We report a novel, versatile, and low-cost approach for fabrication of out-of-plane silicon microneedles for transdermal applications. Unlike state-of-the-art microneedles reported so far, the microneedles of this work feature a built-in reservoir in each single needle-core to be used in future applications for drug storing and delivery after insertion in the skin. The microneedles, with size up to ten times thinner than a human hair, height of about 100 µm, and density of 10000 needles/cm (spatial period 100 µm) are effectively fabricated by silicon electrochemical micromachining (ECM) technology. In-vitro insertion tests, which are carried out on synthetic skins made out of alginate hydrogels with different concentrations, clearly demonstrate penetration reliability of such tiny needles.
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