Smart microneedles empowering programmable and sustained drug delivery

Microneedles (MNs) have emerged as a promising platform for transdermal drug delivery, offering minimally invasive, programmable, and patient-friendly alternatives to conventional routes. Advances in fabrication and materials science have transformed MNs from simple metallic structures to multifunctional, biodegradable systems capable of dynamic drug release. This review analyzes MNs from the perspectives of structural design, material composition, and drug release kinetics. We examine key design parameters such as needle geometry and array configuration, and their effects on mechanical performance and delivery efficiency. MNs are categorized by type and functionality, highlighting innovations in tip design and backing layers for enhanced tissue penetration and payload control. A comparison of fabrication materials—including metals, inorganic nonmetals, natural and synthetic polymers—is presented, focusing on their degradation behavior and correlation with drug release timelines. Drug formulation strategies and pharmacokinetic models are also discussed, linking material–drug interactions to release profiles. Finally, recent applications in wound care, vaccination, hormone therapy, oncology, and ocular treatment are explored. This review bridges design, material, and pharmacokinetic considerations to support the development of next-generation MN systems with optimized spatiotemporal control for clinical applications.