Vertically integrated metal-clad/silicon dioxide-shell microtube arrays for high-spatial-resolution light stimuli in saline

Microdevices composed of integrated microscale light source arrays are powerful tools in optogenetic applications. Herein, we prepared vertically aligned 3-μm inner diameter silicon dioxide (SiO2) tube-based optical light waveguide arrays. To increase the locality of the light stimuli through the tube, we also fabricated metal-cladded SiO2 tubes using iridium (Ir). After filling the tube with a saline solution, the saline-core/Ir-clad/SiO2-shell waveguide exhibited light stimuli without spreading. With a 532-nm wavelength, the half-power width of the light intensity measured 10 μm above the tube tip was 3 μm, while that of the saline/SiO2-shell waveguide was 9.6 μm, which was more than three times wider. Such high-spatial-resolution optical light stimuli will offer a new class of optogenetic applications, including light stimuli for specific regions of a neuron (e.g., axons or dendrites).