substrate manufactured in step S2 with a second flexible substrate;

[0017] S4, printing a printed circuit and lead heads on the second layer of flexible substrate described in step S3, with the lead heads printed on the inclined surface and extending to the lead heads of the bottom layer of flexible substrate, so that the upper and lower layers of circuits are connected together;

[0018] S5. If the number of flexible substrates is greater than two, continue stacking the flexible substrates and printing the corresponding printed circuits and lead headers according to the method of steps S3 and S4, with the inclined surface of the upper flexible substrate set back relative to the inclined surface of the lower flexible substrate to ensure that the lead headers on two adjacent flexible substrates are connected together; otherwise, proceed directly to step S6.

[0019] S6, covering the flexible circuit of the uppermost flexible substrate with a flexible protective layer to complete the preparation of the flexible micro pressure sensor.

[0020] The present invention also provides a use of the flexible micro-pressure sensor, which is used in conjunction with a vector network analyzer for measuring the pressure of blood vessels, organs or arteriovenous fistulas in the medical field.

[0021] In the preparation process of the present invention, inkjet printing is used to directly print microcircuits onto a flexible substrate, eliminating traditional semiconductor processing techniques. This results in a simple and convenient process, eliminates contamination issues such as etching solutions, and allows for the adjustment of sensor structural parameters based on specific applications. The substrate material used exhibits excellent flexibility, ductility, electrical insulation, and high biocompatibility, meeting medical requirements. The unique structure of the flexible micropressure sensor ensures both enhanced sensitivity and reliable monitoring.

[0022] Compared with the existing technology, the present invention has the following more beneficial effects:

[0023] Applied to in-situ monitoring of arteriovenous fistulas, the device can detect deformation in flexible biological tissues, converting tiny pressure fluctuations into electrical signal changes. This avoids the detection errors and other issues associated with traditional solid-state sensors, which lack a firm fit for biological tissue.

[0024] Secondly, the device is small in size and can more accurately monitor tiny biological tissues such as arteriovenous fistulas, and can replace the large-scale inspections currently required by large medical equipment.

[0025] This device has no built-in power supply, and the wireless information transmission feature can achieve real-time monitoring to a certain extent, timely detect lesions in the fistula after long-term hemodialysis, and effectively prevent the occurrence of complications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] By referring to the following drawings, one can have a deeper understanding of other features, objectives, and advantages of the flexible micro pressure sensor of the present invention:

[0027] Figure 1 This is a schematic diagram of the structure of the flexible micro pressure sensor in Example 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the lower flexible substrate and the upper circuit board during the preparation of the flexible micro pressure sensor of the present invention, wherein Figure 2 (a) is a top view, Figure 2 (b) Main view.

[0029] Figure 3 This is a schematic diagram of the upper flexible substrate being covered on the lower flexible substrate during the preparation of the flexible micro pressure sensor of the present invention, wherein Figure 3 (a) is a top view, Figure 3 (b) Main view.

[0030] Figure 4 This is a schematic diagram of the upper flexible substrate and the circuit board thereon during the preparation of the flexible micro-pressure sensor of the present invention, wherein Figure 4 (a) is a top view, Figure 4 (b) Main view.

[0031] Figure 5 This is a schematic diagram of a flexible protective layer covering the upper flexible substrate during the preparation of a flexible micro-pressure sensor according to the present invention, wherein Figure 5 (a) is a top view, Figure 5 (b) Main view.

[0032] Figure 6 This is a schematic structural diagram of the flexible micro-pressure sensor according to Example 2 of the present invention.

[0033] 1-lower flexible substrate, 2-upper flexible substrate, 3-inclined surface, 4-first inductor coil, 5-first lead head, 6-first capacitor plate, 7-first printed circuit, 8-second inductor coil, 9-second lead head, 10-second capacitor plate, 11-second printed circuit, 12-flexible protective layer, 13-top flexible substrate, 14-third printed circuit. DETAILED DESCRIPTION

[0034] The device of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] The present invention is described below by taking a two-layer flexible substrate as an example.

[0036] Example 1: Figure 1As shown, a flexible micro-pressure sensor includes two flexible substrates with micro-deformability and insulation, namely a lower flexible substrate 1 and an upper flexible substrate 2. The two flexible substrates are stacked in sequence, and a printed circuit and a lead head connected to the printed circuit are provided on the upper surface of each flexible substrate. Among them, the lower flexible substrate 1 is provided with a first printed circuit 7 and a first lead head 5, and the upper flexible substrate 2 is provided with a second printed circuit 11 and a second lead head 9; a flexible protective layer 12 is provided on the topmost printed circuit and lead head, and each printed circuit includes a capacitor plate located in the middle and an inductor coil surrounding the capacitor plate, the lower flexible substrate 1 is provided with a first capacitor plate 6 and a first inductor coil 4, and the upper flexible substrate 2 is provided with a second capacitor plate 10 and a second inductor coil 8; the lead heads on the two adjacent flexible substrates are connected by a connecting structure to form an LC circuit for pressure detection.

