Flexible pressure circular array sensor for finger-wearing pulse instrument and preparation method of flexible pressure circular array sensor

Abstract

The invention discloses a flexible pressure circular array sensor for a finger-wearing pulse instrument and a preparation method thereof, the flexible pressure circular array sensor is arranged on a finger stall of the pulse instrument, the flexible pressure circular array sensor comprises a flexible substrate, the flexible substrate is provided with a plurality of fan-shaped interdigital electrodes, and the fan-shaped interdigital electrodes are arranged on the flexible substrate. The fan-shaped interdigital electrodes are arranged at equal intervals from the circle point to the circumference of the circle, and the circle is divided into 3-10 equal parts; and a fan-shaped piezoresistive sensitive layer and a pressure-sensitive substrate film layer are sequentially arranged on the fan-shaped interdigital electrode. According to the invention, a sensor array design is adopted, wherein a flexible pressure sensor array unit is designed into a sector shape. The original point of each fan-shaped sensor unit is located at the center position of the finger pulp of the fingerstall of the pulse instrument, so that all array units can be synchronously sampled, the risk that pulse signals cannot be measured due to failure of a single-point sensor is reduced, and the measurement reliability is improved.

Description

Technical Field

[0001] The invention relates to the technical field of flexible pressure sensors, in particular to a flexible pressure circular array sensor for a finger-worn pulse monitor and a preparation method thereof. Background Art

[0002] Traditional wristband pulse monitors are easily affected by wrist movements and wearing positions when measuring pulse waveforms, which may lead to errors in the measurement process. These errors may be more obvious due to uneven pressure or inaccurate wearing positions, especially in situations where accurate measurement of pulse waveforms is required. Currently, most flexible sensors on the market are single-point designs. During the detection process, once the sensor is damaged or fails, the pulse wave signal cannot be collected, affecting the integrity and reliability of the test results. The traditional array sensor arrangement cannot ensure that each sensor unit can effectively detect the pulse signal. This arrangement may cause some sensor units to be unable to contact the pulse, thereby missing critical pulse data. Within the pulse pressure range, the sensitivity of existing sensors is insufficient and high-quality pulse waveforms cannot be collected. This limits the analysis and diagnostic applications of pulse waveform details.

[0003] In contrast, finger-worn pulse monitors offer greater flexibility and precision. Users can adjust the force applied and the wearing position to ensure the accuracy of the pulse diagnosis position. This self-adjustment capability enables finger-worn pulse monitors to more accurately detect small pressure changes, thereby providing more reliable pulse waveform measurement results. Summary of the invention

[0004] The purpose of the present invention is to provide a flexible pressure circular array sensor for a finger-worn pulse monitor and a preparation method thereof in order to solve the above problems. The sensor unit of the present invention adopts a fan-shaped design, the spacing between units is compact, and the overall circular layout is formed, which effectively improves the area utilization rate. The circle is equally divided into N (3-10) fan-shaped units, which increases the number of sensor units and ensures that each unit can contact the pulse signal when taking a pulse. The dots of the sensor array are pasted directly on the center of the fingertip of the finger sleeve to ensure that each unit can accurately capture the pulse signal when taking a pulse. The flexible sensor substrate adopts polyimide (PI), which provides excellent flexibility and stability. The pressure-sensitive substrate layer adopts PDMS or TPU with microstructures formed by fabric. These microstructures can change the contact area with the electrode under relatively small pressure, thereby improving the sensitivity of the sensor. The fan-shaped pressure-sensitive layer adopts carbon-based materials, such as carbon black, carbon nanotubes, graphene, etc., and is prepared by screen printing technology. The conductive electrode adopts a new fan-shaped interdigital structure to improve the sensitivity and accuracy of signal detection. The electrode output port adopts a double-sided gold finger structure, and holes are made on the PI substrate to facilitate subsequent welding and circuit connection.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A flexible pressure circular array sensor for a finger-worn pulse monitor, wherein the flexible pressure sensor array sensor is arranged on a finger sleeve of the pulse monitor, and the flexible pressure sensor array sensor comprises a flexible substrate, on which a plurality of fan-shaped interdigital electrodes are arranged in equal parts from a circular point to a circumference, dividing the circle into 3-10 equal parts;

[0007] A fan-shaped piezoresistive sensitive layer and a piezoresistive base film layer are sequentially arranged on the fan-shaped interdigitated electrodes.

