Optic-Fiber-Based Optogenetic Stimulator With μLED and 3D-Printed Structures for Brain Stimulation

Optogenetics is an advanced neural stimulation technique with high spatiotemporal precision. Various stimulation devices have been developed using microfabrication techniques to deliver light to specific population of neurons. However, traditional microfabrication techniques rely on clean room facilities, making the overall manufacturing process long and cumbersome. In this paper, we present an optical neural stimulator using an optical fiber coupled with a micro-sized light-emitting diode (μ LED) for neuromodulation. The proposed system utilizes a 3D-printed mount to hold and couple the optical fiber with the μ LED which is also placed on a 3D-printed substrate with micrometer-sized conductive wires for electrical connection. As such, the proposed device fabrication and assembly steps are simple but efficient without using any semiconductor fabrication processes. In addition, the stimulation depth can be easily customized from the depth for the cortex to that of deep brain structures by simply cleaving the fiber with the desired length and integrating it with the mount. Electrical, optical, and thermal properties of the fabricated device are evaluated experimentally. The validation shows that the device can generate enough intensity light on the tip under a low-temperature change for the safety of the brain tissue. For validation of the device's efficacy, the stimulator is implanted in the motor cortex of mice and is used to modulate the subject's motor behaviors. The experiments show that there is an increase in the velocity of mice's movement during the optical stimulation of the motor cortex. These results prove that the proposed device can successfully modulate the target neurons in the cortex.