Flexible optical fiber sensor, preparation method and remote wireless intelligent medical monitoring system

Abstract

The invention provides a flexible optical fiber sensor, a preparation method and a remote wireless intelligent medical monitoring system, and belongs to the technical field of optical fiber sensing. Comprising two plastic optical fibers which are arranged at an interval, non-adjacent end parts of the two plastic optical fibers are respectively connected with a light emitting diode and a photodiode, the light emitting diode is used for emitting an optical signal into the plastic optical fiber at one end, and the photodiode is used for receiving the optical signal and outputting the optical signal after photoelectric conversion; and the hydrogel fiber flexible sensing part is arranged between the adjacent end parts of the two plastic optical fibers in a crossing manner, extends in the axial direction of the two plastic optical fibers, and is used for being in flexible contact with the skin to obtain a strain signal at a human body joint. The sensor is compact in structure and small in size, can be conveniently arranged at different positions on the surface of a human body, has good biocompatibility, is suitable for distributed layout and sampling on the surface of the human body, obtains multiple strain signals and carries out resolving, and therefore the purpose of remote wireless medical monitoring is achieved.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to a flexible optical fiber sensor, a preparation method and a remote wireless intelligent medical monitoring system. Background Art

[0002] Flexible stretchable sensors have become a key component of today's intelligent medical rehabilitation equipment due to their highly reliable human strain detection capabilities. However, due to limitations in biocompatibility and the variable range of motion of the human body, it is still difficult to meet the needs of distributed strain monitoring of the human body. At the same time, the sharp increase in medical needs has also led to a shortage of medical resources, which has spawned the development of the application of flexible stretchable sensors.

[0003] At present, most flexible and stretchable sensors use conductive materials such as graphene and carbon nanotubes to detect strain using piezoelectric, capacitance, and resistance properties. However, they usually have problems such as electromagnetic interference and poor biocompatibility. They are difficult to adapt to strain monitoring of complex curved surfaces of the human body, and may cause skin inflammation after long-term wearing, resulting in low reliability of the sensors. Sensors made of polymer materials have been widely used in human rehabilitation strain monitoring due to their excellent biocompatibility. Some scholars have embedded optical fibers into flexible substrates (such as polydimethylsiloxane) to obtain strain signals from multiple parts of the human body, but their limited strain range makes it difficult to meet the large-scale strain measurement of the human body. Hydrogels have good flexibility and can meet the monitoring needs of human physiological activities. Double-network hydrogels have greatly improved their mechanical strength while improving flexibility, and have become ideal materials for monitoring patient strain signals. In order to achieve long-term monitoring of human strain signals, the sensors need to be sufficiently portable and can be integrated into patients' daily lives. In addition, most of the existing flexible and stretchable sensors focus on the monitoring function of human parameters, and the signals obtained still need to be evaluated based on the experience of doctors.

[0004] Therefore, based on the above situation, it is very necessary to provide a flexible optical fiber sensor with strong ductility, good biocompatibility and high sensitivity, a preparation method and a remote wireless intelligent medical monitoring system. Summary of the invention

[0005] In view of this, the present invention proposes a flexible optical fiber sensor, a preparation method and a remote wireless intelligent medical monitoring system that can better adapt to the variable movement conditions of human joints, has better skin adaptability and high reliability.

[0006] In one aspect, the present invention provides a flexible optical fiber sensor, comprising: Two plastic optical fibers are arranged opposite to each other and spaced apart, and the non-adjacent ends of the two plastic optical fibers are respectively connected to a light emitting diode and a photodiode, the light emitting diode is used to emit light signals into the two plastic optical fibers, and the photodiode is used to receive the light signals and perform photoelectric conversion before output; The hydrogel fiber flexible sensing part is arranged between the adjacent ends of the two plastic optical fibers and is extended along the axial direction of the two plastic optical fibers to contact with the skin and obtain strain signals at human joints.

[0007] On the basis of the above technical solution, preferably, the core diameters of the two plastic optical fibers are not equal to the diameter of the flexible sensing portion of the hydrogel fiber.

