Lotus root silk micro optical fiber, preparation method thereof and optical waveguide application

Abstract

The application belongs to the technical field of optical fiber preparation, and particularly relates to lotus root silk micro optical fiber and a preparation method and optical waveguide application thereof. The lotus root is transversely cut, and lotus root silk bundles are extracted from the transverse section after the lotus root is cut. The obtained lotus root silk bundles are soaked in an inorganic strong alkali solution for alkali treatment to obtain alkali-treated lotus root silk bundles. The alkali-treated lotus root silk bundles are washed and separated to obtain lotus root silk micro optical fiber. The preparation method provided by the application can successfully separate the lotus root silk micro optical fiber by adopting a "chemical auxiliary physical separation" method. The lotus root silk micro optical fiber displays obvious red, green and blue fluorescence under irradiation of laser beams of different wavelengths, and exhibits stable fluorescence intensity. The fluorescence signal can be transmitted along the axial direction of the lotus root silk micro optical fiber, which is similar to the transmission characteristics of a communication optical fiber. The lotus root silk micro optical fiber prepared by the application has unique optical characteristics, flexibility and multifunction, and has wide application attraction. The lotus root silk micro optical fiber is a promising material in the field of photonics applications.

Description

Technical Field

[0001] This invention belongs to the field of waveguide material preparation technology, specifically relating to a lotus root fiber microfiber, its preparation method, and its optical waveguide applications. Background Technology

[0002] In modern biophysics and biomedicine, continuous monitoring of the physiological and pathological states of organisms is crucial, as even minute fluctuations above baseline parameters can signal relevant biological or functional changes in cellular responses. Micro / nano optical biosensors have become powerful tools for researching and diagnosing biological environments, with micro / nano optical fiber-based biosensors proving highly valuable for detecting and monitoring liquid environments and biological activity.

[0003] However, most traditional optical fibers are still based on glass, semiconductor or metal materials, which are not entirely suitable for biological environments. They are easily damaged by physical means such as bending, twisting or squeezing. The loss level of traditional optical fiber materials used in biosensors is 0.1dB / μm, which is a problem of high loss. Moreover, when in contact with biological samples, traditional optical fibers have poor biocompatibility and can easily have adverse effects on the samples. In addition, the signals are prone to cross-interference and have low sensitivity. Summary of the Invention

[0004] The purpose of this invention is to provide a lotus root fiber microfiber, its preparation method, and its optical waveguide application. The lotus root fiber microfiber provided by this invention has the characteristics of high biocompatibility and extremely low active waveguide loss. At the same time, the lotus root fiber microfiber provided by this invention can realize a passive waveguide in the visible light range, and has a small diameter, making it suitable for biosensing applications in extremely small detection areas.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing lotus root fiber micro-optical fibers, comprising the following steps:

[0007] Cut the lotus root horizontally, and extract the lotus root fibrous strands from the cut surface. Soak the obtained lotus root fibrous strands in an inorganic strong alkaline solution for alkaline treatment to obtain alkaline-treated lotus root fibrous strands.

[0008] The lotus root fiber bundles treated with alkali were washed with water and then separated to obtain lotus root fiber microfibers.

[0009] Preferably, the extraction is performed at a uniform speed, which is 5–15 cm / s.

[0010] Preferably, the extraction direction is perpendicular to the cross-section of the lotus root.

[0011] Preferably, the inorganic strong alkali solution is an aqueous solution of sodium hydroxide.

[0012] Preferably, the mass concentration of the inorganic strong alkali solution is 15-25 g / L.

[0013] Preferably, the alkali treatment is performed at room temperature for 1 to 2 hours.

[0014] Preferably, the separation includes the following steps: fixing the washed lotus root filament bundle on a positioning device, and using an optical fiber on the positioning device to separate the lotus root filament bundle to obtain lotus root filament micro-optical fibers.

[0015] Preferably, the positioning device is a fiber optic adjustment frame.

[0016] The present invention provides a lotus root fiber microfiber obtained by the preparation method described above, wherein the lotus root fiber microfiber has a length ≥ 600 μm and a diameter of 3 to 6 μm.