[0008] In a further embodiment, the flexible substrate material is polyimide (PI).

[0009] A further solution is that the fan-shaped interdigitated electrodes are prepared using a standard FPC copper plating gold immersion process and a dry film photolithography process.

[0010] A further solution is that the pressure-sensitive base film layer material is PDMS or TPU with a microstructure formed by fabric.

[0011] In a further solution, the piezoresistive sensitive layer is prepared by screen printing with carbon-based ink, wherein the carbon-based ink includes carbon black (CB), carbon nanotubes (CNTs) or graphene.

[0012] A further solution is that the center of the circle of the flexible pressure sensor array sensor is pasted directly onto the center of the fingertip of the finger cuff to ensure that each unit can receive the pulse signal when taking a pulse.

[0013] The invention also provides a method for preparing the above-mentioned flexible pressure circular array sensor for a finger-worn pulse monitor, comprising the following steps:

[0014] S1: PI material preparation; cutting the polyimide (PI) film into required sizes as the flexible substrate of the sensor; drilling holes on the PI substrate to facilitate double-sided metal conduction at the subsequent gold finger;

[0015] S2: Preparation of electrode layer: using electrochemical plating technology to form a copper plating layer on the substrate, attaching a photosensitive film to the electroplated PI substrate, transferring the circuit pattern to the photosensitive film by photolithography, developing the dry film without photolithography to expose the copper layer outside the circuit pattern, etching the copper layer exposed after development with a corrosive solution, removing the dry film of the circuit pattern with sodium hydroxide to expose the final circuit pattern, and then depositing a gold layer on the copper layer by chemical reaction as a metal protective layer to prevent oxidation of the pad and improve solderability, connection reliability and durability;

[0016] S3: Preparation of pressure-sensitive substrate layer: using fabric to obtain microstructure on the semi-cured PDMS or TPU surface, and then curing to obtain a PDMS or TPU film with surface microstructure;

[0017] S4: preparation of a fan-shaped piezoresistive sensitive layer; printing a fan-shaped piezoresistive sensitive layer on a PDMS or TPU pressure-sensitive substrate layer by screen printing, and drying and curing the layer at a curing temperature of 80° C. to obtain a fan-shaped piezoresistive sensitive layer;

[0018] S5: device packaging; finally, the PI film with the electrode layer and the PDMS film with the pressure-sensitive layer are aligned and bonded, and the device is packaged with packaging glue around to obtain a flexible pressure sensor array.

[0019] A further solution is to use a double-sided gold finger structure for the electrode output port and to make vias in the PI substrate.

[0020] The beneficial effects of the present invention are:

[0021] The present invention adopts a sensor array design, wherein the flexible pressure sensor array unit is designed in a fan-shaped form. The origin of each fan-shaped sensor unit is located at the center of the fingertip of the pulse meter finger cuff, ensuring that all array units can sample synchronously, thereby reducing the risk of failure of single-point sensor to measure pulse signals and improving the reliability of measurement.

[0022] The flexible pressure sensor array prepared by the present invention uses polyimide (PI) as a flexible substrate. PI film is favored for its softness and comfort. The pressure-sensitive substrate layer uses PDMS or TPU with microstructures. These microstructures significantly improve the sensitivity of the sensor and increase the accuracy of the pulse waveform.

[0023] The present invention designs a new fan-shaped unit structure, which makes the spacing between units small and increases the area utilization. The small array element spacing can fully reflect the pressure distribution and changes of blood vessels and surrounding tissues when the pulse beats, and obtain information corresponding to the fingertips of traditional Chinese medicine. The electrode output port adopts a double-sided gold finger structure, and a hole is made on the PI substrate to facilitate subsequent welding. This invention combines a new processing method for flexible sensors with traditional FPC processing to achieve technological innovation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1The present invention is a schematic diagram of the finger cover and sensor position of the finger-worn pulse monitor.

