Superfine non-contact body temperature interference resistant optical fiber protection tube

Abstract

The invention relates to a superfine non-contact body temperature interference resistant optical fiber protection tube which is of a circular hollow coaxial structure and sequentially comprises an inner heat insulation layer, a middle toughness enhancement layer and an outer biocompatible layer from inside to outside. And an inner cavity of the inner heat insulation layer is filled with a heat insulation medium. The optical fiber protection tube disclosed by the invention is accurate and adaptive in size, excellent in heat insulation performance, reliable in mechanical stability, compliant in biocompatibility and high in industrialization feasibility, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of superfine optical fiber endoscopic imaging, and particularly relates to a superfine non-contact antibody temperature interference resistant optical fiber protection tube. BACKGROUND

[0002] As an important direction of current biomedical optics for early lung cancer and gastrointestinal microtumor lesion precise diagnosis, the imaging system core transmission element of superfine optical fiber endoscopic imaging is a multimode optical fiber with a diameter of about 280 μm. The optical fiber needs to enter the deep human tissue through a superfine biopsy channel with an inner diameter of not more than 0.8 mm, for example, the working channel of a baby bronchoscope is usually only 0.8-1.0 mm, to realize cell scale fluorescence and Raman double-mode imaging diagnosis. This application scenario puts forward more stringent comprehensive requirements for the structural design of the optical fiber protection tube. First, the protection tube needs to have an inner cavity diameter of about 300 μm to accommodate the optical fiber while reserving a gap of about 10 μm to avoid refractive index drift caused by heat conduction. Secondly, in the working environment, there is a temperature gradient between the human body temperature and the optical fiber system operating temperature, and this difference will cause significant optical response drift. According to research, at the wavelength of 1550 nm, the temperature sensitivity of the fiber Bragg grating is about 11.4 pm / ℃, and when the temperature changes by 2-3 ℃, the fluorescence signal peak position shift can reach 0.5 cm -1 The above, and the Raman signal intensity fluctuation can also exceed 10%, which will obviously interfere with the qualitative and quantitative analysis of the lesion. In addition, the protection tube also needs to maintain mechanical stability during the bending operation and tissue contact of the bronchoscope, and its structure should be able to prevent the optical fiber from colliding with the inner wall under a bending radius of less than 1 mm, so as to avoid additional contact heat transfer and optical loss of more than 0.5 dB, thereby maintaining the signal-to-noise ratio and resolution of the imaging system.

[0003] However, existing technologies still face significant limitations in the synergistic optimization of size adaptation, thermal insulation performance, and mechanical reliability. Traditional composite tube structures typically employ a three-layer combination of a polyimide insulation layer, a fluorosilicone rubber support layer, and a PEEK outer layer. While offering good thermal insulation and biocompatibility, their total outer diameter usually exceeds 1.0 mm, making it difficult to accommodate ultra-fine channel constraints. If the thickness of each layer is compressed to reduce the outer diameter, such as thinning the middle support material to below 100 μm, the support stiffness decreases significantly. Experiments show that under a bending radius of 1 mm, its plastic deformation rate can reach over 8%, failing to meet the structural toughness required for clinical operation. Non-contact thermal insulation designs also have performance limitations. While air-gap-based solutions avoid direct contact between the optical fiber and the tube wall, the convective heat transfer coefficient of air is approximately 0.026 W / (m·K), resulting in actual temperature fluctuations of around 0.8 ℃, which is insufficient to meet diagnostic accuracy requirements. Using low thermal conductivity materials (such as aramid aerogel) can reduce the thermal conductivity to 0.01-0.03 W / (m·K), but due to molding limitations, the minimum thickness is generally no less than 50 μm, and even after adding other functional layers, it still exceeds size constraints. Furthermore, existing optical fiber restraint structures lack effective radial stabilization mechanisms. Some solutions rely solely on annular protrusions less than 3 μm for restraint, with a radial stiffness of approximately 0.3 N / mm. Under vibration within the breathing frequency range (1-5 Hz), the radial displacement of the optical fiber can reach 5-8 μm, easily leading to accidental collisions with the tube wall. In addition, the commonly used epoxy resin end-capping process also introduces thermomechanical mismatch issues, as the coefficient of thermal expansion of epoxy resin is approximately 60 × 10⁻⁶. -6 / ℃, while optical fiber is only about 5×10 -6 / ℃, temperature changes can cause axial displacement to exceed 10 μm, thereby disrupting the original non-contact state.

