Low-Shrinkage 3D-Printed Polymeric Microneedle Arrays with Electroless Silver Coating for Enhanced Thermal and Mechanical Performance in Dermatological Applications

Microneedling has found various applications in dermatology recently. However, many problems still need to be solved in the fabrication of high-aspect-ratio polymeric microneedles with good mechanical strength, dimensional accuracy and thermal conductivity for energy-assisted treatments. Herein, a low-shrinkage photocurable resin specifically designed for high-precision additive manufacturing was developed in this work to enable the rapid and reproducible fabrication of ultra-long microneedle arrays through photopolymerisation-based 3D printing. Moreover, an even and uninterrupted layer of silver was added to the surface at room temperature via electroless plating. The resulting microneedle arrays have good structural integrity and high mechanical strength, and the thermal conductivity of them has been increased by a factor of 37 compared to that of uncoated polymeric materials. Mechanical tests showed that the compressive strength was high enough, and simulated skin and ex vivo porcine skin penetration experiments also demonstrated a low insertion force and stable microchannel formation. The in vitro cytotoxicity tests showed good cell compatibility both before and after silver coating. Such work has successfully developed an all-purpose and manufacturable microneedle platform that connects high-precision additive manufacturing with energy-based dermatological therapy, which provided a scalable strategy for expanding the application of polymeric microneedles in medical aesthetics and related clinical fields. The complete route from the digital model to the finished silver-coated array takes about 2.5 h and requires no mould, master or dedicated tooling. The arrays are intended to serve as low-cost, single-use and geometrically customisable needle-electrode cartridges for energy-assisted dermatological treatment and in particular for fractional radiofrequency (RF) microneedling.