Figure 4

(a,b) Optical images of AL surface before (a) and after (b) corona treatment. (c) The normalized surface roughness change with using different d^coronas (5–15 mm) and t^coronas (30 and 60 s). The normalized surface roughness was calculated by the surface roughness of AL divided by the surface roughness of pristine leaf (before corona treatment). Each data point represents triplicate measurements.