[0008] In a second aspect, the present invention provides a method for preparing a flexible optical fiber sensor, comprising the following steps: S1: Prepare the hydrogel curing mold in advance; S2: Take appropriate amounts of sodium alginate, acrylamide, methylene bisacrylamide, ammonium persulfate, glycerol and CaCl2 solution and mix them evenly at room temperature until they are completely dissolved to form a uniform and transparent hydrogel precursor solution; S3: placing the hydrogel precursor solution into a vacuum degassing machine to remove bubbles generated during the mixing process, and injecting the degassed hydrogel precursor solution into the hydrogel curing mold with a syringe; S4: peel off the front protective layer of the adjacent ends of the two plastic optical fibers by a length of 5 mm, and insert them into the two ends of the hydrogel curing mold respectively, so that the two plastic optical fibers remain aligned; use ultraviolet light to irradiate the hydrogel curing mold for 20 minutes to complete the polymerization of the hydrogel precursor solution, and obtain the flexible sensing part of the hydrogel fiber; S5: Remove the hydrogel curing mold, clean the flexible sensing part of the hydrogel fiber with deionized water, continue to use ultraviolet light to irradiate the flexible sensing part of the hydrogel fiber for 30 minutes, and then smoothly connect the signal output end of the light-emitting diode and the signal input end of the photosensitive diode to the unstripped ends of the two plastic optical fibers and at the interface to ensure the firmness and stability of the structure, thereby completing the preparation of the flexible optical fiber sensor.

[0009] On the basis of the above technical scheme, preferably, the specific content of step S2 is: dissolving 0.2 g of sodium alginate powder in 10 g of aqueous solution, dropping 0.5 ml of 0.5 wt% CaCl2 solution, stirring at a uniform speed with a magnetic stirrer at room temperature until the sodium alginate powder is fully dissolved, and the stirring time shall not exceed 3 minutes; 5 g of acrylamide powder, 0.02 g of ammonium persulfate powder, and 0.01 g of methylenebisacrylamide powder are added in sequence and continued to stir, and the stirring time shall not exceed 2 minutes; after stirring evenly again, 5 g of glycerol aqueous solution is slowly injected with a syringe, and slowly stirred until a uniform and transparent hydrogel precursor solution is formed.

[0010] Preferably, the overall stirring time of step S2 does not exceed 7 minutes.

[0011] In the third aspect, the present invention also provides a remote wireless intelligent medical monitoring system, comprising the above-mentioned flexible optical fiber sensor, as well as a wireless demodulation module, a power supply and a mobile terminal; the output end of the flexible optical fiber sensor is signal-connected to the wireless demodulation module, and the wireless demodulation module is communicatively connected to the mobile terminal; the flexible optical fiber sensor and the wireless demodulation module are electrically connected to the power supply respectively; the light signal emitted by the light-emitting diode of the flexible optical fiber sensor passes through the plastic optical fiber and the hydrogel fiber flexible sensing part in sequence, and the hydrogel fiber flexible sensing part is stretched and bent when following the joint movement, so that the passing light signal is attenuated, and the attenuated light signal is sent to the photodiode, and the corresponding electrical signal is output through photoelectric conversion; after receiving the electrical signal, the wireless demodulation module decouples the strain and light attenuation, and sends the decoupling result to the host computer in the form of a digital signal, classifies and outputs the signal through the built-in algorithm of the host computer, and sends the classification result wirelessly to the mobile terminal.

[0012] On the basis of the above technical solution, preferably, the built-in algorithm used by the host computer to process the acquired signal is a classification sub-algorithm based on a two-dimensional convolutional neural network.

[0013] Preferably, the classification sub-algorithm based on the two-dimensional convolutional neural network is to perform overlapping sampling on the collected data, and then divide the data into a training set and a test set in a ratio of 8:2; use the training set to train the convolutional neural network CNN model to obtain the optimal model parameters; then use the model to predict the test set, and evaluate the model according to the prediction results; the input of the convolutional neural network CNN model is a voltage signal, and the output of the convolutional neural network CNN model is the walking gait category label of the monitored person; the convolutional neural network CNN model includes an input layer, two convolutional layers, two batch normalization layers, two ReLU activation layers, two maximum pooling layers, a fully connected layer and a Softmax layer; the network training adopts the Adam optimizer and a piecewise decay learning rate strategy.