[0004] In summary, the key challenge of current ultra-fine fiber optic endoscope systems lies in achieving a synergistic balance between compact structure, efficient thermal insulation, and mechanical stability at the micrometer scale. The fundamental difficulty lies in the unresolved optimization of the coupling between material properties and structural layout: if miniaturization is overemphasized, both support and thermal insulation performance are difficult to achieve simultaneously; if thermal and mechanical properties are enhanced, the problem of exceeding outer diameter limits restricts its usability in ultra-fine biopsy channels. The combined effect of material incompatibility and structural design constraints means that such systems have not yet fully met the clinical application needs for imaging lesions in minute cavities. Summary of the Invention

[0005] This invention provides an ultra-fine non-contact antibody temperature interference fiber optic protection tube, aiming to solve three core problems existing in the prior art: First, the outer diameter of traditional protection tubes is too large (≥1mm), which cannot be adapted to ultra-fine biopsy channels ≤0.8mm; second, excessive thinning of the wall thickness will lead to a decrease in heat insulation performance (temperature difference ≥0.8℃), which cannot suppress fiber refractive index drift caused by body temperature; third, the mechanical stability in the non-contact design is insufficient, and the fiber is prone to collision with the tube wall when bent, which affects the stability of imaging signal and increases the risk of light loss.

[0006] This invention provides an ultra-fine non-contact antibody temperature interference optical fiber protection tube. The protection tube has a circular hollow coaxial structure, consisting of an inner heat insulation layer, a middle toughness enhancement layer, and an outer biocompatible layer from the inside out. The inner cavity of the inner heat insulation layer is filled with a heat insulation medium.

[0007] Preferably, the substrate of the protective tube (inner heat insulation layer) is polyimide doped with hollow zirconia nanospheres.

[0008] More preferably, the hollow zirconium oxide nanospheres are modified with a silane coupling agent.

[0009] More preferably, the hollow zirconia nanospheres account for 30-40 wt% of the mass of the inner insulation layer.

[0010] Preferably, the inner wall of the inner insulation layer is provided with an integrally formed spiral rib, which surrounds the optical fiber and maintains a spacing of 3μm.

[0011] Preferably, the substrate of the intermediate toughness reinforcement layer is medical fluorosilicone rubber doped with hydroxylated boron nitride nanotubes.

[0012] More preferably, the hydroxylated boron nitride nanotubes account for 10-20 wt% of the mass of the intermediate toughness reinforcement layer.

[0013] Preferably, the substrate of the outer biocompatible layer is medical polyetheretherketone doped with graphene nanosheets.

[0014] More preferably, the graphene nanosheets are treated with oxygen plasma.

[0015] More preferably, the graphene nanosheets account for 1 to 10 wt% of the outer biocompatible layer.

[0016] Preferably, the heat insulation medium is medical-grade fluorosilicone oil.

[0017] Furthermore, the protective tube is provided with end fixing structures at both ends.

[0018] Preferably, the end fixing structure includes a shrinkage section, an annular protrusion, and a potting section.

[0019] Beneficial effects

[0020] (1) Precise size fit: This invention can directly pass through ultra-fine biopsy channels of ≤0.8mm, expanding the application scenarios of fiber optic endoscopy imaging in the diagnosis of lesions in small cavities.

[0021] (2) Excellent thermal insulation performance: The total thermal resistance of the triple thermal insulation structure formed by the inner thermal insulation layer, hollow zirconia nanospheres, and thermal insulation medium is 8.25×10. -4 m 2 • K / W, maximum fiber core temperature fluctuation ≤0.48℃ at 37℃, effectively suppressing refractive index drift and ensuring signal stability (peak position shift ≤0.2cm) -1 Intensity fluctuation ≤3%).

[0022] (3) Reliable mechanical stability: When the bending radius of the present invention is ≤1mm, there are no cracks or delamination after 10,000 cycles of bending, the maximum radial displacement of the optical fiber is ≤3.5μm, there is no risk of contact heat transfer, and the change in optical loss is ≤0.2dB.

