Flexible polymer-based optical fiber and preparation method and application thereof

Abstract

The invention discloses a flexible polymer-based optical fiber and a preparation method and application thereof, and belongs to the technical field of flexible optical fibers. TPU is used as a matrix material of a fiber core, a cladding layer is formed by light-cured resin, and the flexible polymer-based optical fiber is provided with a fiber core cladding layer structure. The mechanical performance of the optical fiber is controlled by adjusting the soft segment and hardness proportion in the synthesized TPU and the diameter of the optical fiber, and the unique microphase separation structure of the TPU enables the optical fiber to have high elasticity, low elastic modulus and creep resistance. As a sensor, the optical fiber provided by the invention has high sensitivity and quick response, the transient response time is as low as 85ms, human body movement can be monitored in real time, the durability is high, the multi-scene adaptability is good, the optical fiber is successfully applied to bending monitoring of joints such as fingers, elbows and knees, signal output is highly related to joint deformation, and the optical fiber is flexible, light and thin as a sensor, and has good application prospects. And the optical signal detection mechanism is resistant to electromagnetic interference, so that the anti-interference optical fiber is suitable for a complex environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible optical fibers, and in particular relates to a flexible polymer-based optical fiber and a preparation method and application thereof. Background Art

[0002] Fiber optic sensors have attracted much attention in the fields of industrial monitoring, healthcare, and wearable devices due to their resistance to electromagnetic interference, corrosion resistance, and high sensitivity. Although traditional fiber optic materials (such as glass and brittle plastics) have excellent sensing performance, their rigidity leads to extremely poor deformation capacity (maximum strain <1%), making them unable to adapt to the dynamic monitoring needs of human joint movements (deformation >30%) or complex curved surfaces. Although electronic sensors (such as resistors and capacitors) have solved some of the deformation problems through flexible substrate materials (such as PDMS), they still face the disadvantages of electromagnetic interference, signal drift, and insufficient long-term stability.

[0003] Flexible polymer-based fiber optic sensors have become a research hotspot in recent years. Existing flexible fiber optic sensing materials, such as cross-linked polyurethane (thermosetting PU) and polydimethylsiloxane (PDMS), typically have elastic deformation rates of 100-300%, which does not meet the requirements of flexible fiber optic sensors in extreme deformation scenarios. Furthermore, cross-linked polyurethane's thermosetting properties limit processing, while PDMS's rubbery properties, low heat resistance, and low melt viscosity make it unsuitable for traditional preform-based hot-stretching processes. Typically, a single preparation length is only tens of centimeters, making large-scale production impossible and severely restricting industrial applications. Summary of the Invention

[0004] The present invention provides a flexible polymer-based optical fiber and a preparation method and application thereof, which can solve the problem in the prior art that the elastic properties of flexible polymer-based optical fibers are difficult to meet application requirements.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A flexible polymer-based optical fiber has a core-cladding structure, wherein the core material is TPU and the optical fiber cladding is a light-curing resin.

[0007] Furthermore, the core diameter of the flexible polymer-based optical fiber is 0.5-1.5 mm.

[0008] The present invention also provides a method for preparing a flexible polymer-based optical fiber, comprising the following steps:

[0009] Step 1: synthesizing TPU, and preparing a TPU optical fiber preform using the synthesized TPU as a raw material;

[0010] Step 2: hot-stretching the optical fiber preform to form a TPU optical fiber;

[0011] Step 3: Spray the light-curing resin onto the surface of the TPU optical fiber and cure it under ultraviolet light to form a core-cladding structure, resulting in a flexible polymer-based optical fiber with a smooth surface and uniform diameter distribution.

