JP2009067684A - Low-boiling compound-including hollow fine particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hollow fine particles in which the release of a substance contained in hollow fine particles can be controlled by the operation from the outside. <P>SOLUTION: The hollow fine particles have an average particle diameter of ≥50 nm and ≤100 μm and have hollow shells having liquid-permeable fine through-holes and a water-insoluble low-boiling compound that is enclosed in the hollow shell and has a boiling point of ≥40°C and ≤100°C. The hollow fine particles are cooled in a solution to the boiling point of the low-boiling compound or below, the low-boiling compound is liquefied and the pressure in the hollow fine particles is reduced to take the solution in the hollow fine particles. The hollow fine particles are heated to the boiling point of the low-boiling compound or above, so that the low-boiling compound is vaporized and the pressure in the hollow fine particles is increased, to release an aqueous solution in the hollow fine particles to the outside of the hollow fine particles. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to hollow fine particles encapsulating a low-boiling compound, and particularly relates to low-boiling compound-containing hollow fine particles in which a liquid is encapsulated in hollow fine particles and the liquid can be released by raising the temperature.

  Particles that form a hollow shell and encapsulate substances having various functions inside the shell are widely used as microcapsules and nanocapsules. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-281143) discloses a microcapsule that is dyed to develop color by pressure and temperature and is used as a recording material for pressure-sensitive recording paper or thermal recording paper. Yes. There are also microcapsules encapsulating materials with low dielectric constants and microcapsules as lightweight substances, microcapsules encapsulating agricultural chemicals and microcapsules encapsulating catalysts, and by encapsulating drugs in microcapsules Some microcapsules are designed to regulate release. In addition, when the hollow shell is made of ferrite, in addition to the function as a normal microcapsule, it can be induced by using magnetic force or induction heating using an alternating magnetic field. Since applications using the magnetic properties of shells are possible, new applications are expected.

  In addition to microcapsules encapsulating solids and liquids, the importance of microcapsules encapsulating gas is increasing. Utilizing the property that the scattering of ultrasonic waves is larger than that of liquid or the like, a microcapsule containing a gas is used as a contrast agent for an ultrasonic imaging apparatus. In addition, it is described in, for example, Patent Document 2 (Japanese Patent Publication No. 9-510204) that microcapsules enclosing gas are effective as a contrast agent for MRI.

Various materials such as polymers and lipids are used as the material for forming the hollow shell of the microcapsule. It is known to use inorganic particles such as silica for the hollow shell. In addition, attempts have been made to use magnetic ferrite in the hollow shell of the microcapsule. If the hollow shell can be formed of ferrite, there can be obtained an advantage that the hollow shell can be moved using magnetic force and the response of the ferrite to the AC electromagnetic field can be used. For this reason, various methods for producing hollow ferrite fine particles have been reported. One of them is the method described in Non-Patent Document 1 (F. Caruso et al., Chem. Mater. 2001, 13, 109-116). In this method, a polymer fine particle is used as a template, a ferrite nanoparticle made into a colloidal shape is adsorbed on the surface thereof, a layer is formed and dried, and this is heated and fired at 500 ° C. It is thermally decomposed to obtain ferrite hollow fine particles. In the method described in Patent Document 3 (Japanese Patent Laid-Open No. 6-23271), the polymer fine particles of the template are dipped in an aqueous solution of FeCl ₃ to adsorb iron ions on the surface of the polymer fine particles, and a layer is formed. It is calcined at ℃ to form alpha iron oxide hollow fine particles, which are further heat-treated at 350 ° C. in hydrogen to form magnetite hollow fine particles. In addition, the method described in Non-Patent Document 2 (Materials Chemistry and Physics 100 (2006) 10-14) is a method in which hollow polystyrene particles are manufactured and the surface of the polystyrene particles is covered with ferrite to form a shell. The hollow ferrite fine particles in which the strength is secured by polystyrene are obtained. Furthermore, according to the method described in Non-Patent Document 3 (J. of Magn. And Magn. Mat. 311 (2007) 578-582), the strength of the shell is ensured by silica to obtain hollow ferrite and silica composite fine particles. Is.
JP 2006-281143 A JP-T 9-510204 JP-A-6-23271 F. Caruso et al., Chem. Mater. 2001, 13, 109-116 Materials Chemistry and Physics 100 (2006) 10-14 J. of Magn. And Magn. Mat. 311 (2007) 578-582