[0023] (4) Biocompatibility compliance: All materials of this invention have passed ISO 10993 series certification, have a cell survival rate of ≥97.8%, are non-sensitizing and non-irritating, and meet the requirements for clinical in vivo use;

[0024] (5) High industrialization feasibility: The production of this invention is based on mature processes such as injection molding, extrusion, and laser welding. It can be mass-produced by simply adjusting the mold and parameters, and the conversion cycle is ≤5 months. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the cross-sectional structure of the protective tube of the present invention.

[0026] Figure 2 This is a schematic diagram of the longitudinal section structure of the protective tube of the present invention.

[0027] In this structure, A is the outer biocompatible layer, B is the middle toughness-enhancing layer, C is the inner thermal insulation layer, D is the thermal insulation medium, and E is the optical fiber. Detailed Implementation

[0028] Depend on Figure 1 and Figure 2 As shown, this invention constructs a three-layer composite optical fiber protection tube through a technical solution of "material performance enhancement + precise structural dimension matching," and designs multiple mechanical stabilization mechanisms, as detailed below:

[0029] (1) Overall structural design

[0030] The protective tube is a circular, hollow, coaxial structure, consisting of an inner thermal insulation layer, a middle toughness-enhancing layer, and an outer biocompatible layer, arranged from the inside out. The inner cavity of the thermal insulation layer is filled with a thermal insulation medium (achieving contactless heat transfer), and end-fixing structures are provided at both ends. Key dimensional parameters: total outer diameter 730μm (compatible with ≤0.8mm biopsy channels), total wall thickness 215μm (inner layer 35μm + middle layer 150μm + outer layer 30μm), inner cavity diameter 300μm (compatible with 280μm multimode optical fiber), and a uniform 10μm gap between the inner cavity and the optical fiber.

[0031] (2) Layered structure and material design

[0032] ① Inner thermal insulation layer: A polyimide (PI) substrate is used, doped with 30-40 wt% hollow zirconia nanospheres (80 nm particle size). The nanospheres are modified with a silane coupling agent to improve compatibility with the PI substrate. The inner layer is 35 μm thick, and the inner wall has an integrally formed spiral rib (150 μm pitch, 5 μm height, 8 μm width), maintaining a 3 μm gap between the spiral rib and the optical fiber surface. This layer forms a "micro-airbag thermal insulation array" through the hollow zirconia nanospheres to block heat conduction, while the spiral rib achieves radial restraint of the optical fiber, preventing contact heat transfer while limiting excessive displacement.

[0033] ② Middle layer for toughness reinforcement: Using medical-grade fluorosilicone rubber as the base material, 10-20 wt% of hydroxylated boron nitride nanotubes (50 nm in diameter, aspect ratio 50) are added. The middle layer is 150 μm thick. The mechanical properties are improved through the "fiber reinforcement effect" of the boron nitride nanotubes. The 150 μm thickness can achieve the bending toughness of traditional 250 μm thick fluorosilicone rubber. When bending, it absorbs extrusion stress and bending stress through elastic deformation.

[0034] ③ Outer biocompatible layer: Medical-grade PEEK substrate is selected, doped with 1-10 wt% graphene nanosheets (thickness 1-3 nm, sheet diameter 5 μm), and treated with oxygen plasma. The outer layer is 30 μm thick. The graphene nanosheets improve surface hardness and wear resistance, and the plasma treatment introduces hydroxyl groups to improve biocompatibility and reduce tissue adhesion.

[0035] ④ Thermal insulation medium: Medical-grade fluorosilicone oil with a viscosity of 1200 cSt, a refractive index of 1.38 (matching the refractive index of the optical fiber cladding of 1.45, with a difference ≤0.07), and a thermal conductivity of 0.08 W / (m・K) is used. It has the functions of thermal insulation, lubrication and optical signal transmission adaptation, and is filled in the inner cavity.

[0036] ⑤ End Fixation Structure: Includes a shrinkage section, annular protrusions, and a filling section. The shrinkage section is 2mm long and 650μm in outer diameter, facilitating insertion into the biopsy channel; the inner wall has 8 annular protrusions per circumference (6μm high, 100μm spacing), which are interference-fitted with the fiber coating (fit tolerance +2μm); the filling section is 2mm long and filled with medical UV-cured epoxy resin (curing shrinkage rate ≤0.4%), providing ≥4N axial fixation force to prevent fiber displacement during surgery.

