Butterfly-shaped optical fiber sweat surface tension sensor and detection method thereof

Abstract

The invention discloses a butterfly-shaped optical fiber sweat surface tension sensor and a detection method thereof, and relates to the technical field of liquid surface tension detection.The butterfly-shaped optical fiber sweat surface tension sensor comprises a butterfly-shaped micro optical fiber, a bearing part, a movable part and an injection part, and the surface tension of the liquid drop to be measured is determined through the change of the butterfly micro optical fiber interference spectrum wavelength. According to the invention, hydrogen flame tapering parameters are accurately controlled to form the butterfly-shaped micro optical fiber with weak rigidity and small girdling diameter, a conical transition area excites a low-order guided mode and interferes with an optical fiber fundamental mode, an evanescent field is enhanced by combining the weak rigidity characteristic of the butterfly-shaped micro optical fiber, and the sensitivity of the sensor to liquid surface tension detection is remarkably improved; moreover, through the arrangement of an injector, a liquid inlet hole and the like, the sensor can detect multiple batches of sweat samples, the packaging part is prevented from being disassembled and assembled for multiple times, and the detection time of the liquid drops to be detected is shortened to a certain extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid surface tension detection, and in particular to a butterfly-shaped optical fiber sweat surface tension sensor and a detection method thereof. BACKGROUND

[0002] As an important component of body fluid, the change of sweat surface tension is closely related to electrolyte concentration, skin barrier function and metabolic state. By detecting the surface tension, the electrolyte abnormalities of genetic diseases such as cystic fibrosis (e.g. the increase of sweat chloride ions leading to the decrease of surface tension) can be indirectly evaluated, or the dehydration and electrolyte imbalance in exercise and high temperature environment can be monitored, and non-invasive data support can be provided for diabetes management, drug metabolism detection, etc.

[0003] At present, in the field of liquid surface tension measurement, the existing technologies such as traditional pendant drop method, platinum ring method and commercial tension meter usually require a large sample size and are difficult to realize in-situ, real-time and continuous monitoring, and cannot detect and analyze micro-sweat.

[0004] Although some existing technologies use optical fibers to detect sweat, the micro-nano optical fiber sensor for sensing liquid properties mainly relies on the change of optical properties caused by the change of environmental refractive index, that is, the liquid composition (such as ion concentration) is detected by the change of refractive index; the response sensitivity of this method to the mechanical property of liquid surface tension is insufficient (generally less than 50 mN / m-1), and the surface tension of sweat cannot be accurately detected.

[0005] More importantly, there are significant defects in the packaging process for practical applications: the existing packaging methods (such as simple adhesive fixation or open structure) are difficult to reliably fix the fragile micro-nano optical fiber structure, and are prone to displacement or fracture under operation or environmental disturbance.

[0006] Moreover, there is a conflict between the characteristics of micro-sweat and measurement, that is, the evaporation rate of micro-sweat is fast, which requires the detection device to complete the measurement of sweat in a short time, but the existing packaging structure itself may introduce additional stress or interference (such as capillary force interference) to cause long detection time, and even the measurement accuracy may be reduced and the service life of the sensor may be shortened due to its interference, so that the existing packaging structure cannot reliably complete the surface tension detection of micro-sweat droplets to realize the indirect qualitative evaluation of sweat ion concentration.

[0007] Therefore, the present application provides a butterfly-shaped optical fiber sweat surface tension sensor and a detection method thereof to solve the above problems. SUMMARY

[0008] The present application aims to provide a butterfly-shaped optical fiber sweat surface tension sensor and a detection method thereof to solve the technical problems raised in the background.

[0009] To achieve the above object, the present application provides the following technical scheme: a butterfly-shaped optical fiber sweat surface tension sensor, comprising: The butterfly-shaped micro optical fiber comprises a waist region in the middle of the optical fiber, and a tapered transition region and a thick optical fiber region are formed on both sides of the waist region, respectively; A carrier is used to carry the butterfly-shaped micro optical fiber; A movable part is arranged below the carrier and cooperates with the carrier, comprising a lower glass sheet, and a to-be-measured region is arranged in the middle of the lower glass sheet to carry a to-be-measured droplet; An injection part is arranged on one side of the movable part to send the to-be-measured droplet into the to-be-measured region; When the movable part moves up and down and makes the butterfly-shaped micro optical fiber immerse in and out of the to-be-measured droplet, the surface tension of the to-be-measured droplet is determined by the change of the interference spectrum wavelength of the butterfly-shaped micro optical fiber.