[0014] Preferably, the decoupling of strain and light attenuation is as follows: the flexible sensing portion of the hydrogel fiber is regarded as a solvent, and the intensity of the incident light signal of the light emitting diode to the flexible sensing portion of the hydrogel fiber is I 0 , the transmitted light intensity is I t The absorbed light intensity is I a ,satisfy I 0 = I t + I a; The ratio of the intensity of transmitted light to the intensity of incident light is the transmittance T , T = I t / I 0 ; The negative logarithm of transmittance is absorbance A , A =- lgT , according to the Beer-Lambert law, A = ECL , E is the molar absorbance of the substance, C is the concentration of the solution, L is the optical path length; when the flexible sensing part of the hydrogel fiber is subjected to external strain The change in optical path length is , is the initial length of the flexible sensing part of the hydrogel fiber, and the light intensity loss calculation formula is: ,in represents the light intensity loss, represents the extinction coefficient, which indicates the light absorption value of the flexible sensing part of the hydrogel fiber; Indicates the optical coupling loss at the connection between the flexible sensing part of the hydrogel fiber and the plastic optical fiber; extinction coefficient and the concentration of the solution C The light intensity loss remains unchanged during the deformation of the flexible sensing part of the hydrogel fiber. With external strain Positive correlation.

[0015] Preferably, the wireless demodulation terminal includes an analog-to-digital conversion chip ADS1256 and an MCU connected in sequence. The analog-to-digital conversion chip ADS1256 performs analog-to-digital conversion on the electrical signal output by the photodiode and inputs the analog-to-digital signal into the MCU. The MCU has a built-in algorithm and is wirelessly connected to the mobile terminal.

[0016] The flexible optical fiber sensor, preparation method and remote wireless intelligent medical monitoring system provided by the present invention have the following beneficial effects compared with the prior art: (1) The sensor of the present application has a compact structure and small size, and is easy to be arranged at different positions on the human body surface. It has good biocompatibility and is suitable for distributed layout and sampling on the human body surface to obtain multi-channel strain signals and adapt to the activities of different parts of the human body. Through the built-in algorithm, combined with the change in the light intensity signal output by the photodiode relative to the theoretical value, since the degree of stretching and bending of the human joints is proportional to the degree of light intensity attenuation, the relationship between the strain size and the light intensity change can be obtained, thereby correlating the different joint movements of the human body with the light intensity change. (2) This application can classify and identify joint movements through a built-in algorithm, decouple based on the relationship between strain degree and light intensity attenuation, and then transmit the classification and decoupling results wirelessly to achieve distributed process monitoring, thereby improving the scope of application and comfort of medical monitoring. Moreover, after training with the help of a neural network, it has high reliability, does not require the intervention of a doctor, and greatly reduces the manual workload. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, 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.

[0018] Figure 1 The flexible optical fiber sensor, preparation method and structure diagram of the flexible optical fiber sensor of the remote wireless intelligent medical monitoring system of the present invention; Figure 2 It is a schematic diagram of the process of the flexible optical fiber sensor, the preparation method and the preparation method of the remote wireless intelligent medical monitoring system of the present invention; Figure 3 The system architecture diagram of the flexible optical fiber sensor, preparation method and remote wireless intelligent medical monitoring system of the present invention; Figure 4 This is a structural diagram of a classification sub-algorithm based on a two-dimensional convolutional neural network for the flexible optical fiber sensor, preparation method, and remote wireless intelligent medical monitoring system of the present invention.