[0037] (3) Mechanical stabilization mechanism

[0038] Non-contact mechanical stability is achieved through a triple mechanism of "fluid support + microstructure constraint + end fixation": ① Fluid support: 1200cSt high-viscosity fluorosilicone oil balances the radial displacement of the optical fiber through Stokes resistance, absorbs high-frequency vibrations of 1-5Hz (such as breathing motion), and avoids collision with the tube wall; ② Microstructure constraint: The radial stiffness of the inner spiral rib is 0.7N / mm, which limits the maximum radial displacement of the optical fiber to within 3.5μm, and the axial stiffness is 0.6N / mm, which allows for small axial sliding to release thermal stress; ③ End fixation: The interference fit of the annular protrusion and the epoxy resin potting work together to achieve stable axial fixation of the optical fiber.

[0039] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0040] Example 1

[0041] This embodiment provides an ultra-fine, non-contact, antibody-temperature interference-resistant optical fiber protection tube, as detailed below:

[0042] (a) Material preparation

[0043] 1. Inner layer materials: polyimide resin, hollow zirconia nanospheres (particle size 80nm, purity 99.9%), KH-560 silane coupling agent, N-methylpyrrolidone (NMP) solvent;

[0044] 2. Middle layer materials: medical grade fluorosilicone rubber (hardness 55 Shore A), boron nitride nanotubes (diameter 50nm, aspect ratio 50), hydroxylation modifier;

[0045] 3. Outer layer materials: medical-grade PEEK powder (particle size 5μm), graphene nanosheets (thickness 1-3nm), oxygen plasma treatment device;

[0046] 4. Thermal insulation medium: Fluorosilicone oil (viscosity 1200 cSt, refractive index 1.38);

[0047] 5. Potting material: Medical UV-curable epoxy resin (curing shrinkage rate 0.3%).

[0048] (II) Preparation steps

[0049] 1. Molding of PI tube with inner heat insulation layer: Polyimide (PI) resin is heated to 390℃ to melt and injected into a precision injection mold (cavity inner diameter 300μm, including spiral rib forming groove). The injection pressure is 5.5MPa, and after holding the pressure for 10s, it is cooled to room temperature and demolded to obtain PI tube. Hollow zirconia nanospheres are modified with KH-560 and dispersed in NMP solvent to prepare an 18wt% dispersion. The dispersion is uniformly sprayed onto the inner wall of the PI tube using an electrostatic spraying device and dried at 85℃ for 25min to form a 35μm thick inner heat insulation layer with a spiral rib height of 5μm and a pitch of 150μm.

[0050] 2. Intermediate toughness reinforcement layer coating: Fluorosilicone rubber and hydroxylated boron nitride nanotubes are mixed at a mass ratio of 85:15 and added to a twin-screw extruder for melt blending (temperature 85℃). Then, the mixture is fed into the extrusion coating machine barrel. The PI tube is inserted into the extruder head, and the traction speed is controlled at 6m / min to form a 150μm thick fluorosilicone rubber layer. The mixture is then placed in a 150℃ vulcanizing furnace for 50min to ensure complete curing.

[0051] 3. Outer biocompatible layer composite: PEEK powder and graphene nanosheets were mixed at a mass ratio of 95:5, heated to 385℃ to melt, and pressed into a 30μm thick composite film using a calender. The film surface was treated with an oxygen plasma treatment instrument (60W, 40s, argon flow rate 10L / min), and then the film was spirally wound onto the middle layer surface. The joint was welded using a laser welding machine (power 18W, spot diameter 40μm, welding speed 10mm / s). The outer diameter was monitored online with a laser diameter gauge to ensure that the total outer diameter was controlled at 730μm.

[0052] 4. Insulation medium filling: Fluorosilicone oil is injected from one end of the tube using a micro-injection pump at a flow rate of 1.2 μL / min. The other end is connected to a vacuum pump (vacuum degree -0.09 MPa) to assist in filling by evacuating the vacuum. After filling, the tube is left to stand vertically for 2.5 hours to ensure that there are no air bubbles left in the gaps.

