Scalable and Customizable Tri-material Microneedle Electrochemical Biosensor Platform with Cleanroom-Free Fabrication

This work reports a rapid, cleanroom-free route for fabricating three-electrode microneedle electrochemical biosensors by repurposing the high speed wire bonding technique from the semiconductor industry. 50 μm diameter Au, Pt and 30μm Ag wires were bonded to commercial printed circuit boards (PCBs) to produce freestanding microneedles (MNs) that served as working (WE), counter (CE) and reference (RE) electrodes. Ag MNs were galvanostatically chlorinated to form Ag/AgCl reference electrodes with low drift, -3 ± 0.3 mV over 24 h in phosphate-buffered saline. Au MNs were coated with PEDOT:PSS/glucose oxidase for amperometric glucose sensing from 5–25 mM (sensitivity = 0.37 μA mM-1, +0.50 V working voltage), covering the physiologic range for diabetes management. Platform versatility was demonstrated by nanomolar-range detection after the addition of an aptamer self-assembled monolayer on wire bonded Au MNs. This fully automated, additive wire bonding process provides sub-millimetre electrode spacing, < US$2 materials cost per tri-electrode array, and seamless integration with external sensing hardware for wearable applications owing to the PCB-substrate based approach. We demonstrate a scalable pathway toward multiplexed MN patches for continuous ISF monitoring and other microneedle-based minimally invasive biosensing applications.