[0010] Preferably, a taper angle is formed between the waist region and the tapered transition region, and the taper angle is an acute angle and the angle is between 0.3° and 1°.

[0011] Preferably, the carrier comprises: An upper glass sheet with a first surface in a rectangular structure; Two isolation sheets are arranged on both sides of the first surface, and the butterfly-shaped micro optical fiber is fixedly connected to the middle of the lower side of the isolation sheet; A first cover glass sheet is fixedly arranged on the lower side of the isolation sheet, and the butterfly-shaped micro optical fiber is located between the first cover glass sheet and the isolation sheet.

[0012] Preferably, a limiting part is further arranged between the carrier and the movable part to limit the relative position of the carrier and the movable part.

[0013] Preferably, the limiting part comprises two symmetrically arranged limiting plates, the limiting plate comprises a horizontal plate fixedly connected to the side surface of the upper glass sheet and the isolation sheet, the lower side of the horizontal plate is fixedly connected with a vertical plate, the lower glass sheet is fixedly connected with two symmetrically arranged limiting strips on both sides, respectively, a slot is formed between two adjacent limiting strips, and the vertical plate slides in the slot.

[0014] Preferably, the injection part comprises two symmetrically arranged glass plates, the lower glass sheet has a second surface, the to-be-measured region and the two glass plates are arranged on the second surface, the second cover glass sheet is arranged on the side of the two glass plates away from the second surface, a glass channel is formed between the second cover glass sheet and the two glass plates, one side of the glass channel is communicated with the to-be-measured region, the other side of the glass channel is provided with a syringe, and a liquid inlet hole is formed in the circumferential side of the syringe.

[0015] Preferably, the to-be-tested region is a rectangular structure, and the liquid level of the to-be-tested droplet is greater than the thickness of the to-be-tested region.

[0016] Preferably, the two ends of the butterfly-shaped micro optical fiber are respectively connected with a broadband light source and a spectrometer.

[0017] Preferably, the preparation method of the butterfly-shaped micro optical fiber comprises: Step one: a single-mode optical fiber with a length greater than the upper glass plate is cut, the coating layer is removed by wire strippers, and then the single-mode optical fiber is wiped clean with a dust-free cloth dipped in alcohol; Step two: the two ends of the single-mode optical fiber are respectively fixed on two stretching platforms of an optical fiber tapering machine through a magnet; Step three: the heating part of the single-mode optical fiber is heated by a hydrogen generator, and the two stretching platforms are controlled to move relative to each other to taper the single-mode optical fiber; Step four: after the tapering stops, the relaxation of the single-mode optical fiber is calibrated by a cold correction function.

[0018] A detection method of a butterfly-shaped optical fiber sweat surface tension, comprising the following steps: Step one: a sensor composed of a carrier, a movable piece, a butterfly-shaped micro optical fiber and an injection member is installed and calibrated by a plurality of known solutions, specifically including the following contents: S101: the two ends of the carrier are fixed on a support platform, and the movable piece is installed on a lifting device that can move up and down; S102: the known solution is sent into the to-be-tested region through a syringe and a glass channel, and the lifting device drives the movable piece to immerse and immerse the butterfly-shaped micro optical fiber in the known solution in an intermittent and fixed interval manner; S103: the wavelength difference of the wave trough of the known solution is obtained by recording the wavelength of the wave trough after completely immersing in the known solution and the wavelength of the wave trough after completely moving out of the known solution into the air, and the sensitivity coefficient S is calculated according to the wavelength difference of the wave trough and the surface tension of the plurality of known solutions; Step two: the to-be-tested sweat is detected, specifically including the following contents: S201: the to-be-tested sweat is sent into the syringe through the liquid inlet hole, and the wavelength difference of the wave trough of the to-be-tested sweat is obtained after repeating step S102; S202: the surface tension of the to-be-tested sweat is calculated based on the sensitivity coefficient S and the wavelength difference of the wave trough, and the surface tension value of the to-be-tested sweat is obtained.

