JP3107725B2 - Manufacturing method of optical fiber probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical fiber probe in which the tip of a protruding portion having a core protruding from a clad is sharpened, and more particularly to an optical fiber sensor for detecting the environment around the tip of an optical fiber probe. The present invention relates to a method for manufacturing an optical fiber probe used as a device.

[0002]

2. Description of the Related Art Conventionally, at one end of an optical fiber comprising a core and a clad, a core is projected from the clad, and a sharpened portion is formed by sharpening the projected core into a tapered tip. An optical fiber sensor in which a detection unit is formed by adhering a dye, a reagent, and the like, that is, a so-called super chip is known.

In such an optical fiber sensor, an emission spectrum or an absorption spectrum changes when an environment around a detection section, for example, pH, a certain functional substance to be detected, or the like is detected. For this reason, for example, detection light is incident on the optical fiber from the other end of the sharp portion, or detection light is incident on the sharp portion from the outside, and the spectrum of the detection light detected at the tip of the probe or the other end of the sharp portion is detected. By doing so, measurement of pH, a functional substance to be detected, and the like is performed. In such an optical fiber sensor, by reducing the size of the detection unit, the spatial resolution of detection is improved as compared with a conventional electric sensor, and the measurement of pH, a functional substance to be detected, and the like in a minute area is performed. be able to.

In order to manufacture such an optical fiber sensor, one end of the optical fiber is etched to form a sharpened portion 32 in which the distal end of the optical fiber 31 is tapered as shown in FIG. Then, a solvent 33 in which a dye or the like is mixed is put in a container, and the tip of the sharp portion 32 is brought into contact with the solvent 33 to form a detection section in which the solvent is attached to the tip of the sharp portion 32.

[0005]

However, when the tip of the sharp portion 32 is brought into contact with the solvent 33 in the container as described above, it is difficult to accurately control the position of the optical fiber 31. As shown in FIG.
The solvent also adheres to portions other than the front end of No. 2, and the detection section 34 becomes large. In particular, when the tip of the sharp portion 32 becomes smaller than the wavelength of light, the position of the tip of the sharp portion 32 cannot be detected by an optical method. 34 becomes difficult to form.

Since the spatial resolution of the optical fiber sensor depends on the size of the detection section 34, as described above, if the detection section 34 becomes large due to the solvent adhering to other than the tip of the sharp section 32, the detection space becomes large. There is a problem that the resolution is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a method of manufacturing an optical fiber probe capable of adhering a dye only to a minute tip.

[0008]

According to the present invention, there is provided a method for manufacturing an optical fiber probe, comprising: a tip having an optical fiber comprising a core and a cladding which covers the periphery of the core; A tapered point is formed.
Then, a solvent mixed with a functional substance whose optical characteristics change according to the surrounding environment is injected into a capillary made of a cored glass tube having an opening with an inner diameter larger than the flat portion at the tip of the sharpened portion at the tip. Further, the flat portion is brought into contact with the solvent at the tip of the capillary to form a detection portion having a functional substance attached to the surface of the flat portion.

Further, in the method of manufacturing an optical fiber probe according to the present invention, when the functional substance or the solvent has a color and the detecting portion is formed, the flat portion is brought close to the tip of the capillary, and the flat portion is formed by the capillary. After confirming the color of the functional substance or the solvent that is exposed from the tip of the capillary when the tip comes into contact with the solvent, the tip is separated from the tip of the capillary.

[0010]

In the method of manufacturing an optical fiber probe according to the present invention, first, the tip of an optical fiber comprising a core and a clad surrounding the core has a tapered tip having a flat portion having a wavelength equal to or smaller than the wavelength of the detection light at the tip. A sharp portion is formed.

Next, a solvent in which a functional substance whose optical characteristics change according to the surrounding environment is mixed in a capillary tube made of a cored glass tube having an opening with an inner diameter larger than that of the flat portion at the tip of the sharp portion. inject. Thus, the injected solvent is transferred to the tip of the capillary by capillary action.

