Surface-modified side-emitting optical fiber

Abstract

The modified side-emitting optical fiber includes a core containing optical fiber and a UV-C transparent polymer coating on the core. The UV-C transparent polymer coating has an average surface roughness in the range of about 0.3 μm to about 0.7 μm, as measured by root-mean-square distance difference measurements of the surface of the UV-C transparent polymer coating. Fabricating the modified side-emitting optical fiber includes contacting the coated optical fiber with a solvent, where the coated optical fiber includes a UV-C transparent polymer coating, and dissolving at least a portion of the UV-C transparent polymer coating in the solvent to obtain the modified side-emitting optical fiber, where the UV-C transparent polymer coating has an average surface roughness in the range of about 0.3 μm to about 0.7 μm.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Patent Application No. 63 / 424,195, filed November 10, 2022, which is incorporated herein by reference in its entirety. Government Support Statement

[0002] This invention was made with government support under award number 1449500 from the National Science Foundation (NSF) and award number 80NSSC21C0034 from the National Aeronautics and Space Administration (NASA). The government has certain rights in this invention. [Background technology]

[0003] The present invention relates to a side-emitting optical fiber with a modified surface for use in germicidal ultraviolet-C (UV-C) disinfection. Summary of the Invention [Problem to be solved by the invention]

[0004] Germicidal ultraviolet-C (UV-C) disinfection is a widely used technology, typically achieved using mercury lamps, which have several drawbacks. Light-emitting diodes (LEDs) are mercury-free, and advances over the past decade have improved their efficiency in the UV-C range. A contemporary limitation of LEDs is their relatively small and limited irradiance area per chip, limiting the area or zone over which they can disinfect microorganisms in water or surface biofilms. [Means for solving the problem]

[0005] A low-cost, scalable fabrication method is described for flexible glass optical fibers with ultraviolet-C (UV-C) transparent polymer coatings, with core diameters ranging from approximately 125 μm to approximately 1500 μm, that enable side-emission of germicidal light into air or water along the fiber length. Optical fibers that emit light along their length are fabricated by partially dissolving away the UV-C transparent polymer coating that covers the optical fiber core. The partial dissolution of the polymer coating creates a textured or roughened surface that facilitates side-emission of light from the optical fiber core. The optical fiber design facilitates the use of UV-LED-based light for disinfection, oxidation, or other purposes. The size and flexibility of side-emitting optical fibers (SEOFs) enable germicidal UV-C irradiation in hard-to-reach areas where microbial growth frequently occurs.

[0006] While the disclosed inventive concepts include those defined in the appended claims, it is to be understood that the inventive concepts may also be defined according to the following embodiments.

[0007] Embodiment 1 is a core containing an optical fiber; and Contains a UV-C transparent polymer coating on the core The modified side emitting optical fiber includes a UV-C transparent polymer coating having an average surface roughness in the range of about 0.3 μm to about 0.7 μm as measured by root mean square distance difference measurements of the surface of the UV-C transparent polymer coating.

[0008] Embodiment 2 is 10. The modified side-emitting optical fiber of embodiment 1, wherein the optical fiber comprises glass or quartz.

[0009] Embodiment 3 is 3. The modified side-emitting optical fiber of embodiment 1 or 2, wherein the core has a diameter in the range of about 125 μm to about 1500 μm.

[0010] Embodiment 4 is The optical fiber is the modified side emitting optical fiber of any one of embodiments 1 to 3, having a refractive index in the range of about 1.4 to about 1.6.

[0011] Embodiment 5 is The optical fiber is the modified side-emitting optical fiber of any one of embodiments 1-4, having a numerical aperture in the range of about 0.1 to about 0.5.

[0012] Embodiment 6 is 6. The modified side emitting optical fiber of any one of embodiments 1-5, wherein the UV-C transparent polymer coating has a thickness before modification in the range of about 5 μm to about 50 μm.

[0013] Embodiment 7 is 7. The modified side-emitting optical fiber of any one of embodiments 1-6, wherein the UV-C transparent polymer coating comprises a fluorinated polymer.

[0014] Embodiment 8 is 8. The modified side-emitting optical fiber of any one of embodiments 1-7, wherein the UV-C transparent polymer coating comprises nanoparticles having a diameter in the range of about 100 nm to about 500 nm.