[0012] Furthermore, the steps of synthesizing TPU are as follows:

[0013] S1. Completely melt polytetrahydrofuran ether glycol to obtain a colorless transparent liquid, and transfer the liquid to a desiccator for later use;

[0014] S2. Mix the melted polytetramethylene glycol, isophorone diisocyanate, and 1,4-butanediol in a volume ratio of 2:(0.8-1.4):(0.15-0.20), add trimethylolpropane, stir until completely dissolved, seal with tin foil, and perform ultrasonic treatment to obtain a reaction solution;

[0015] S3, stirring and heating the reaction solution under nitrogen atmosphere, the reaction temperature is 85-95 ° C;

[0016] S4. After the reaction is completed, cool to 55-65°C, add dibutyltin dilaurate (DBTDL) as a catalyst, stir evenly and pour into the mold, cool to room temperature after thermal curing, demold and set aside.

[0017] Thermoplastic polyurethane (TPU), an advanced polymer material that combines thermoplastic processability with elastomeric properties, has a unique molecular structure composed of alternating hard segments (composed of diisocyanates and short-chain extenders) and soft segments (composed of long-chain polyols). This microphase-separated structure is formed by a dynamic hydrogen-bonded network of urethane groups (-NH-COO-). This nanoscale, two-phase morphology endows TPU with gradient physical properties: the crystalline regions formed by the hard segments provide high strength and creep resistance, while the amorphous regions of the soft segments contribute to excellent elastic recovery. TPU not only possesses the high elasticity of rubber and the high strength of plastic, but also exhibits properties such as meltability, high mechanical strength, a wide hardness range, excellent mechanical properties, solvent resistance, and biocompatibility.

[0018] The synthesis of TPU involves two main reactions: prepolymerization and chain extension. This reaction is based on the chemical reaction between isophorone diisocyanate (IPDI) and polytetramethylene ether glycol (PTMEG) (Mn=1000). With PTMEG as the soft segment and IPDI as the hard segment, PTMEG and IPDI are prepolymerized and then chain extended with 1,4-butanediol (BDO) and trimethylolpropane (TMP). The resulting TPU exhibits high tensile strength and light transmittance.

[0019] Furthermore, the added amount of the trimethylolpropane is 0.5-2% of the total mass of the polytetramethylene ether glycol and isophorone diisocyanate.

[0020] Furthermore, the reaction time of the stirring and heating reaction is 2-4 hours, and the stirring rate is 200-400 rpm.

[0021] Furthermore, the dibutyltin dilaurate is 0.05-0.1% of the mass of the reaction solution.

[0022] Furthermore, the preparation steps of the TPU optical fiber preform are as follows:

[0023] Step 1: Prepare a Teflon tube, heat the Teflon tube until it becomes soft, and then nest it with the stainless steel base to form a mold;

[0024] Step 2: Cut the synthesized TPU into pellets, rinse with ethanol, and dry. Place the dried pellets into a mold and place a metal block on top to squeeze the molten material out of the mold. The melting temperature of the metal block is higher than that of the TPU. To prevent the material from swelling when it melts, the metal block is usually placed at a height of 2 / 3-3 / 4 of the Teflon tube height.

[0025] Step 3: preheat the mold in step 2 in an oven under vacuum conditions, and continue heating after the temperature is raised to completely melt the TPU;

[0026] Step 4: Degas the oven until there are no bubbles in the preform, then take out the preform to obtain a TPU optical fiber preform.

[0027] Furthermore, the preheating temperature is 80-90° C., the preheating time is 40-60 minutes, the continuous heating temperature is 120-140° C., and the continuous heating time is 5-6 hours.

[0028] Furthermore, the temperature of the drawing tower for the hot stretching is set as follows:

[0029] The initial temperature was 80°C, which was increased by 20°C at 10-min intervals until it reached 140°C, and then kept constant at 140°C for 20 min.

[0030] The hot stretching process enables the large-scale preparation of TPU optical fibers, and tens of meters of optical fibers can be drawn in 1 hour, with repeatable processing.

[0031] The present invention also provides an application of a flexible polymer-based optical fiber. The flexible polymer-based optical fiber described above can be used as a wearable flexible optical fiber sensor to monitor human health and motion status.

