Implantable neural probes, essential for brain electrophysiological research, have advanced with ultraflexible designs to mitigate immune responses and postoperativecomplications. Strategies of shuttleassisted implantation and temporary stiffening address issues in penetrating these probes into the target region, avoiding undesired bending. However, the risk of intraoperative bleeding remains due to these implants’ necessary rigidity during insertion. Here, we describe a neural probe with mechanical compliance accompanying self-implantation along the principal axis in the absence of bleeding. Crucial to the behavior is its anisotropic relaxation, which is dominated by the cross-sectional in-plane deformation inhibition due to interchain interactions between the parallel backbones in the globally aligned polymer system. We observed the ensured upright insertion of the probe into the brain while avoiding angiorrhexis with a two-photon microscope and a high-speed camera. The probes permit electrophysiological studies with minimal foreign body responses and imageological compatibility, underscoring their clinical potential.