[0015] Embodiment 9 is 9. The modified side-emitting optical fiber of embodiment 8, wherein the nanoparticles comprise silicon, silica oxide, gold, silver, other metals, or other metal oxides.

[0016] Embodiment 10 is 10. The modified side-emitting optical fiber of embodiment 9, wherein the nanoparticles are functionalized with aminated organic compounds, carboxylated organic compounds, or neutral organic ligands.

[0017] Embodiment 11 is A method for making a modified side-emitting optical fiber, comprising: contacting a coated optical fiber with a solvent, wherein the coated optical fiber comprises a UV-C transparent polymer coating; and dissolving at least a portion of the UV-C transparent polymer coating in the solvent to obtain a modified side-emitting optical fiber, wherein the UV-C transparent polymer coating has an average surface roughness in the range of about 0.3 μm to about 0.7 μm.

[0018] Embodiment 12 is 12. The method of embodiment 11, wherein said average surface roughness corresponds to the root mean square of distance difference measurements on the surface of the UV-C transparent polymer coating.

[0019] Embodiment 13 is 13. The method of embodiment 11 or 12, wherein the solvent comprises an organic solvent.

[0020] Embodiment 14 is 14. The method of embodiment 13, wherein the organic solvent comprises a fluorinated organic solvent.

[0021] Embodiment 15 is 15. The method of embodiment 14, wherein the fluorinated organic solvent comprises perfluorotributylamine.

[0022] The details of one or more embodiments of the presently disclosed subject matter are set forth in the accompanying drawings and description. Other features, aspects, and advantages of the subject matter will become apparent from the description, drawings, and claims. [Brief explanation of the drawings]

[0023] [Figure 1] 1 shows a portion of a side-emitting optical fiber (SEOF) optically connected to a light-emitting diode (LED). [Figure 2] Figure 1 shows the surface roughness of a glass optical fiber coated with a UV-C transparent polymer by varying the duration of treatment with perfluorotributylamine. [Figure 3] 1 shows the integrated light intensity along a glass optical fiber by varying the duration of perfluorotributylamine treatment. [Figure 4] 1 shows the results of load tests to mechanical failure for a control optical fiber and optical fibers with low, medium, and high roughness. [Figure 5] The table shows the minimum allowable diameter when bending optical fibers having low, medium, and high surface roughness. [Figure 6] Zones of inhibition of P. aeruginosa surrounding the control and modified SEOFs are shown. [Figure 7] 1 shows the feedwater concentrations for each day of the biofilm inhibition experiment in the pipeline system. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present disclosure relates to ultraviolet-C (UV-C) side-emitting optical fibers (SEOFs) for use in biofilm control and microbial inactivation in water or air. The exterior surface of a UV-C transparent polymer coating on an optical glass fiber can be chemically and / or mechanically modified (e.g., etched, textured, roughened) to induce light scattering along the length of the fiber. The manufacturing process for creating modified side-emitting optical fibers can be tailored to induce different levels of side emission of UV-C light. In some cases, this surface modification can be achieved during manufacturing. In other cases, this surface modification is achieved by partial removal of a polymer uniformly coated on the optical fiber.

[0025] The transmission and reflection of light between two different media (e.g., an optical fiber and an outer polymer layer) is affected by the refractive index (RI) of the environment and the angle of incidence at the interface. The UV-C transparent polymer CYTOP® used in the fiber has a refractive index (RI) of 1.34, which corresponds to a critical angle (θc) of 48° for total internal reflection (TIR) ​​according to Snell's law. Therefore, when the angle of incidence (θ) is between 0° (normal to the surface) and 48°, all light rays from within the optical fiber into the CYTOP® layer can be side-emitted. When the polymer layer is uniform, only a portion of the light can be side-emitted.

[0026] Modifying the surface of the outer polymer layer changes the refraction angle of light in the polymer coating, leading to side-emission of UV-C light along the length of the fiber. Light rays that would nominally undergo total internal reflection (TIR) ​​can interact with portions of the boundary altered by surface roughness, causing θ<θc, thus causing a change in the direction of the reflected light rays that can lead to transmission out of the fiber and further transmission through the boundary. Figure 1 shows a portion of a side-emitting optical fiber 100 having a core 102 and a UV-C transparent polymer coating 104 on the core. The degree of surface modification of the polymer is a tunable parameter that can be varied to adjust the amount of UV-C light side-emitted from the fiber.