[0019] The beneficial effects of the present application are: The application forms the butterfly-shaped micro optical fiber with weak rigidity and small waist diameter by precisely controlling the hydrogen flame tapering parameters, excites low-order guided modes in the taper transition zone, interferes with the fiber base mode, enhances the evanescent field in combination with the weak rigidity characteristics of the butterfly-shaped micro optical fiber, significantly improves the sensitivity of the sensor to liquid surface tension detection, avoids the butterfly-shaped micro optical fiber from being adsorbed on the upper glass slide due to bending or static electricity through the optimization of the mounting mode of the isolation plate and the butterfly-shaped micro optical fiber and the isolation plate, and comprehensively solves the problems of low precision, short service life and micro sample detection failure caused by weak mechanical response and poor packaging reliability of the traditional sensor, in addition, through the setting of the syringe and the liquid inlet hole, the sensor can detect multiple batches of sweat samples, avoid the packaging part from being disassembled multiple times, and to a certain extent, shorten the detection time of the to-be-detected liquid drops. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a whole structure schematic diagram of a butterfly-shaped optical fiber sweat surface tension sensor of the application.

[0021] Figure 2 It is a structure schematic diagram of a butterfly-shaped micro optical fiber in the application.

[0022] Figure 3 It is a cross-sectional view schematic diagram of a sensor in the application.

[0023] Figure 4 It is a structure schematic diagram of a butterfly-shaped micro optical fiber in the application.

[0024] Figure 5 It is a structure cross-sectional view of a liquid inlet hole and a liquid outlet cavity in the application.

[0025] Figure 6 It is a structure schematic diagram of a bearing piece provided with sealing plates on the front and back sides in the application.

[0026] Figure 7 It is an interference spectrum diagram of a butterfly-shaped optical fiber sweat surface tension sensor of the application.

[0027] Figure 8 It is a frequency spectrum diagram of a sensor interference spectrum after Fourier transform in the application.

[0028] Figure 9 It is a wave trough movement and longitudinal displacement change diagram of a sensor in different solutions in the application.

[0029] Figure 10 It is a relationship diagram of surface tension and wavelength difference of a sensor in the application.

[0030] The reference signs are: 1, butterfly-shaped micro optical fiber; 11, waist zone; 12, taper transition zone; 13, thick optical fiber zone; 2, bearing; 21, upper glass sheet; 211, first surface; 22, spacer; 23, first cover glass; 3, movable part; 31, lower glass sheet; 311, second surface; 32, to-be-measured area; 4, injection part; 41, glass plate; 42, second cover glass; 43, glass channel; 44, syringe; 441, liquid inlet hole; 442, liquid outlet cavity; 443, liquid inlet cavity; 5, limiting part; 51, limiting plate; 511, horizontal plate; 512, vertical plate; 52, limiting strip. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] Embodiment 1 In actual detection, the prior art requires a large amount of sample for sweat detection, and the existing packaging methods (such as simple adhesive fixation or open structure) are difficult to reliably fix the fragile micro-nano optical fiber structure, which is easy to displace or break under operation or environmental disturbance; and based on the conflict between the characteristics of micro-sweat and measurement, that is, the evaporation rate of micro-sweat is fast, which requires the detection device to complete the measurement of sweat in a short time, but the existing packaging structure itself may introduce additional stress or interference (such as capillary force interference) to cause the detection time to be too long. To solve the above problems, the embodiment is invented.

[0033] Please refer to Figures 1 to 10 The butterfly-shaped optical fiber sweat surface tension sensor of one embodiment of the present application includes a detection part, a packaging part and an injection part. The detection part includes a butterfly-shaped micro optical fiber 1, which is connected in sequence with a broadband light source (wavelength range: 1530-1610 nm) and a spectrometer (Anritsu, CMA5000, wavelength resolution: 0.02 pm) through optical fiber fusion splicing. The packaging part includes a bearing 2 and a movable part 3. The injection part includes an injection part 4.

[0034] Please refer to Figure 2 The butterfly-shaped micro optical fiber 1 includes a waist region 11 located in the middle of the optical fiber. The two sides of the waist region 11 are formed with a tapered transition region 12 and a thick optical fiber region 13, respectively, and a taper angle is formed between the waist region 11 and the tapered transition region 12. The taper angle is an acute angle and its angle is between 0.3°-1°.