[0019] Figure numerals: 101, light emitting diode; 102, flexible sensing part of hydrogel fiber; 103, plastic optical fiber; 104, photodiode; 201, hydrogel precursor solution; 202, ultraviolet lamp; 203, hydrogel curing mold. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Existing flexible stretchable sensors mostly use conductive materials such as graphene and carbon nanotubes to detect strain using piezoelectric, capacitance, and resistance properties. However, they usually have problems such as electromagnetic interference and poor biocompatibility. They are difficult to adapt to strain monitoring on complex curved surfaces of the human body, and may cause skin inflammation after long-term wearing, resulting in low reliability of the sensor. Figure 1 As shown, the present invention provides a flexible optical fiber sensor, comprising: The two plastic optical fibers 103 are spaced apart from each other, and the non-adjacent ends of the two plastic optical fibers 103 are respectively connected to the light emitting diode 101 and the photodiode 104. The light emitting diode is used to emit light signals into the plastic optical fiber 103, and the photodiode 104 is used to receive light signals and output them after photoelectric conversion.

[0022] The hydrogel fiber flexible sensing part 102 is arranged between the adjacent ends of the two plastic optical fibers 103 and extends along the axial direction of the two plastic optical fibers 103 to contact the skin and obtain strain signals at the human joints. When the human body moves, the joints will undergo certain deformations, which will cause the hydrogel fiber flexible sensing part 102 to stretch and twist, causing the intensity of the light passing through the hydrogel fiber flexible sensing part 102 to attenuate. By obtaining the change in light intensity, the motion state of the human joints can be further identified. The main part of the hydrogel fiber flexible sensing part 102 is PMA / SA-Ca 2+ Double-network hydrogel fibers, with low modulus and excellent flexibility, can adapt well to the complex skin surface.

[0023] As a preferred embodiment, the core diameters of the two plastic optical fibers 103 are not equal to the diameter of the hydrogel fiber flexible sensing portion 102. More preferably, the core diameter of the plastic optical fiber 103 is smaller than the diameter of the hydrogel fiber flexible sensing portion 102, so as to facilitate connection of the ends of the two.

[0024] Second, as Figure 2 As shown, the present invention also provides a method for preparing a flexible optical fiber sensor, comprising the following steps: S1: Prepare a hydrogel curing mold 203 in advance; the hydrogel curing mold 203 is a tubular silicone mold.

[0025] S2: Take appropriate amounts of sodium alginate, acrylamide, methylenebisacrylamide, ammonium persulfate, glycerol and CaCl2 solution and mix them evenly at room temperature until they are completely dissolved to form a uniform and transparent hydrogel precursor solution 201; for the specific process, refer to Figure 2 (a) in the figure.

[0026] The specific ratio of step S2 is: dissolve 0.2 g sodium alginate powder in 10 g aqueous solution, drop 0.5 ml 0.5 wt% CaCl2 solution, stir at a constant speed with a magnetic stirrer at room temperature until the sodium alginate powder is fully dissolved, and the stirring time shall not exceed 3 minutes; add 5 g acrylamide powder, 0.02 g ammonium persulfate powder, and 0.01 g methylenebisacrylamide powder in sequence and continue stirring, and the stirring time shall not exceed 2 minutes; after stirring evenly again, slowly inject 5 g glycerol aqueous solution with a syringe, and slowly stir until a uniform and transparent hydrogel precursor solution 201 is formed. The overall stirring time of step S2 shall not exceed 7 minutes.

[0027] S3: Put the hydrogel precursor solution 201 into a vacuum degassing machine to remove bubbles generated during the mixing process, and inject the degassed hydrogel precursor solution into the hydrogel curing mold 203 with a syringe; the process is referred to Figure 2 (b) in the figure.

[0028] S4: peel off the front protective layer of the adjacent ends of the two plastic optical fibers 103 by 5 mm, and insert them into the two ends of the hydrogel curing mold 203 respectively, so that the two plastic optical fibers 103 are kept in the center; use the ultraviolet lamp 202 to irradiate the surface of the hydrogel curing mold 203 for 20 minutes to complete the polymerization of the hydrogel precursor solution 201, and obtain the hydrogel fiber flexible sensing part 102; this process refers to Figure 2 (c) in.

