title: Brownian motion of tethered nanowires.
abstract: Brownian motion of slender particles near a boundary is ubiquitous in biological systems and in nanomaterial assembly, but the complex hydrodynamic interaction in those systems is still poorly understood. Here, we report experimental and computational studies of the Brownian motion of silicon nanowires tethered on a substrate. An optical interference method enabled direct observation of microscopic rotations of the slender bodies in three dimensions with high angular and temporal resolutions. This quantitative observation revealed anisotropic and angle-dependent hydrodynamic wall effects: rotational diffusivity in inclined and azimuth directions follows different power laws as a function of the length, ∼ L(-2.5) and ∼ L(-3), respectively, and is more hindered for smaller inclined angles. In parallel, we developed an implicit simulation technique that takes the complex wire-wall hydrodynamic interactions into account efficiently, the result of which agreed well with the experimentally observed angle-dependent diffusion. The demonstrated techniques provide a platform for studying the microrheology of soft condensed matters, such as colloidal and biological systems near interfaces, and exploring the optimal self-assembly conditions of nanostructures.
authors.affiliation: NSF Nano-scale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA and Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA.
authors.forename: Sadao
authors.initials: S
authors.lastname: Ota
authors.affiliation: NSF Nano-scale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA and Material Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA.
authors.forename: Tongcang
authors.initials: T
authors.lastname: Li
authors.affiliation: NSF Nano-scale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA.
authors.forename: Yimin
authors.initials: Y
authors.lastname: Li
authors.affiliation: NSF Nano-scale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA.
authors.forename: Ziliang
authors.initials: Z
authors.lastname: Ye
authors.affiliation: NSF Nano-scale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Labno
authors.affiliation: NSF Nano-scale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA and Material Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Yin
authors.affiliation: Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA.
authors.forename: Mohammad-Reza
authors.initials: MR
authors.lastname: Alam
authors.affiliation: NSF Nano-scale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA and Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA and Material Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhang
mesh_terms: D003198:Computer Simulation; D004058:Diffusion; D008956:Models, Chemical; D008958:Models, Molecular; D015233:Models, Statistical; D009038:Motion; D053770:Nanowires / Q000737:chemistry* / Q000648:ultrastructure*