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Optical trapping carbon nanotubes. Jianlong Zhang et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 284 (2006) 369. Itoh Lab Yasuhiko Saito. Contents. Introduction Optical manipulation Radiation force Carbon nanotube (CNT) Set up
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Optical trapping carbon nanotubes Jianlong Zhang et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects284 (2006) 369 Itoh Lab Yasuhiko Saito
Contents • Introduction Optical manipulation Radiation force Carbon nanotube (CNT) • Set up • Experimental results • Summary
Optical manipulation “Manipulation” means “skillful handling”. Optical manipulation is the technique for handling small objectsusing radiation force without contact. Attracting much attention from the field of biology, chemistry, material engineering and medical science Ref.)D.G.Grier, Nature Vol.424,810 (2003)
Radiation force Gradient force Absorbing force Scattaring force Potential field + Laser Resultantforce Interaction energy Gradient force Law of conservation of momentum
Carbon nanotube (CNT) • hollow cylinders of graphite sheets • grouped into a single-walled CNTs (SWNTs)and a multi-walled CNTs (MWNTs) by the number of graphite sheets in CNTs • SWNT have various electrical properties which depend on their chirality. Metal Semiconductor Metal Semiconductor Metal http://otfl.hanyang.ac.kr/research/new%20CNT%20new.htm Applied to field effect transistor, complex material, etc
motivation • In order to construct nanostructures by CNTs, exact controls of CNTs in the optical trap are required. • Optical manipulation is a powerful tool for processing nanosize objects and it’s suitable for controlling of CNTs.
Set up Beam expander (convex lenses) Laser diode 834nm 124mW Linearly polarized Aqueaus solution of CNTs
Horizontal and vertical trapping Vertical trapping of CNTs Horizontal trapping of CNTs Laser CNTs bundle
Vertical trapping Laser Laser Laser CNTs bundle Trapping one end of CNTs Increasing trapping depth Vertical trapping
Controlling the orientation of the CNTs bundle Long CNTs bundle Torque can’t orientate CNTs bundle. Torque isn’t induced. Short CNTs bundle Short CNTs bundle Long CNTs bundle
Discussion Polarization of laser beam decides the orientation of trapping CNTs bundles direction. Interaction energy Electric field Electric field polarization polarization
Rotation of CNTs bundle Solution convection by heating effect The dotted circle indicates the position of the optical trap. One end of CNTs bundle is trapped. Jianlong Zhang et al. Optics Communicaitons 267 260(2006)
Summary • Authors succeeded in controlling CNTs bundle by optical manipulation. • By controlling trapping depth , CNTs bundle can be vertically trapped from horizontal trapped. • CNTs bundle can be rotated by the solution convection.