[0032] In flexible sensor applications, TPU's high elasticity and low elastic modulus give the device excellent mechanical adaptability. Due to the material's inherent low elastic modulus, it can fit closely to human joints or robot surfaces, and achieve highly sensitive signal responses through slight deformations. In addition, TPU has low hysteresis loss and can quickly restore its original shape during repeated deformations, avoiding signal drift caused by plastic deformation, thereby improving the long-term stability of the sensor. From a processing and manufacturing perspective, TPU's thermoplastic properties facilitate the large-scale production of flexible sensors. Through processes such as injection molding, extrusion, and 3D printing, TPU can be processed into thin films, fibers, or porous structures to meet the requirements of different sensor designs for substrate morphology.

[0033] Beneficial effects of the present invention:

[0034] (1) The present invention uses thermoplastic polyurethane elastomer (TPU) as the base material, combined with its unique microphase separation structure (hard segments provide high strength, and soft segments impart high elasticity), so that the optical fiber has high elasticity (elongation at break exceeds 700%), low elastic modulus (fits well to human joints), and anti-creep properties.

[0035] (2) This invention controls mechanical properties (elastic deformation range 460%-800%) by adjusting synthesis parameters (such as the IPDI ratio) and fiber diameter (0.5-1.5 mm) to meet diverse application needs. The UV curing process forms a core-cladding structure, enhancing the mechanical strength and optical stability of the fiber.

[0036] (3) The optical fiber provided by the present invention has high sensitivity and fast response as a sensor, with an instantaneous response time as low as 85ms. It can monitor human body movements (such as finger bending) in real time and has strong durability. After 2000 stretching cycles, the voltage attenuation rate is less than ±5%. It has excellent long-term stability and good adaptability to multiple scenarios. It has been successfully applied to the bending monitoring of joints such as fingers, elbows, and knees, and the signal output is highly correlated with joint deformation.

[0037] (4) The optical fiber provided by the present invention is flexible, thin, and can fit closely to the curved surface of the human body. It is very comfortable to wear. The optical signal detection mechanism is resistant to electromagnetic interference and is suitable for complex environments (such as medical monitoring and sports tracking). BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described below with reference to the accompanying drawings.

[0039] Figure 1 This is a physical picture of the flexible polymer-based optical fiber prepared in Example 1 of the present invention in a bent, knotted, and stretched state;

[0040] Figure 2 is a stress-strain curve of the flexible polymer-based optical fiber prepared in Example 1 of the present invention;

[0041] Figure 3 is the response time of the flexible polymer-based optical fiber prepared in Example 1 of the present invention under a weight loading-unloading test;

[0042] Figure 4 is the voltage change during the 2000-cycle stretch recovery process of the flexible polymer-based optical fiber prepared in Example 1 of the present invention;

[0043] Figure 5 Schematic diagram of the structure of the flexible polymer-based optical fiber wearable sensing test system prepared in Example 1 of the present invention;

[0044] Figure 6 The light intensity signal changes of the flexible polymer-based optical fiber prepared in Example 1 of the present invention on the fingers, elbows, and knees. DETAILED DESCRIPTION

[0045] 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 embodiments described 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0046] Example 1

[0047] This embodiment provides a flexible polymer-based optical fiber, and the preparation steps are as follows:

[0048] Step 1: Synthesize TPU:

[0049] Place a vial of polytetramethylenetetramethylene glycol (PTMEG 1000) in a 50°C drying oven for 2 hours. Once completely melted into a colorless, transparent liquid, transfer it to a desiccator for later use. Using a graduated cylinder, measure 26.7 mL of PTMEG 1000, 13.35 mL of IPDI, and 2.4 mL of BDO, respectively, and pour them into a 100 mL beaker. Then, using an electronic balance, weigh 0.4 g of TMP and add it to the beaker. Stir continuously until completely dissolved. Seal the beaker with tin foil and sonicate for 5 minutes in an ultrasonic processor. Use a 250 mL standard three-necked flask equipped with a magnetic rotor and nitrogen inlet system. Ensure the flask is clean, free of residue, and the markings on the back of the flask are clearly visible. Open the bottom opening of the flask and slowly pour the measured mixed solution of PTMEG 1000, IPDI, BDO, and TMP into the flask. Close the bottom opening. Nitrogen was introduced into the flask from one end for 10 minutes to protect the reaction system from oxygen. The reaction was then stirred continuously at 90°C in an oil bath for 2 hours (stirring rate 300 rpm). To ensure uniform heating during the reaction, the oil level in the oil bath must be higher than the liquid level of the reaction system. The temperature of the reaction system was rapidly cooled to 60°C. At this time, 0.05% of the mass of the mixed solution of DBTDL was added to the mixed solution as a catalyst. After stirring evenly, the mixture was poured into a mold and placed in an oven preheated to 80°C for curing. The oven step curing procedure was as follows: 80°C for 12 hours, then raised to 90°C for 6 hours, and finally raised to 100°C for 6 hours. The mixture was naturally cooled to room temperature for demoulding and allowed to stand for three days before use.

[0050] Step 2: Make preform:

[0051] (1) Before the experiment begins, wipe all the necessary experimental equipment, including the Teflon tube (250 mm long and 20 mm in diameter), stainless steel base, and beaker, with anhydrous ethanol and dry them for later use. Heat the Teflon tube at 120°C until it softens, and then nest it with the stainless steel base to form a mold.

[0052] (2) The synthesized thermoplastic polyurethane (TPU) was cut into pellets, washed with ethanol, and dried in a vacuum oven at 60°C for 1 h. The dried pellets were placed in a mold, and a 400 g metal iron block was placed on top to squeeze the molten material in the mold. The height after adding the metal was about 180 mm.

[0053] (3) First, evacuate the oven until the scale line points to -0.1 MPa, and the vacuum extraction is complete. The Teflon tube mold filled with TPU is placed in an oven at 80°C for preheating. After 1 hour, the oven temperature is raised to 130°C and heated for 5 hours.

[0054] (4) After the TPU is completely melted, the oven is vented and the preform is taken out after observing that there is no bubble in the preform. It is placed at room temperature for three days to obtain a TPU optical fiber preform.

[0055] Step 3: Hot stretching:

[0056] A TPU optical fiber preform rod is placed on a drawing tower for drawing. The tower temperature is initially set at 80°C and then increased by 20°C every 10 minutes until it reaches 140°C. The preform rod is heated at 140°C for approximately 20 minutes. The melted portion of the rod sags and tapers under the influence of gravity. The rod is then guided by the drawing tower's traction mechanism to an automatic take-up device for rewinding. By controlling the tower's traction speed and the rod's removal rate, the fiber diameter is maintained at 1mm.

[0057] Step 4: Cladding

[0058] The ultraviolet curing device in the drawing tower is used to evenly spray the light-curing resin on the surface of the TPU optical fiber. After ultraviolet irradiation, a core-cladding structure is formed. The flexible polymer-based optical fiber finally prepared has a smooth surface and a uniform diameter distribution.

[0059] The mechanical properties of the flexible polymer-based optical fiber prepared in Example 1 were tested. Figure 2 As shown in FIG, the optical fiber can achieve an elastic deformation of more than 600% at room temperature, and its elongation at break exceeds 700%.

[0060] The flexible polymer-based optical fiber prepared in Example 1 was tested for transient response time. Figure 3 As shown in the figure, during the weight loading test, the transient response time is 85ms, which is less than 0.1s. The flexible polymer-based optical fiber is sufficient as a sensor to quickly detect human motion.

[0061] The flexible polymer-based optical fiber prepared in Example 1 was used as a sensor for a stretch cycle test, which showed the stability of the electrical signal output during the stretch recovery process. Figure 4 As shown, even after 2000 repeated strain cycles at 1 Hz, the voltage decay rate of the sensor is less than ±5%, demonstrating its durability and repeatability.