[0037] The present invention provides a specific connection structure: an incision is opened on the upper flexible substrate 2, cutting out a slope leading to the lead head area of ​​the lower layer; the lead head on the upper flexible substrate 2 is printed on the slope and extends to align and connect with the lead head of the lower flexible substrate 1. When the upper and lower flexible substrates are superimposed, the upper and lower lead heads contact at the slope to form a connection structure.

[0038] As a preferred embodiment, the flexible substrate of the present invention is an insulating polymer material containing C. Specifically, the insulating polymer material containing C includes but is not limited to polydimethylsiloxane, polytrimethylene carbonate, and the like.

[0039] As a preferred embodiment, the printed circuit is an inkjet printed circuit. Through inkjet printing, the thickness of the printed circuit is at the micron level, so that two adjacent layers of flexible substrates can be directly stacked, and the packaging is completed after the air in the middle is removed, without the need for other packaging structures such as adhesives.

[0040] As a preferred embodiment, in the printed circuit of the multi-layer flexible substrate, the capacitor plates are parallel to each other, positioned opposite to each other and have the same size.

[0041] As a preferred embodiment, in a multi-layer flexible substrate, the printed circuits are identical and positioned relative to each other, forming a mirror image relationship between the printed circuits on the XY plane (a plane parallel to the flexible substrate), thereby improving the stability of the LC circuit and the consistency during the detection process.

[0042] As a preferred embodiment, all flexible substrates have the same thickness, greater than 0.5-2 mm, and 1 mm in this embodiment. This thickness can ensure both flexibility and a certain degree of stretch and deformation ability. In this way, the change in the distance between the capacitor plates is sufficient to cause a change in the resonant frequency, which can be detected by an external vector network analyzer, thereby establishing a relationship between pressure changes and resonant frequency changes, and realizing pressure detection.

[0043] As a preferred embodiment, the flexible protective layer 12 can be made of the same material as the flexible substrate and have the same size and area.

[0044] As a preferred embodiment, the thickness of the flexible circuit and the lead head is micron-level, which does not affect the adhesion between the layers of flexible substrates. More preferably, the thickness of the flexible circuit and the lead head is about 20um.

[0045] like Figures 2 to 5 As shown, the preparation process of the flexible micro pressure sensor in this embodiment is as follows:

[0046] S1, prepare the upper and lower flexible substrates of the micro pressure sensor, and cut a slope 3 with a certain slope on the upper flexible substrate;

[0047] S2, inkjet printing a first printed circuit 7 and a first lead head 5 on the upper surface of the lower flexible substrate 1;

[0048] S3, covering the upper flexible substrate 2 on the flexible substrate manufactured in step S2;

[0049] S4, inkjet printing a second printed circuit 11 and a second lead head 9 on the upper flexible substrate 2 described in step S3, the second lead head 9 being printed onto the inclined surface 3 to form a sloped lead, which extends to the first lead head 5 of the bottom flexible substrate, thereby connecting the upper and lower circuits together;

[0050] S5 , covering the flexible circuit of the upper flexible substrate 2 with a flexible protective layer 12 , thereby completing the preparation of the flexible micro-pressure sensor.

[0051] Example 2: Figure 6 As shown, the other structures are the same as those in the embodiment, except that the flexible substrate has three layers, and the cutout on the top flexible substrate 13 is set back relative to the cutout on the upper flexible substrate 2, so that the third lead head on the top flexible substrate 13 can be connected to the second lead head 9 on the upper flexible substrate 2, forming an LC circuit of a three-plate capacitor.

[0052] The preparation process of this embodiment is as follows:

[0053] S1: Prepare a three-layer flexible substrate for the micro-pressure sensor and cut inclined surfaces 3 with a certain slope on the upper flexible substrate 2 and the top flexible substrate 13. The inclined surface 3 on the top flexible substrate 13 is set back relative to the inclined surface 3 on the upper flexible substrate 2.

[0054] S2, inkjet printing a first printed circuit 7 and a first lead head 5 on the upper surface of the lower flexible substrate 1 to form a circuit board;

[0055] S3, covering the upper flexible substrate 2 on the flexible substrate manufactured in step S2;

[0056] S4, inkjet printing a second printed circuit 11 and a second lead head 9 on the upper flexible substrate 2 described in step S3 to form a circuit board; the second lead head 9 is printed onto the inclined surface 3 and extends to the first lead head 5 of the bottom flexible substrate, so that the upper and lower circuits are connected together;

[0057] S5, continuing to stack the top flexible substrate 13 and the third printed circuit 14 and the third lead head printed thereon according to the method of steps S3 and S4, and extending the third lead head to the second lead head 9 on the inclined surface 3 of the upper flexible substrate 2, thereby connecting the third lead head and the second lead head 9 to ensure that the lead heads on the two adjacent flexible substrates are connected together;

[0058] S6, covering the flexible circuit of the top flexible substrate 13 with a flexible protective layer 12, thereby completing the preparation of the flexible micro-pressure sensor.

[0059] It should be noted that the present invention can realize three-dimensional connectivity of multi-layer circuits (not limited to 2 layers, 3, 4, ..., n layers can be realized by similar superposition methods) as needed, and perform pressure detection in the Z-axis (perpendicular to the XY plane) direction.