  It is desired that a liquid substance such as a drug encapsulated in hollow fine particles can be released at an appropriate timing at a target location. For example, it may be desirable to allow the contained liquid substance to be released by raising the temperature of the hollow microparticles.

  As a result of repeated studies, the present inventors have found that the substance encapsulated in the hollow microparticles can be released by evaporating the low boiling point compound encapsulated in the hollow microparticles by increasing the temperature. The present invention provides a hollow fine particle capable of releasing a substance encapsulated in a hollow fine particle by raising the temperature of the hollow fine particle, and also probe the hollow fine particle containing a low boiling point compound and a liquid. The present invention provides a temperature sensor capable of checking the temperature rise by detecting changes in the ultrasonic scattering intensity of the probe particles due to the temperature rise.

  The low-boiling compound-containing hollow fine particles of the present invention form hollow fine particles having a hollow portion by a shell having fine through holes, and the low-boiling compound and a liquid substance having a higher boiling point than the low-boiling compound are formed in the hollow portion. The low boiling point compound is insoluble in the liquid substance.

  By using such low-boiling compound-containing hollow fine particles of the present invention, the hollow fine particles contain a low-boiling compound liquid and a liquid containing a predetermined substance, and the temperature is raised to a temperature higher than the boiling point of the low-boiling compound. By increasing the internal pressure of the hollow fine particles by increasing the vapor pressure of the low boiling point compound, a liquid containing a predetermined substance can be extruded at this internal pressure and released to the outside of the hollow fine particles.

  In the low-boiling compound-containing hollow fine particles of the present invention, it is particularly preferable that the low-boiling compound has a vapor pressure of 1 atm. If the vapor pressure of the low boiling point compound has such a temperature change, it can be stored stably at room temperature, and the above liquid discharge operation can be performed by heating this and raising the temperature to above room temperature. This is convenient.

  In the low-boiling compound-containing hollow fine particles of the present invention, those in which the shell of the hollow fine particles is composed of ferrite are particularly preferable. If the shell of the hollow fine particles is made of ferrite, the fine particles are selectively heated from the outside by induction of fine particles with magnetic force using the magnetism of ferrite or induction heating with an alternating magnetic field. Can be warmed.

  In addition, the temperature sensor of the present invention checks the temperature rise by detecting changes in the ultrasonic scattering intensity of the probe particles due to temperature rise by using hollow fine particles containing a low boiling point compound and a liquid as probe particles. It is characterized by that.

  When the hollow fine particles encapsulating the low boiling point compound and the liquid rise in temperature and exceed the boiling point of the low boiling point compound, the low boiling point compound is vaporized, and the hollow part of the hollow fine particles increases in internal pressure, and the hollow fine particles are contained in the hollow fine particles. Since the liquid encapsulated in is discharged to the outside of the hollow fine particles and the hollow portion is filled with gas, the ultrasonic scattering intensity of the hollow fine particles changes significantly at this temperature. By using this property, it was found that high-sensitivity and precise temperature checks can be performed even at locations where ordinary temperature sensors cannot be used. The low boiling point compound used in this temperature sensor is selected and used according to the temperature to be checked.

  According to the present invention, a liquid substance such as a drug and a low boiling point compound are encapsulated in hollow fine particles, and the temperature is raised to release the liquid substance such as a drug contained in the solvent encapsulated in the hollow fine particles. Became possible. It can be used for various applications that utilize this feature. Further, by utilizing the properties of the low-boiling compound-containing hollow fine particles of the present invention, it has become possible to perform a highly sensitive and precise temperature check even at locations where a normal temperature sensor cannot be used.