[0035] Please refer to Figure 3 andFigure 4 As shown, the butterfly-shaped micro fiber 1 is fixedly connected with the carrier 2 by UV ultraviolet curing glue, the carrier 2 comprises an upper glass sheet 21, isolation sheets 22 and a first cover glass sheet 23, wherein the upper glass sheet 21 is of a rectangular structure and has a first surface 211, the isolation sheets 22 are provided with two and are respectively located at two sides of the first surface 211, the butterfly-shaped micro fiber 1 is fixedly connected to the middle of the lower side of the isolation sheet 22, the first cover glass sheet 23 is fixedly arranged on the lower side of the isolation sheet 22, the butterfly-shaped micro fiber 1 is located between the first cover glass sheet 23 and the isolation sheet 22, and the isolation sheet 22 is fixed between the first surface 211, the butterfly-shaped micro fiber 1 and the isolation sheet 22 and the first cover glass sheet 23 and the isolation sheet 22 respectively by UV ultraviolet curing glue, wherein the function of the isolation sheet 22 is to prevent the butterfly-shaped micro fiber 1 from being adsorbed on the upper glass sheet 21 due to electrostatic adsorption and bending effect, so as to reduce the extinction ratio of the spectrum.

[0036] The movable part 3 can move up and down and is arranged below the carrier 2, the movable part 3 comprises a lower glass sheet 31, the middle of the lower glass sheet 31 is provided with a to-be-measured area 32 for carrying a to-be-measured liquid drop, wherein the lower glass sheet 31 adopts a glass sheet with hydrophilicity and its size is similar to that of the upper glass sheet 21, the length is consistent with or slightly smaller than the length of the upper glass sheet 21, and the to-be-measured area 32 is of a rectangular structure, in the embodiment, the to-be-measured area 32 is enclosed by a plurality of glass sheets with a thickness consistent with that of the first cover glass sheet 23, and the liquid surface height of the to-be-measured liquid drop in the to-be-measured area 32 is greater than the thickness of the to-be-measured area 32.

[0037] When the movable part 3 moves up and down and makes the butterfly-shaped micro fiber 1 immerse in and out of the to-be-measured liquid drop, the surface tension of the to-be-measured liquid drop is determined by the change of the interference spectrum wavelength of the butterfly-shaped micro fiber 1.

[0038] The injection part 4 is arranged on one side of the movable part 3 for feeding the to-be-measured liquid drop into the to-be-measured area 32, in the embodiment, the injection part 4 comprises two symmetrically arranged glass plates 41, the lower glass sheet 31 has a second surface 311, the to-be-measured area 32 and the two glass plates 41 are arranged on the second surface 311, the two glass plates 41 are provided with a second cover glass sheet 42 away from the second surface 311, a glass channel 43 is formed between the second cover glass sheet 42 and the two glass plates 41, one side of the glass channel 43 communicates with the to-be-measured area 32, and the other side is provided with a syringe 44, in the embodiment, the syringe 44 adopts a needle tube without a needle, the end part after removing the needle is fixedly sealed with organic silicone sealant between the inner wall of the glass channel 43, when the detection personnel pushes the push rod to drive the piston to move, the to-be-measured liquid drop in the needle tube enters the glass channel 43 through the outlet end thereof, and gathers in the to-be-measured area 32 after passing through the glass channel 43.

[0039] Please refer to Figure 3 and Figure 5As shown, in order to enable the sensor to detect multiple batches of sweat samples, avoid disassembling the packaging part multiple times, especially after the injection needle 4 and the two glass plates 41 are fixed by the silicone sealant, the injection needle 44 is not convenient to disassemble, therefore, the liquid inlet hole 441 is arranged on the circumference side of the injection needle 44, the piston inside the injection needle 44 divides the needle cylinder into the liquid outlet cavity 442 and the liquid inlet cavity 443, when the detection personnel control the push rod to drive the piston to move, the volume of the liquid outlet cavity 442 and the liquid inlet cavity 443 changes accordingly, in the initial state, the liquid inlet hole 441 is in communication with the liquid inlet cavity 443, at this time, the droplet to be detected is located in the liquid outlet cavity 442, as the piston gradually moves to one side of the liquid outlet cavity 442, the droplet to be detected enters the detection area 32 through the glass channel 43, when it is necessary to detect different batches of sweat samples, the sweat in the detection area 32 and the glass channel 43 is removed first, then the piston is controlled to move to one side of the liquid inlet cavity 443, until the liquid inlet hole 441 is in communication with the liquid outlet cavity 442, then clean water is injected into the liquid outlet cavity 442, the piston is pushed to move to clean the glass channel 43 and the detection area 32, finally, the above-mentioned action is repeated, new sweat to be detected is injected into the liquid outlet cavity 442 through the liquid inlet hole 441, after the sample replacement is completed, the piston is pushed to move, so that the liquid inlet hole 441 is in communication with the liquid inlet cavity 443.

