SEMICONDUCTOR NANOWIRE MANIPULATION USING

IPTOELECTRONIC TWEEZERS

Arsh Jamshidi, Peter J. Pauzauskie, Aaron T. Ohta , Pei-Yu Chiou, Peidong Ya

ng and Ming C, Wu

University of Caligormia, Berkeley,USA

IEEE MEMS2007

報告人 :蘇聖欽

Outline Motivation Theoretical Background

Optical Tweezers Optoelectronic tweezers Theory Optoelectronic tweezers Force Device Structure

Experimental Results Experimental Setup Manipulation of Silicon Nanowires Speed and Trapping Radius Measurements Nanowires Assembly

Conclusion

Motivation

The ability of optical tweezers to perform parallel assembly is hampered by their high optical power density (107w/cm2) and small area (approximately 1 um*1 um) .

Dielectrophoresis can trap nanowires ,but he trapping sites are fixed the electrode pattern .

OET is capable of manipulating a large number of microparticles or cells over a large area .

Outline Motivation Theoretical Background

Optical Tweezers Optoelectronic tweezers Theory Optoelectronic tweezers Force Device Structure

Experimental Results Experimental Setup Manipulation of Silicon Nanowires Speed and Trapping Radius Measurements Nanowire Assembly

Conclusion

Optical Tweezers Mie regime(米氏定理 ) :

適用的粒子大小 diameter of particle >> 。 動量守恆原理。

Rayleigh regime(雷利定理 ) : 適用的粒子大小 diameter of particle << 。 電磁波理論，變動的電場使粒子極化，產生引力。

electric field

particle

Optoelectronic tweezers Theory

They use AC voltage producing electric field .

Arsh Jamshidi,2007

OET

Mechanical

Optical Tweezers Dielectrophoresis

Optical Electrical

Electric field

OET device

Optoelectronic tweezers Force

Optoelectronic tweezers force under an AC bias is given by:

Drag force:

)(Re)6/( 22 EKlrF mDEP

)1)ln(2/(8 lrlvFDrag

η:viscous

V:nanowires velocity

Re(K):depolarization factor

l:nanowirws length

r:nanowires radius

Arsh Jamshidi,2007

Device Structure

OET device apparatus : a top indium-tin–oxide (ITO) electrode a 1–um-thick layer of photoconductive material (amorph

ous silicon) An applied AC bias of 20

Vpp at 50kHz

Arsh Jamshidi,2007

15um ITO

Liquid

1um amorphous silicon

20Vpp

Outline Motivation Theoretical Background

Optical Tweezers Optoelectronic tweezers Theory Optoelectronic tweezers Force Device Structure

Experimental Results Experimental Setup Manipulation of Silicon Nanowires Speed and Trapping Radius Measurements Nanowire Assembly

Conclusion

Experimental Setup

4mW HeNe Laser

Attenuator

40x

OET Device

mirror

Motorizesed stage

20x

CCD Camera

Equipment :

-A 632nm HeNe laser -A 40X objective lens-Solution of DI water and KCl-Olympus BX51M microscopy using a CCD camera

Manipulation of Silicon Nanowires

The long-axis of the nanowires (CdS) aligned with the electric field in the liquid layer .

Si nanowires experienced an attractive force towards the illuminated area after turning on the laser .

Arsh Jamshidi,2007

r:100nm

l:1-5um

Speed and Trapping Radius Measurements

Si nanowires with 390Ω-cm magnitudes comparable to the experimental results .

Figure shows the measured maximum speed of the nanowires versus the applied AC voltage .

Arsh Jamshidi,2007

Max speed:

135um/s

Max radius:

120um

Separation of two nanowires

Nanowires within a trapping radius can still be trapped individually by controlling the scanning speed of the laser spot .

Arsh Jamshidi,2007

r:100nm

l:1-5um

Nanowire Assembly

A spherical lens is used to create a line laser pattern for movement of Si nanowires in arrays of 2 or 3 .

Arsh Jamshidi,2007

Conclusion The flexibility of the optoelectronic tweezers devic

e, low required optical power intensity (optical tweezers power 107w/cm2, OET power 100w/cm2) .

Large working area makes OET a very attractive tool for the manipulation for nanowires (arrays of 2 or 3) .

A maximum velocity of 135um/s and a trapping rad

ius of 122um are achieved using this method .

Reference

[1] Arsh Jamshidi, Peter J. Pauzauskie, Aaron T. Ohta , Pei-Yu Chiou, Peidong Yang and Ming C, Wu, “SEMICONDUCTOR NANOWIRE MANIPULATION USING IPTOELECTRONIC TWEEZERS ”, IEEE MEMS,pp155-158(2007).

[2]Aaron T. Ohta, Pei Yu Chiou, and Min C. Wu, ”Dynamic DMD-Driven Optoelectronic Tweezers for Microscopic Particle Manipulation”, University of California,Los Angeles(2004).

The End