  Hereinafter, the embodiments of the present invention will be described with reference to the drawings, and further details of the present invention will be described.

1. FIG. 1 is a diagram schematically showing uptake of a liquid substance into a hollow microparticle and release of a liquid substance from the hollow microparticle.
In FIG. 1, first, as shown in FIG. 1 (a), the hollow portion 104 surrounded by the shell 102 of the hollow fine particles 100 is filled with a low-boiling compound 106 in a gaseous state at a temperature higher than the boiling point of the low-boiling compound. Fill and immerse in liquid material 108.
When the hollow fine particles filled with the low boiling point compound in the gaseous state are cooled to a temperature lower than the boiling point of the low boiling point compound, the low boiling point compound 106 in the gaseous state becomes the low boiling point compound 107 in the liquid state. At this time, the volume rapidly decreases, the pressure of the hollow portion decreases, and the shell has a through-hole. Through this through-hole, the hollow portion of the hollow fine particles is taken in and encapsulated from the surroundings. .

  Next, as shown in FIG. 1B, the hollow fine particles 100 enclosing the liquid substance 108 and encapsulating the low-boiling compound 107 in the liquid state are heated to a temperature higher than the boiling point of the low-boiling compound. As a result, the low-boiling compound 107 in the liquid state becomes the low-boiling compound 106 in the gas state and increases its volume. Therefore, the pressure in the hollow portion increases, and the encapsulated liquid substance passes through the through-holes to the outside of the hollow fine particles. Released. At this time, the release of the vaporized low-boiling compound gas is hindered by the surface tension of the liquid substance filling the through-holes of the shells 102 of the hollow microparticles 100.

  In addition, when the shell 102 of the hollow fine particles 100 is formed of ferrite, induction heating using an alternating magnetic field can be used as a means for heating and raising the temperature to a temperature equal to or higher than the boiling point of the low boiling point compound.

  FIG. 2 is a view showing a configuration of an apparatus for enclosing a low boiling point compound and a liquid substance in hollow fine particles according to an embodiment of the present invention. In FIG. 2, first, a suspension obtained by suspending hollow fine particles 202 in water is put into a sealed container 204, and the inside of the sealed container 204 is evacuated using a vacuum pump 206 to dry the hollow fine particles 202 and The hollow part is evacuated. Subsequently, the piping cock 208 to the vacuum pump 206 is closed, and the low boiling point compound is injected into the sealed container 204 using the low boiling point compound injector 210.

  Next, using the temperature control device 212, the temperature of the contents of the sealed container 204 is increased until the temperature exceeds the boiling point of the injected low-boiling compound, and the low-boiling compound is vaporized. By doing so, the hollow portion of the hollow fine particle 202 is also filled with the gas of the low boiling point compound.

  Thereafter, a liquid substance such as an aqueous solution of the drug is placed in the sealed container. Subsequently, the temperature of the sealed container 204 is lowered below the boiling point of the low boiling point compound by the temperature control device 212. By doing so, the low boiling point compound in the hollow fine particles 202 is liquefied, the pressure in the hollow fine particles 202 is lower than that around the hollow fine particles 202, and the surrounding liquid substance is drawn into the hollow portion of the hollow fine particles 202. Included. The through-holes of the hollow fine particle 202 shell are also filled with this liquid substance. The liquid substance contained here may be various drugs, and for example, various antibiotics, anticancer agents, antirheumatic agents, immunomodulators and the like can be included.

  Thus, the low boiling point compound is encapsulated in the hollow fine particles and the aqueous solution of the target substance.

  In this way, the hollow microparticles 202 contain the low-boiling compound in a liquid state and water or an aqueous solution at a temperature lower than the boiling point of the low-boiling compound. Next, when the hollow fine particles 202 are heated to a temperature equal to or higher than the boiling point of the low boiling point compound, the low boiling point compounds are vaporized, and the water or the aqueous solution contained in the hollow fine particles 202 with the vapor pressure is hollow hollow fine particles. It is discharged out of the hollow fine particles 202 through the through-holes of the shell of 202. At this time, the release of the vaporized low-boiling compound gas is hindered by the surface tension of water or an aqueous solution filling the through-holes of the shells of the hollow fine particles 202.

