Optical Trapping and Integration of Semiconductor Nanowire Assemblies in Water

The use of nanowires in scientific, biomedical, and microelectronic applications is greatly restricted due 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 above 100 can be trapped and transported in three dimensions, enabling the construction of nanowire architectures which may function as active photonic devices. Moreover, nanowire structures can now be assembled in physiological environments, offering novel forms of chemical, mechanical, and optical stimulation of living cells.