Then, the flat portion is brought into contact with the solvent at the tip of the capillary. Here, when the functional substance or the solvent has a color, when the functional substance or the solvent is exposed from the tip of the capillary when the flat portion comes into contact with the solvent at the tip of the capillary, these colors can be confirmed. Therefore, by checking the color of the functional substance or the solvent exposed from the tip of the capillary, it can be confirmed that the solvent has come into contact with the flat portion.
Then, after confirming that the solvent has contacted the flat portion, the sharp portion and the tip of the capillary are separated.

Accordingly, the tip of the optical fiber has a tapered tip having a flat portion at the tip which is smaller than the wavelength of the detection light, and the optical characteristics change on the surface of the flat portion according to the surrounding environment. An optical fiber probe having a detection unit to which a functional substance is attached is formed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for manufacturing an optical fiber probe according to the present invention will be described below with reference to the drawings.

In the method of manufacturing an optical fiber probe according to this embodiment, for example, as shown in FIG. 1, a sharpening step S for etching one end of an optical fiber to sharpen the tip of a core.
1, an injection step S2 of injecting a solvent in which a functional substance whose optical properties change according to the surrounding environment is mixed into the capillary, and an injection step S2, and the tip of the optical fiber is brought into contact with the solvent at the tip of the capillary to perform the above function. And an attaching step S3 for attaching the active substance.

Hereinafter, each of the above steps will be described in detail.

In the sharpening step S1, one end of an optical fiber composed of a core made of quartz SiO ₂ to which germanium oxide GeO ₂ is added and a clad made of quartz SiO ₂ or the like is connected with an aqueous solution of ammonium fluoride, hydrofluoric acid and water. Etching is performed using a buffered hydrofluoric acid solution.

[0018] performing such _{etching, SiO 2: SiO 2 + 6HF} → H 2 SiF 6 + 2H 2 O H 2 SiF 6 + 2NH 3 → (NH 4) 2 SiF 6 GeO 2: GeO 2 + 6HF → H 2 The cladding 2 and the core 1 are etched by a chemical reaction of GeF ₆ + 2H ₂ OH ₂ GeF ₆ + 2NH ₃ → (NH ₄ ) ₂ GeF ₆ .

There is a difference in the dissolution rate in the buffered hydrofluoric acid solution between the core made of quartz to which germanium oxide GeO ₂ is added and the clad made of quartz. Here, the density 4
0 wt% ammonium fluoride aqueous solution and 50 wt% concentration
Assuming that the volume ratio of hydrofluoric acid to water is X: 1: Y (Y = arbitrary), the difference between the dissolution rates of the core and the clad has a strong correlation with the volume ratio X of ammonium fluoride NH ₄ F.

For this reason, although there is some variation depending on the temperature of the liquid, when X = about 1.5 to 1.7, the etching rates of the core and the clad are almost equal, and X <1.5 (or X <1.
In 7), the etching rate of the core is relatively high, and X> 1.5
(Or X> 1.7), the clad dissolution rate is relatively high. Therefore, by using this buffered hydrofluoric acid solution as an etchant, the core and the clad can be selectively etched.

In the sharpening step S1, an optical fiber obtained by adding about 25 mol% of germanium oxide GeO ₂ to the core has a volume ratio X of ammonium fluoride NH ₄ F of about 10 and a volume ratio Y of water of 1. Etching is performed in a buffered hydrofluoric acid solution at a temperature of 25 ° C. for about 60 minutes. This optical fiber is made of germanium oxide Ge added to the core.
The density distribution is provided so that the O ₂ core has a high density at the center of the core and a low density at the outer periphery of the core.

When such etching is performed, the volume ratio X of ammonium fluoride NH ₄ F in the etching solution becomes 10
Therefore, the etching rate of the clad is higher than the etching rate of the core, and the clad is etched first to form a protrusion in which the core protrudes from the tip of the clad.

When the etching is completed in about 60 minutes, the tip of the conical sharpened core is not completely sharpened. For example, as shown in FIG. A flat portion 5 remains at the tip of a sharp portion 4 projecting from the clad 3 in a tapered shape. Specifically, the cladding 3 diameter d ₀ is about 123 μm, and the core 2 diameter d _c is 3.4 μm.
In the case of using the optical fiber 1 of about m, as shown in FIG. 3, the diameter d ₁ of the flat portion 5 is about 300 nm. Thereby, detection light, for example, 400 to 7 which is the wavelength of visible light
A flat portion 5 having a diameter of 50 μm or less is formed.

