Verification of bending strength of vapor-liquid-solid grown high-aspect-ratio silicon-neuroprobes

MEMS-based penetrating probe electrode devices have opened a new class of multi-site electrophysiological recordings of neurons/cells in a tissue with a high spatial resolution. Although these probes becomes a powerful tool in electrophysiology, the challenge still remains the tissue penetrations with small diameter probes for further low-invasive and safe tissue penetrations. However, it is difficult to penetrate small diameter probes with a high aspect ratio (e.g., a micro-scale diameter probe with the length of several hundred microns or more), due to the buckling of the probe during the tissue penetration (Fig.1). To realize the tissue penetration with small diameter needle with a high aspect ratio, quantitative discussions of the penetration force and the buckling/bending properties of the probe are further required. Here we verify the bending strength of silicon-microprobe with a high aspect ratio using in situ force-measurement-system (FMS) inside the SEM. In addition, these silicon probes are coated with a metal of iridium (Ir) with a high Young's modulus as the exoskeleton (shell), quantitatively confirming the increased stiffness of the probe. Such data can be used to design stiff probes and realize the minimization of the probe diameter, enhancing the penetrating capability of small probes for further low-invasive and safe tissue penetrations.