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Differential mobility analyzer, particle measuring system, and particle sorting system

外国特許コード F190009903
整理番号 07734-US
掲載日 2019年8月26日
出願国 アメリカ合衆国
出願番号 97941510
公報番号 20120001067
公報番号 8698076
出願日 平成22年12月28日(2010.12.28)
公報発行日 平成24年1月5日(2012.1.5)
公報発行日 平成26年4月15日(2014.4.15)
優先権データ
  • 特願2010-021552 (2010.2.2) JP
発明の名称 (英語) Differential mobility analyzer, particle measuring system, and particle sorting system
発明の概要(英語) In order to provide a differential mobility analyzer and the like that allows (i) easy increase of an upper limit of particle size of charged particle which can be classified and (ii) analysis of charged particles whose particle size is variable, a DMA (Differential Mobility Analyzer) includes: a classification tank in which an inlet electrode having an inlet slit, an intermediate electrode having a slit, and an outlet electrode having an outlet slit are arranged in sequence in such a manner that adjacent electrodes are disposed opposing each other at predetermined intervals; a gas supply section supplying the classification tank with sheath gas; and a voltage generator applying a predetermined voltage between the electrodes disposed opposing each other, the classification tank including a first classification section and a second classification section each formed by the electrodes disposed opposing each other, and the gas supply section controlling a flow rate of the sheath gas to be supplied to the classification tank individually per first classification section and second classification section.
従来技術、競合技術の概要(英語) BACKGROUND ART
In recent years, fine particles such as dust and mist suspended in gaseous atmosphere have been receiving attention, in association with suppression of particle contamination in a semiconductor manufacturing process, development of quantum nanoscale material, clarification of generating mechanism of acid rain and smog in the air, and so on.
Differential mobility analyzers (DMAs) have been used to classify aerosol particles that are of nanometer-scale to micrometer-scale particle size. The DMAs make use of a phenomenon that electrical mobility of charged particles in airflow is dependent on their particle size. Cylindrical differential mobility analyzers (CDMAs) are widely used among the DMAs (see Non Patent Literature 1). As a result of significant progress in the recent years, the DMAs are now capable of classifying charged particles having such minimal particle size as 10 nanometers or less at the smallest, and are operable even under reduced pressure (see Patent Literature 1).
FIG. 9 illustrates an example of a conventional CDMA. As illustrated in FIG. 9, a CDMA 800 has a double cylinder structure including a central rod (inner cylinder) 1 and a surrounding body (outer cylinder) 2. A predetermined voltage is applied between an inner peripheral surface of the surrounding body 2 (outer cylinder electrode) and an outer peripheral surface of the central rod 1 (inner cylinder electrode) by a variable voltage generator. Sheath gas is supplied from a supply opening (not illustrated) provided above the surrounding body 2 so as to form a laminar flow in a space between the surrounding body 2 and the central rod 1. The surrounding body 2 has an annular inlet slit 3 in its upper part, from which the charged particles are introduced into the analyzer. The central rod 1 has an annular outlet slit 4 in its lower part, from which the charged particles having been classified are discharged outside the analyzer.
The following description deals with a principle of classifying particles in the CDMA 800. Assume that, in the CDMA 800, a laminar flow condition of the sheath gas is not effected by sample gas containing the charged particles while the sample gas containing the charged particles is introduced via the inlet slit 3 at a predetermined flow rate Qa and discharged from the outlet slit 4 at the same flow rate Qa with respect to a sufficient flow rate of the sheath gas. The charged aerosol particles (charged particles), once entered via the inlet slit 3 into the analyzer, travels downwards in a central axis direction along the inner wall of the surrounding body 2, together with the sheath gas forming the laminar flow in the space between the surrounding body 2 and the central rod 1. Meanwhile, due to an effect caused by an electric field (electrostatic attraction) generated by the variable voltage generator between the surrounding body 2 and the central rod 1, just the aerosol particles of one polarity are attracted toward the central rod 1 at velocities corresponding to their electrical mobility. The electrical mobility is dependent on the particle size of each particle. On this account, just the aerosol particles having a particular particle size reach the outlet slit 4 and are discharged outside the analyzer via the outlet slit 4.
The electrical mobility Zp of the charged particle is calculated by the following equation (1):

