The shapes of the activation area visualized by the 58 mN/m test ink on the HDPE substrate for configurations A, C and G. The sizes of the substrates seen in pictures for A and C are 50 mm × 50 mm. The treatment times are 100 ms, 3 s, 10 s, 1 s and 20 s for A1, A2, C1, C2, and G1−3 respectively.