[0027] As described herein, the optical fiber core (e.g., glass or quartz) is typically coated with a flexible, UV-C transparent polymer. Suitable examples of these polymer materials include fluorinated polymers (e.g., CYTOP®). The optical fiber core diameter typically ranges from about 125 μm to about 1500 μm, the optical fiber refractive index typically ranges from about 1.4 to about 1.6, and its numerical aperture typically ranges from about 0.1 to about 0.5. In some examples, the thickness of the polymer coating before modification ranges from about 5 μm to about 50 μm. The polymer protects the side-emitting optical fiber from physical damage and allows it to bend (i.e., maintains its strength).

[0028] The polymer-coated optical fiber can be contacted with a solvent to partially dissolve the polymer coating and produce a modified (e.g., roughened) surface layer. In some examples, suitable solvents for partially dissolving the polymer include organic solvents (e.g., perfluorotributylamine, perfluoro-N-isopropylmorpholine, perfluoro-1,2-dimethylcyclohexane, or perfluorodecalin). In some examples, perfluorotributylamine is used to partially dissolve the polymer. The contact time for the polymer-coated optical fiber and solvent is typically up to about 5 hours. Figure 2 shows the surface roughness of a 500 μm optical fiber by varying the duration of treatment with perfluorotributylamine. Varying the contact time with the solvent at different locations along the optical fiber can result in an optical fiber with varying roughness along its length.

[0029] Surface-modified UV-C side-emitting optical fibers can be fabricated to include nanoparticles in a polymer coating to facilitate light scattering along the length of the fiber. Suitable nanoparticle materials include silicon, silica oxide, gold, silver, or other metals or metal oxides. These materials can be functionalized with aminated organic compounds to generate a cationic surface charge, carboxylated organic compounds to generate an anionic surface charge, or neutral organic compounds. The nanoparticles can have diameters ranging from about 100 nm to about 500 nm.

[0030] Mechanical testing confirmed the ability of the roughened optical fiber to maintain the desired flexibility and mechanical strength of the roughened UV-C polymer-coated optical fiber. Surface roughness was calculated using pixelated data with spatial subnanometer-scale resolution collected with an optical profilometer by taking the root-mean-square of distance difference measurements for hundreds of data points collected at multiple locations on the fiber surface of the modified UV-C transparent polymer coating and the control (unmodified polymer-coated fiber). In some examples, side-emitting optical fibers had average surface roughness ranging from approximately 0.3 μm to approximately 0.7 μm after contact with solvent. Accompanying data collected by scanning electron microscopy (SEM) confirmed the optical profilometer data, demonstrating that the surface modification altered the surface roughness. By varying the solvent contact time at different locations along the optical fiber, optical fibers with varying roughness along their length can be obtained.

[0031] Herein, we disclose a "subtractive engineering" approach in which the surface roughness of the outer CYTOP® polymer layer of a SEOF is created through partial removal of the outer CYTOP® polymer coating. This is achieved by exposing the SEOF to a solvent that dissolves the CYTOP® polymer (see Experiment 1), generating surface roughness. The degree of surface roughness was controlled by exposing the SEOF to the solvent (e.g., perfluorotributylamine) for various treatment times. Longer treatment times in the solvent resulted in greater "unevenness" or "roughness" on the outer polymer layer, with surface roughness values ​​increasing from 0.3 μm to 0.6 μm or greater. The resulting surface changes were monitored using SEM and optical profilometer measurements and quantified as a surface roughness parameter (SR, see Example 5).

[0032] The original coating had a very low SR value of 0.3 ± 0.02 μm, which is consistent with online optical measurements performed on a draw tower. Treating the SEOF in solvent for different times increased the SR value up to 0.65 ± 0.03 μm, producing a rougher surface (Figure 2).