Next, in the injection step S2, a solvent in which a functional substance whose optical characteristics change according to the surrounding environment is mixed into the capillary.

As shown in FIG. 4, for example, as shown in FIG. 4, the capillary tube used in this injection step is expanded while heating a cored glass tube having a glass rod 7 attached to the inner wall of a glass tube 6a.
The inner diameter of the opening 8 at the distal end is made smaller until the inner diameter of the flat portion 5 at the distal end of the sharp portion 4 is slightly larger than the inner diameter. In this case, the inner diameter d ₃ of the opening 8 is set to about 600 nm, which is about twice the diameter d ₁ of the flat part 5.

Further, this implantation step, using ethanol as solvent, Rhodamine 6G is a laser dye which emits light in accordance with the intensity of ambient light as functional material This ethanol (Rhodamine 6G) to 6.3 × 10 ^- mixed at a concentration of about ² M. Then, the ethanol mixed with the rhodamine 6G is injected into the capillary 6 from the opposite side of the opening 8 using a syringe.

As a result, as shown in FIG. 5, for example, the ethanol 9 injected into the capillary 6 is transferred to the vicinity of the opening 8 at the tip of the capillary 6 along the glass tube 6a and the glass rod 7 by capillary action.

Next, in the attaching step S3, as shown in FIG. 5, the sharp portion 4 and the tip of the capillary 6 are brought closer to each other and transferred to the flat portion 5 at the tip of the sharp portion 4 and to the opening 8 at the tip of the capillary 6. To the ethanol 9 thus obtained.

More specifically, in this attaching step S3, FIG.
The capillary 6 into which the ethanol 9 was injected as described above was moved using the micromanipulator shown in FIG.
Is made to approach the sharpened portion 4 of the optical fiber 1 fixed to the fixing portion 10.

The micromanipulator comprises a driving system 12 for moving the capillary 6 in response to a user's operation of the operation unit 11, and a light source 13 for irradiating the sharpened portion 4 of the optical fiber 1 and the capillary 6, which are the subject, with irradiation light. An optical system 15 that forms an image of the light incident through the subject on the imaging system 14,
A display unit 16 for displaying an image based on the imaging output from the imaging system 14.

Then, the user looks at the image of the sharp section 4 and the capillary 6 displayed on the display section 16 while operating the operation section 11.
Is operated to move the capillary 6 so that the flat portion 5 at the tip of the sharp portion 4 comes into contact with the ethanol 9 transferred to the opening 8 at the tip of the capillary 6. Here, since the rhodamine 6G mixed with the ethanol 9 is red, when the flat portion 5 and the ethanol 9 in the opening 8 come into contact with each other and the ethanol 9 is exposed from the opening 8, the exposed ethanol 9 is imaged. System 14
The image of the ethanol 9 exposed in accordance with the imaging output is displayed on the display unit 16.

The user can confirm that the flat portion 5 and the ethanol 9 in the opening 8 are in contact with each other by viewing the image of the exposed ethanol 9. When the user confirms that the flat portion 5 and the ethanol 9 in the opening 8 are in contact with each other, the user operates the operation portion 11 to separate the capillary 6 from the sharp portion 4. That is, after confirming that the ethanol 9 has come into contact with the flat portion 5, the user can separate the sharpened portion 4 and the tip of the capillary 6, and can securely attach ethanol to the flat portion 5.

As a result, ethanol mixed with rhodamine 6G adheres to the surface of the flat portion 5, and as shown in FIG. 7, an optical fiber probe 20 having the detecting portion 18 formed on the surface of the flat portion 5 is formed. .

The diameter of the detection unit 18 formed in this manner is such that ethanol is adhered only to the flat portion 5,
As shown in FIG. 8A, the diameter is about the diameter of the flat portion 5.
That is, when the diameter of the flat portion 5 is about 300 nm as described above, the diameter of the detection section 18 is about 300 nm as shown in FIG.