[0040] Further need to be supplemented is that the preparation method of the butterfly-shaped micro optical fiber 1 comprises: Step one: cut a single-mode optical fiber with a length greater than the upper glass plate 21, remove the coating layer with wire strippers, and then wipe it clean with a dust-free cloth dipped in alcohol.

[0041] Step two: fix the two ends of the single-mode optical fiber on the two stretching platforms of the optical fiber tapering machine through the magnetite, and the initial distance between the two stretching platforms is 2 cm.

[0042] Step three: heat the part to be heated of the single-mode optical fiber through the hydrogen generator, and control the relative movement of the two stretching platforms to taper the single-mode optical fiber, wherein after turning on the switch of the hydrogen generator, 30 s are waited before ignition, after clicking the start button, the fire head runs to the set position to heat for about 3 s, and then the stretching platform starts to work, and the moving speed of the two stretching platforms is 180 μm / s, and the hydrogen flow is 160 ml / min.

[0043] Step four: after the tapering stops, the piezoelectric driver applies a micro-tension with a step precision of 1 μm through the cold correction function to gradually eliminate the thermal shrinkage deformation and calibrate the relaxation of the single-mode optical fiber.

[0044] Please refer to Figure 6As shown, in order to delay the evaporation time of trace sweat, glass sealing plates are arranged on the front and back sides of the carrier 2. Since the upper glass sheet 21 and the lower glass sheet 31 are both in the shape of an elongated rectangle, only the front and back sides are sealed and shielded. This not only prevents most dust from interfering with the droplet to be tested, but also effectively prevents the trace sweat from evaporating too quickly.

[0045] The packaging method of the packaging part and the cooperation mode of the packaging part with the detection part and the injection part are supplemented as follows: When installing the butterfly-shaped micro optical fiber 1 on the carrier 2, first, a rectangular glass sheet is selected as the upper glass sheet 21, and two isolation sheets 22 are fixed on the first surface 211 along the length direction of the upper glass sheet 21. The length of the isolation sheet 22 is consistent with the width of the upper glass sheet 21. After covering a small amount of UV curing adhesive on the surface of the isolation sheet 22, the two isolation sheets 22 are adhered and fixed to the two ends of the butterfly-shaped micro optical fiber 1, and the first cover glass sheet 23 is placed on the isolation sheet 22 and the butterfly-shaped micro optical fiber 1 to maintain the flatness of the contact surface between the carrier 2 and the movable part 3.

[0046] It should be noted that during the fixing of the isolation sheet 22 and the butterfly-shaped micro optical fiber 1, the butterfly-shaped micro optical fiber 1 remains stationary. By installing the upper glass sheet 21 and the isolation sheet 22 on the four-dimensional displacement platform and slowly adjusting the deflection angle and height of the upper glass sheet 21 by the displacement platform, the two ends of the butterfly-shaped micro optical fiber 1 can be in contact with the corresponding isolation sheet 22.

[0047] Finally, a glass sheet with the same size as the upper glass sheet 21 or slightly smaller and hydrophilic material is selected as the lower glass sheet 31. The test area 32 is made by surrounding a plurality of glass sheets with a thickness of 1 mm. The glass sheets are sealed and bonded between each other. An opening is formed on one side of the test area 32. Two glass plates 41 with the same size are placed on both sides of the opening. A glass channel 43 is formed between the two glass plates 41. After covering the second cover glass sheet 42 on the top of the two glass channels 43, the end of the syringe 44 is fixed to the inner wall of the glass channel 43 by organic silicone sealant. At this time, the syringe 44 is in communication with the glass channel 43 and the test area 32.

[0048] In addition, the support platform for installing the carrier 2 and the lifting device for installing the movable part 3 are supplemented as follows: the upper glass sheet 21, the isolation sheet 22, and the first cover glass sheet 23 of the carrier 2 are all located on the upper side of the support platform, and the first cover glass sheet 23 is in contact with the support platform. After fixing the coarse optical fiber area 13 on the support platform by the magnet, the carrier 2 is installed on the support platform. The movable part 3 only needs to be placed on the lifting device and cooperated with the carrier 2 in an up-down manner.