[0053] 5. End fixing structure processing: Cut both ends of the tube body with a precision lathe (spindle speed 10000r / min) to process a 2mm long shrinkage section (outer diameter 650μm). Use a laser engraving machine to process annular protrusions (height 6μm, spacing 100μm) on the inner wall of the shrinkage section. Inject medical UV-curable epoxy resin into the 2mm area inside the shrinkage section and cure it for 25s under 365nm UV light (intensity 120mW / cm²) to form the potting section.

[0054] (III) Performance Testing and Verification

[0055] 1. Dimensional accuracy test: The total outer diameter of the protective tube is 730μm, the inner layer thickness is 35μm, the middle layer thickness is 150μm, the outer layer thickness is 30μm, the inner cavity diameter is 300μm, the gap is 10μm, and the deviation of each dimension is ≤±1μm, which meets the design requirements.

[0056] 2. Thermal insulation performance test: After the protective tube is covered with optical fiber, it is placed in a constant temperature chamber at 37℃ and continuously monitored for 1 hour with a fiber optic grating thermometer (accuracy ±0.05℃). The maximum temperature fluctuation of the optical fiber core is 0.48℃, which meets the index of ≤0.5℃.

[0057] 3. Mechanical stability test: The fiber was cyclically bent 10,000 times at a bending radius of 1 mm and a frequency of 10 times / min on a bending tester. The maximum radial displacement of the fiber was 3.5 μm as monitored by the laser displacement sensor, and there was no collision with the tube wall. The axial fixing force was tested at 4.8 N by the tensile tester, and the optical loss change was detected at 0.15 dB by the optical power meter.

[0058] 4. Biocompatibility test: The cytotoxicity test was conducted according to ISO 10993-5 standard. After co-culturing L929 cells with the protective tube extract for 48 hours, the survival rate was 97.8%. The sensitization test was conducted according to ISO 10993-10 standard. No sensitization reaction was observed in guinea pig skin.

[0059] 5. Abrasion resistance test: The friction tester (load 5N, speed 5mm / s) was used to simulate friction with the inner wall of the biopsy channel. After 1000 friction cycles, the outer layer wear was 4.2μm, with no damage or exposure of the substrate.

Claims

1. An ultra-fine non-contact antibody temperature-dry interference optical fiber protection tube, characterized in that, The protective tube is a circular hollow coaxial structure, sequentially comprising an inner heat insulation layer, a middle toughness enhancement layer and an outer biocompatible layer from inside to outside; and the inner cavity of the inner heat insulation layer is filled with a heat insulation medium.

2. The ultra-fine non-contact antibody temperature-dry interference optical fiber protection tube according to claim 1, characterized in that, The base material of the protective tube is polyimide doped with hollow zirconium oxide nanospheres.

3. The ultra-fine non-contact antibody temperature-dry interference optical fiber protection tube according to claim 2, characterized in that, The hollow zirconium oxide nanospheres are modified by a silane coupling agent.

4. The ultra-fine non-contact antibody temperature-dry interference optical fiber protection tube according to claim 1, characterized in that, The inner wall of the inner heat insulation layer is provided with integrally formed spiral ribs, which are arranged around the optical fiber and kept at a distance.

5. The ultra-fine non-contact antibody temperature-dry interference optical fiber protection tube according to claim 1, characterized in that, The base material of the middle toughness enhancement layer is medical fluorosilicone rubber doped with hydroxylated boron nitride nanotubes.

6. The ultra-fine non-contact antibody temperature-dry immune optical fiber protection tube according to claim 1, characterized in that, The base material of the outer biocompatible layer is medical polyether ether ketone doped with graphene nanosheets.

7. The ultra-fine non-contact antibody temperature-dry interference optical fiber protection tube according to claim 6, characterized in that, The graphene nanosheets are treated by oxygen plasma.

8. The ultra-fine non-contact antibody temperature-dry immune optical fiber protection tube according to claim 1, characterized in that, The heat insulation medium is medical fluorosilicone oil.

9. The ultra-fine non-contact antibody temperature-dry immune optical fiber protection tube according to claim 1, characterized in that, Both ends of the protective tube are provided with end fixing structures.

10. The ultra-fine non-contact antibody temperature-dry interference optical fiber protection tube according to claim 9, characterized in that, The end fixing structure comprises a shrinkage section, an annular protrusion and a potting section.

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