[0033] The control SEOF was 124 ± 6 μW / cm at the proximal end. 2 is emitted from the side, and 8±2μW / cm at the end 2 From the as-received unmodified (control) fiber (SR = 0.3 ± 0.02 μm) to the fiber exposed to solvent for the longest duration (SR ~ 0.6 μm), the light irradiance at the proximal end was 147 ± 6 μW / cm 2 to 610±120μW / cm 2 11±0.8μW / cm at the end 2 to 57±11μW / cm 2 The surface roughness thus positively affected the UV-C light emitted from the SEOF. The side emission reached a plateau when the SR exceeded 0.5 μm, and further increases in roughness did not significantly enhance the side emission (Figure 3). Based on the observed increase in side emission at each SR value, we define "low SR" herein as approximately 0.3 to approximately 0.4 μm, "medium SR" herein as approximately 0.4 to approximately 0.5 μm, and "high SR" herein as a roughness greater than approximately 0.5 μm, to achieve variable (i.e., tunable) irradiance of the side-emitted light for different subtractively engineered SEOFs. Overall, we found that the side emission increased by at least fivefold at any location along the fiber after solvent treatment.

[0034] Before solvent treatment, a uniform CYTOP® layer with a thickness of 15 μm was observed, but varying the dissolution time resulted in less and less polymer remaining on the fiber. After 5 hours of treatment, the polymer layer was completely dissolved in perfluorotributylamine.

[0035] Based on the increased side-emission intensity, a higher SR is desirable. However, modified SEOFs with a high SR are physically more brittle and less flexible. Tensile tests were performed on each fiber to measure the effect of surface roughness on tensile strength. Figure 4 shows the tensile load-elongation response of the fiber up to the breaking load. The nominal tensile strength was calculated using a 500 μm diameter by pulling the two ends of the fiber axially, using an axial force to break the fiber. The as-received fiber with a uniform polymer coating had a tensile strength of 750 MPa. SEOFs with SRs ranging from 0.35 μm to 0.5 μm showed a degradation in strength to 540 MPa and 650 MPa, respectively. For the two most brittle samples, no statistically significant difference in tensile strength was observed between the higher thickness and bare glass fiber without polymer. To correlate the tensile strength and allowable compliance of fibers bent in a tube, flexibility measurements were performed by sequentially bending fibers with SEOFs of different SR values ​​around circular mandrels of various sizes. Higher bending capacity was observed with higher curvatures. SEOFs with SRs in the range of 0.35 μm to 0.5 μm met the criterion of an average curvature of 0.1–0.2 mm−1, which is sufficient for installation in almost all water systems. Further increases in roughness reduced flexibility until there was no statistical difference across the bare glass fiber diameter tolerance range. Overall, the introduction of low or medium SR (SR < 0.5 μm) on polymer-coated fibers increased side radiation while maintaining flexibility. The flexibility of the modified SEOFs (i.e., the ability to bend around a curve with a 1 cm radius) makes them suitable for many water applications (i.e., bends in domestic plumbing and inside POU reactors).

[0036] When bacteria were subjected to UV-C stress from the SEOF, biofilm formation was inhibited, resulting in an "inhibition zone" (see Example 6). An unmodified (control) SEOF was placed 0.5 cm above a biofilm on an agar plate inoculated with P. aeruginosa, and overnight (12 hours) UV-C exposure resulted in a 0.5 cm-wide inhibition zone. The same experiment was performed using fibers with SEOFs with varying SR values ​​(solvent treatment times). Two situations were compared: 1) varying the polymer subtraction (solvent treatment) time with the same UV-C exposure time, and 2) varying the UV-C exposure with the same polymer subtraction (solvent treatment) time. As shown in Figure 6, the inhibition zone of P. aeruginosa biofilm obtained from the tunable side radiation from the SEOF significantly increased compared to the control.