[0017] This invention provides the application of lotus root fiber microfiber as a waveguide material as described in the above technical solution.

[0018] This invention provides a method for preparing lotus root fiber microfibers, comprising the following steps: lotus root is cross-cut, and lotus root fiber bundles are extracted from the cross-section. The obtained lotus root fiber bundles are immersed in an inorganic strong alkaline solution for alkali treatment, resulting in alkali-treated lotus root fiber bundles. The alkali-treated lotus root fiber bundles are then washed with water and subsequently straightened and separated to obtain lotus root fiber microfibers. The preparation method provided by this invention uses a "chemical-assisted physical separation" method to successfully separate lotus root fiber microfibers (monofilaments). Compared with traditional optical fiber preparation methods, the preparation method provided by this invention has the advantages of simple procedures and highly stable production yield. The lotus root fiber microfibers prepared by this invention exhibit wide-band fluorescence emission characteristics. Compared with traditional fibers, the lotus root fiber microfibers prepared by this invention have higher luminous efficiency and are suitable for various application environments. Furthermore, the lotus root fiber microfibers prepared by this invention have high stability, low toxicity, and good biocompatibility and biodegradability, making them an ideal choice for biological applications, especially in biosensing. The lotus root fiber microfibers can also demonstrate excellent optical transmission capabilities by coupling lasers of different wavelengths. In summary, the lotus root fiber microfiber prepared by this invention possesses unique optical properties, flexibility, and multifunctionality, making it highly attractive for a wide range of applications and a promising material for photonics. The results of the embodiments demonstrate that the lotus root fiber microfiber prepared by this invention has a uniform diameter, a smooth surface, and virtually no optical porosity, making it an extremely suitable optical waveguide material. Under irradiation with lasers of different wavelengths (365, 420, and 546 nm), the lotus root fiber microfiber exhibits distinct red, green, and blue fluorescence with stable fluorescence intensity. This fluorescence signal can propagate along the axial direction of the lotus root fiber microfiber, and its active waveguide loss is only 0.051 dB / μm, which is lower than the loss level (0.1 dB / μm) of commonly used materials in the field of biosensor waveguides. Furthermore, the lotus root fiber microfiber prepared by this invention can not only generate low-loss active waveguides but also realize passive waveguides in other visible light ranges. Inside the lotus root fiber microfiber, the passive waveguide loss is 0.160 dB / μm for blue light, 0.144 dB / μm for green light, and 0.138 dB / μm for red light. This indicates that the lotus root fiber microfiber can effectively transmit optical signals in the visible light region, similar to the transmission characteristics of communication optical fibers. Furthermore, the lotus root fiber microfiber prepared in this invention possesses good flexibility and can be bent into different shapes, making it suitable for integrating micro- and nano-optical devices. Experiments have shown that the fluorescence intensity at the endpoints of the lotus root fiber microfiber prepared in this invention is significantly higher than that at the end face, providing the possibility of utilizing this fluorescence property to activate other luminescent materials. Attached Figure Description

[0019] Figure 1 A schematic diagram illustrating the fabrication process and performance testing of lotus root fiber microfibers provided in this embodiment of the invention;

[0020] Figure 2A scanning electron microscope image of the lotus root fiber microfiber prepared in Example 1 of this invention;

[0021] Figure 3 The passive waveguide test diagram of the lotus root fiber micro-optical fiber prepared in Example 1 of the present invention;

[0022] Figure 4 The active waveguide test diagram of the lotus root fiber micro-optical fiber prepared according to an embodiment of the present invention;

[0023] Figure 5 Test methods and results for designing a pH sensor based on the active waveguide characteristics of lotus root fiber microfiber;

[0024] Figure 6 To verify the repeatability of the lotus root fiber microfiber in this invention;

[0025] Figure 7 Test methods and results for designing a bacterial sensor based on the passive waveguide characteristics of lotus root fiber microfiber. Detailed Implementation

[0026] This invention provides a method for preparing lotus root fiber micro-optical fibers, comprising the following steps:

[0027] Cut the lotus root horizontally, and extract the lotus root fibrous strands from the cut surface. Soak the obtained lotus root fibrous strands in an inorganic strong alkaline solution for alkaline treatment to obtain alkaline-treated lotus root fibrous strands.

