Optical Tweezers(광집게)의원리와 응용

Optical tweezers?

두 빔에 의한 포획 광학 부상 (optical levitation)

광

섬

유

빛의 산란에의한 힘

중력

대물렌즈

Optical tweezers(광집게)

History and Issues

1970, Ashikin : Optical levitation

1986, Ashikin et al : Optical tweezers

1990, Burns et al : Periodic structures by using interference patterns

1997, Chiou et al : Trapping and manipulation of micro particles

by using interference fringes

…

<Issues>

- Optical force model

- Manipulation(patterning) of multi-particles

- Bio-Medical applications

1. Optical force models

Optical tweezers

Electromagnetic model

Ray Optics model

- For R <<10

- For R >>10

1) Electromagnetic model

The change in the electrostatic energy ;

1

2

dVtrdVW T

VV

),(E2

)()EE)((

2

1 2

112

1212

11

V1

22

2

2

22

2

201

22exp

2)(

2)(

w

z

w

yx

w

PrE

cnrI

dVrIcn

nn

V

1

)()(

1

2

1

2

20

WF

2

0

22

222

0

2

1

2

1

2

20 sinh2

exp2

)(4

w

Rza

w

Raz

w

Raerf

cn

PnnF ccc

ax

2

0

2

222

0

1

2

1

2

20 sinh2

exp22

)(4

w

Ra

w

Ra

w

Raerf

w

Raerf

cn

PnnF cccc

tr

2) Ray optics model

scattering force

gradient force

A B

F

beam axis

1 234

y

x

z

O

O

r

PRP

TRP

T2RP

FA

Fs

Fg

FAF

B

S

Qc

PnF 1

collimated beam

Fg < Fs

focused beam

Fg > Fs

Generally, optical trapping force

Fg : gradient force

Fs : scattering force

- Optical force

(1) Axial trapping

dPqc

ngdF

dPqc

nsdF

gg

ss

1

1

ˆ

,ˆ

where,

2

2

121

2

1

2

2

121

2

1

2cos21

]2sin)(2[sin2cos

,2cos21

]2cos)(2[cos2cos1

RR

RTRq

RR

RTRq

g

s

gsnet FdFdFd

0

0

2

0

22

02

0

)sincos)(/2exp(2

4

sgax qqwrrdrdQ

ax

sgax

Qc

Pn

qqwrrdrdc

PnF

1

0

2

0

22

02

0

1 0

)sincos)(/2exp(2

4

- Axial trapping efficiency

- Axial trapping force

(2) Transverse trapping

IdSqqc

ndF sgnet )cossin(1

tr

sg

Qc

Pn

qq

rrdrdc

PnF

1

0 0

2

0

2

2

0

1

)sincos(

)/2exp(4 0

Experimental setup

Laser

diode

Objctive

lens

lens

PBS

lens1 lens2

CCD

Dichroic

mirror

Hallogen lamp

Z-axis

Y-axis

Motorized translation

stage

Trapping Image according to trapping direction

Axial trapping

transverse trapping

논의점 - 광포획 효율의 변화 (포획 깊이)

Laser

diode

Lens 1Lens 2

Dichroic

mirror

chamber

Cover glass

Slide glass

Index matching oil

R

(aperture size)

Beam radius

stage

Objctive lens

논의점 - 광포획 효율의 변화 (빔반경)

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6

0.005

0.010

0.015

0.11

0.12

0.13

0.14

0.15

0.16

0.17

Q

ratio (0 / R)

For small particle

For big particle

3) Beam optics model

2

0

2

0

2

0

2

0 1

z

r

2

0

2

0

2

0

22

0

2

0

2

0

2

0

11

z

rz

rzR

2

0

2

0

2

0

2

0

z

rzz

The calculation for existing model was performed the fixed incident angle for all

particle. That is, incident angle independent of particle diameter.

2

0

2

0

2

0

22

0

2

0

2

0

2

0

2

0

2

0

2

0

2

0

11

1

z

rz

rz

z

r

ArcSinR

ArcSin

Incident angle

2. Manipulation(patterning) of multi-particles

CNT

SWNT

( single-walled cabon nanotube)

MWNT

(Mulit-walled cabon nanotube)

1) Carbon nanotubes

CNT trap실험 장치도

Lens 1

Laser

diode

Dichroic

mirror

Lens 2

Cover glass

Slide glass

Index matching oil

Objctive lens

CCD

Hallogen lamp

PC

5m

HY letters

X

Y

5m

X,Y letters

CCD image of aligned CNT SEM Image of ring pattern

시간에 따른 CNT Ring Pattern 형성

00:03

00:10

22:3000:05

01:3000:07

00:00

Laser On 5m

Laser Off

Sequential CCD image of CNT to form ring pattern in the chamber

- OPTICAL TWEEZERS: MICROBUBBLES AND NANOTUBES

Dr. Phil Jones , 6 March 2007

- Nanofabrication with Holographic Optical Tweezers

Pamela Korda, Gabriel C. Spalding, Eric R. Dufresne, David G. Grier

November 16, 2000

- Single-particle microelectrophoresis with optical tweezers

Van Heiningen, Hill, 2007

2) Micro-patterning

Surface tension-enhanced optical

trapping for lateral close-packing

Cell-to-cell interactions

Cell fusion dynamics

1) Raman spectroscopy

RayleighScattering

RamanScatteringE

3. Bio-Medical applications

0

0

0

Rayleigh Stokes Anti-Stoke

m

0 m

0

Schematic Diagram of Experimental Set-up

objective

lens

CCD

camera

chamber

dichroic

mirror

beam-

splitter

LD

monochromater

PC

PMT

grating

dichroic

mirror

source : 0 = 834 nm

The McCreery Research Group(The Ohio State spectrum)

LTRS system 상용 Raman microscopy

5 m

LTRS system 상용 Raman microscopy

m2

포획 깊이에 따른 Raman peak 크기 변화

(1) (2)

2) Yeast trap and manipulation

PC

Laser

CCD

OL

L L

M

M

M

M

L : Lens

M : Mirror

BS : Beam Splitter

OL : Objective lens

BS

Michelson

interferometer

광 포획된 yeast의 발아

발아 하고 있는 yeast

발아하고 있는 yeast의 딸세포에 대한 주위 세포들의 영향

Yeast의 딸세포의 발아.

(a) Living yeast cells (b)Dead yeast cells

Changan Xie et. al. Optics Letters 27, 4, 2002

Tying a knot in the protein actin. By using optical tweezers

to manipulate the ends of the molecule, the chain is curl..)

3) Biological applications

Calibration of optical trapping efficiency

Dependence of the optical trapping efficiency of

a biconcave red blood cell flowing in a rectangular

microchannel on the sphericity index and the channel geometry

Applicational example) Malaria-infected RBC

Combined microchannel-type erythrocyte (RGB) deformability test with optical tweezers

Cell damage during femtosecond optical trapping

Damage thresholds for biological cells(RBC)

Platelet(혈소판)

RBC-under threshold

RBC-above threshold

6 mW 20 mWLaser power : 90% of the damage threshold (1.8 mW)

t=0 t=7m 30s

t=13m 5s t=20m

t=30m

damage

scar

Cell disruption