[0049] In summary, by means of the butterfly-shaped micro fiber 1, the carrier 2, the movable piece 3 and the injection piece 4, the hydrogen flame tapering parameters are precisely controlled to form the butterfly-shaped micro fiber 1 with weak stiffness and small waist diameter, the taper transition zone 12 of which excites low-order guided modes and interferes with the fiber base mode, and the weak stiffness of the butterfly-shaped micro fiber 1 enhances the evanescent field, thereby significantly improving the detection sensitivity. In addition, by means of the isolation plate and the mounting mode of the butterfly-shaped micro fiber 1 and the isolation plate, the butterfly-shaped micro fiber 1 is prevented from being adsorbed on the upper glass slide 21 due to bending or static electricity, the droplet input is pollution-free transported by taking the needle tube as a template, in-situ stable measurement is realized, and the problems of low precision, short service life and ineffective micro sample detection caused by weak mechanical response and poor packaging reliability of the traditional sensor are comprehensively solved.

[0050] In addition, by means of the syringe 44 and the liquid inlet hole 441, the sensor can detect multiple batches of sweat samples, avoid multiple disassembly of the packaging part, and to some extent, shorten the detection time of the droplet to be detected.

[0051] Embodiment 2 In actual detection, it is found that when the detection personnel respectively install the carrier 2 and the movable piece 3 on the support platform and the lifting device, since the lifting device does not limit the movable piece 3, only the naked eye is used to determine that the to-be-detected area 32 and the butterfly-shaped micro fiber 1 are in the same position, and the problem of large misalignment between the butterfly-shaped micro fiber 1 and the to-be-detected area 32 is likely to occur. Further improvement is made on the basis of the above-mentioned embodiments.

[0052] Please refer to Figure 1 The limiting piece 5 is arranged between the carrier 2 and the movable piece 3 to limit the relative position of the carrier 2 and the movable piece 3.

[0053] The limiting piece 5 comprises two symmetrically arranged limiting plates 51, the limiting plate 51 comprises a horizontal plate 511 fixedly connected to the side surface of the upper glass slide 21 and the isolation plate 22, and the lower side of the horizontal plate 511 is fixedly connected with a vertical plate 512, the lower glass slide 31 is fixedly connected with two symmetrically arranged limiting strips 52 on both sides, respectively, a slot is formed between two adjacent limiting strips 52, and the vertical plate 512 slides in the slot. In this embodiment, the limiting strip 52 has a “T” shape.

[0054] On the basis of the above-mentioned embodiments, when the two ends of the carrier 2 are installed on the support platform, before the movable piece 3 is placed on the lifting device, the two vertical plates 512 are inserted into the corresponding slots, and if the relative position of the movable piece 3 and the carrier 2 is deviated, the position of the movable piece 3 is self-adaptively adjusted under the cooperation of the limiting strip 52 and the slot.

[0055] In summary, by the cooperation of the limiting member 5 and the carrier 2 and the movable member 3, the large positional deviation between the to-be-measured area 32 and the butterfly-shaped micro optical fiber 1 during manual operation is avoided, thereby affecting the detection accuracy of the sweat surface tension; meanwhile, after the carrier 2 and the movable member 3 are installed, no excessive human intervention is needed for the calibration work, the detection time of the to-be-measured sweat is shortened, and in the detection of multiple batches of sweat, the problem of mispositioning of the movable member 3 and the carrier 2 does not need to be worried about.

[0056] Embodiment 3 The embodiment also provides a detection method of the butterfly-shaped optical fiber sweat surface tension, comprising the following steps: Step one: install the sensor composed of the carrier 2, the movable member 3, the butterfly-shaped micro optical fiber 1 and the injection member 4, and calibrate the sensor by using multiple known solutions, which specifically includes the following contents: S101: fix the two ends of the carrier 2 on the support platform, and install the movable member 3 on the lifting device which can move up and down; S102: send the known solution into the to-be-measured area 32 through the syringe 44 and the glass channel 43, and control the lifting device to drive the movable member 3 to immerse and immerse out the butterfly-shaped micro optical fiber 1 from the known solution in an intermittent and fixed interval manner, that is, the lifting device only drives the movable member 3 to ascend or descend a certain distance at a time, and after ascending or descending multiple equal distances, the butterfly-shaped micro optical fiber 1 is completely immersed in or immersed out of the to-be-measured liquid drop; S103: record the spectral trough wavelength after completely immersing in the known solution and the trough wavelength after completely immersing out of the known solution into the air, obtain the trough wavelength difference of the known solution, and calculate the sensitivity coefficient S according to the trough wavelength difference and the surface tension of the multiple known solutions.

