Surface Fluidic Microneedle Patches for Lymphatic Delivery of Diagnostic and Therapeutic Agents

Abstract Microneedles (MNs) are promising tools for painless delivery of fluids, such as drugs and contrast agents, through the skin. However, conventional MNs suffer from limited loading capacity. In this study, a new type of MN patch (MNP), referred to as surface fluidic MNP (SFMNP), is developed to deliver fluids from a reservoir through a macroscale hole to MNs by spreading the fluids across micro‐ and nanogrooved surfaces via capillary forces. The design incorporates microchannels that enable a stepwise flow from a macroscale reservoir to the interstitium through multiscale grooves, enhancing delivery capacity. Nanogrooves on the MN surfaces are fabricated by photopolymerizing a photocurable prepolymer using guided light along the microgrooves. These multiscale structures are easily reproduced through a simple molding, offering a cost‐effective fabrication approach. The medical effectiveness of the SFMNP in vivo is validated in animal models, particularly for lymphangiography. The SFMNP achieved in vivo delivery levels of contrast agents comparable to those of syringe injections and maintained high delivery capacity, even in states affected by lymphedema disease. Beyond lymphangiography, the ability of the SFMNP to deliver large volumes of fluid suggests its potential for broader clinical applications, particularly in diagnostics and therapeutics involving drug delivery into lymphatic system.