[0028] After the alkali-treated lotus root fibers were washed with water, they were straightened and separated in sequence to obtain lotus root fiber microfibers.

[0029] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0030] The preparation process of the lotus root fiber microfiber provided by this invention is as follows: Figure 1 As shown, the following is combined Figure 1 The process shown provides a detailed description of the preparation method of the lotus root fiber microfiber.

[0031] This invention involves cross-slicing a lotus root and extracting lotus root fibers from the cross-section. The resulting fibers are then soaked in a strong inorganic alkaline solution for alkali treatment, yielding alkali-treated lotus root fibers. In this invention, the diameter of the lotus root is preferably 5-10 cm, more preferably 8 cm. The cross-section is preferably made at the midpoint of the lotus root's length. This invention preferably cuts the cross-section from the center of the lotus root's length to ensure a neat and smooth cut surface. When the cross-section is neat and smooth, the individual fibers in the lotus root fibers are arranged more neatly and orderly, and the overall structure is more regular. In this invention, the extraction point is preferably the center of the cross-section. The lotus root fibers in the center of the cross-section possess superior characteristics, including a more uniform diameter and better fiber arrangement. This invention selects the lotus root fibers from the center of the cross-section as the raw material for preparing lotus root fiber microfibers. Such high-quality lotus root fiber raw material will help ensure the preparation of high-quality, high-performance lotus root fiber microfibers. In this invention, the extraction direction is preferably perpendicular to the cross-section of the lotus root, the extraction is preferably performed at a uniform speed, and the extraction speed is preferably 5-15 cm / s, more preferably 10 cm / s. In this invention, the extraction speed is preferably 5-15 cm / s, more preferably 10 cm / s, which ensures the stability of the quality and diameter of the lotus root fibers (e.g., Figure 1 (As shown in b). The purpose of controlling the extraction speed in this invention is preferably 5 to 15 cm / s, and more preferably 10 cm / s, to avoid excessively fast extraction speeds that could cause instability in the diameter of the lotus root fibers and affect the quality.

[0032] The lotus root filament bundles obtained by this invention exhibit a spiral structure. This spiral structure may be due to the tissue structure and growth characteristics of the lotus root filament bundles, giving the lotus root filaments a high elastic deformation capacity, which can reach 10 times the elastic deformation.

[0033] In this invention, the inorganic strong alkaline solution is preferably an aqueous sodium hydroxide solution. The mass concentration of the inorganic strong alkaline solution is preferably 15–25 g / L, more preferably 20 g / L. The alkali treatment temperature is preferably room temperature, and the treatment time is preferably 1–2 hours. The purpose and function of using the inorganic strong alkaline solution for alkali treatment in this invention is to remove pectin, polysaccharides, and other fatty substances from the surface of the lotus root fiber microfiber, obtaining lotus root fiber microfibers with uniform diameter and smooth surface. After treatment with the inorganic strong alkaline solution, the adhered lotus root fiber bundles become looser, the surface becomes smoother, and the gap between the individual filaments in the lotus root fiber bundle is approximately 1 μm, facilitating subsequent separation.

[0034] After obtaining the alkali-treated lotus root fiber bundle, the present invention washes the alkali-treated lotus root fiber bundle with water and then separates it to obtain lotus root fiber microfibers. In the present invention, the water washing is preferably performed by transferring the alkali-treated lotus root fiber bundle onto a glass slide and rinsing it with deionized water. The number of rinsings is preferably 5 to 6 times. The present invention preferably removes the residual inorganic strong alkali solution in the alkali-treated lotus root fiber bundle by water washing.