In this method of manufacturing an optical fiber probe,
As described above, the detection portion 18 is formed by adhering a solvent containing a functional substance such as a dye to only the surface of the flat portion 5 having a wavelength equal to or less than the wavelength of the detection light at the tip of the sharp portion 4 of the optical fiber 1. Can be.

In the optical fiber probe 20 formed as described above, when light enters the detection unit 18, the rhodamine 6G of the detection unit 18 emits red light in accordance with the incident light. The diameter of the detection unit 18 is about 300 nm and 400 to 7
Since it is smaller than the wavelength of visible light of about 50 μm, this optical fiber probe 20 can detect light emission in a minute region equal to or smaller than the wavelength of visible light. This makes it possible to accurately measure the emission intensity distribution of the object.

In this method of manufacturing an optical fiber probe,
It is possible to form the detection unit 18 by adhering a solvent mixed with a functional substance whose optical characteristics change according to the surrounding environment, such as a dye, only to the tip of the flat portion 5 having a size equal to or smaller than the wavelength of the detection light. it can. Optical fiber probe 2 thus formed
A value of 0 can improve the spatial resolution of detection because the size of the detection unit 18 is extremely small, that is, about the wavelength of the detection light or less.

The functional substance to be mixed with ethanol and adhered to the flat part 5 is not limited to rhodamine 6G, which is the above laser dye, but also depends on the pH around the detecting part 18, the functional substance to be detected, and the like. For example, a functional substance or the like whose optical characteristics such as an absorbance and a refractive index change can be used.

For example, by using a substance whose emission characteristics change in accordance with the ion concentration of the ion to be detected as the functional substance, the ion concentration around the detecting section 18 can be detected. Specifically, the concentration of calcium ions can be detected by using a so-called fluoro-3 (Fluo-3), calcium green, Rhod-2, Fura-Red, or the like as the functional substance. Further, as the functional substance, so-called methyl red (Methyl Red), bromothymol blue (Bromothymol)
Blue), phenolphthalein (Phenolphthalein) or the like can be used to detect the concentration of hydrogen ions.

Further, as a functional substance, 1-anilinonaphthalene-8-sulfonic acid (ANS) whose optical property changes according to the polarity of the substance around the detection unit 18.
phthalein 8-sulfonic acid), N-methyl-2-anilinonaphthalene-6-sulfonic acid (MANS: N-methyl
2-anilino naphthalein 6-sulfonic acid), 2-p
-Toluidinyl naphthalene-6-sulfonic acid (TNS:
By using 2-para-toluidinyl naphthalein 6-sulfonic acid) or the like, the polarity of the substance around the detection unit 18 can be detected.

The membrane potential can be measured by using a so-called cyanine dye or oxol dye as the functional substance. By using acridine orange, 9-aminoacridine, or the like as a functional substance, it can be used to investigate the macroscopic structure of DNA.

The temperature or pressure can be detected by using, as a functional substance, so-called spiropyranine, fluoran, or the like whose optical characteristics change according to the temperature or pressure around the detecting section 18. Also,
Using so-called photochemical hole-burning materials such as quinizarin and porphyrin dyes as functional materials, and utilizing their nonlinearity and resonance effect, they can be applied to basic experiments of optical memory using the light amplification effect. be able to. Further, N- (4-
Nitrophenyl)-(L) -proninol (N- (4-nitro
phenyl) (L) pronynole: NPP), 4 (dimethylamino) -4-nitrostilbene
By using a non-linear optical material such as rostilbene (DANS), non-linear photodetection characteristics can be obtained.

As the solvent for mixing the above-mentioned functional substances, other than the above-mentioned ethanol, other organic solvents such as alcohols and ketones may be used, or a low-temperature organic solvent such as a sol-gel method may be used. May be used.

When such a solvent is used, the above-mentioned functional substance is mixed with the solvent in the above-described injection step, and the mixture is injected into the capillary 6. In the attaching step, the solvent is attached to the flat portion 5.

