2 350 Water nanopolystyrene Few dispersed nanospheres 14 9,000 −1,000 0.6 4,100 50:50 water nanopolystyrene/distilled water + 1.5% formic acid Semi-covered layer of scattered nanospheres 14 9,000 −1,000 2.2 350 Water nanopolystyrene Tens of 3D ordered layers In all the processes, the humidity was monitored during deposition and typically was 20%. Results and discussion Following the experiments shown in Table 1, in this section, SEM observations and optical measurements are shown.

When the conditions for a Taylor cone formation are not met, drops fall on top of the substrate, and when they dry, no significant order is observed in the nanosphere aggregation, as can be seen in Figure 3. The results obtained using the experimental conditions described in Table 1 can be summarized into two main groups: (1) some order is reached in semi-covered areas (Figure 4), and (2) complete 3D order is achieved in the whole area high throughput screening assay (Figures 5, 6, 7, 8). Figure 3 SEM pictures BMS345541 price showing a layer of 360-nm-diameter nanospheres after droplets falling onto the substrate dried. In the top images, the SU5402 scale bar is 10 μm, and in the bottom images, it is 2 μm. Figure 4 Semi-covered layer of scattered nanospheres. SEM pictures showing a monolayer of 360-nm polystyrene nanospheres deposited under the conditions shown in the eighth row of Table 1. The semi-covered monolayer follows the patterned

contact, a squared electrode in the center of the left image and a path for electrical conduction at the top. Scale bar is 200 μm. Figure 5 Front surface view of an electrosprayed layer. Light is coming from four different incident angles at 55°, 35°, Astemizole 30°, and 20°, from top left to down right, and reflecting light corresponding to purple, blue, green, and orange wavelength. The sample displayed area is 5 × 5 mm2. Figure

6 SEM pictures of 360-nm-diameter polystyrene nanosphere layers. (a) Cut surface showing [1 0 0] and [1 1 1] ordered facets, (b) close view of the perpendicular cut, (c) close view of the [1 1 1] face, and (d) top view of the [1 0 0] (top) and [1 1 0] order (bottom). Figure 7 SEM pictures of 760-nm-diameter polystyrene layers. Scale bars are 1 μm. Figure 8 Top view of large domains of polystyrene nanosphere layer. SEM pictures of a colloidal crystal of 360-nm-diameter polystyrene nanospheres electrosprayed onto a silicon substrate deposited under the conditions described for Figure 6: (a) surface of the crystal showing the several domains and (b) a closer view of the dislocation between domains. Scale bars are 1 μm. Figure 4 shows the SEM pictures of a layer deposited using the conditions reported in the eighth row of Table 1. As can be seen, the layer involves scattered nanospheres with no 3D order. Metal areas are patterned on the surface of the substrate to define electrode areas that, when high voltage is applied, act as collection points where the nanospheres are self-assembled.