Figure 1

(Color online) Top, SPP excitation in a $100\mathrm{microns}$ deep chamber results in crystal formation of a 2D hexagonal close packed structure. This figure shows an accumulated array of approximately 2800 particles. The image is a composite of 12 frames; inset shows hexagonal ordering. Middle, a Voronoi plot showing the Wigner-Seitz cell for each colloid in the aggregation indicates that at the center there is a predominantly closed-packed crystalline arrangement (hexagonal), where as at the periphery, particles are more fluidlike with no preferred nearest neighbor arrangement. Bottom, reflectivity of the incident light and mean velocity (curve is a guide to the eye) of the particles as a function of incident angle. Mean particle velocities were determined by tracking colloid motion over set interval $\left(100\mathrm{\mu }\mathrm{m}\right)$ at a distance of $100\mathrm{\mu }\mathrm{m}$ from the center of the aggregation. Measurements were averaged over 20 particles for each incident angle.Reuse & Permissions

Figure 2

A temperature dependent fluorescent dye (BCECF) was used to assess the extent of heating in the chamber under SPP excitation. (a) Shows fluorescence spectra from BCECF dye in the sample chamber when heated to a known temperature, measured using a thermocouple. The change in the peak intensity, (b), was used to estimate the sample temperature for different SPP excitation powers.Reuse & Permissions

Figure 3

Successive frames showing the behavior of colloidal particles ($5\mathrm{\mu }\mathrm{m}$ diameter) as a function on increasing power in a thin sample chamber. We observe the formation of linear arrays as can be seen in frame 4 due to an enhanced optical interaction from the SPP excitation. Notably the power required to form such chains is approximately a factor of 3 less than that for standard evanescent wave with the same beam parameters.Reuse & Permissions

Figure 4

Increasing the power in a thin chamber reveals lateral thermophoresis occurring which results in the repulsion of particles form the region of SPP excitation (hot to cold) and the arrangement of the repelled colloids into linear arrays in the periphery of the region. The frames show light scattered by the colloids (no white light illumination). The top and bottom inset are a detailed view (illuminated with white light) of the linear ordering of the accumulated particles.Reuse & Permissions