[0026] Figure 2 The present invention is a schematic diagram of a flexible pressure circular array sensor for a finger-worn pulse monitor.

[0027] Figure 3 It is a schematic diagram of the cross-sectional structure of the sensor of the present invention.

[0028] Figure 4 It is a schematic diagram of the microstructure of the fan-shaped piezoresistive sensitive layer and the piezoresistive base film layer of the present invention.

[0029] Notes on the accompanying drawings: 1: finger sleeve; 2: flexible pressure circular array sensor; 3: flexible substrate; 4: fan-shaped interdigitated electrodes; 5: fan-shaped piezoresistive sensitive layer; 6: pressure-sensitive substrate film layer. DETAILED DESCRIPTION

[0030] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0031] In any embodiment, if Figure 1 As shown, the flexible pressure circular array sensor for a finger-worn pulse monitor of the present invention comprises: the flexible pressure sensor array sensor is arranged on a finger sleeve 1 of the pulse monitor, and the sensor array is integrated on the finger sleeve of the pulse monitor, ensuring a close fit with the user's finger. The flexible pressure sensor array sensor comprises a flexible substrate 3, on which a plurality of fan-shaped interdigital electrodes 4 are arranged in equal parts from a circular point to a circumference, dividing the circle into 3-10 equal parts; thereby improving the spatial resolution of the sensor.

[0032] The sector-shaped interdigital electrodes 4 are provided with a sector-shaped piezoresistive sensitive layer 5 and a piezoresistive base film layer 6 in sequence.

[0033] The flexible substrate 3 is made of polyimide PI, which provides excellent flexibility and durability.

[0034] The fan-shaped interdigital electrodes are prepared using standard FPC copper plating gold immersion process and dry film photolithography process to ensure the accuracy and reliability of the electrodes. The pressure-sensitive base film layer uses PDMS or TPU material and uses fabric to form a microstructure, which enhances the sensitivity of the sensor to pressure changes.

[0035] The piezoresistive sensitive layer is made of carbon-based inks, including carbon black, carbon nanotubes or graphene, and is precisely prepared using screen printing technology, ensuring the sensor's high sensitivity and fast response.

[0036] The center of the sensor array is designed to be directly opposite to the center of the fingertip attached to the finger cuff, ensuring that each sensor unit can effectively receive the pulse signal during the pulse diagnosis process.

[0037] In a specific embodiment, the method for preparing the flexible pressure circular array sensor for a finger-worn pulse monitor of the present invention comprises the following steps:

[0038] PI material preparation:

[0039] The polyimide (PI) film was cut into the required size to serve as the flexible substrate of the sensor.

[0040] Drilling is performed on the PI substrate to form through holes so as to achieve double-sided metal conduction at the gold fingers later.

[0041] Preparation of electrode layer:

[0042] forming a copper plating layer on the substrate by using electrochemical plating technology;

[0043] Paste the photosensitive film and transfer the circuit pattern to the photosensitive film through photolithography technology;

[0044] During the development process, the unphotoetched dry film is removed to expose the copper layer;

[0045] Etching the copper layer exposed after development using a corrosive solution;

[0046] The dry film of the circuit pattern is removed by sodium hydroxide to expose the final circuit pattern;

[0047] Gold is deposited on the copper layer to form a metal protective layer to prevent pad oxidation and enhance solderability, connection reliability and durability;

[0048] Preparation of pressure-sensitive base layer:

[0049] forming a microstructure on the surface of the semi-cured PDMS or TPU, and then curing the PDMS or TPU film to obtain a PDMS or TPU film with a surface microstructure;

[0050] Preparation of fan-shaped piezoresistive sensitive layer:

[0051] Printing a fan-shaped piezoresistive sensitive layer on the PDMS or TPU pressure-sensitive substrate layer by screen printing, and drying and curing at 80° C. to form a fan-shaped piezoresistive sensitive layer;

[0052] Device Package:

[0053] The PI film with the electrode layer and the PDMS film with the pressure-sensitive layer are aligned and bonded, and the device is encapsulated around with encapsulation glue to obtain a flexible pressure sensor array.