  When the shell of the hollow fine particles 202 is formed of ferrite, induction heating using an alternating magnetic field can be used as means for heating the hollow fine particles 202 to a temperature higher than the boiling point of the low boiling point compound.

2. Hollow fine particles In the present invention, the hollow fine particles encapsulating the low-boiling-point compound are composed of hollow shells having fine through-holes through which liquid can pass, and are composed of various substances used in microcapsules. Hollow fine particles can be used. Examples of such substances include organic monomers and polymers that are insoluble in the liquid used, carbon such as titanium oxide (titania) and silicon oxide (silica), ferrite, and graphite, and metals. . The hollow fine particles preferably have an average particle size of 50 nm or more and 100 μm or less from the viewpoint of being easily dispersed in the liquid and exhibiting the function of releasing the liquid. For these reasons, the average particle size of the hollow fine particles encapsulating the low boiling point compound is more preferably 100 nm or more, and further preferably 200 nm or more. Moreover, it is more preferable that it is 50 micrometers or less, and it is further more preferable that it is 30 micrometers or less.

  Among these substances, hollow fine particles composed of ferrite are particularly preferable. As already mentioned, if the shell of hollow fine particles made of ferrite is used, the magnetism of ferrite can be used, and the particles can be manipulated magnetically and induction heating using an alternating magnetic field is possible. It is. The hollow ferrite fine particles can be produced by using silica fine particles or the like as template particles, performing ferrite plating on the surface of the template particles, and then dissolving and removing the template. By producing ferrite hollow fine particles by this method, particles having good particle shape and good dispersibility, and having fine through-holes and necessary strength can be obtained.

3. Low-boiling point compound The low-boiling point compound used in the present invention is a compound having a relatively low boiling point, and the vapor pressure rapidly increases when the boiling point is exceeded by temperature rise. If it is such a compound and it is insoluble with respect to the liquid to be used, there will be no restriction | limiting in particular. Among such compounds, for example, a compound that is liquid at room temperature and easily reaches the boiling point when the temperature rises above the room temperature, and vaporizes when the temperature rises beyond the boiling point, and the vapor pressure increases is preferable. . In particular, a compound having a vapor pressure of 1 atm at an appropriate temperature higher than room temperature, for example, a compound having a vapor pressure of 1 atm or more of 40 ° C. or more and 100 ° C. or less is a low boiling point compound used in the present invention. It is preferable.

  The low boiling point compound used in the present invention must be insoluble in the liquid encapsulated in the hollow fine particles. If the low boiling point compound encapsulated in the hollow microparticles is dissolved in the liquid encapsulated in the hollow microparticles, a vapor pressure sufficient to release the liquid from the hollow microparticles cannot be obtained even when the temperature is raised. Examples of low boiling point compounds insoluble in aqueous liquids such as physiological saline include CFC-113 (CAS 76-13-1, boiling point 47.6 ° C), HCFC-225cb (CAS 507-55-1, boiling point 55.1 ° C), HFC Fluorocarbons such as -43-10mee (CAS 138495-42-8, boiling point 55.6 ° C) and HFC365mfc, CSF-14 (CAS 406-58-6, boiling point 40.2 ° C) can be used. Also, n-hexane (boiling point 68.7 ° C), n-butane (boiling point 98.4 ° C), i-hexane (boiling point 60.3 ° C), 2-2-dimethylbutane (boiling point 49.7 ° C), 2-3 dimethylbutane ( Aliphatic saturated hydrocarbons such as boiling point 58.0 ° C. and 3-methylpentane (boiling point 63.3 ° C.) can also be used.

