Controllable-pore porous microneedles for high-speed extraction and biomarker detection of interstitial fluid.

Porous microneedles have attracted considerable attention as minimally invasive tools for interstitial fluid sampling and biomarker analyses. However, existing porous microneedle fabrication methods often suffer from low extraction efficiency, primarily because of the inherent trade-off between increasing porosity and maintaining sufficient mechanical strength. Herein, we present a novel approach for fabricating porous microneedles with controllable pore sizes and enhanced extraction performance. Monodisperse polylactic acid microspheres, produced via microfluidic techniques, are thermally bonded to form porous microneedles with interconnected pore networks originating from the connected voids between the microspheres. By precisely adjusting the microsphere diameter, we optimize the pore size to achieve high extraction efficiency while preserving structural integrity. Following surface treatment and bonding parameter optimization, the resulting porous microneedles exhibit sufficient mechanical strength to penetrate human skin and achieve an in vitro extraction rate of 0.95 μL/min per needle-the highest reported to date. Furthermore, porous microneedles are integrated with a colorimetric paper-based sensor for glucose detection, demonstrating a linear correlation between glucose concentration and the colorimetric response of the sensor. This work provides a promising tool for high-speed interstitial fluid extraction and expands the fabrication strategy for porous structures in biosensing applications.