[0035] In this invention, the separation preferably includes the following steps: fixing the washed lotus root filament bundle onto a positioning device, and using an optical fiber on the positioning device to separate the lotus root filament bundle to obtain lotus root filament microfibers. In this invention, the positioning device is an optical fiber adjustment frame with a precision of 50 nm. This invention uses an optical fiber on a 50 nm precision optical fiber adjustment frame to separate the washed lotus root filament bundle, enabling precise control of the optical fiber and achieving the separation of lotus root filament microfibers. The washed lotus root filament bundle is preferably fixed to the positioning device with double-sided adhesive. This invention preferably uses an optical fiber for separating the lotus root filament microfibers. In this invention, the optical fiber is preferably a SiO2 tapered optical fiber, with a core diameter preferably of 50 μm, a cladding diameter preferably of 125 μm, an insertion loss (dB) of 0.11 dB to 0.13 dB, and a return loss > 65 dB. The lotus root filament microfibers obtained by this invention have a helical structure. This invention preferably uses a positioning device to straighten the lotus root filament microfibers.

[0036] In a specific embodiment of the present invention, the preferred separation process is as follows: using two fiber optic adjustment frames, two tapered optical fibers are inserted into the same gap in the lotus root fiber bundle. The fiber optic adjustment frames are gradually adjusted to allow the optical fibers to penetrate deeper into the lotus root fiber bundle. During insertion, moderate force is applied, concentrated on the thicker portion of the optical fiber. This helps to separate other fibers from the lotus root fiber bundle. These separated fibers can be broken and adhered to double-sided adhesive. Finally, a lotus root fiber micro-optical fiber with a uniform diameter and smooth surface is obtained. The separation process of the present invention utilizes physical principles and mechanical properties to separate and process the fibers in the lotus root fiber bundle, ultimately preparing the desired micro-optical fiber.

[0037] The preparation method provided by this invention uses lotus root as the raw material. Lotus root is a low-cost and abundant food ingredient, and its internal lotus root fibers have excellent structure and texture. This invention successfully prepared lotus root fiber microfibers through precise micromanipulation. These microfibers have uniform diameter and smooth surface, making them a natural waveguide material with significant advantages such as excellent biofriendliness, biodegradability, and flexibility. Furthermore, the fluorescence emission under different wavelengths of laser irradiation is demonstrated, proving that the lotus root fiber microfibers can emit distinct blue, green, and red fluorescence and exhibit good light emission stability.

[0038] The present invention provides a lotus root fiber microfiber obtained by the preparation method described above, wherein the lotus root fiber microfiber has a length ≥ 600 μm and a diameter of 3 to 6 μm.

[0039] In this invention, the length of the lotus root fiber microfiber is preferably 600μm to 10cm, and the diameter is preferably 3 to 5μm.

[0040] The lotus root fiber microfiber prepared by this invention possesses excellent properties, including uniform diameter, smooth surface, and virtually no optical porosity, making it an excellent optical waveguide material. Furthermore, the lotus root fiber microfiber provided by this invention exhibits distinct red, green, and blue fluorescence under illumination with different wavelengths of laser light (365, 420, and 546 nm), demonstrating stable fluorescence intensity. This fluorescence signal can propagate along the axial direction of the lotus root fiber microfiber, similar to the transmission characteristics of communication optical fibers. In addition, the lotus root fiber microfiber exhibits good flexibility and can be bent into different shapes, making it suitable for integrating micro / nano optical devices. Preliminary experiments have shown that the fluorescence intensity at the endpoints of the lotus root fiber microfiber is significantly higher than that at the end face, providing the possibility of utilizing this fluorescence property to activate other luminescent materials. These findings provide a foundation for further research and application of lotus root fiber microfibers.

[0041] This invention provides the application of lotus root fiber microfiber as a waveguide material as described in the above technical solution.

[0042] In this invention, the waveguide material is preferably a waveguide material used in biosensors.

[0043] This invention introduces lasers of different wavelengths into lotus root fiber microfibers through optical fiber coupling, and observes bright light spot signals at their ends, highlighting the excellent optical propagation characteristics and low optical loss coefficient of the lotus root fiber microfibers, proving that the lotus root fiber microfibers provided by this invention can serve as excellent waveguide materials.