  The insolubility of the low boiling point compound in the liquid of the present invention is preferably 0.5 mM / l or less, more preferably 50 μmM / l or less, more preferably 5 μmM / l or less at 25 ° C. and 1 atm. .

4). Surface Modification of Hollow Fine Particles The surface of the low boiling point compound-encapsulating hollow fine particles of the present invention can be modified according to the application. For example, in order to increase the dispersibility of the fine particles in an aqueous solution, a surfactant can be adsorbed on the surface. In addition, for example, in order to use the fine particles in a living body and keep the residence time in a specific part of the living body long, a substance having stealth property can be provided on the surface. In order to adsorb these fine particles to cancer cells and release a drug that attacks the cancer cells there, the surface can be modified with a substance that specifically adsorbs to the cancer cells. Similarly, in the case of administration of antibiotics or anti-rheumatic drugs, surface modification of fine particles suitable for each purpose can be performed.

5). Application as a local temperature sensor The low-boiling compound-containing hollow fine particles of the present invention can be used as a temperature sensor that can check a local temperature, which is difficult to measure by ordinary methods, by combining with an ultrasonic imaging device. Can do. If there are hollow microparticles that contain a low-boiling compound and a liquid in the liquid, and the liquid temperature exceeds the boiling point of the low-boiling compound, the vapor pressure of the low-boiling compound increases rapidly, and the microparticles are contained in the liquid. Release. As a result, the inside of the fine particles is filled with gas. When this is observed with an ultrasonic imaging device, if the temperature of the liquid holding the fine particles is lower than the boiling point of the low boiling point compound, the image of the fine particles is only weak, but the temperature of the liquid holding the fine particles is low. When the vaporization exceeds the boiling point of the compound, the scattering of ultrasonic waves from the fine particles becomes strong, and the image of the fine particles becomes sharply sharp. Therefore, the temperature can be checked by using a low boiling point compound whose boiling point is the temperature to be checked.

  In hyperthermia, temperature management in a living body is very important, and it is required to manage temperature correctly. The low-boiling compound-containing hollow fine particles of the present invention are suitable for such applications.

Example 1 Hollow silica fine particles encapsulating decafluoropentane Encapsulation of low-boiling compounds First, a suspension of hollow silica fine particles having an average particle diameter of 2 μm and having a hollow sphere shape and monodispersed was placed in a four-necked 300 ml separable flask. One of the four mouths of the separable cover was closed with a rubber cap, two with a glass stopper with a cock, and one with a rubber stopper with a pressure gauge.

  Next, the cover was attached. Subsequently, the inside of the flask was evacuated by a pump, the particles were dried, and the inside of the hollow fine particles was also evacuated, and then the cock was closed to shut off the pump. Thereafter, 2H, 3H-decafluoropentane having a boiling point of 53.6 ° C. was added as a low boiling point compound with a needle inserted through the mouth of the rubber cap using a syringe.

  Next, the separable flask was heated to 55 ° C. with a water bath to vaporize the low boiling point compound, and the gaseous low boiling point compound was encapsulated in the hollow silica fine particles. Thereafter, an aqueous glucose solution was added into the separable flask using a syringe. Subsequently, the cock was opened, the separable cover was removed, and the vaporized low boiling point compound and air were replaced. At this time, the temperature was maintained at 55 ° C. with a water bath.

2. Encapsulation of glucose aqueous solution Thereafter, the separable flask is cooled with cold water to liquefy the low boiling point compound in the particles, thereby bringing the inside of the particles to a negative pressure and drawing the surrounding glucose aqueous solution into 2H and 3H which are low boiling point compounds. -Silica hollow fine particles enclosing a decafluoropentane droplet and an aqueous glucose solution were obtained.

3. Release of Encapsulated Glucose Aqueous Solution A suspension of 2H, 3H-decafluoropentane droplets obtained in this manner and silica hollow microparticles encapsulating a glucose aqueous solution suspended in pure water is heated to 55 ° C. in a water bath to produce 2H , 3H-decafluoropentane was vaporized, and the aqueous glucose solution was released from the ferrite hollow fine particles into the suspension outside the hollow fine particles by the vapor pressure of 2H, 3H-decafluoropentane accompanying the vaporization.

