Metal/silicon dioxide microtube improves optical and electrical properties of neuroprobe

Here we report vertical metal/silicon dioxide (SiO 2 ) multiwalled microtube arrays as electrical and optical neuroprobes for "optogenetic". Three-dimensional metal/SiO 2 -microtube arrays can be fabricated by vapor-liquid-solid (VLS) growth of silicon-wire, followed by the SiO 2 /metal depositions and the core-silicon etching. As the inside metal, we use iridium (Ir) with a low electrical electrolyte/electrode interfacial impedance in saline. An optical propagation through the Ir/SiO 2 -tube calculated by finite-difference time-domain (FDTD) method clearly indicates the effect of the inside Ir on the improved locality of light stimuli with the spot diameter of