Abstract

Microneedle (MN) devices that sample skin interstitial fluid (ISF) without an external vacuum offer strong point-of-care potential, but are often limited by insufficient extraction flux and fabrication complexity. Here, we present macroporous-channel hollow microneedles (MPC HMNs) that integrate three features in a single photopatterning step: a rigid polymer shell for mechanical support, an interconnected micrometer-scale porous network formed by porogen removal, and an axially enriched macroporous conduit formed by a percolated chain of interconnected spherical cavities. This architecture establishes multiscale capillarity that drives vacuum-free ISF sampling. When coupled to a paper-wick collector or an on-patch sensing module, the interface enables rapid wicking and on-device readout without pumps or tubing. In ex vivo skin models and in vivo rat studies, MPC HMNs achieved ISF yields and start-up times that were comparable to those of negative-pressure collectors under matched conditions, while maintaining agreement between ISF and paired blood measurements for representative electrolytes and metabolites. Electrochemical modules quantified potassium (potentiometry) and glucose (amperometry), and a colorimetric panel reported glucose, acetoacetate, and creatinine. Viewed as a capillarity-driven transducer, MPC HMNs link structure to function and reduce system complexity. The resulting disposable, compact format supports vacuum-free ISF sampling and on-patch analysis, offering a practical path toward minimally invasive, near-patient monitoring. Statement of significance We introduce macroporous-channel hollow microneedles that combine a rigid polymer shell, an interconnected macroporous network, and an axial lumen created in a single photopatterning step. This architecture establishes multiscale capillarity that supports vacuum-free dermal interstitial-fluid sampling and enables on-patch electrochemical or colorimetric readout without pumps or tubing. Across ex v