Zp=Qs·ln(R2/R1)/(2·π·V·L)  (1)
In the equation (1), Qs is a flow rate of the sheath gas, R2 is a radius of the surrounding body 2, and R1 is a radius of the central rod 1, as illustrated in FIG. 9. L is a distance between the inlet slit 3 and the outlet slit 4 along a direction parallel to the central axis. V is the voltage applied between the inner peripheral surface of the surrounding body 2 and the outer peripheral surface of the central rod 1.
The electrical mobility Zp of the charged particle can also be calculated by the following equation (2):

Zp=q·e·Cc/(3·π·μ·Dp)  (2)
In the equation (2), q is a charge amount of the charged particle, e is an elementary electric charge, Cc is a Cunningham correction factor, μ is a coefficient of viscosity of the sheath gas, and Dp is a particle diameter of the charged particle.
By solving the equations (1) and (2) simultaneously, the following equation (3) is achieved:

Dp=(2·V·L·q·e·Cc)/(3·μ·Qs·ln(R2/R1))  (3)
It is understood from the equation (3) that the particle diameter Dp of the charged particle to be classified is calculated as a function of the applied voltage V.
特許請求の範囲(英語) [claim1]
1. A differential mobility analyzer classifying charged particles according to electrical mobility, the differential mobility analyzer comprising:
a classification tank including n electrodes (where n is an integer equal to or greater than 3), each electrode having a planar shape, disposed in sequence in such a manner that the electrodes oppose each other as pairs, each pair having a predetermined space provided each of the electrodes, each of the n electrodes having at least one slit through which the charged particles pass;
a gas supply section supplying the classification tank with sheath gas; and
a voltage supply section applying a predetermined voltage between each of the pairs of the electrodes disposed opposing each other in the classification tank,
wherein the classification tank includes (n-1) stages of classification sections for classifying the charged particles, each of the classification sections being formed by a respective one of the pairs of the electrodes disposed opposing each other, and each of the classification sections having a sheath-gas inlet,
wherein the gas supply section controls a flow rate of the sheath gas supplied to the classification tank per classification section,
wherein the gas supply section includes: (i) gas supply tubes connected to each respective sheath-gas inlet of the classification sections; and (ii) gas supply controlling means provided to each of the gas supply tubes, and
wherein the sheath gas is flowed into at least one pair of adjacent classification sections in such a manner that the sheath gas is flowed into one classification section of the pair of adjacent classification sections in a direction opposite to that of the other classification section of the pair of adjacent classification sections.

[claim2]
2. A particle sorting system comprising:
a differential mobility analyzer according to claim 1; and
a particle sorting device sorting and collecting particles that have a predetermined particle size, the particles being classified by the differential mobility analyzer.

[claim3]
3. The differential mobility analyzer according to claim 1, wherein the gas supply means is a massflow controller.

[claim4]
4. The differential mobility analyzer according to claim 1, wherein the voltage supply section controls the voltage to be applied per pair of the electrodes disposed opposing each other.

[claim5]
5. The differential mobility analyzer according to claim 1, wherein the n of electrodes are shaped as flat plates and are disposed parallel to each other in the classification tank.

[claim6]
6. The differential mobility analyzer according to claim 1, wherein the gas supply section supplies the sheath gas to each of the classification sections at a substantially same flow rate as a discharge flow rate of the sheath gas discharged from the respective classification section.