  It was confirmed by the change in the color of the liquid solution that the aqueous glucose solution was thus released into the suspension outside the hollow microparticles.

(Example 2) Decafluoropentane-encapsulated ferrite hollow fine particles Next, silica encapsulated fine particles used in Example 1 were replaced with ferrite hollow fine particles, and the same inclusion and release were performed. That is, the suspension of ferrite hollow fine particles was placed in a four-necked 300 ml separable flask. One of the four mouths of the separable cover was closed with a rubber cap, two with a glass stopper with a cock, and one with a rubber stopper with a pressure gauge, and the cover was attached. Subsequently, the inside of the flask was evacuated with a pump, the particles were dried, and the inside of the hollow fine particles was also evacuated, and then the cock was closed to shut off the pump. Thereafter, 2H, 3H-decafluoropentane having a boiling point of 53.6 ° C. was added as a low boiling point compound with a needle inserted from the mouth of the rubber cap using a syringe. Next, the separable flask was heated to 55 ° C. with a water bath to vaporize the low boiling point compound, and the gaseous low boiling point compound was encapsulated in the ferrite hollow fine particles. Thereafter, an aqueous glucose solution was added into the separable flask using a syringe. Subsequently, the cock was opened, the separable cover was removed, and the vaporized low boiling point compound and air were replaced. At this time, the temperature was maintained at 55 ° C. with a water bath. Thereafter, the separable flask is cooled with cold water to liquefy the low boiling point compound in the particles, thereby bringing the inside of the particles to a negative pressure and drawing the surrounding aqueous glucose solution into the ferrite hollow fine particles. -Decafluoropentane and an aqueous glucose solution were included.

  The suspension of ferrite fine particles containing 2H, 3H-decafluoropentane droplets and an aqueous glucose solution thus obtained suspended in pure water was heated to 55 ° C. in a water bath to obtain 2H, 3H-decafluoropentane. And the aqueous glucose solution was released from the ferrite hollow fine particles into the suspension outside the hollow fine particles by the vapor pressure of 2H, 3H-decafluoropentane accompanying the vaporization. It was confirmed by the change in the color of the liquid solution that the aqueous glucose solution was thus released into the suspension outside the hollow microparticles.

Example 3 Release of Encapsulated Glucose Aqueous Solution by Application of AC Magnetic Field FIG. 3 is a diagram showing a state in which ferrite hollow microparticles are induction heated using an AC magnetic field. In this figure, a suspension 302 of ferrite hollow fine particles whose concentration was adjusted to 25 mg / ml was covered with expanded polystyrene 304 used as a heat insulating material and placed in the center of a magnetic field generating coil 306. An alternating magnetic field was generated in this arrangement, and ferrite hollow fine particles were heated by induction heating. The temperature of the suspension was monitored using an optical fiber thermometer 308.

  FIG. 4 is a diagram showing the results. The condition was that the ferrite hollow fine particles were not surface-modified, and the suspension 302 was adjusted to have the concentration of 25 mg / ml and the magnetic field strength of the alternating magnetic field was 4.2 kA / m.

  FIG. 4 shows that in the frequency range from 100 kHz to 900 kHz, the higher the frequency of the alternating magnetic field, the better the heating. In the case of the configuration shown in FIG. 3, it was found that a saturation tendency was observed when the application time of the AC magnetic field exceeded 20 minutes, and that the heat generation and heat dissipation were balanced.

  A suspension obtained by suspending ferrite hollow fine particles enclosing 2H, 3H-decafluoropentane droplets and an aqueous glucose solution obtained in Example 2 in pure water was adjusted to 25 mg / ml, and this suspension is shown in FIG. As shown in the figure, it is covered with polystyrene foam and placed in the center of the magnetic field generating coil. An alternating magnetic field having a frequency of 800 kHz and a magnetic field strength of 4.2 kA / m is applied for 20 minutes to heat, and an aqueous glucose solution encapsulating hollow ferrite fine particles Was released into the suspension outside the hollow microparticles. Thus, it was confirmed by the change in the color of the liquid solution that the aqueous glucose solution was released into the suspension outside the hollow microparticles.