[0029] S5: Remove the hydrogel curing mold 203, clean the hydrogel fiber flexible sensing part 102 with deionized water to remove the residual substances on the surface, and continue to use the ultraviolet lamp 202 to irradiate the surface of the hydrogel fiber flexible sensing part 102 for 30 minutes. For details, refer to Figure 2 (d) and Figure 2 (e) in.

[0030] Then, the signal output end of the light emitting diode 101 and the signal input end of the photodiode 104 are smoothly connected to the unstripped ends of the two plastic optical fibers 103 and at the interface to ensure the firmness and stability of the structure, thereby completing the preparation of the flexible optical fiber sensor. To remove the hydrogel curing mold 203, tweezers are used to clamp one end of the hydrogel curing mold 203 and gently peel off the hydrogel curing mold 203.

[0031] Thirdly, Figure 3As shown, the present invention also provides a remote wireless intelligent medical monitoring system, including the above-mentioned flexible optical fiber sensor, as well as a wireless demodulation module, a power supply and a mobile terminal; the output end of the flexible optical fiber sensor is signal-connected to the wireless demodulation module, and the wireless demodulation module is communicatively connected to the mobile terminal; the flexible optical fiber sensor and the wireless demodulation module are electrically connected to the power supply respectively; the light signal emitted by the light emitting diode 101 of the flexible optical fiber sensor passes through the plastic optical fiber 103 and the hydrogel fiber flexible sensing part 102 in sequence, and the hydrogel fiber flexible sensing part 102 is stretched and bent when following the joint movement, so that the passing light signal is attenuated, and the attenuated light signal is sent to the photodiode 104, and the corresponding electrical signal is output through photoelectric conversion; after receiving the electrical signal, the wireless demodulation module decouples the strain and the light attenuation, and also sends the decoupling result to the host computer in the form of a digital signal, classifies and outputs the signal through the algorithm built into the host computer, and wirelessly sends the classification result to the mobile terminal.

[0032] The light emitting diode 101 can be selected from Infineon's SFH756, which can emit 660nm light; the photodiode 104 can be selected from Infineon's SFH250, which can receive light in the 400-1100nm band and output an electrical signal. The wireless demodulation terminal includes an analog-to-digital conversion chip ADS1256 and an MCU connected in sequence. The analog-to-digital conversion chip ADS1256 converts the electrical signal output by the photodiode 104 into an analog-to-digital signal and inputs it into the MCU. The MCU is wirelessly connected to the mobile terminal. The MCU can be configured with Bluetooth wireless transmission or other similar wireless transmission terminals to wirelessly transmit the signal to a host computer, cloud or smart phone, etc., to achieve remote sharing of information and better realize wireless intelligent medical monitoring. In this embodiment, the MCU uses an STM32 microcontroller or a similar product, and the MCU decouples strain from light attenuation.

[0033] In this embodiment, the built-in functions of the wireless demodulation module include sending the acquired electrical signal to the host computer via Bluetooth; the built-in algorithm of the host computer for processing the acquired signal is a classification sub-algorithm based on a two-dimensional convolutional neural network.

[0034] As a preferred implementation, a classification sub-algorithm based on a two-dimensional convolutional neural network performs overlapping sampling on the collected data, and then divides the data into a training set and a test set in a ratio of 8:2; uses the training set to train a convolutional neural network CNN model to obtain optimal model parameters; then uses the model to predict the test set, and evaluates the model based on the prediction results; the input of the convolutional neural network CNN model is a voltage signal, and the output of the convolutional neural network CNN model is a walking gait category label of the monitored person; the convolutional neural network CNN model includes an input layer, two convolutional layers, two batch normalization layers, two ReLU activation layers, two maximum pooling layers, a fully connected layer and a Softmax layer; the network training adopts the Adam optimizer and a piecewise decay learning rate strategy.