[0054] The electrode output port of the present invention adopts a double-sided gold finger structure, and a via is made on the PI substrate to facilitate subsequent welding. This design combines a new processing method for flexible sensors with traditional FPC processing, thereby improving the manufacturing efficiency and performance of the sensor.

[0055] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further explain various possible combinations. In addition, the various different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A flexible pressure circular array sensor for a finger-worn pulse monitor, characterized in that: A flexible pressure circular array sensor for a finger-worn pulse monitor, wherein the flexible pressure sensor array sensor is arranged on a finger sleeve of the pulse monitor, and the flexible pressure sensor array sensor comprises a flexible substrate, on which a plurality of fan-shaped interdigital electrodes are arranged in equal parts from a circular point to a circumference, dividing the circle into 3-10 equal parts; A fan-shaped piezoresistive sensitive layer and a piezoresistive base film layer are sequentially arranged on the fan-shaped interdigitated electrodes.

2. The flexible pressure circular array sensor for a finger-worn pulse monitor as claimed in claim 1, characterized in that: The flexible substrate material is polyimide.

3. The flexible pressure circular array sensor for a finger-worn pulse monitor as claimed in claim 1, characterized in that: The fan-shaped interdigital electrodes are prepared by using a standard FPC copper-immersion gold plating process and a dry film photolithography process.

4. The flexible pressure circular array sensor for a finger-worn pulse monitor as claimed in claim 1, characterized in that: The pressure-sensitive base film layer material is PDMS or TPU using fabric to form a microstructure.

5. The flexible pressure circular array sensor for a finger-worn pulse monitor as claimed in claim 1, characterized in that: The piezoresistive sensitive layer is prepared by screen printing with carbon-based ink, wherein the carbon-based ink includes carbon black, carbon nanotubes or graphene.

6. The flexible pressure circular array sensor for a finger-worn pulse monitor as claimed in claim 1, characterized in that: The center of the circle of the flexible pressure sensor array sensor is pasted to the center position of the fingertip of the finger sleeve.

7. A method for preparing a flexible pressure circular array sensor for a finger-worn pulse monitor as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1: PI material preparation; Cut the polyimide film into required sizes as the flexible substrate of the sensor; drill holes on the PI substrate to make through holes for the subsequent double-sided metal conduction at the gold finger; S2: Preparation of electrode layer: using electrochemical plating technology to form a copper plating layer on the substrate, pasting a photosensitive film on the electroplated PI substrate, transferring the circuit pattern to the photosensitive film by photolithography, developing the dry film without photolithography to expose the copper layer outside the circuit pattern, using a corrosive solution to etch away the copper layer exposed after development, removing the dry film of the circuit pattern by sodium hydroxide to expose the final circuit pattern, and then depositing a gold layer on the copper layer by chemical reaction as a metal protective layer; S3: Preparation of pressure-sensitive base layer; Using fabric to obtain microstructures on the semi-cured PDMS or TPU surface, and then curing to obtain a PDMS or TPU film with a surface microstructure; S4: preparation of a fan-shaped piezoresistive sensitive layer; printing a fan-shaped piezoresistive sensitive layer on a PDMS or TPU pressure-sensitive substrate layer by screen printing, and drying and curing the layer at a curing temperature of 80° C. to obtain a fan-shaped piezoresistive sensitive layer; S5: device packaging; finally, the PI film with the electrode layer and the PDMS film with the pressure-sensitive layer are aligned and bonded, and the device is packaged with packaging glue around to obtain a flexible pressure sensor array.

8. The method for preparing the flexible pressure circular array sensor for the finger-worn pulse monitor as claimed in claim 7, characterized in that: The electrode output port adopts a double-sided gold finger structure, and the PI substrate is opened to make vias.

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