Robust minimally-invasive microfabricated stainless steel neural interfaces for high resolution recording.

Understanding brain function and developing effective neurotherapeutics require high-resolution electrophysiologyical recording across large primate brains. To achieve this goal, minimally invasive, compact, long, and high-density implantable neural probes are needed. Conventional silicon-based probes, designed for rodents, cannot be directly scaled to larger brains because silicon's brittleness restricts long, high-aspect-ratio designs. Stainless steel is a biocompatible, resilient, and less brittle alternative for making neural probes, though its microfabrication is less explored. Here, we introduce "steeltrodes", customizable microfabricated stainless steel neural probes enabling high-density multi-layer electrode integration. We demonstrate 8 cm long, ~300 µm wide probes, featuring rigid shanks with optional flexible cables for in vivo high-resolution laminar recording from macaque auditory cortex. In rats, these probes can be safely implanted through intact dura with minimal cortical damage. High-fidelity recordings of single units and local field potentials in macaques highlight the potential of steeltrodes for translation to human applications, enabling both inter- and intraoperative neural recordings.