Brain Machine Interface Sample Projects

Custom skull cap with precision guides for deep insertion of cellular-scale microwire into rat brain

This study developed a custom skull cap with precision guide holes to stabilize the brain and dura, provide sufficient support to microwire along the insertion path, and minimize the unsupported length of microwire during dura penetration and deeper insertion. A cap matched to individual skull anatomy with offset for brain stabilization was designed based on computed tomography (CT) scan of the rat head and fabricated by stereolithography. Micro-milling and wax molding were conducted to fabrication precision insertion guide inside the cap. Through a test cube with precision guide, a 25 µm diameter tungsten microwire penetrated through the dura mater and was manually inserted over 10 mm into the brain without buckling. In comparison, without the precision guide, insertion of the same microwire caused over 2 mm dimpling of the dura without penetration and finally led to wire buckling.

Force and dimpling evaluation for pia and dura penetration during microelectrode insertion

A cantilever beam-based flexible high-resolution system for evaluation of microelectrode force and membrane dimpling depth was developed. The easily duplicable and reconfigurable system was shown feasible for in vivo evaluation of both the pia-only and dura-pia penetration process with either microwires or silicon-based probe shanks. For the first time, we revealed the linear relationship between microwire diameter and membrane rupture force/dimpling depth for in vivo rat brain insertion and for dura penetration.

Laser sharpening of miniaturized carbon fiber microelectrode arrays

A laser-based non-contact carbon fiber microelectrode processing method to enable controllable and repeatable production of carbon fiber microelectrode arrays of custom electrode lengths, insulation stripping lengths, and sharpened tips. Compared to conventional labor-intensive manual scissor cutting method, hard-to-control fire torch burning method, and hard-to-mass produce electrical discharge machining method, the laser-based procedure could complete fiber cut-off, tip sharpening, and insulation layer stripping in one path.

Ultimate goal: large-scale brain-wide chronic electrophysiological recordings/stimulation with ultra-miniaturized minimal trauma flexible microelectrodes at custom locations and depths