Fig. 1: Trapping of microparticles above a nanopatterned surface.
a Artist rendition of a spherical (left) and a disk-shaped (right) microparticle trapped above a circular uncoated pattern within a thin gold layer coated on a glass surface. The insets illustrate the notation used in this article. b Scanning electron microscope (SEM) images of a gold-coated glass surface with circular patterns of diameters 2a between 1 μm and 2.8 μm. The thickness of the gold-coating is 25nm. c SEM images of microdisks (upright coins) with diameter 2R = 2.4 μm. d A microsphere is freely diffusing in the xy-plane (blue trajectory) at ΔT = ( − 0.30 ± 0.02)K off the critical temperature Tc, e while it gets confined above the circular pattern (red trajectory) for ΔT = (0.00 ± 0.02)K, i.e., much closer to Tc. f Experimentally measured potentials at ΔT = ( − 0.30 ± 0.02)K (blue lines) and ΔT = (0.00 ± 0.02)K (red lines). g Theoretically predicted potentials at ΔT ≈ − 0.3K (blue lines) and ΔT ≈ − 0.15K (red lines). h A microdisk is trapped already at ΔT = ( − 0.30 ± 0.02)K (blue trajectories), and (i) even more strongly at ΔT = (0.00 ± 0.02)K (red trajectories). This is confirmed by (j) the experimentally measured and (k) theoretically calculated potentials. See Supplementary Fig. S8 for calculations of forces and torques acting on the microdisk. Source data are provided as a Source Data file.
