Figure 2

SEM images of the cylindrical hole pattern with a diameter of 150 nm and 300-nm spacing (300 nm in height), and images of the mould and DOX-doped SDNA microneedle patches. (a-1) Cross-sectional scanning electron microscopy (SEM) image of the master structure. (a-2) High-magnification SEM image of the second replica with UV resin. (a-3) High-magnification SEM image of the SDNA pattern. (a-4) Tilted SEM image of the SDNA pattern. (b-1) SEM image of the master template, 300 μm. (b-2) SEM image of the PDMS mould for the 300-μm microneedle. (b-3) SEM image of the SDNA microneedle (300 μm). (b-4) SEM image of the 3 × 3 array of the SDNA microneedle (300 μm). (c-1) SEM image of the master template (1000 μm). (c-2) SEM image of the PDMS mould for the 1000-μm microneedle. (c-3) SEM image of the single SDNA microneedle (1000 μm). (c-4) SEM image of the 3 × 3 array of the SDNA microneedle (1000 μm).