[0035] See attached Figure 4 , the gait signal of the medical monitoring object obtained by sequential overlapping sampling is used as the input of the model input layer. The neural network algorithm includes a sequentially set convolution layer and ReLU activation layer Conv-1&ReLU, the first batch normalization layer, that is, the batch normalization 1 mark in the figure, and the first maximum pooling layer, that is, the maximum pooling 1 mark in the figure; followed by a sequentially set convolution layer and ReLU activation layer Conv-2&ReLU, the second batch normalization layer, that is, the batch normalization 2 mark in the figure, and the second maximum pooling layer, that is, the maximum pooling 2 mark in the figure; finally, the fully connected layer FC layer and the Softmax layer. The Softmax layer is an activation function for multi-classification problems, which is used to convert real vectors into probabilities, and finally outputs the classification results of what kind of action the gait belongs to and whether the gait is normal.

[0036] The flexible optical fiber sensor consists of a hydrogel fiber and two plastic optical fibers connected at both ends. The plastic optical fiber is used as an optical transmission element. The light signal generated by the light-emitting diode is introduced through the plastic optical fiber and then passes through the hydrogel optical fiber. When strain or bending occurs, the intensity of the light signal in the hydrogel optical fiber decays. The relationship between them follows the Beer-Lambert law, that is, when a beam of monochromatic light enters a uniform medium, part of the light is absorbed, while the rest passes through the medium, and another part of the light is reflected by the surface of the medium.

[0037] The decoupling of strain and light attenuation is as follows: the hydrogel fiber flexible sensing part 102 is regarded as a solvent, and the intensity of the incident light signal of the light emitting diode 101 to the hydrogel fiber flexible sensing part 102 is I 0 , the transmitted light intensity is I t The absorbed light intensity is I a , the reflected light intensity is I r ,satisfy I0 = I t + I a + I r ; Usually in spectrophotometry, the measured solvent and the reference solvent are placed in two light absorption cells of different thickness and material, so the above formula can be simplified to I 0 = I t + I a .

[0038] The ratio of the intensity of transmitted light to the intensity of incident light is the transmittance T , T = I t / I 0 ; The negative logarithm of transmittance is absorbance A , A =- lgT , according to the Beer-Lambert law, A = ECL , E is the molar absorbance of the substance, C is the concentration of the solution, L is the optical path length; when the hydrogel fiber flexible sensing portion 102 is subjected to external strain The change in optical path length is , is the initial length of the hydrogel fiber flexible sensing portion 102, and the light intensity loss calculation formula is: ,in represents the light intensity loss, represents the extinction coefficient, which represents the light absorption value of the hydrogel fiber flexible sensing portion 102; represents the optical coupling loss at the connection between the hydrogel fiber flexible sensing part 102 and the plastic optical fiber 103, which is independent of the wavelength; the extinction coefficient and the concentration of the solution C During the deformation of the hydrogel fiber flexible sensing portion 102, the light intensity loss remains unchanged. With external strain Positive correlation.

[0039] The attenuated light intensity is measured by using light-emitting diodes and photodiodes. When the human body moves, each joint and muscle will produce different degrees of activity. By monitoring the changes in light intensity of the corresponding sensing parts of different parts, distributed data collection and monitoring can be achieved.

