Figure 1.

Swelling of microneedle patches made of cross-linked hydrogel. Microneedle patches were prepared by casting and drying an aqueous solution of poly(methyl vinyl-alt-maleic acid) and poly(ethylene glycol) into a micromold, after which the polymers were cross-linked by incubation at 80 °C (a). In the dry state, each microneedle measured 600 μm in height and 300 μm in width at the base (b1, c1). Upon incubation in water for 24 h, microneedles swelled to different sizes depending on the degree of hydrogel cross-linking during molding: cross-linking for 72 h (b2, c2) and 24 h (b3, c3).