For example, tetramethoxysilane (hereinafter referred to as TM
When a solution based on so-called methyl silicate nSi (OCH ₃ ) ₄ (OS: Tetra metoxi siran) is hydrolyzed and polymerized, hydrolysis: nSi (OCH ₃ ) ₄ +4 nH ₂ O → nSi (OH) ₄ +4 nCH ₃ OH polymerization reaction: Si (OH) ₄ + Si (OH) ₄ → (OH) ₃ Si—O—Si (OH) ₃ + H ₂ O (OH) ₃ Si—O—Si (OH) ₃ + Si (OH) ₄ → (OH) ₃ Si—O—Si (OH) ₂ —O—Si (OH) ₃ + H ₂ O The reaction proceeds and the viscosity of the solution increases. At this time,
The volume of the solvent adhering to the flat portion 5 is reduced and solidified to form a transparent gel.

Thus, an amorphous layer containing a functional substance can be formed on the surface of the flat portion 5 at a lower temperature than when glass is processed at a high temperature. The detection unit 18 having a functional material that is destroyed can be formed. In addition, since the functional material is mixed in the amorphous layer, the peel strength of the detection unit 18 can be improved.

When such a solvent is used, semiconductor fine particles such as cadmium selenium CdS _x Se _1-x , cuprous chloride CuCl, and cuprous bromide CuBr can be used as the functional substance. When these functional substances are used, the refractive index and the like change according to the environment around the detection unit 18.

By forming the detection section 18 using these functional substances, the optical characteristics of the detection section 18 change according to the environment around the detection section 18. Since the size of the detection unit 18 is equal to or smaller than the wavelength of the detection light such as visible light as described above, by detecting a change in the optical characteristics of the detection unit 18 on the opposite side of the detection unit 18 of the optical fiber 1. It is possible to measure the environment in the region below the wavelength of the detection light such as visible light.

As a result, it is possible to measure the environment of an area that cannot be measured by an optical method, and it is possible to improve the spatial resolution of the measurement.

The above-described optical fiber probe 20
Since the rhodamine 6G of the detection unit 18 absorbs light around the detection unit 18 and emits red light, it can be used as an optical sensor that detects light incident on the detection unit 18.

Also, such an optical fiber probe 20
Since the diameter of the detection unit 18 is smaller than the wavelength of detection light such as visible light, it can be used to detect so-called evanescent light existing in a region equal to or less than the wavelength of light on the surface of a substance.

At the time of performing, a so-called photon scanning tunneling microscope is used to irradiate a laser beam from the back surface of the sample surface 19, and the distance between the tip of the detection unit 18 and the sample surface 19 is set to be about the wavelength of the laser beam or less. The sample surface 19 is scanned by the detection unit 18.

When a laser beam is made incident on the back surface of the sample surface 19 at a total reflection angle, so-called evanescent light is generated from the sample surface in a region of about the wavelength of the laser beam or less. Since the intensity of the evanescent light decreases as the distance from the sample surface 19 increases, evanescent light having an intensity corresponding to the distance from the sample surface 19 enters the detection unit 18.

The rhodamine 6G of the detecting unit 18 absorbs the incident evanescent light and emits red light according to the intensity of the absorbed evanescent light. This light emission is generated by the sharp part 4
And enters the core 2 via the. Thus, if the intensity of the light incident on the core 2 is detected on the side opposite to the sharp part 4, the distance between the detection unit 18 and the sample surface 19 can be detected. Then, the shape of the sample surface 19 can be measured by obtaining the light intensity distribution according to the scanning of the detection unit 19.

Further, in the optical fiber probe 20 used for detecting evanescent light as described above,
When scanning the sample surface with the sharp part 4, the cladding 3
May strike the sample surface 19 and damage the sample surface 19 or the optical fiber probe 20 itself.

[0056] Therefore, prior to the etching of the sharpening process S1 described above, one end of the optical fiber 1 is etched by hydrofluoric acid, a cladding 3 as small diameter, after forming the small-diameter portion having a diameter of about d _3, sharp The etching in the conversion step S1 may be performed.

In this case, as shown in FIG. 10, a small-diameter portion 25 having a thin clad can be formed at the base end of the above-mentioned sharp portion 4. Thereby, it is possible to prevent the periphery of the tip of the clad 3 from colliding with the sample surface 19.