[0040] The hydrogel fiber flexible sensing part 102 is similar to a multimode optical fiber in light guiding characteristics, so a multimode plastic optical fiber is connected at both ends. At this time, after the two ends are connected with the plastic optical fiber, optical coupling loss will occur at the connection, that is, . Define connection loss , where the transmittance T It can be expressed as , , P R represents the received power, P T Indicates the output power; a R and a T are respectively the core radius of the plastic optical fiber 103 and the radius of the hydrogel fiber flexible sensing portion 102, k is the ratio of the core radius of the plastic optical fiber 103 to the radius of the hydrogel fiber flexible sensing portion 102; is the radius difference between the plastic optical fiber 103 and the hydrogel fiber flexible sensing portion 102; is the core radius difference coefficient between optical fibers, which can be defined as the difference between the core radius of the plastic optical fiber and the core diameter of the hydrogel fiber flexible sensing portion 102; is the radial coordinate of the flexible optical fiber sensor, indicating the distance from the center to the electrical path on the cross section of the flexible optical fiber sensor; is the transmission function of light in the flexible optical fiber sensor, which represents the radial position The transmission characteristics of light at is the angle variable in polar coordinates; and They are the distribution parameters of the plastic optical fiber 103 on the transmitting side and the plastic optical fiber 103 on the receiving side, respectively, and are used to describe the light intensity distribution characteristics of the plastic optical fiber. In addition to the light loss caused by artificial stretching during the experiment and the connection loss between the plastic optical fiber and the polymer, the plastic optical fiber itself may also produce certain losses due to its preparation process and materials. It mainly exists in the absorption loss of the plastic material in the core cladding and the scattering loss of light coupling into the plastic optical fiber. However, since it is a fixed loss, it will not produce changes sufficient to affect the experiment under experimental conditions. Therefore, this loss can be ignored.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A flexible optical fiber sensor, characterized in that: include: Two plastic optical fibers (103) are arranged at intervals from each other, and non-adjacent ends of the two plastic optical fibers (103) are respectively connected to a light emitting diode (101) and a photodiode (104), the light emitting diode being used to emit a light signal into the plastic optical fiber (103) at one end, and the photodiode (104) being used to receive the light signal and perform photoelectric conversion for output; The hydrogel fiber flexible sensing portion (102) is arranged between the adjacent ends of the two plastic optical fibers (103) and is extended along the axial direction of the two plastic optical fibers (103) to be in flexible contact with the skin and obtain strain signals at human joints.

2. A flexible optical fiber sensor according to claim 1, characterized in that: The core diameters of the two plastic optical fibers (103) are not equal to the diameter of the hydrogel fiber flexible sensing portion (102).

3. A method for preparing a flexible optical fiber sensor according to any one of claims 1 to 2, characterized in that: The steps include: S1: preparing a hydrogel curing mold in advance (203); S2: Take appropriate amounts of sodium alginate, acrylamide, methylene bisacrylamide, ammonium persulfate, glycerol and CaCl2 solution and mix them evenly at room temperature until they are completely dissolved to form a uniform and transparent hydrogel precursor solution (201); S3: placing the hydrogel precursor solution (201) into a vacuum degassing machine to remove bubbles generated during the mixing process, and injecting the degassed hydrogel precursor solution into the hydrogel curing mold (203) using a syringe; S4: peeling off the front protective layer of the adjacent ends of the two plastic optical fibers (103) by a length of 5 mm, and inserting them into the two ends of the hydrogel curing mold (203) respectively, so that the two plastic optical fibers (103) are kept in the center; using an ultraviolet lamp (202) to irradiate the hydrogel curing mold (203) for 20 minutes to complete the polymerization of the hydrogel precursor solution (201), thereby obtaining a hydrogel fiber flexible sensing part (102); S5: Remove the hydrogel curing mold (203), clean the hydrogel fiber flexible sensing part (102) with deionized water, continue to use the ultraviolet lamp (202) to irradiate the hydrogel fiber flexible sensing part (102) for 30 minutes, and then smoothly connect the signal output end of the light-emitting diode (101) and the signal input end of the photodiode (104) to the unstripped ends of the two plastic optical fibers (103) at the interface to ensure the firmness and stability of the structure, thereby completing the preparation of the flexible optical fiber sensor.

4. The method for preparing a flexible optical fiber sensor according to claim 3, characterized in that: The specific contents of step S2 are as follows: dissolving 0.2 g of sodium alginate powder in 10 g of aqueous solution, dropping 0.5 ml of 0.5 wt% CaCl2 solution, stirring at a constant speed with a magnetic stirrer at room temperature until the sodium alginate powder is fully dissolved, and the stirring time shall not exceed 3 minutes; adding 5 g of acrylamide powder, 0.02 g of ammonium persulfate powder, and 0.01 g of methylenebisacrylamide powder in sequence and continuing to stir, and the stirring time shall not exceed 2 minutes; after stirring evenly again, slowly injecting 5 g of glycerol aqueous solution with a syringe, and slowly stirring until a uniform and transparent hydrogel precursor solution (201) is formed.