[0057] Step two: detect the to-be-measured sweat, which specifically includes the following contents: S201: send the to-be-measured sweat into the syringe 44 through the liquid inlet hole 441, and obtain the trough wavelength difference of the to-be-measured sweat after repeating step S102; S202: calculate the surface tension of the to-be-measured sweat based on the sensitivity coefficient S and the trough wavelength difference, and obtain the surface tension value of the to-be-measured sweat.

[0058] Based on the taper angle setting of the tapered transition region 12 and the waist region 11, Figure 7 As can be seen from the taper angle, part of the low-order guided mode is excited, and at the transition between the tapered transition region 12 and the waist region 11, the refractive index mutation will cause Fresnel reflection, and the reflected light and the transmitted light will interfere to generate periodic oscillation interference fringes.

[0059] The interference spectrum is subjected to fast Fourier transform, and the obtained spatial frequency distribution diagram is shown in FIG. 6. Figure 8 As can be seen from the taper angle, part of the low-order guided mode is excited, and at the transition between the tapered transition region 12 and the waist region 11, the refractive index mutation will cause Fresnel reflection, and the reflected light and the transmitted light will interfere to generate periodic oscillation interference fringes.Figure 8 The spectrum diagram shown contains two distinct characteristic peaks, corresponding to frequencies of 0.025 MHz and 0.025 MHz respectively. -1 and 0.075m -1 The intensity of the first main peak is weaker than that of the second main peak, so the free spectral range in the output interferogram does not change significantly. Furthermore, the spatial frequency after Fourier transform is proportional to the effective refractive index difference between the two interference modes. Therefore, the smaller the waist diameter, the larger the spatial frequency of the interference mode. In this embodiment, the diameter of the waist region 11 is 5 μm.

[0060] In this embodiment, the solutions are known to be saline solutions of different concentrations (NaCl solution and distilled water). Due to the different concentrations of the saline solutions, their refractive indices and surface tensions are different. Figure 9 As shown, during the sensor immersion process, with the increase of longitudinal displacement, the wavelengths of the spectral troughs in solutions with different refractive indices all exhibited a blue shift. For liquids with refractive indices of 1.3333, 1.355, and 1.3772, the sensitivity responses to liquid surface tension differed, with sensitivities of -21.19 pm / μm, -33.96 pm / μm, and -42.99 pm / μm, respectively. Furthermore, due to the larger surface tension of high-refractive-index solutions, the intermolecular cohesive forces increase with the increase of the solution's refractive index; therefore, the sensor is more sensitive to depth changes.

[0061] The relationship between the liquid surface tension calibrated based on the theoretical value of salt water at 20℃ and the final trough wavelength difference during the sensor immersion and leaching processes is as follows: Figure 10 As shown, the slope of the fitted curve is 37.29 pm / (mN / m), which is the sensitivity coefficient S of 37.29, representing the sensitivity of the sensor during the interaction with the droplet.

[0062] After obtaining the sensitivity coefficient S using the above method, when detecting the surface tension of sweat, it is only necessary to calculate the surface tension of sweat based on the sensitivity coefficient S and the difference in wavelength between the troughs of the sweat being tested, according to the following formula: The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A butterfly-shaped fiber optic sweat surface tension sensor, characterized in that, include: A butterfly-shaped microfiber includes a waist region located in the middle of the fiber, and a tapered transition region and a thick fiber region are formed on both sides of the waist region, respectively. A carrier element for supporting the butterfly-shaped micro-optical fiber; The movable component, which can move up and down and is located below the carrier, includes a lower glass slide, the middle of which is provided with a test area to hold the test droplet; An injection unit, located on one side of the movable part, is used to deliver the test droplet into the test area; As the movable component moves up and down, immersing and leaching the butterfly-shaped microfiber into and out of the test droplet, the surface tension of the test droplet is determined by the change in the wavelength of the interference spectrum of the butterfly-shaped microfiber.