[0062] The flexible polymer-based optical fiber prepared in Example 1 was used as a sensor for wearable sensing testing. The test system included an LED white light source, a flexible polymer-based optical fiber, a photodetector (PD), a DAQ device, and a computer. The structure is as follows: Figure 5As shown in Figure 6, the test results show that the finger is gradually bent as shown in Figure (a), and remains stationary when reaching the four states a, b, c, and d. We found that as the finger bends, the sensor output voltage decreases. When the finger is fully extended, the strain reading returns to the baseline. In addition, during the period when the finger bends and remains stationary at each stage, the sensor output amplitude will fluctuate slightly. This phenomenon is mainly attributed to the fact that human movement is not a simple mechanical movement. When the subject subjectively controls the bending of the finger at a certain angle and remains stationary, the finger may also experience slight tremors. Alternatively, when the finger remains stationary, changes in the stretch state of the finger skin and changes in blood flow rate under the sensor may affect the optical power at the sensor's receiving end. Figures (b), (c), and (d) represent the sensor output signal waveforms of the finger, elbow, and knee, respectively. Due to the different sizes and bending degrees of the joints, the vibration amplitudes of the waveforms vary. Based on the waveforms, each joint can be easily identified.

[0063] Example 2

[0064] The only difference from Example 1 is that the diameter of the optical fiber after thermal stretching in step three is adjusted to 0.5 mm, and the other steps and conditions are the same as Example 1.

[0065] The mechanical properties of the flexible polymer-based optical fiber prepared in Example 2 were tested. The optical fiber could achieve an elastic deformation exceeding 527% at room temperature, and its elongation at break exceeded 600%.

[0066] The prepared flexible polymer-based optical fiber was tested for transient response time, and during the weight loading test, the transient response time was 150ms.

[0067] The flexible polymer-based optical fiber prepared in Example 2 was subjected to a tensile cycle test, which showed the stability of the electrical signal output during the stretching recovery process. Even after 2000 repeated strain cycles at 1 Hz, the voltage decay rate was less than ±5%, demonstrating durability and repeatability.

[0068] Example 3

[0069] The only difference from Example 1 is that the diameter of the optical fiber after thermal stretching in step three is adjusted to 1.5 mm, and the other steps and conditions are the same as Example 1.

[0070] The mechanical properties of the flexible polymer-based optical fiber prepared in Example 3 were tested. The optical fiber could achieve an elastic deformation of more than 720% at room temperature, and its elongation at break was more than 800%.

[0071] The flexible polymer-based optical fiber prepared in Example 3 was tested for transient response time. During the weight loading test, the transient response time was 180 ms.

[0072] The flexible polymer-based optical fiber prepared in Example 3 was subjected to a tensile cycle test, which showed the stability of the electrical signal output during the stretching recovery process. Even after 2000 repeated strain cycles at 1 Hz, the voltage decay rate was less than ±5%, demonstrating durability and repeatability.

[0073] Example 4

[0074] The only difference from Example 1 is that the proportion of IPDI in the system is increased during the synthesis of TPU. Other steps and conditions are the same as in Example 1. The steps for synthesizing TPU are as follows:

[0075] Place a vial of polytetramethylenetetramethylene glycol (PTMEG 1000) in a 50°C drying oven for 2 hours. Once completely melted into a colorless, transparent liquid, transfer it to a desiccator for later use. Using a graduated cylinder, measure 26.7 mL of PTMEG 1000, 18 mL of IPDI, and 2.4 mL of BDO, respectively, and pour them into a 100 mL beaker. Then, using an electronic balance, weigh 0.4 g of TMP and add it to the beaker. Stir continuously until completely dissolved. Seal the beaker with tin foil and sonicate for 5 minutes in an ultrasonic processor. Use a 250 mL standard three-necked flask equipped with a magnetic rotor and nitrogen inlet system. Ensure the flask is clean, free of residue, and the markings on the back of the flask are clearly visible. Open the bottom of the flask and slowly pour the measured mixed solution of PTMEG 1000, IPDI, BDO, and TMP into the flask. Close the bottom of the flask. Nitrogen was introduced into the flask from one end for 10 minutes to protect the reaction system from oxygen. The reaction was then stirred continuously at 90°C in an oil bath for 2 hours (stirring rate 300 rpm). To ensure uniform heating during the reaction, the oil level in the oil bath must be higher than the liquid level of the reaction system. The temperature of the reaction system was rapidly cooled to 60°C. At this time, 0.05% of the mass of the mixed solution of DBTDL was added to the mixed solution as a catalyst. After stirring evenly, the mixture was poured into a mold and placed in an oven preheated to 80°C for curing. The oven step curing procedure was as follows: 80°C for 12 hours, then raised to 90°C for 6 hours, and finally raised to 100°C for 6 hours. The mixture was naturally cooled to room temperature for demoulding and allowed to stand for three days before use.

[0076] The mechanical properties of the flexible polymer-based optical fiber prepared in Example 4 were tested. The optical fiber could achieve an elastic deformation of more than 460% at room temperature, and its elongation at break was more than 550%.

[0077] The flexible polymer-based optical fiber prepared in Example 4 was tested for transient response time. During the weight loading test, the transient response time was 220 ms.

[0078] The flexible polymer-based optical fiber prepared in Example 4 was subjected to a stretching cycle test, which showed the stability of the electrical signal output during the stretching recovery process. Even after 2000 repeated strain cycles at 1 Hz, the voltage decay rate was less than ±5%, demonstrating durability and repeatability.

[0079] Example 5

[0080] The only difference from Example 1 is that the proportion of IPDI in the system is reduced during the synthesis of TPU. Other steps and conditions are the same as in Example 1. The steps for synthesizing TPU are as follows:

[0081] Place a vial of polytetramethylenetetramethylene ether glycol (PTMEG 1000) in a 50°C drying oven for 2 hours. Once completely melted into a colorless, transparent liquid, transfer it to a desiccator for later use. Using a graduated cylinder, measure 26.7 mL of PTMEG 1000, 11 mL of IPDI, and 2.4 mL of BDO, respectively, and pour them into a 100 mL beaker. Then, using an electronic balance, weigh 0.4 g of TMP and add it to the beaker. Stir continuously until completely dissolved. Seal the beaker with tin foil and sonicate for 5 minutes in an ultrasonic processor. Use a 250 mL standard three-necked flask equipped with a magnetic rotor and nitrogen inlet system. Ensure the flask is clean, free of residue, and the markings on the back of the flask are clearly visible. Open the bottom opening of the flask and slowly pour the measured mixed solution of PTMEG 1000, IPDI, BDO, and TMP into the flask. Close the bottom opening. Nitrogen was introduced into the flask from one end for 10 minutes to protect the reaction system from oxygen. The reaction was then stirred continuously at 90°C in an oil bath for 2 hours (stirring rate 300 rpm). To ensure uniform heating during the reaction, the oil level in the oil bath must be higher than the liquid level of the reaction system. The temperature of the reaction system was rapidly cooled to 60°C. At this time, 0.05% of the mass of the mixed solution of DBTDL was added to the mixed solution as a catalyst. After stirring evenly, the mixture was poured into a mold and placed in an oven preheated to 80°C for curing. The oven step curing procedure was as follows: 80°C for 12 hours, then raised to 90°C for 6 hours, and finally raised to 100°C for 6 hours. The mixture was naturally cooled to room temperature for demoulding and allowed to stand for three days before use.

[0082] The mechanical properties of the flexible polymer-based optical fiber prepared in Example 5 were tested. The optical fiber could achieve an elastic deformation of more than 420% at room temperature, and its elongation at break was more than 500%.