[0044] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] according to Figure 1 The preparation process of the lotus root fiber micro-optical fiber is illustrated in the schematic diagram:

[0047] Step 1: Select a clean and intact lotus root (8cm in diameter), and make a precise horizontal cut in the middle, ensuring a neat and smooth cut (e.g., ...). Figure 1(As shown in a). This cut lotus root reveals a more orderly and uniform arrangement of individual filaments within the lotus root fiber bundles, resulting in a more regular overall structure. The lotus root fibers in the central part of the cross-section possess superior characteristics, including a more uniform diameter and better fiber arrangement. Due to these characteristics, high-quality lotus root fibers from the central part of the cross-section are selected as the raw material for preparing lotus root fiber microfibers.

[0048] Step 2: Extract the lotus root fibers along the axial direction of the lotus root at a constant speed of 10 cm / s to ensure the quality and diameter of the lotus root fibers remain stable (e.g., Figure 1 In b), it was observed that the lotus root fibers exhibited a spiral structure during the extraction process, giving the lotus root fibers a high elastic deformation capacity, which can reach 10 times the elastic deformation.

[0049] Step 3: Soak the lotus root fibers extracted in Step 2 in a sodium hydroxide aqueous solution with a mass concentration of 20 g / L for 2 hours (e.g., ...). Figure 1 (c) Then, using optical fibers, the lotus root fibers are transferred to a clean glass slide, and deionized water is added repeatedly six times to remove residual sodium hydroxide solution. Using a fiber optic adjustment frame with a precision of 50 nanometers, the optical fiber can be precisely manipulated to separate the lotus root fiber micro-optics (e.g., ...). Figure 1 d) Lotus root fiber microfiber is obtained, which has a helical structure.

[0050] Test case

[0051] (1) Morphological characterization of lotus root fiber microfibers

[0052] The lotus root fiber microfibers prepared in Example 1 were separated and fixed onto a test substrate (a pathological microscope slide), initially maintaining a helical structure. As the experiment progressed, the helical structure of the lotus root fiber microfibers gradually disappeared due to the action of double-sided adhesive, and eventually the lotus root fiber microfibers were straightened.

[0053] The specific experimental method is as follows: The lotus root fiber microfiber prepared by the above method is taken out and transferred to a clean silicon wafer. After drying in an oven at 25°C for 30 minutes, a scanning electron microscope is turned on at 20KV. Secondary electron emission is used, and microscopic observation is performed under a 3.5K magnification microscope in a high vacuum environment to obtain the microscopic surface structure of the lotus root fiber microfiber (e.g., ...). Figure 2 (As shown). By Figure 2 As shown, the lotus root fiber microfiber exhibits a one-dimensional cylindrical structure with a length greater than 600 μm and a diameter of 3–5 μm. From Figure 2 As can be clearly seen, the lotus root fiber microfiber has a uniform diameter, a smooth surface, and few optical pores. Based on these morphological characteristics, it is preliminarily determined that the lotus root fiber microfiber possesses relatively excellent optical waveguide performance.

[0054] (2) Study on the passive waveguide characteristics of lotus root fiber microfiber

[0055] Microscopic control of lotus root fiber microfibers was achieved using a 10x objective lens and a three-dimensional inverted microscope. A 20μm diameter microfluidic channel was then constructed, suspending the lotus root fiber microfibers above the channel. Spectral information of the lotus root fiber microfibers, including absorption, transmission, and fluorescence spectral characteristics, was acquired using a Zeiss CRAIC 20 / 30PV™ microspectrophotometer. Figure 1 (e). This setup enables high-resolution microscopic observation and spectral acquisition of lotus root fiber microfibers, providing a powerful tool for further research on optical properties.

[0056] The specific experimental method is as follows: A single-mode optical fiber was selected. First, the outer sheath and polymer layer of the fiber were removed to expose the inner core. Then, the fiber was tapered using a flame melting method to form a tapered structure. Next, the fiber surface was cleaned with acetone, alcohol, and deionized water to ensure cleanliness. Finally, the treated fiber was placed in a 45°C oven for drying. During the experiment, a laser was used to emit light at a wavelength of 655nm (…). Figure 3 a) 532nm Figure 3 (b) and 440nm ( Figure 3 The laser in c) is coupled into a lotus root fiber micro-optical fiber to achieve passive optical waveguide transmission. The specific experimental procedure is as follows: Figure 3 As shown in a to c, this process provides fundamental data for further research on the transmission characteristics of passive optical waveguides.

