Fig. 3

a–c The optical microscope images and d–g the SEM images of Ag nanoparticles aggregation on the original PTFE with different multiples. h, i The optical microscope images and j, k the SEM images of Ag nanoparticles aggregation on the engraved PTFE with different multiples. The whole orange small boxes represent the magnified area and the white dotted line circles the finial area of Ag nanoparticles accumulation