BCIwiki (bciwiki.com) — This preprint was published on bioRxiv on July 15, 2026, and has not been peer-reviewed. Brain-computer interfaces face a fundamental trade-off between the signal fidelity of non-invasive systems and the surgical burden of invasive systems. Non-invasive BCIs suffer from low signal quality due to the skull barrier, while existing invasive BCIs rely on traumatic surgical procedures or brain-penetrating electrodes, limiting scalability and patient acceptance.
Researchers Li Z., Liu N., Wan L., Liu M., and Wu C. from Sun Yat-sen University introduce a minimally invasive hybrid BCI architecture that uses the skull as a distributed interface layer rather than treating it solely as a barrier. The hybrid BCI comprises four integrated components: safe and smart micro-hole craniotomy; distributed microelectrodes subcutaneously implanted in skull micro-holes with the distal end contacting the dura; an external bi-directional wearable headset for coupling, recording, stimulation, and channel selection; and an AI-assisted planning and control agent.
Animal studies showed that micro-holes with a diameter of 300-800 um can be safely prepared at any predefined skull locations without impairing the dura. In vivo rat experiments demonstrated that the hybrid BCI with skull-implanted microelectrodes evidently increases resting-state spectral power and improves the signal-to-noise ratio of somatosensory and steady-state visual evoked responses compared to scalp EEG. Computational modelling showed that distributed skull-dura microelectrodes can increase intracranial electrical field strength and steer focused temporal-interference fields towards predefined deep brain targets. The researchers propose this hybrid BCI as a distinct minimally invasive paradigm with potential as a distributed, scalable, and upgradable neural interface for expanding clinical applications.