For every sample tested three sampl

For every sample tested three sample areas

(each of approximately 10 mm  10 mm) have been measured.
2.3. Photo-stability measurements of the substrate
Each substrate has been tested in order to assess its photo- stability under UV/vis/IR radiation. To the best of our knowledge this type of characterization has never been reported before. Different samples for each material considered have been exposed by using an ORIEL 300 W full spectrum solar simulator equipped with air mass 0 filter. It emits a uniform, collimated, 50 mm  50 mm output beam with a close spectral match to sunlight. This simulator produces a maximum power equivalent to 2 suns, but with optional air mass filters it is possible to simulate various solar conditions and altitudes. When the sample has been exposed to full UV + vis + IR spectrum, a WG 295 Edmund band- pass filter has been used to block contaminating wavelengths below 290 nm. In order to expose samples only to vis + IR radiation, a GG 395 Melles Griot band-pass filter has been used to cut all the wavelengths below 395 nm. In both cases, the substrates have been exposed for 1, 3, 5 and 10 min. The full spectrum exposures have been repeated by using other two standard band-pass filters: WG 305 and WG 320. They cut all the wavelengths below 300 and 315 nm respectively. The UV output irradiance (in presence of the WG295 filter) has been measured by an HD9021 calibrated radiometer (DeltaOhm S.r.l.), equipped with two detector heads, one for UVB 280– 315 nm spectral region and another for UVA 315–400 nm one. Both the UVB and UVA irradiances have been measured, being the results values 1.8 and 9.5 mW/cm2 respectively. An erythemal irradiance of 0.5 mW/cm2 has been measured by an erythema like radiometer [19],towhichcorrespondtoadoseof 3, 9, 15 and 30 SED for the four different exposure times
Table 1 RMS surface roughness of the different materials tested.
RMS surface roughness (mm) In Vivo Skin 16.30.2 Transpore1 7.30.5 Vitro-SkinTM 16.10.3 Roughened quartz 1.80.1 PMMA plates 2.60.1 PTFE 4.70.1
Fig. 1. (20 optical zoom) (a) In vivo microscopic image of skin; (b) microscopic image of Transpore 3M; (c) microscopic image of hydrated Vitro-Skin; (d) microscopic image of not-hydrated Vitro-Skin; (e) microscopic image of roughened quartz; (f) microscopic image of roughened PMMA plate; (g) microscopic image of one PTFE sample.
Table 2 Sunscreens main ingredients.
SPF 4 SPF 6 SPF 8 SPF 12 SPF 15 SPF 20 SPF 30
Bis-ethylhexyloxyphenol methoxyphenyl triazine X X X X X Butyl methoxydibenzoylmethane X X X X X X X Disodium phenyl dibenzimidazole tetrasulfonate X X Ethylhexyl methoxycinnamate XX Ethylhexyl triazone X X X Octocrylene X X X Titanium dioxide XXXX