Advanced non-planar architecture: Nanoporous alumina (NPA) millirods

Nanoporous alumina (NPA) millirods were developed in a milli-sized dimension by coaxially growing a highly ordered NPA layer on aluminum (Al) wire through a two-step electrochemical anodization. This non-planar architecture addresses the brittleness and limited active sites of conventional planar NPA membranes, producing mechanically robust and three-dimensional active sites for functionalization. The fabrication strategy, which involved polytetrafluoroethylene (PTFE) coatings and transverse cutting, produced multiple identical millirods from a single Al wire, ensuring reproducibility and cost-effectiveness. Growing the NPA to a rigid Al wire substrate provided NPA with solid physical support and ease of handling. These characteristics resulted in enhanced binding-site density, rapid mass transport, and direct electrical contact, making the NPA millirods ideal for high-sensitivity electrochemical sensing and various nanomaterial applications.