5. The method for preparing a flexible optical fiber sensor according to claim 4, characterized in that: The overall stirring time of step S2 does not exceed 7 minutes.

6. A remote wireless intelligent medical monitoring system, characterized in that: The invention comprises a flexible optical fiber sensor as claimed in any one of claims 1 to 2, as well as a wireless demodulation module, a power supply and a mobile terminal; the output end of the flexible optical fiber sensor is signal-connected to the wireless demodulation module, and the wireless demodulation module is communicatively connected to the mobile terminal; the flexible optical fiber sensor and the wireless demodulation module are electrically connected to the power supply respectively; the light signal emitted by the light emitting diode (101) of the flexible optical fiber sensor passes through the plastic optical fiber (103) and the hydrogel fiber flexible sensing part (102) in sequence, and the hydrogel fiber flexible sensing part (102) is stretched and bent when following the joint movement, so that the passing light signal is attenuated, and the attenuated light signal is sent to the photodiode (104), and the corresponding electrical signal is output through photoelectric conversion; after receiving the electrical signal, the wireless demodulation module decouples the strain and the light attenuation, and also sends the decoupling result to the host computer in the form of a digital signal, classifies and outputs the signal through the algorithm built into the host computer, and wirelessly sends the classification result to the mobile terminal.

7. A remote wireless intelligent medical monitoring system according to claim 6, characterized in that: The built-in algorithm used by the host computer to process the acquired signals is a classification sub-algorithm based on a two-dimensional convolutional neural network.

8. A remote wireless intelligent medical monitoring system according to claim 7, characterized in that: The classification sub-algorithm based on the two-dimensional convolutional neural network is to perform overlapping sampling on the collected data, and then divide the data into a training set and a test set in a ratio of 8:2; use the training set to train the convolutional neural network CNN model to obtain the optimal model parameters; then use the model to predict the test set, and evaluate the model based on the prediction results; the input of the convolutional neural network CNN model is a voltage signal, and the output of the convolutional neural network CNN model is the walking gait category label of the monitored person; the convolutional neural network CNN model includes an input layer, two convolutional layers, two batch normalization layers, two ReLU activation layers, two maximum pooling layers, a fully connected layer and a Softmax layer; the network training adopts the Adam optimizer and a piecewise decay learning rate strategy.

9. A remote wireless intelligent medical monitoring system according to claim 7, characterized in that: The decoupling of strain and light attenuation is as follows: the hydrogel fiber flexible sensing portion (102) is regarded as a solvent, and the intensity of the incident light signal of the light emitting diode (101) on the hydrogel fiber flexible sensing portion (102) is I 0 , the transmitted light intensity is I t The absorbed light intensity is I a ,satisfy I 0 = I t + I a ; The ratio of the intensity of transmitted light to the intensity of incident light is the transmittance T , T = I t / I 0 ; The negative logarithm of transmittance is absorbance A , A =- lgT , according to the Beer-Lambert law, A = ECL , E is the molar absorbance of the substance, C is the concentration of the solution, L is the optical path length; when the hydrogel fiber flexible sensing portion (102) is subjected to external strain The change in optical path length is , is the initial length of the hydrogel fiber flexible sensing portion (102), and the light intensity loss calculation formula is: ,in represents the light intensity loss, represents the extinction coefficient, which represents the light absorption value of the hydrogel fiber flexible sensing portion (102); represents the optical coupling loss at the connection joint between the hydrogel fiber flexible sensing portion (102) and the plastic optical fiber (103); extinction coefficient and the concentration of the solution C During the deformation of the hydrogel fiber flexible sensing portion (102), the light intensity loss remains unchanged. With external strain Positive correlation.

10. A remote wireless intelligent medical monitoring system according to claim 6, characterized in that: The wireless demodulation terminal comprises an analog-to-digital conversion chip ADS1256 and an MCU connected in sequence. The analog-to-digital conversion chip ADS1256 performs analog-to-digital conversion on the electrical signal output by the photodiode (104) and inputs the analog-to-digital signal into the MCU. The MCU has a built-in algorithm and is wirelessly connected to the mobile terminal.

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