title: Measuring three-dimensional interaction potentials using optical interference.
abstract: We describe the application of three-dimensional (3D) scattering interferometric (iSCAT) imaging to the measurement of spatial interaction potentials for nano-objects in solution. We study electrostatically trapped gold particles in a nanofluidic device and present details on axial particle localization in the presence of a strongly reflecting interface. Our results demonstrate high-speed (~kHz) particle tracking with subnanometer localization precision in the axial and average 2.5 nm in the lateral dimension. A comparison of the measured levitation heights of trapped particles with the calculated values for traps of various geometries reveals good agreement. Our work demonstrates that iSCAT imaging delivers label-free, high-speed and accurate 3D tracking of nano-objects conducive to probing weak and long-range interaction potentials in solution.
authors.affiliation: Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen, Switzerland.
authors.forename: Nassir
authors.initials: N
authors.lastname: Mojarad
authors.forename: Vahid
authors.initials: V
authors.lastname: Sandoghdar
authors.forename: Madhavi
authors.initials: M
authors.lastname: Krishnan
mesh_terms: D021621:Imaging, Three-Dimensional / Q000379:methods*; D007368:Interferometry / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D012031:Refractometry / Q000295:instrumentation*