[0057] Figure 3 The laser beam was clearly shown to have been successfully coupled into the lotus root fiber micro-optical fiber and propagated along its length. During transmission through the lotus root fiber micro-optical fiber, the rapid attenuation and evanescent wave scattering phenomena were relatively weak, and a bright spot of light could be observed at the end of the lotus root fiber micro-optical fiber. Figure 3 (d, e, and f in the original text). Next, a power meter was connected via another optical fiber, and the spectral intensity at the end of the lotus root fiber micro-optical fiber was collected step by step at different transmission distances using the truncation method. Subsequently, the transmission loss coefficients of blue, green, and red light were calculated using Formula 1 to be 0.160 dB / μm, 0.144 dB / μm, and 0.138 dB / μm, respectively.

[0058] α={-10×log(P out / P in Formula 1;

[0059] In Formula 1: P out It is the output optical signal intensity, P in L is the input optical signal intensity, and L is the optical transmission distance.

[0060] (3) Study on the active waveguide characteristics of lotus root fiber microfiber

[0061] Red, green, and blue lasers are coupled into lotus root fiber micro-optical fibers at different locations for transmission (e.g., ...). Figure 1 (f) This design effectively reduces scattering losses during light transmission in the lotus root fiber microfiber because the refractive index of the lotus root fiber microfiber is much greater than that of air. At the end of the lotus root fiber microfiber, the intensity of passive optical signals at different transmission distances was successfully detected, realizing optical transmission of passive optical waveguides. Next, blue light was coupled into the lotus root fiber microfiber using an optical fiber, causing the microfiber to produce green fluorescence. The fluorescence signal propagates along the length of the lotus root fiber microfiber at different distances. After being processed by the objective lens, filter, slit, and grating of the Zeiss CRAIC 20 / 30PV™ microspectrophotometer, the light carrying spectral information finally reaches the detector to complete spectral acquisition. This process realizes optical transmission of active waveguides, providing key data for further research on optical waveguide characteristics.

[0062] The specific experimental method was as follows: A Zeiss CRAIC 20 / 30PV™ microspectrophotometer was used to collect the fluorescence spectrum of the lotus root fiber microfiber. The experimental procedure included opening the LambdaFire software and using xenon and mercury lamps. First, the absorption, transmission, and reflection spectra of the lotus root fiber microfiber were collected. Then, the lotus root fiber microfiber was micromanipulated using a 10x objective lens, and excited using a fiber-coupled laser. The signal generated by the excited lotus root fiber microfiber was processed through the objective lens, filter, slit, and grating. Finally, the light carrying spectral information was transmitted to the detector, completing the spectral acquisition and recording of the fluorescence spectrum. Figure 4 As shown in the figure. During the test, the PL spectral signal scan time was set to 5ms, and the diameter of the focused sampling area was approximately 2μm. Simultaneously, a background spectrum from a clean glass slide was acquired for comparison. A 10x objective lens was used in the lotus root fiber microfiber test, with a slit width of 100μm and a spectral resolution of 0.32nm. The PL spectral acquisition range was 300 to 1000nm. These parameter settings ensured accurate acquisition of the fluorescence spectrum of the lotus root fiber microfiber.

[0063] Blue light was coupled into a lotus root fiber microfiber using an optical fiber, stimulating the microfiber to produce green fluorescence, which propagates along the length of the microfiber. The green fluorescence spectra of the lotus root fiber microfiber were collected using a Zeiss CRAIC 20 / 30PVTM microspectrophotometer at different transmission distances. The transmission loss of the green fluorescence was calculated to be 0.051 dB / μm using Equation 1. The experiment also showed that the lotus root fiber microfiber can illuminate other materials with intersecting geometries, such as fibers.

[0064] α={-10×log(P out / P in Formula 1;

[0065] In Formula 1: P out It is the output optical signal intensity, P in It is the green fluorescence intensity measured at the minimum transmission distance, where L is the light transmission distance.

