In particular, roughness is partially responsible for the different optical properties. The RMS (roughness measurement system) surface roughness of the different substrates has been measured using a Tencor 40T profilometer. The values are derived from the mean roughness measured on five different samples. The results of these measurements, with the relative error, are reported in Table 1. It is evident that there is a good reproducibility on the measured roughness. The values are compared with the RMS roughness obtained on a silicone mould of in vivo skin.
2.2. Spectro-photometric measurements
All substrates have been characterized by transmittance and reflectance measurements (total and diffuse). Measurements have been performed with a Varian Cary 5000 UV/VIS/NIR (ultraviolet– visible–near infrared) spectrophotometer using a UV/VIS/NIR integrating sphere. The instrument spans a spectral wavelength range from 175 up to 3300 nm. Its optical system ensures a maximum level of light throughput that produces accurate