[claim7]
7. A differential mobility analyzer classifying charged particles according to electrical mobility, the differential mobility analyzer comprising:
a classification tank including n electrodes (where n is an integer equal to or greater than 3), each electrode having a planar shape, disposed in sequence in such a manner that the electrodes oppose each other as pairs, each pair having a predetermined space provided each of the electrodes, each of the n electrodes having at least one slit through which the charged particles pass;
a gas supply section supplying the classification tank with sheath gas; and
a voltage supply section applying a predetermined voltage between each of the pairs of the electrodes disposed opposing each other in the classification tank,
wherein the classification tank includes (n-1) stages of classification sections for classifying the charged particles, each of the classification sections being formed by a respective one of the pairs of the electrodes disposed opposing each other, and each of the classification sections having a sheath-gas inlet,
wherein the gas supply section controls a flow rate of the sheath gas supplied to the classification tank per classification section, and
wherein the gas supply section includes: (i) gas supply tubes connected to each respective sheath-gas inlet of the classification sections; and (ii) gas supply controlling means provided to each of the gas supply tubes,
wherein the n of electrodes include an electrode having a plurality of slits, the plurality of slits including a slit serving as a slit for discharging the charged particles outside the classification tank, and the plurality of slits being opened at different heights of that electrode,
wherein the gas supply section controls a direction in which the sheath gas flows, per classification section, and
wherein the gas supply section is capable of redirecting the direction, in which the sheath gas flows, to an opposite direction within at least one of the classification sections.

[claim8]
8. A particle measuring system comprising:
a differential mobility analyzer according to claim 7; and
a particle component measuring device analyzing chemical component of particles classified by the differential mobility analyzer.

[claim9]
9. A particle sorting system comprising:
a differential mobility analyzer according to claim 7; and
a particle sorting device sorting and collecting particles that have a predetermined particle size, the particles being classified by the differential mobility analyzer.

[claim10]
10. A differential mobility analyzer classifying charged particles according to electrical mobility, the differential mobility analyzer comprising:
a classification tank including n electrodes (where n is an integer equal to or greater than 3), each electrode having a planar shape, disposed in sequence in such a manner that the electrodes oppose each other as pairs, each pair having a predetermined space provided each of the electrodes, each of the n electrodes having at least one slit through which the charged particles pass;
a gas supply section supplying the classification tank with sheath gas; and
a voltage supply section applying a predetermined voltage between each of the pairs of the electrodes disposed opposing each other in the classification tank,
wherein the classification tank includes (n-1) stages of classification sections for classifying the charged particles, each of the classification sections being formed by a respective one of the pairs of the electrodes disposed opposing each other, and each of the classification sections having a sheath-gas inlet,
wherein the gas supply section controls a flow rate of the sheath gas supplied to the classification tank per classification section, and
wherein the gas supply section includes: (i) gas supply tubes connected to each respective sheath-gas inlet of the classification sections; and (ii) gas supply controlling means provided to each of the gas supply tubes; and
a position changing mechanism including a pair of guide rails for guiding continuous movement of one of the electrodes in a pair of the electrodes disposed opposing each other in the direction in which the sheath gas flows or the opposite direction in at least one of the classification sections, the position changing mechanism changing the relative position of the slits in the pair of electrodes disposed opposing each other by the continuous movement of the electrode.

[claim11]
11. A particle measuring system comprising:
a differential mobility analyzer according to claim 10; and
a particle component measuring device analyzing chemical component of particles classified by the differential mobility analyzer.

[claim12]
12. A particle sorting system comprising:
a differential mobility analyzer according to claim 10; and
a particle sorting device sorting and collecting particles that have a predetermined particle size, the particles being classified by the differential mobility analyzer.

[claim13]
13. A particle measuring system comprising:
a differential mobility analyzer according to claim 1; and
a particle component measuring device analyzing chemical component of particles classified by the differential mobility analyzer.
  • 発明者/出願人(英語)
  • ORII Takaaki
  • KUDOH Satoshi
  • RIKEN
国際特許分類(IPC)

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