Pauzauskie, P. J. et al. Optical trapping and integration of semiconductor nanowire assemblies in water. Nature Mater. 5, 97-101

Department of Physics, University of California, Berkeley, Berkeley, California, United States
Nature Materials (Impact Factor: 36.5). 03/2006; 5(2):97-101. DOI: 10.1038/nmat1563
Source: PubMed


Semiconductor nanowires have received much attention owing to their potential use as building blocks of miniaturized electrical, nanofluidic and optical devices. Although chemical nanowire synthesis procedures have matured and now yield nanowires with specific compositions and growth directions, the use of these materials in scientific, biomedical and microelectronic applications is greatly restricted owing to a lack of methods to assemble nanowires into complex heterostructures with high spatial and angular precision. Here we show that an infrared single-beam optical trap can be used to individually trap, transfer and assemble high-aspect-ratio semiconductor nanowires into arbitrary structures in a fluid environment. Nanowires with diameters as small as 20 nm and aspect ratios of more than 100 can be trapped and transported in three dimensions, enabling the construction of nanowire architectures that may function as active photonic devices. Moreover, nanowire structures can now be assembled in physiological environments, offering new forms of chemical, mechanical and optical stimulation of living cells.

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    • "Optical manipulation and control of nanoparticles is potentially important in many areas of physical and life sciences [1]. In particular, controlling the position and orientation of elongated objects leads the way towards exciting applications: in nanotechnology, optically trapped semiconducting nanowires have been translated, rotated, cut and fused in order to realize complex nanostructures [2] [3] [4]; in spectroscopy, the composition and morphology of a sample have been probed by scanning optically trapped nanowires [5] and polymer nanofibres [6] over the sample's surface; in biophysics, many bacteria, viruses and macromolecules with rod-like shapes have been optically manipulated and studied [7]. However, optical manipulation of nanoobjects is particularly challenging; in fact, the techniques developed for optical manipulation of microparticles and, in particular, standard threedimensional optical tweezers — i.e., tightly focused laser beams capable of confining microparticles [8] [9] — cannot be straightforwardly scaled down to the nanoscale. "
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    • "DDA and T-Matrix calculations on true ellipsoids and cylinders show that C 0 is stable with very small particles, but perpendicular configurations have been predicted as well [15]. Experiments with nanoribbons by Pauzauskie et al. [10], small rods [19] and with microdisks [20] [21] also indicate that only a dynamical equilibrium may be reached, with the particle constantly oscillating in the laser beam. Below (Section 2) we report on optical levitation of polystyrene ellipsoids of different aspect ratios (k). "
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