Review on engineered polymer microneedles for drug delivery and disease diagnosis.

The minimally invasive and painless microneedle (MN) technology has become a promising platform for drug delivery and disease diagnosis. In this review, we first introduce the classification of MNs according to their sources and then summarize the preparation methods of MNs, including the stretching method, droplet-born air blowing, micromolding method, and 3D printing method. Subsequently, we also introduce how to prepare different types of MNs, such as solid, coated, hollow, dissolving, and frozen MNs, through material structure design. More importantly, the development of MNs in drug delivery, biosensing, wearable devices, cancer therapy and tissue regeneration in recent years has been reviewed. Finally, several significant challenges for further exploration in the field of MNs as well as perspectives and outlooks on future MN research, are also discussed in this review.