Fig. 2: Characterization of the MN materials.

A, B Transmittance microscopic images of microneedle array from different angles. C Mechanical compression strength of the MN patch before and after sterilization by gamma irradiation. A compressive force in the longitudinal direction of the MNs was generated at a speed of 0.5 mm/min. D SEM image showing the inner morphology and porosity of the fabricated patch. Scale bar = 200 μm. E Swelling ratio of the MN patch after immersing in PBS solution. (n = 3 independent samples, mean ± SD). F The force-displacement curves of adhesion of the synthesized hydrogel to the glass slides coated with a medical tape to mimic skin-like texture; inset shows a photograph of the hydrogel adhered to the skin of the finger.