Stiffness-Tunable Neurotentacles for Minimally Invasive Implantation and Long-Term Neural Activity Recordings.

Flexible microelectrodes are ideal for chronic neural recordings; however, their low bending strength poses challenges during probe insertion. Here, a stiffness-tunable polyimide probe, termed Neurotentacle, is proposed for deep brain implantation. Its tunability is enabled by embedded microchannels with controllable liquid pressure. 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 novel ultra-thin microchannel fabrication technique enables the Neurotentacle to maintain dimensions similar to conventional 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-assisted 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.