*2.2. Wettability*

Water contact angle measurement is a practical tool to determine the wettability of a surface. Contact angle values were measured using a Digidrop instrument. At least two drops were measured for each surface and the measurements averaged. Measurements were conducted after exposure in light, either SUNTEST CPS+ (xenon arc, filtered with special window glass, 550 W/m2 across the irradiance range 320–800 nm) or UVA light (Philips blacklight, 10–12 W/m<sup>2</sup> across the irradiance range 350–400 nm), or after storage in the dark.
