Stiffness-tunable neurotentacles for minimally invasive implantation and long-term neural activity recordings

Flexible microelectrodes are ideal for chronic neural recordings but face challenges in probe insertion due to low bending strength. Here we have proposed a stiffness-tunable polyimide probe for deep brain implantation, referred to as Neurotentacle, enabled by embedded microchannels in which the liquid pressure is controllable. During insertion, the neurotentacle becomes stiff under elevated internal pressure, allowing penetration of brain tissue without additional materials or tools. Once inserted, it regains flexibility by reducing the internal pressure. The proposed multilayer microfabrication process maintains structural dimensions similar to traditional flexible probes. This minimizes tissue damage during insertion while ensuring long-term biocompatibility and stability, confirmed by histological evaluations in both acute and chronic animal models. In long-term recordings, neurotentacles outperform traditional shuttle-based implantation methods. The technique is straightforward, controllable, and does not require complex devices, making it ideal for minimally invasive implantation and long-term neural recordings.