[0037] To demonstrate that SR-modified fibers are flexible enough to be used in narrow geometries and perform better than unmodified fibers in controlling biofilms, a recirculating pipe loop experiment was conducted (see Example 7). Five parallel pipelines, each 1 meter long and with two 180° bends (bend diameter = 10 cm), were installed on a peg boat. A SEOF was inserted into each pipeline. The light intensity from the SEOFs was measured as they were bent within the pipe. Light measurements were made through 3 cm holes located every 10 cm along the pipeline, allowing the radiometer access to the interior of the pipe. There was less side radiation at the bends than along the straight sections of the SEOF. Two dark controls were included: one without an SEOF and the other without an LED. One reactor was equipped with as-received coated optical fiber (SR = 0.3 μm) and emitted 10 μW / cm along the first 30 cm of its length. 2 Over 3 μW / cm between 30 cm and 100 cm 2 Next, there were two replicate systems with SEOFs with medium SR, which provided side emission that was over 10 times higher and significantly more uniform than the as-received fiber; the side emission was 55 ± 7.5 μW / cm at the proximal end. 2 , 25±2.5μW / cm at the end 2The distance between the optical fiber and the inner surface of the pipeline ranged from about 0 to about 0.5 cm.

[0038] To grow biofilms at high and low bacterial densities, the initial feedwater concentration was set at 10 3.9 ±0.07 CFU / mL and 10 5.9 Two separate experiments were performed with a concentration of P. aeruginosa of ±0.1 CFU / mL. The P. aeruginosa concentrations in the feedwater during the 6 days of recirculation for these two experiments are shown in Figure 7. Without UV-C exposure, the dark control tubes contained a uniform concentration of ~800 CFU / cm. 2 Biofilm (10 2.9 ±0.12CFU / cm 2 ) was produced. In the reactor equipped with fiber without SR modification (SR = 0.3 μm), the calculated wall irradiance was ~4.5 μW / cm 2 For the first 20 cm of the pipe, biofilm was below the EPA recommended limit of 100 CFU / cm. 2 However, between 20 and 100 cm of the piping in the same reactor, there were 100-800 CFU / cm along the length. 2 was measured. There was no statistical difference between biofilm formation at the end of the reactor equipped with fibers without SR modification and the dark control. In both replicate piping systems with surface-modified SEOF, biofilm densities measured at all locations were ~10 CFU / cm. 2 (10 0.68 ±0.5CFU / cm 2 ), which was below the EPA-recommended level. Overall, the calculated 275 nm irradiance at the wetted surface of the tube wall was 4.5 μW / cm 2 At 1000 kJ / kg, viable bacteria in the biofilm were approximately 2 logs lower.

[0039] The rate of biofilm formation and growth or accumulation may be related to the level of planktonic bacteria in the water flowing through the piping system. To control microbial growth on surfaces, the rate of UV-C inhibition was expected to be greater than the rate of biofilm growth. Therefore, higher Pseudomonas aeruginosa planktonic levels (10 in recirculation) were associated with5 A second set of pipe loop tests was conducted using feedwater containing plankton levels of >10 CFU / mL. The same as-received and surface-modified fibers were used. Biofilm growth in the dark control (10 CFU / mL) was observed using this feedwater with plankton levels of >10 CFU / mL. 4.3 ±0.1CFU / cm 2 ) was higher. All three reactors with surface-modified SEOFs had lower biofilm densities compared to the control reactor, following the same trend observed at low P. aeruginosa plankton levels. 2 When >4.5 μW / cm was delivered, biofilm densities >1 log lower were observed in any reactor. 2 However, SEOF was similar to experiments with lower P. aeruginosa plankton levels (i.e., 100 CFU / cm). 2 (less than 100%) did not inhibit biofilm growth.

[0040] To integrate data from the two pipe loop studies, the logarithmic reduction in viable biofilm density due to UV-C (compared to unirradiated controls) was combined across all experiments. The resulting trend was observed from the SEOF to the pipe wall at 10 μW / cm. 2 Super~20μW / cm 2 showed that delivering UV-C irradiance to a surface of aquatic life resulted in a greater than 1-log reduction in biofilm growth compared to controls. This finding is particularly relevant to continuous recirculation systems, suggesting that higher UV-C irradiance levels may be required to maintain sufficient inactivation rates relative to the net growth rate of planktonic bacterial communities capable of continuous surface deposition.

