**2.2.4 Surfaces with bimodal II roughness**

Substrates with adhering 470 nm particles (Figure 1c), rinsed and dried, were again conditioned with PAH (10-5 M, pH=7, I=10-3 M) (Figure 1e), rinsed with water then with isopropanol and dried, as described for the adhesion of a single colloid layer. These samples were then placed horizontally in wells of another culture plate. 1ml of a 0.1% suspension of 65 nm particles was poured into wells and left in contact with the substrate for at least 2 h (Figure 1f). The samples were rinsed and dried using the same procedure as described for adhesion of a single colloid layer.