2. The butterfly-shaped fiber optic sweat surface tension sensor according to claim 1, characterized in that, A taper angle is formed between the waist region and the tapered transition region. The taper angle is acute and its angle is between 0.3° and 1°.

3. The butterfly-shaped fiber optic sweat surface tension sensor according to claim 1, characterized in that, The carrier includes: The upper glass slide has a rectangular structure and a first surface; The isolation sheet has two parts, which are located on both sides of the first surface, and the butterfly-shaped micro-optical fiber is fixedly connected to the middle of the lower side of the isolation sheet; The first cover glass is fixedly disposed on the underside of the spacer, and the butterfly-shaped microfiber is located between the first cover glass and the spacer.

4. The butterfly-shaped fiber optic sweat surface tension sensor according to claim 1, characterized in that, A limiting element is also provided between the carrier and the movable element to limit their relative positions.

5. The butterfly-shaped fiber optic sweat surface tension sensor according to claim 1, characterized in that, The limiting component includes two symmetrically arranged limiting plates. Each limiting plate includes a horizontal plate fixedly connected to the side of the upper glass slide and the isolation sheet. A vertical plate is fixedly connected to the lower side of the horizontal plate. Two symmetrically arranged limiting strips are fixedly connected to both sides of the lower glass slide. A slot is formed between two adjacent limiting strips, and the vertical plate slides within the slot.

6. The butterfly-shaped fiber optic sweat surface tension sensor according to claim 1, characterized in that, The injection device includes two symmetrically arranged glass plates. The lower glass plate has a second surface. The test area and the two glass plates are both disposed on the second surface. A second cover glass is disposed on the side of the two glass plates away from the second surface. A glass channel is formed between the second cover glass and the two glass plates. One side of the glass channel is connected to the test area, and the other side is provided with an injector. An inlet hole is opened on the circumferential side of the injector.

7. The butterfly-shaped fiber optic sweat surface tension sensor according to claim 1, characterized in that, The test area is a rectangular structure, and the height of the liquid surface of the test droplet is greater than the thickness of the test area.

8. The butterfly-shaped fiber optic sweat surface tension sensor according to claim 1, characterized in that, The butterfly-shaped microfiber is connected to a broadband light source and a spectrometer at its two ends, respectively.

9. A butterfly-shaped fiber optic sweat surface tension sensor according to claim 1, characterized in that, The method for fabricating the butterfly-shaped microfiber includes: Step 1: Cut a single-mode fiber longer than the upper glass slide, remove its coating with wire strippers, and then wipe it clean with a lint-free cloth soaked in alcohol. Step 2: Fix both ends of the single-mode fiber to the two stretching platforms of the fiber tapering machine using magnets; Step 3: Heat the part of the single-mode fiber to be heated using a hydrogen generator, and control the relative movement of the two stretching platforms to taper the single-mode fiber. Step 4: After the tapering stops, calibrate the relaxation of the single-mode fiber using the cold correction function.

10. A method for detecting the surface tension of sweat using a butterfly-shaped optical fiber, comprising a butterfly-shaped optical fiber sweat surface tension sensor as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Assemble the sensor, which consists of the carrier, moving parts, butterfly-shaped micro-optical fiber, and injection unit, and calibrate the sensor using various known solutions. This includes the following: S101: Fix both ends of the load-bearing component to the support platform and install the movable component on the lifting device that can move up and down; S102: A known solution is delivered into the test area through a syringe and a glass channel. The lifting device is controlled to drive the movable parts to immerse the butterfly-shaped micro-fiber in and out of the known solution in an intermittent and fixed-interval manner. S103: By recording the trough wavelengths of the spectrum after complete immersion in the known solution and the trough wavelengths after complete removal from the known solution into the air, the trough wavelength difference of the known solution is obtained, and the sensitivity coefficient S is calculated based on the trough wavelength difference and the surface tension of various known solutions. Step Two: Test the sweat sample, which includes the following: S201: The sweat to be tested is fed into the syringe through the inlet hole, and after repeating step S102, the trough wavelength difference of the sweat to be tested is obtained. S202: The surface tension of the sweat to be tested is calculated based on the sensitivity coefficient S and the difference in wavelength at the trough, and the surface tension value of the sweat to be tested is obtained.

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