[0041] Example Example 1. Preparation and surface modification of SEOF A custom solarized silica optical fiber with a core diameter of 500 μm was manufactured at Molex (AZ, USA) with the following characteristics: core refractive index 1.51, numerical aperture 0.39. A smooth 15 μm-thick CYTOP® polymer layer (BELLEX International Crop, Wilmington, DE) was coated onto the fiber using a commercial optical fiber draw tower (Polymicro / Molex), resulting in an outer fiber diameter of 528 ± 0.63 μm. To tailor the surface roughness, 15 solvents were evaluated for their ability to gradually dissolve the CYTOP® layer and produce a roughened surface. Of these, the fluorinated solvent perfluorotributylamine (ThermoFisher, A19126) was preferred. This solvent could be substituted with other perfluorinated chemicals (i.e., perfluoro-N-isopropylmorpholine, perfluoro-1,2-dimethylcyclohexane, perfluorodecalin). The SEOF was immersed in the solvent for 0–5 h at 30-min intervals. The fiber was cut into 30 cm or 1 m lengths using a fiber cleaver (Vytran Fiber Cleaver, Thorlabs, NJ), and a uniform, clean surface was confirmed using an inspection microscope (FS201, 200X, Thorlabs, NJ). The SEOF was assembled into SMA905 connectors and connected to an 80 mW UV-C LED driver (PearlLab Beam, AquiSense Technologies, Kentucky, USA) at 1 mm intervals. The UV-C LED module included a small fan and heat sink behind the LED to dissipate heat.

[0042] Example 2. Flexibility Measurement, Method A To quantify the flexibility of the SEOF due to varying surface roughness, tensile tests were conducted on the modified SEOF. Thirty-cm SEOFs with varying solvent treatment times were mounted on an MTS810 load frame and an MTS Exceed 42.503 load frame (MTS Headquarters, MN, USA). The SEOF was designed to conform to any curved surface, even when the light from the UV lamp or LED chip was difficult to reach. Tensile strength tests were conducted under a constant strain rate via two grips on either side of the fiber. The stress (force, N) required to pull the fiber out and the diameter (cm) required to bend the fiber into a circle until the sample broke were collected and compared for different treatments. The force required for peeling to break was equal to the stress required for bending to break.

[0043] Example 3. Flexibility Measurement, Method B To quantify the flexibility of the SEOFs with varying surface roughness, tensile tests were conducted on the modified SEOFs. 15 cm SEOFs with varying solvent treatment times were clamped on an MTS810 load frame and an MTS Exceed 42.503 load frame (MTS Headquarters, MN, USA). Tests were conducted under a constant strain rate via two grips on either side of the fiber. The tensile strength (MPa) required to pull the fiber apart and the curvature (mm) required to bend the fiber into a circular shape until the sample broke were determined. -1 ) were collected and compared for different treatments (Figure 5). Higher bending capacity was evidenced by higher curvature.

[0044] Example 4. Light Measurement and Attenuation Model The optical irradiance (μW / cm) emitted from the LED, launched into the fiber, side-emitted from the surface of the SEOF, or exiting the end of the fiber 2) was measured by an optical spectrophotoradiometer (AvaSpec-2048L, Avantes, CO). Measurements along the length of the fiber or distance measurements perpendicular to the fiber surface were recorded. Measurements were performed on the as-fabricated fiber and on fibers with different reductions in surface roughness modification. The UV-C dose at the surface was calculated using Equation 1: UV-C dose (mJ / cm 2 ) = light intensity (mW / cm 2 ) x time (sec) (1) The light intensity perpendicular to the SEOF is the actual light intensity irradiated on the surface. Light attenuates in air according to the Beer-Lambert law, which shows an exponential decrease with distance. The light intensity at 0.5cm, 1cm, 1.5cm, and 2cm from each fiber was measured by a radiometer. Based on these measurements, a mathematical model was developed according to Eq. I (μW / cm 2 )=I0e -kd (2) Here, I (μW / cm 2 ) is the light intensity at a distance d (cm) perpendicular to the SEOF, I0 (μW / cm 2 ) is the light intensity measured on the SEOF surface, k(cm -1 ) is the damping coefficient. The cumulative power (mW) radiated along the SEOF was calculated using Equation 3:

number

[0045] Example 5. Surface morphology measurement Cross sections of SEOFs with and without surface modification were imaged using a scanning electron microscope (SEM) (FEI Philips XL-30, Eindhovem, The Netherlands) to observe changes in the CYTOP® layer. Before testing at 10 kV, the samples were fixed with graphite adhesive and coated with carbon. The surface roughness was further quantified using an optical profilometer (Zygo ZeScope). SEOFs treated with solvents for 0, 1, 2, 3, 4, and 5 hours were selected. A 50x objective lens combined with a 1.25x magnification changer was used for optimal visualization of the fiber surface. At least three measurements were taken along the length of each fiber sample, resulting in a 100 μm × 50 μm three-dimensional image for each measurement. The root mean square roughness (Rrms) of the surface was then reported to compare the surface roughness between samples. Figure 2 shows the surface roughness of a 500 μm optical fiber treated with perfluorotributylamine for varying durations. To measure the changes in functional groups associated with the CYTOP® layer before and after surface roughness modification, an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometer (IFS 66v / S, Bruker Instruments, Billerica, MA, USA) was used. The spectrometer was equipped with a diamond crystal at a 45° angle, and an average of 64 scans was collected per scan during the measurement process.

[0046] Example 6. UV-C exposure and zone of inhibition analysis First, P. aeruginosa (ATCC 15692) was cultured overnight at 37°C in LB medium (see Table 1). Then, 1 ml of the suspension was transferred to 25 ml of fresh LB medium, and approximately 10 9 The suspension was incubated at 37°C until it reached an optical density of 1 cm-1, indicating a bacterial concentration of CFU / mL. The suspension was diluted 100-fold with phosphate-buffered saline (PBS) solution (see Table 1) and diluted 10 7After obtaining CFU / mL cultures, they were plated on gridded square LB agar plates. The intention was to create a thick layer of cells to represent a biofilm. The SEOF was placed in the center of the Petri dish, with a distance of approximately 0.5 cm between the SEOF and the surface. Immediately after cell plating, UV-C exposure was applied for 1, 2, or 3 hours using the surface-modified SEOF.

[0047] After UV-C irradiation, the fibers were removed, and the plates were incubated at 37°C for 12 hours. The distance between the two border edges, centered on the location of the SEOF, where no biofilm grew was designated the inhibition zone. The light irradiance at the edge was calculated using Equation 2 and correlated with the inhibition zone (cm) to determine the UV-C dose required for biofilm control on the nutrient-rich agar surface. In addition, three controls were performed: 1) an inoculated agar surface without an SEOF; 2) an inoculated agar surface with an unmodified SEOF inserted and no UV-C exposure; and 3) an inoculated agar surface with an unmodified SEOF inserted and overnight UV-C exposure. Triplicate data were obtained using three different optical fibers on three different agar plates.

[0048] Example 7. Biofilm inhibition experiments in water using flexible plastic tubing reactors A feedwater storage reactor (4 L) containing 0.1X M9 medium (see Table 1) was spiked with P. aeruginosa. The initial feedwater concentration was adjusted to 10 to 10% for biofilm growth at high and low bacterial densities, respectively. 3.9 ±0.07 CFU / mL and 10 5.9Two separate experiments were conducted, with a mean concentration of ±0.1 CFU / mL. The feedwater P. aeruginosa concentrations during 6 days of recirculation for these two experiments are shown in Figure 7. Because the size of typical residential POU piping (i.e., water heaters, bathroom / kitchen sinks) ranges from 0.5 cm to 1.9 cm, a 1 cm piping size was chosen. A single pump continuously recirculated feedwater through five parallel tube reactors (1 cm diameter, 1 m long, polypropylene). Polypropylene was chosen because it is commonly used for residential POU piping. A needle valve controlled the flow rate through each tube reactor, which was set to 200 mL / min and monitored by an in-line flow meter. Each 1-meter-long polypropylene tube reactor contained two 180° bends to simulate potential realistic POU applications where a flexible self-extracting electron microscope (SEOF) may be more suitable than a single point light source. The SEOF was inserted into the tube reactor.