In the above embodiment, the case where the sharp end is formed by etching one end of the optical fiber has been described. However, the sharp end having a flat portion whose wavelength is equal to or smaller than the wavelength of the detection light may be formed. If possible, the sharpened portion may be formed by stretching the optical fiber while heating it. Further, in the above-described embodiment, visible light is assumed as the detection light, and the flat portion 5 is detected.
Is about 300 μm, but in the case where ultraviolet light or the like is used as the detection light, the diameter of the flat portion 5 may be set to be equal to or less than the wavelength of the ultraviolet light. Various modifications are possible.

[0059]

According to the present invention, at the tip of an optical fiber comprising a core and a cladding covering the periphery of the core, a tapered tip having a flat portion having a wavelength equal to or smaller than the wavelength of the detection light is formed at the tip. Inject a solvent mixed with a functional substance whose optical properties change according to the surrounding environment into a capillary tube made of a cored glass tube having an opening with an inner diameter larger than that of the flat portion at the tip of the flat portion. The solvent can be attached only to the tip of the sharp portion by contacting the solvent at the tip of the tip. Thus, an optical fiber probe with improved spatial resolution for detection can be produced.

Further, in the present invention, the color of the functional substance or the solvent exposed from the tip of the capillary when the flat portion comes into contact with the solvent at the tip of the capillary can be confirmed. After confirming that, the sharp portion and the tip of the capillary can be separated. For this reason, the solvent can be reliably attached to the flat portion.

[Brief description of the drawings]

FIG. 1 is a process chart showing steps of a method for manufacturing an optical fiber probe to which the present invention is applied.

FIG. 2 is a cross-sectional view showing a structure of an optical fiber formed by a sharpening step of the method for manufacturing an optical fiber probe.

FIG. 3 is a side view showing the shape of a protruding portion at the tip of the optical fiber.

FIG. 4 is a perspective view showing a shape of a tip end of a capillary used in an injection step of the method for manufacturing an optical fiber probe.

FIG. 5 is a view for explaining an attaching step of the method for manufacturing an optical fiber probe.

FIG. 6 is a diagram for explaining the attaching step.

FIG. 7 is a cross-sectional view showing a structure of an optical fiber probe formed by the method for manufacturing an optical fiber probe.

FIG. 8 is a side view showing a structure of a sharpened portion of the optical fiber probe.

FIG. 9 is a view for explaining measurement of the shape of the sample surface using the optical fiber probe.

FIG. 10 is a cross-sectional view showing the structure of another optical fiber probe formed by the method for manufacturing an optical fiber probe.

FIG. 11 is a view for explaining a step of attaching a solvent to the tip of an optical fiber in a conventional method of manufacturing an optical fiber probe.

FIG. 12 is a cross-sectional view showing a structure of an optical fiber probe formed by the above-mentioned conventional method for manufacturing an optical fiber probe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Core 3 Cladding 4 Sharp part 5 Flat part 6 Capillary tube 8 Opening 9 Solvent 18 Detecting part

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI G02B 6/10 G02B 6/10 D (56) References JP-A-7-261039 (JP, A) JP-A-7-146126 ( JP, A) JP-A-7-260459 (JP, A) JP-A-5-241076 (JP, A) JP-A-6-94540 (JP, A) Actual opening Hei 5-39145 (JP, U) Actual opening Hei 2-126512 (JP, U) WO 95/32207 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/00-21/61 G02B 6/00-6 / 10 G01N 35/00-35/08

Claims (2)

(57) [Claims] 1. An optical fiber comprising a core and a clad covering the periphery of the core, a tapered tip having a flat portion having a wavelength equal to or smaller than the wavelength of the detection light is formed at the tip. A solvent mixed with a functional substance whose optical properties change according to the surrounding environment is injected into a capillary made of a cored glass tube having an opening with an inner diameter larger than the flat portion at the tip, and the flat portion is made into a tip of the capillary. A method for producing an optical fiber probe, comprising: forming a detection section in which the functional substance is adhered to the surface of a flat section by contacting with a solvent. 2. The method according to claim 1, wherein the functional substance or the solvent has a color, and when forming the detection unit, the flat part approaches the tip of the capillary, and the flat part comes into contact with the solvent at the tip of the capillary. The method for manufacturing an optical fiber probe according to claim 1, wherein after confirming the color of the functional substance or the solvent exposed from the tip of the capillary, the sharp part and the tip of the capillary are separated.