Figure 11.

Different types of microneedles and their characteristics. (A) The structures of solid, hollow, coated, polymer, and hydrogel microneedles. (B) Each of these microneedles has different drug delivery properties. Solid microneedles are well suited for penetration and increasing drug permeability. Hollow microneedles create pathways for drug infusion. Coated microneedles contain drugs on their surface that dissolve after insertion into the skin. Microneedles made with biocompatible and biodegradable polymers contain drugs that fully dissolve in the skin to release their encapsulated reagents. Hydrogel microneedles made with non-dissolving, liquid-absorbing materials can be used for fluid and materials diffusion [180].