System and method for finding the size of one of more individual particles, such as nanoparticles for example, in real time utilizing a microsphere's whispering gallery modes (“WGMs”)

Patent metadata

Field	Value
Publication number	US-9709476-B2
Application number	US-201514858342-A
Country	US
Kind code	B2
Filing date	Sep 18, 2015
Priority date	Sep 18, 2014
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

Example systems and methods are provided to determine the size and/or mass of a particle, such as a nanoparticle for example, deterministically (i.e., non-statistically). At least two resonances of the same radial order, having the same angular momentum number l but different azimuthal numbers m (−l<m<l) are excited in a WGM resonator. The particle's latitude angle on the WGM resonator is located using a ratio of detected resonance wavelength shifts. Finally, at least one of (A) the particle's size, and (B) the particle's mass, is determined from the latitude angle of the particle.

First claim

What is claimed is:

1. A method for determining the size of a particle, the method comprising:
a) exciting at least two resonances of the same radial order, having the same angular momentum number l but different azimuthal numbers m (−l<m<l) in a WGM resonator on which the particle has been adsorbed;
b) locating the particle's latitude angle on the WGM resonator using a ratio of detected resonance wavelength shifts; and
c) determining at least one of (A) the particle's size, and (B) the particle's mass, from the latitude angle of the particle.

2. The method of claim 1 wherein the act of locating the particle's latitude angle on the WGM resonator using a ratio of detected resonance wavelength shifts includes determining:

ξ
p

=

arctan
⁡

(

l

2
⁢
l

⁢

(

Δλ

l
,

l
-
1

Δλ

l
,
l

-

2
l

)

)

where λ l and λ l−1 are resonance wavelengths at polar modes of the WGM resonator.

3. The method of claim 1 wherein the act of determining at least one of (A) the particle's mass, and (B) the particle's size from a polar angle of the particle position includes determining:

a
3

⁢

g
⁡

(

a
/
L

)

≅

(

n
s
2

-

n
e
2

)

⁢

R
3



Y

l
,
l

⁡

(

ξ
p

)



2

⁢
4
⁢
π
⁢

⁢

n
e
2

⁢

n
p
2

-

n
e
2

n
p
2

+

n
e
2

⁢

Δλ

l
,
l

λ

where λ is the resonant wavelength of the microsphere,
a is the particle's radius, a 3 is the particle's volume,

α
=

α
ex

ɛ
0

=

4
⁢
π
⁢

⁢

n
e
2

⁢

n
p
2

-

n
e
2

n
p
2

+

2
⁢

n
e
2

⁢

a
3

is the “geometric” pola

Assignees

• Arnold Stephen
• Keng Ta Kang
• Shopova Siyka
• Univ New York

Inventors

• Arnold Stephen
• Keng Ta Kang
• Shopova Siyka

Classifications

• G01N15/0205 Primary

  by optical means · CPC title

• G01N2015/0038

  Investigating nanoparticles · CPC title

• G01N21/31

  Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry {(G01N21/72 takes precedence)} · CPC title