[0083] The flexible polymer-based optical fiber prepared in Example 5 was tested for transient response time. During the weight loading test, the transient response time was 266 ms.

[0084] The flexible polymer-based optical fiber prepared in Example 5 was subjected to a stretching cycle test, which showed the stability of the electrical signal output during the stretching recovery process. Even after 2000 repeated strain cycles at 1 Hz, the voltage decay rate was less than ±5%, demonstrating durability and repeatability.

[0085] Comparative Example 1

[0086] The only difference from Example 1 is that thermosetting PU is used instead of TPU as the fiber core material in this comparative example. The preparation steps are as follows:

[0087] Step 1: Synthesize thermosetting PU:

[0088] A polyethylene glycol (PEG 200) bottle was placed in a vacuum drying oven at 110°C for 2 hours, cooled, and transferred to a desiccator for later use. 100g of PEG 200 was weighed and placed in a three-necked flask, heated to 80°C, and stirred until melted. 40g of diphenylmethane isocyanate (MDI) was then slowly added to the flask. Nitrogen was introduced from one end of the flask for 10 minutes to protect the reaction system from oxygen. The reaction was then stirred continuously in an oil bath at 90°C for 2 hours (at a stirring rate of 300 rpm). To ensure uniform heating during the reaction, the oil level in the oil bath must be above the liquid level of the reaction system. After 2 hours of reaction, the reaction system was rapidly cooled to 60°C. The bottom of the flask was opened, and 1.8g of glycerol was added to the mixed solution. After stirring, the mixture was poured into a polymer capillary tube and allowed to stand at room temperature for 24 hours. The mixture was then cured in an oven at 80°C for 3 hours and removed from the polymer capillary tube to obtain a thermoset PU fiber core.

[0089] Step 2: Cladding:

[0090] The photocurable resin is evenly sprayed on the surface of the thermosetting PU optical fiber using an ultraviolet curing device. After ultraviolet irradiation, a core-cladding structure is formed to obtain a flexible polymer-based optical fiber.

[0091] The mechanical properties of the flexible polymer-based optical fiber prepared in Comparative Example 1 were tested. The elastic deformation rate of the optical fiber at room temperature was 150%, and the elongation at break was 185%.

[0092] The flexible polymer-based optical fiber prepared in Comparative Example 1 was tested for transient response time. During the weight loading test, the transient response time was 165 ms.

[0093] Comparative Example 2

[0094] The only difference from Example 1 is that polydimethylsiloxane (PDMS) is used instead of TPU as the fiber core material in this comparative example. The preparation steps are as follows:

[0095] Step 1: Prepare PDMS core:

[0096] Weigh polydimethylsiloxane monomer and curing agent (DBP) in a 5:1 mass ratio and pour into a glass beaker. Stir at a low, constant speed with a glass rod for 5-10 minutes to ensure thorough mixing and avoid excessive bubbles. Place the mixture in a vacuum drying oven and pump at -0.1 MPa for 5-15 minutes until all bubbles disappear. A polymer capillary tube is used as a mold. Pour the degassed liquid into the pretreated mold and cure at room temperature for 48 hours. After removal from the mold, the PDMS fiber core is obtained.

[0097] Step 2: Cladding:

[0098] The photocurable resin is evenly sprayed on the surface of the PDMS optical fiber using an ultraviolet curing device, and a core-cladding structure is formed after ultraviolet irradiation to obtain a flexible polymer-based optical fiber.

[0099] The photocurable resin is evenly sprayed on the surface of the thermosetting PU optical fiber using an ultraviolet curing device. After ultraviolet irradiation, a core-cladding structure is formed to obtain a flexible polymer-based optical fiber.

[0100] The mechanical properties of the flexible polymer-based optical fiber prepared in Comparative Example 1 were tested. The elastic deformation rate of the optical fiber at room temperature was 210%, and the elongation at break was 280%.

[0101] The flexible polymer-based optical fiber prepared in Comparative Example 1 was tested for transient response time. During the weight loading test, the transient response time was 150 ms.