(Example 4) Temperature sensor In the same manner as in Example 1, silica hollow fine particles having an average particle diameter of 2 µm were encapsulated with a gas of 2H, 3H-decafluoropentane as a low boiling point compound at 55 ° C. Was immersed in pure water, cooled to room temperature to liquefy 2H, 3H-decafluoropentane, and pure water was taken up into the hollow portions of the silica hollow fine particles to be filled. Next, a hole was provided in a 13 cm × 11 cm surface of a rectangular parallelepiped agar block having dimensions of 13 cm × 11 cm × 8 cm, and a liquid in which silica hollow fine particles were dispersed in pure water was poured into the hole to fill the hole. .

An ultrasonic probe was brought into contact with the 11 cm × 8 cm side surface of the agar, and the agar was heated to examine the change in the ultrasonic scattering in the hole portion of the agar block as the temperature rose. As a result, it was found that when the temperature exceeds 53.6 ° C., which is the boiling point of 2H, 3H-decafluoropentane, ultrasonic scattering rapidly increases. It was also found that when the temperature was cooled to a temperature lower than 53.6 ° C., the ultrasonic scattering again became smaller, and the change in ultrasonic scattering due to the temperature change was reversible.

  According to the present invention, by raising the temperature of the hollow fine particles encapsulating the liquid substance and the low boiling point oxide, the low boiling point compound encapsulated in the hollow fine particles is vaporized to release the encapsulated liquid substance, It became possible to change the ultrasonic scattering intensity. Utilizing this property, it can be used as a temperature sensor for supplying a liquid substance to a required site or sensing a temperature at a place where a normal temperature sensor is difficult to arrange. Therefore, it is considered that the industrial applicability of the present invention is great.

It is the figure which showed typically the uptake | capture of the liquid substance to the hollow microparticles in this invention, and the liquid substance discharge | release from a hollow microparticle. It is the figure which showed the structure of the apparatus for enclosing a low boiling-point compound in the hollow microparticles of one Embodiment of this invention. It is the figure which showed the condition which carries out the induction heating of the ferrite hollow microparticles using the alternating current magnetic field in one Embodiment of this invention. FIG. 4 is a diagram showing the relationship between the AC magnetic field application time and the temperature rise when the ferrite hollow fine particles are heated by applying an AC magnetic field and induction heating in the embodiment of the present invention having the arrangement shown in FIG. 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Hollow fine particle, 102 ... Shell, 104 ... Hollow part, 106 ... Low boiling point compound in a gaseous state, 107 ... Low boiling point compound in a liquid state, 108 ... Liquid substance, 202 ... Hollow fine particle, 204 ························································································································································· 208 ················································· , 306 ... Magnetic field generating coil, 308 ... Optical fiber thermometer.

Claims (5)

A hollow fine particle having a hollow portion is formed in a shell having a minute through hole, and a low boiling point compound and a liquid substance having a higher boiling point than the low boiling point compound are included in the hollow portion,
Low-boiling compound-containing hollow fine particles, wherein the low-boiling compound is insoluble in the liquid substance.   The low-boiling compound-containing hollow fine particles according to claim 1, wherein the low-boiling compound has a vapor pressure of 1 atm.   3. The low-boiling compound-containing hollow fine particles according to claim 1, wherein the shell is made of silica.   The low-boiling compound-containing hollow fine particles according to claim 1 or 2, wherein the shell is made of ferrite.   A temperature sensor characterized in that a hollow fine particle containing a low-boiling-point compound and a liquid is used as a probe particle, and a change in ultrasonic scattering intensity of the probe particle due to a temperature rise is detected to check a temperature rise.

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