MEMS neural probe array for multiple-site optical stimulation with low-loss optical waveguide by using thick glass cladding layer

We present a MEMS neural probe array for multiple-site optical stimulation with low-loss SU-8 optical waveguides. An embedded 20-μm-thick cladding layer was formed by glass reflow process; due to this embedded structure, no additional thickness was required. In addition, optical loss was reduced by using the thick cladding layer and integrating a thick SU-8 layer as a core layer. The low-loss optical waveguide enables multiple-site stimulation with two-step optical splitters. Using the presented probe array, we also demonstrate a successful in-vivo optical stimulation through recording of neural signals from the hippocampus of a transgenic ChR2-YFP mouse. Recorded neural signals were synchronized with light pulses, which confirms that neurons were successfully stimulated by the blue light and the integrated electrode array successfully recorded the neural signals from activated neurons.