Liquid Gallium in 3D Microneedles Cuts Impedance 1,000-Fold, Records Spikes
A team from the University of Utah, Kangwon National University and the University of Georgia describes a silicon-free route to neural microelectrode arrays: soft polymeric 3D microneedles are printed by two-photon polymerization, then turned into electrodes by injecting liquid gallium into the hollow channels. A newly defined retention number predicts whether the gallium stays put under physiological conditions. Coating the surface with gold nanoparticles and PEDOT doped with tetrafluoroborate cut impedance by roughly 3 orders of magnitude, and in vivo recordings in an invertebrate model captured neural spikes with no gallium leakage. The study was published in ACS Sensors on August 31, 2026.