[0049] There were five parallel tube reactors: 1) one control without SEOFs, 2) one control with SEOFs that were not irradiated (i.e., without LEDs), 3) one unmodified SEOF connected to LEDs to represent low UV-C dose conditions; 4) and 5) were identical replicates with two medium-roughness modified SEOFs connected to LEDs to represent high UV-C dose conditions. Experiments were conducted over 1-7 days with continuous water flow through the tube reactors. At the end of each experiment, a 1-m section of tubing was removed from the quick-disconnects and cut into 10 equal-length coupons (3 cm) at 10 cm intervals using a sterile razor. Each coupon was sonicated separately for 15 min to transfer the biofilm from the surface into a phosphate-buffered saline (PBS) solution. The transferred bacteria were cultured and quantified on LB agar plates, and the data were used to calculate the biofilm density (CFU / cm) on a 3 cm section of piping. 2 ) was used to calculate

[0050] Table 1: Characteristics of LB broth, M9 medium, and PBS solution [Table 1]

[0051] While the present disclosure includes details of many specific embodiments, these should not be construed as limitations on the scope of the subject matter or what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this disclosure in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although the foregoing features may be described as acting in particular combinations, and even if originally claimed as such, one or more features from a claimed combination may, in some cases, be removed from that combination, and the claimed combination may be directed to a subcombination or variations of the subcombination.

[0052] Specific embodiments of the subject matter have been described. Other embodiments, modifications, and permutations of the described embodiments, as will be apparent to those skilled in the art, are within the scope of the following claims. Although the figures or claims depict operations in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or sequentially, or that all of the illustrated operations be performed (although some operations may be considered optional) to achieve desirable results.

[0053] Therefore, the example embodiments set forth above do not define or limit the present disclosure, and other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0054] 100 Side-emitting optical fiber 102 cores 104 UV-C transparent polymer coating θ angle of incidence θc critical angle

Claims

1. a core containing an optical fiber; and a modified side emitting optical fiber comprising a UV-C transparent polymer coating on said core; The modified side emitting optical fiber, wherein the average surface roughness of the UV-C transparent polymer coating ranges from about 0.3 μm to about 0.7 μm as measured by root mean square distance difference measurements of the surface of the UV-C transparent polymer coating.

2. 10. The modified side-emitting optical fiber of claim 1, wherein the optical fiber comprises glass or quartz.

3. 10. The modified side-emitting optical fiber of claim 1, wherein said core has a diameter ranging from about 125 μm to about 1500 μm.

4. 10. The modified side emitting optical fiber of claim 1, wherein said optical fiber has a refractive index ranging from about 1.4 to about 1.

6.

5. 10. The modified side-emitting optical fiber of claim 1, wherein said optical fiber has a numerical aperture in the range of about 0.1 to about 0.

5.

6. 10. The modified side emitting optical fiber of claim 1, wherein the UV-C transparent polymer coating has a thickness before modification in the range of about 5 μm to about 50 μm.

7. 10. The modified side emitting optical fiber of claim 1, wherein said UV-C transparent polymer coating comprises a fluorinated polymer.

8. 10. The modified side-emitting optical fiber of claim 1, wherein the UV-C transparent polymer coating comprises nanoparticles having a diameter ranging from about 100 nm to about 500 nm.

9. 9. The modified side-emitting optical fiber of claim 8, wherein the nanoparticles comprise silicon, silica oxide, gold, silver, other metals, or other metal oxides.

10. 10. The modified side-emitting optical fiber of claim 9, wherein the nanoparticles are functionalized with aminated organic compounds, carboxylated organic compounds, or neutral organic ligands.

11. contacting the coated optical fiber with a solvent, wherein the coated optical fiber comprises a UV-C transparent polymer coating; dissolving at least a portion of the UV-C transparent polymer coating in the solvent to obtain a modified side-emitting optical fiber, wherein the UV-C transparent polymer coating has an average surface roughness in the range of about 0.3 μm to about 0.7 μm; 1. A method for making a modified side-emitting optical fiber, comprising:

12. 12. The method of claim 11, wherein the average surface roughness corresponds to the root mean square of distance difference measurements on the surface of the UV-C transparent polymer coating.

13. The method of claim 11 , wherein the solvent comprises an organic solvent.

14. The method of claim 13 , wherein the organic solvent comprises a fluorinated organic solvent.

15. 15. The method of claim 14, wherein the fluorinated organic solvent comprises perfluorotributylamine.

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