High‐density implantable neural electrodes and chips for massive neural recordings

High‐density neural recordings with superior spatiotemporal resolution powerfully unveil cellular‐scale neural communication, showing great promise in neural science, translational medicine, and clinical applications. To achieve such, many design and fabrication innovations enhanced the electrode, chip, or both for biocompatibility improvement, electrical performance upgrade, and size miniaturization, offering several thousands of recording sites. However, an enormous gap exists along the trajectory toward billions of recording sites for brain scale resolution, posing many more design challenges. This review tries to find possible insight into mitigating the gap by discussing the latest progress in high‐density electrodes and chips for neural recordings. It emphasizes the design, fabrication, bonding techniques, and in vivo performance optimization of high‐density electrodes. It discusses the promising opportunities for circuit‐level and architecture‐level multi‐channel chip design innovations. We expect that joint effort and close collaboration between high‐density electrodes and chips will pave the way to high‐resolution neural recording tools supporting cutting‐edge neuroscience discoveries and applications. High‐density neural recordings with superior spatiotemporal resolution are powerful in unveiling cellular‐scale neural communication for cutting‐edge neuroscience discoveries and applications. The number of channels in both electrodes and chips has grown from a few to thousands or even tens of thousands in recent decades. By bridging the breakthroughs between electrodes and chips, more evolutionary tools for brain‐wide recordings will be boosted at a fast pace.