Thermal and optical characterization of micro-LED probes for in vivo optogenetic neural stimulation

TLDR

Optogenetics requires compact light sources capable of delivering light with high spatial, temporal, and spectral resolution to deep brain structures. The study demonstrates a custom GaN‑based LED probe for deep brain optogenetic stimulation. The probe’s electrical, optical, and thermal properties were analyzed. The probe delivers sufficient power density and emission spectrum to stimulate channelrhodopsin‑2, produces light intensities far exceeding neuronal stimulation thresholds, and maintains brain temperature rise below 0.5 °C in pulsed mode, marking a significant advance for optogenetics.

Abstract

Within optogenetics there is a need for compact light sources that are capable of delivering light with excellent spatial, temporal, and spectral resolution to deep brain structures. Here, we demonstrate a custom GaN-based LED probe for such applications and the electrical, optical, and thermal properties are analyzed. The output power density and emission spectrum were found to be suitable for stimulating channelrhodopsin-2, one of the most common light-sensitive proteins currently used in optogenetics. The LED device produced high light intensities, far in excess of those required to stimulate the light-sensitive proteins within the neurons. Thermal performance was also investigated, illustrating that a broad range of operating regimes in pulsed mode are accessible while keeping a minimum increase in temperature for the brain (0.5°C). This type of custom device represents a significant step forward for the optogenetics community, allowing multiple bright excitation sites along the length of a minimally invasive neural probe.