[0102] The optical fiber fabricated in this embodiment exhibits superior overall performance as a sensor, far exceeding the mechanical properties of conventional polymer optical fibers. These mechanical performance data demonstrate that TPU optical fibers possess high reliability and durability in practical applications, along with high sensitivity and rapid response. As a sensor, they are flexible, lightweight, and can conform closely to the curves of the human body, providing high wear comfort.

[0103] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0104] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A flexible polymer-based optical fiber, characterized in that: The flexible polymer-based optical fiber has a core-cladding structure, the core material is TPU, and the optical fiber cladding is a light-curing resin.

2. The flexible polymer-based optical fiber according to claim 1, characterized in that: The core diameter of the flexible polymer-based optical fiber is 0.5-1.5 mm.

3. A method for preparing a flexible polymer-based optical fiber according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: synthesizing TPU, and preparing a TPU optical fiber preform using the synthesized TPU as a raw material; Step 2: hot-stretching the optical fiber preform to form a TPU optical fiber; Step 3: Spray the light-curing resin on the surface of the TPU optical fiber, and form a core-cladding structure after curing by ultraviolet irradiation to obtain a flexible polymer-based optical fiber.

4. The method for preparing a flexible polymer-based optical fiber according to claim 3, wherein: The steps of synthesizing TPU are as follows: S1. Completely melt polytetrahydrofuran ether glycol to obtain a colorless transparent liquid, and store in a desiccator for later use; S2. Mix the melted polytetramethylene glycol, isophorone diisocyanate, and 1,4-butanediol in a volume ratio of 2:(1.0-1.4):(0.15-0.20), add trimethylolpropane, stir until completely dissolved, seal with tin foil, and perform ultrasonic treatment to obtain a reaction solution; S3, stirring and heating the reaction solution under nitrogen atmosphere, the reaction temperature is 85-95 ° C; S4. After the reaction is completed, cool to 55-65°C, add dibutyltin dilaurate as a catalyst, stir evenly and pour into a mold, cool to room temperature after thermal curing, demold and set aside.

5. The method for preparing a flexible polymer-based optical fiber according to claim 4, characterized in that: The added amount of the trimethylolpropane is 0.5-2% of the total mass of the polytetramethylene ether glycol and isophorone diisocyanate.

6. The method for preparing a flexible polymer-based optical fiber according to claim 4, wherein: The dibutyltin dilaurate accounts for 0.05-0.1% of the mass of the reaction solution.

7. The method for preparing a flexible polymer-based optical fiber according to claim 3, wherein: The preparation steps of the TPU optical fiber preform are as follows: Step 1: Prepare a Teflon tube, heat the Teflon tube until it becomes soft, and then nest it with the stainless steel base to form a mold; Step 2: Cut the synthesized TPU into pellets, wash with ethanol and dry them, put the dried pellets into a mold, and place a metal block on top to squeeze the molten material in the mold; Step 3: preheat the mold in step 2 in an oven under vacuum conditions, and continue heating after the temperature is raised to completely melt the TPU; Step 4: Degas the oven until there are no bubbles in the preform, then take out the preform to obtain a TPU optical fiber preform.

8. The method for preparing a flexible polymer-based optical fiber according to claim 7, characterized in that: The preheating temperature is 80-90° C., the preheating time is 40-60 minutes, the continuous heating temperature is 120-140° C., and the continuous heating time is 5-6 hours.

9. The method for preparing a flexible polymer-based optical fiber according to claim 3, wherein: The temperature of the drawing tower for the thermal stretching is set as follows: The initial temperature was 80°C, which was increased by 20°C at 10-min intervals until it reached 140°C, and then kept constant at 140°C for 20 min.

10. An application of a flexible polymer-based optical fiber, characterized in that: The flexible polymer-based optical fiber according to any one of claims 1 to 2 is used as a wearable flexible optical fiber sensor for monitoring human health and motion status.

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