Nonconservative dynamics of optically trapped high-aspect-ratio nanowires

Wen Jun Toe, Ignacio Ortega-Piwonka, Christopher N. Angstmann, Qiang Gao, Hark Hoe Tan, Chennupati Jagadish, Bruce I. Henry, and Peter J. Reece

We investigate the dynamics of high-aspect-ratio nanowires trapped axially in a single gradient force optical tweezers. A power spectrum analysis of the dynamics reveals a broad spectral resonance of the order of kHz with peak properties that are strongly dependent on the input trapping power. A dynamical model incorporating linear restoring optical forces, a nonconservative asymmetric coupling between translational and rotational degrees of freedom, viscous drag, and white noise provides an excellent fit to experimental observations. A persistent low-frequency cyclical motion around the equilibrium trapping position, with a frequency distinct from the spectral resonance, is observed from the time series data.

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