[0060] The present invention also provides a use of a flexible micro-pressure sensor. The prepared flexible micro-pressure sensor is attached to an arteriovenous fistula. A vector network analyzer is set outside the arteriovenous fistula. The external vector network analyzer detects changes in the resonant frequency of the flexible micro-pressure sensor, thereby detecting pressure changes. The detection principle is as follows:

[0061] Tiny pressure fluctuations within the arteriovenous fistula act on the flexible micro-pressure sensor, changing the distance between its multiple capacitor plates and causing a change in capacitance. The flexible micro-pressure sensor converts the physical signal of pressure change into an electrical signal. An external vector network analyzer then senses the changes in the resonant frequency of the flexible micro-pressure sensor, analyzing the fluctuations in the fistula and enabling real-time monitoring of the artificial fistula's status. This allows for timely medical attention based on the actual situation, preventing blockage and thrombosis in the arteriovenous fistula.

[0062] Advantages of the present invention:

[0063] The present invention realizes three-dimensional connectivity of multi-layer circuits (not limited to 2 layers, and can realize 3, 4, ..., n layers by similar superposition method), and can perform pressure detection in the z-axis direction.

[0064] The inkjet printing circuit process involved in the present invention is relatively simple and easy to operate.

[0065] LC flexible circuits have high detection sensitivity.

[0066] The flexible material used has good flexibility, ductility, electrical insulation and high biocompatibility, which ensures the reliability of the detection and can meet medical requirements.

[0067] The present invention is primarily used to monitor tiny vibrations in artificial fistulas. These tiny changes alter the distance between the upper and lower capacitor plates of a micro-pressure sensor, causing capacitance changes. The sensor converts physical signals into electrical signals. An external vector network analyzer then senses changes in the sensor's resonant frequency, analyzing the fluctuations in the fistula and enabling real-time monitoring of the fistula's status.

[0068] The monitoring achieved by the flexible micro-pressure sensor in the present invention is superior to traditional monitoring technology, with more accurate positioning and greater sensitivity, and can reflect the true status of the artificial fistula. Patients can seek medical treatment in a timely manner based on the monitored conditions to prevent complications such as arteriovenous fistula blockage and thrombosis.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several technical improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A process for preparing a flexible micro-pressure sensor, characterized in that: The flexible micro-pressure sensor includes at least two flexible substrates with micro-deformation capabilities and insulation. The multiple flexible substrates are stacked in sequence. A printed circuit and a lead head connected to the printed circuit are provided on the upper surface of each flexible substrate. A flexible protective layer is provided on the top printed circuit and the lead head. Each printed circuit includes a capacitor plate located in the middle and an inductor coil surrounding the capacitor plate. The lead heads on two adjacent layers of flexible substrates are connected by a connecting structure to form an LC circuit for pressure detection. The thickness of the printed circuit is at the micron level. The preparation process comprises the following steps: S1, prepare a corresponding number of flexible substrates according to the number of layers of the flexible micro-pressure sensor, and cut inclined surfaces with a certain slope on the flexible substrate except the bottom layer. If the flexible substrate has more than two layers, adjacent inclined surfaces are staggered; S2, inkjet printing of printed circuits and lead heads on the upper surface of the flexible substrate serving as the bottom layer; S3, covering the flexible substrate manufactured in step S2 with a second flexible substrate; S4, inkjet printing a printed circuit and lead heads on the second flexible substrate described in step S3, with the lead heads printed on the inclined surface and extending to the lead heads of the bottom flexible substrate, so that the upper and lower circuits are connected together; S5. If the number of flexible substrates is greater than two, continue stacking the flexible substrates and inkjet-printing the corresponding printed circuits and lead heads according to the method of steps S3 and S4, with the inclined surface of the upper flexible substrate set back relative to the inclined surface of the lower flexible substrate to ensure that the lead heads on two adjacent flexible substrates are connected together; otherwise, proceed directly to step S6. S6, covering the flexible circuit of the uppermost flexible substrate with a flexible protective layer to complete the preparation of the flexible micro pressure sensor.

2. The preparation process of the flexible micro pressure sensor according to claim 1, characterized in that: In the multi-layer flexible substrate, the printed circuits are identical and have relative positions, forming a mirror image relationship between the printed circuits.

3. The preparation process of the flexible micro pressure sensor according to claim 1, characterized in that: The flexible substrate is an insulating polymer material containing C, and the insulating polymer material containing C includes polydimethylsiloxane and polytrimethylene carbonate.

4. The process for preparing the flexible micro-pressure sensor according to claim 1, wherein: In step S1, the slope of the inclined surface is less than 30 degrees.

5. A flexible micro pressure sensor, characterized in that: The invention is prepared by the preparation process according to any one of claims 1 to 4.

6. Use of the flexible micro-pressure sensor according to claim 5, characterized in that: Used in conjunction with a vector network analyzer for pressure measurement of blood vessels, organs, or arteriovenous fistulas in the medical field.

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