Silicon wafers were used as solid substrates and cleaned with 30% nitric acid, distilled water, ethanol, and acetone. The wafers were immersed vertically in the center of the trough before compression. The nanoparticle film was compressed at 10 mm•min⁻¹ to the target pressure and allowed to reach equilibrium for 25 minutes, after which the substrate was withdrawn at a rate of 13 mm•min⁻¹.