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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 Experimental results Summary Optical manipulation “Manipulation” means “skillful handling”. Optical manipulation is the technique for handling small objects using 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 + Laser Resultant force F k dN dt Law of conservation of momentum Potential field Interaction energy U PE E2 2 Gradient force F U E 2 Carbon nanotube (CNT) hollow cylinders of graphite sheets grouped into a single-walled CNTs (SWNTs) and a multiwalled CNTs (MWNTs) by the number of graphite sheets in CNTs SWNT have various electrical properties which depend on their chirality. Metal Semiconductor Metal Metal Semiconductor 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 Horizontal trapping of CNTs Laser CNTs bundle Vertical trapping of CNTs 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. Short CNTs bundle Torque isn’t induced. Long CNTs bundle Short CNTs bundle Discussion Polarization of laser beam decides the orientation of trapping CNTs bundles direction. Interaction energy U P E 2 polarization Electric field Electric field Rotation of CNTs bundle Solution convection by heating effect The dotted circle indicates the position of the optical trap. Jianlong Zhang et al. Optics Communicaitons 267 260(2006) One end of CNTs bundle is trapped. 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.