Brushing-Assisted Two-Color Quantum-Dot Micro-LED Array Towards Bi-Directional Optogenetics

Bi-directional optogenetics at single-cell level requires localized, bright, and multi-color light sources to activate both excitatory and inhibitory opsins. To this end, here we report a simple fabrication method of high-density, two-color, quantum dot (QD) based micron-sized light emitting diode (micro-LED) arrays. In particular, we micro-patterned InP/ZnS QDs on top of GaN-based micro-LED pixels via a simple brushing method, and coated them with a spectral filter. The resulting array featured sub- $20~\mu \text{m}$ sized light spots near both 462 nm and 623 nm, with their optical power density being ca. 0.1 – 1.0 mW/mm². Combined with its low crosstalk and fast response, our two-color QD-LED array may hold promise for bi-directional optogenetics ultimately at the cellular level.