[0066] Application examples

[0067] (1) pH sensor design based on the active waveguide properties of lotus root fiber microfiber: The fluorescence intensity of the lotus root fiber microfiber can be reversibly changed by altering the pH value of the solution. In an acidic environment, the increase in cations leads to charge repulsion, thereby inhibiting nonradiative transitions in the intramolecular interactions of cellulose nanoclusters (the main component of lotus root fiber is cellulose) and enhancing their fluorescence intensity. In an alkaline environment, the intermolecular interactions of cellulose nanoclusters weaken, resulting in loose crystal stacking, reduced crystallinity, and a significant increase in scattering loss, thus leading to a decrease in fluorescence intensity.

[0068] Experimental steps: Couple blue light to one end of a lotus root fiber micro-optical fiber using an optical fiber ( Figure 5 (a) In the above, the intensity of 560nm light signal was collected at different transmission distances in solutions with different pH values. Figure 5 c), Figure 5 In the case of c: among sensing lengths of 25μm, 65μm, 105μm, 145μm, and 185μm, the photoluminescence signal intensity is highest and more pronounced at 65μm. Therefore, the optimal sensing length L = 65μm for the lotus root micro-optical fiber is determined. The light intensity spectrum at a transmission distance of 65μm is as follows: Figure 5 b in the middle, where Figure 5 The inset in section b shows the photoluminescence (PL) spectra of the lotus root fiber micro-optical fiber at different pH solutions under the optimal sensing length (L = 65 μm). The horizontal axis represents the solution pH value, and the vertical axis represents the photoluminescence intensity at the center wavelength of 560 nm. The "black spheres" in the inset represent the numerical values ​​of photoluminescence intensity under different pH conditions. The average optical loss transmission coefficient calculated using Equation 1 for solutions at different pH values ​​is 0.016 dB / μm. Figure 5 (d)

[0069] Conclusion: When the transmission distance is constant, the intensity of the optical signal decreases as the pH value increases.

[0070] To verify the repeatability of lotus root fiber micro-optics (e.g. Figure 6 As shown), under constant power, samples were collected from blue light-excited at pH values ​​ranging from 3 to 9. Figure 6 a) Photoluminescence (PL) spectrum and in solutions with pH values ​​of 9–3 Figure 6b) PL spectrum. From pH=3 to pH=9, and back to pH=3, after 10 consecutive cycles ( Figure 6 (c) In solutions with pH values ​​of 3, 7, and 9, the PL intensity of the lotus root fiber microfiber remained stable. Between pH 3 and pH 9, after cyclical changes in the pH solution, the PL intensity of the lotus root fiber microfiber exhibited periodic variations. Figure 6 The result in d) indicates that the lotus root fiber microfiber has repeatability.

[0071] (2) Mechanism of bacterial sensor design based on passive waveguide characteristics of lotus root fiber microfiber: During bacterial apoptosis, changes in bacterial cell membrane permeability lead to the gradual release of enzymatic substances from the bacterial cell interior into the surrounding liquid microenvironment. In the liquid microenvironment, the enzymatic substances can interact with the hydroxyl groups on the cellulose surface through the enzyme's active site and adhere to the surface of the lotus root fiber microfiber. The enzymatic substances are captured by the lotus root fiber microfiber, thereby changing the surface roughness and thickness of the lotus root fiber microfiber, and consequently altering the intensity of the light signal detected by fiber2.

[0072] Experimental steps: Blue light is coupled through fiber 1, and the blue light propagates on the surface of the lotus fiber in the form of an evanescent wave. Fiber 2 detects the intensity of the light signal. Figure 7 (a-c) In the solution, 30% H2O2 apoptosis agent was added. With increasing time, the amount of bacterial cell death increased, the surface roughness of the lotus root fiber microfiber increased, and evanescent wave scattering was enhanced, thereby weakening the intensity of the light signal detected by fiber2. Figure 7 (d)

[0073] To verify the increase in bacterial cell death within 50 minutes, Raman spectra of bacterial cells with and without apoptosis-inducing agents were collected. It was found that in the absence of apoptosis-inducing agents ( Figure 7 In the case of f), the spectral intensity remains constant as time increases, especially when an apoptotic agent is present. Figure 7 In equation e), the spectral intensity gradually decreases with time.

