Integrating Polymeric 3D-Printed Microneedles with Wearable Devices: Toward Smart and Personalized Healthcare Solutions

The wearable healthcare is shifting from a passive tracking to an active, closed-loop care by integrating the polymeric three-dimensional (3D)-printed microneedle arrays (MNAs) with the soft electronics and wireless modules. This review is surveying about the design, materials, and the manufacturing routes that enable the skin-conformal MNA wearables for a minimally invasive access to the interstitial fluid and precise but localized drug delivery. The 3D printing processes, including the stereolithography (SLA), digital light processing (DLP), and two-photon polymerization (2PP), are providing a micron-scale control on the needle geometry, lumen formation, and also surface features. The biocompatible polymers and the stimuli-responsive composites are underpinning the dissolving, hydrogel-forming, conductive, and the drug-loaded architectures. We are highlighting the biomedical applications spanning the continuous biosensing, neuromuscular and cardiovascular biopotential recording, painless vaccination, and also the on-demand or closed-loop therapeutics through microfluidics, acoustics, or iontophoresis. The powering and the connectivity strategies, from the energy harvesting and inductive links to the smartphone-based analytics, are advancing the autonomous operation. Looking ahead, the converging advances in the multimaterial printing, nano/biofunctional coatings, and the artificial Intelligence (AI)-driven control are promising the “wearable clinics” that can personalize the monitoring and therapy in real time, thus accelerating the translation of MNA-integrated wearables from the laboratory prototypes to the clinically robust, patient-centric systems.