[0074] As can be seen from the above embodiments, the present invention has the following three technical advantages:

[0075] 1. Lotus root fiber microfibers possess abundant available material resources, are easy to collect, and require no subsequent synthetic processing. Compared to synthetic polymer fibers, lotus root fiber microfibers exhibit superior biofriendliness and biodegradability. Their mechanical properties and flexibility also surpass those of other common natural fibers. The interior of lotus root fiber microfibers is rich in cellulose, which contains functional groups such as hydroxyl or amino groups, allowing it to interact with metal ions (e.g., Mn) through electrostatic interactions. 2+ Fe 3+ Co 2+ Ni 2+ and Cu 2+The interaction between the fibers and other components transforms them into flexible carrier fibers. This interaction provides lotus root fiber microfibers with a flexible matrix structure and surface active sites, offering potential application prospects.

[0076] 2. Lotus root fiber microfibers possess excellent optical waveguide properties. Their uniform diameter, smooth surface, and near-absence of optical apertures make them an extremely suitable optical waveguide material. Their active waveguide loss is only 0.051 dB / μm, lower than the loss level (0.1 dB / μm) of commonly used materials in the field of biosensor waveguides. Furthermore, lotus root fiber microfibers can not only generate low-loss active waveguides but also realize passive waveguides in other visible light ranges. Experiments have shown that within lotus root fiber microfibers, the passive waveguide loss for blue light is 0.160 dB / μm, for green light it is 0.144 dB / μm, and for red light it is 0.138 dB / μm. This indicates that lotus root fiber microfibers can effectively transmit optical signals in the visible light region.

[0077] 3. Compared to existing preparation processes, this invention employs a unique chemical-assisted physical separation method. In this process, the commonly used chemical reagent is sodium hydroxide solution. Lotus root fibers are placed in the sodium hydroxide solution (chemical assistance), washed with deionized water, and then separated into microfibers through microscopic manipulation (physical separation). Compared to traditional preparation processes, this method offers numerous advantages, eliminating the need for complex and cumbersome steps and achieving a highly stable yield.

[0078] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing lotus root fiber micro-optical fibers, characterized in that, Includes the following steps: The lotus root is cut horizontally, and the lotus root fibers are extracted from the cross-section of the lotus root. The extraction is carried out at a uniform speed of 5-15 cm / s. The obtained lotus root fibers are soaked in an inorganic strong alkaline solution for alkali treatment to obtain alkali-treated lotus root fibers. After the alkali-treated lotus root filament bundle is washed with water, it is fixed to the fiber optic adjustment frame with double-sided tape for separation to obtain lotus root filament microfibers. The separation is carried out by using two fiber optic adjustment frames to insert two tapered optical fibers into the same gap of the lotus root filament bundle. The fiber optic adjustment frames are gradually adjusted to make the tapered optical fibers penetrate deeper into the lotus root filament bundle. During the insertion process, force is applied and concentrated on the thicker part of the tapered optical fiber to help separate other fibers in the lotus root filament bundle. The diameter of the lotus root fiber microfiber is 3~6 µm.

2. The preparation method according to claim 1, characterized in that, The extraction direction is perpendicular to the cross-section of the lotus root.

3. The preparation method according to claim 1, characterized in that, The inorganic strong alkali solution is an aqueous solution of sodium hydroxide.

4. The preparation method according to claim 1 or 3, characterized in that, The mass concentration of the inorganic strong alkali solution is 15~25 g / L.

5. The preparation method according to claim 1 or 3, characterized in that, The alkali treatment was performed at room temperature for 1-2 hours.

6. The lotus root fiber microfiber obtained by the preparation method according to any one of claims 1 to 5, characterized in that, The length of the lotus root fiber microfiber is ≥600 µm.

7. The application of the lotus root fiber microfiber as described in claim 6 as a waveguide material.

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