Optical fibers are commonly inserted into living tissues such as the brain in order to deliver light to deep targets for neuroscientific and neuroengineering applications such as optogenetics, in which light is used to activate or silence neurons expressing specific photosensitive proteins. However, an optical fiber is limited to delivering light to a single target within the threedimensional structure of the brain. We here demonstrate a multi-waveguide probe capable of independently delivering light to multiple targets along the probe axis, thus enabling versatile optical control of sets of distributed brain targets. The 1.45 cm long probe is microfabricated in the form of a 360 micron-wide array of 12 parallel silicon oxynitride (SiON) multi-mode wave-guides clad with SiO 2 and coated with aluminum; probes of custom dimensions are easily created as well. The waveguide array accepts light from a set of sources at the input end, and guides the light down each waveguide to an aluminum corner mirror that efficiently deflects light away from the probe axis. Light losses at each stage are small (input coupling loss, 0.4 ± 0.3 dB; bend loss, negligible; propagation loss, 3.1 ± 1 dB/cm using the out-scattering method and 3.2 ± 0.4 dB/cm using the cut-back method; corner mirror loss, 1.5 ± 0.4 dB); a waveguide coupled, for example, to a 5 mW source will deliver over 1.5 mW to a target at a depth of 1 cm.The ability to deliver light into the brain for the purposes of controlling neural activity and other biological processes has opened up new frontiers in both basic neuroscience and neuroengineering. One arena of great activity is in the use of microbial opsins such as channelrhodopsin-2 [1], N. pharaonis halorhodopsin [2,3], and archaerhodopsin-3 [4] to make neurons activatable or silenceable by different colors of light, thus enabling assessment of the causal contribution of specific neurons, brain regions, or neural pathways to normal and abnormal behaviors and neural computations. To date, numerous in vivo studies have used optical fibers to deliver blue, yellow, or green laser light into brain targets in which certain neurons are expressing these opsins, but optical fibers can target just a single region. An implantable probe capable of delivering light to multiple points along the probe axis would enable more versatile optical control, opening up the ability to deliver patterned light to manipulate neural activity in different parts of a brain circuit in a systematic fashion, while greatly reducing surgical complexity and brain damage. We here describe the design and fabrication of a linear probe capable of multipoint independent light delivery, and find that this design enables the efficient delivery of light to multiple targets * Corresponding author: esb@media.mit.edu.OCIS codes: 170.0170, 130.2755, 130.3120, 130.3990, 230.3990, 230.7370 NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript along the probe axis, appropriate for delivering light to different lami...

To deliver light to the brain for neuroscientific and neuroengineering applications like optogenetics, in which light is used to activate or silence neurons expressing specific photosensitive proteins, optical fibers are commonly used. However, an optical fiber is limited to delivering light to a single target within the three-dimensional structure of the brain. We here describe the design and fabrication of an array of thin microwaveguides which terminate at a 3-dimensionally distributed set of points, appropriate for delivering light to targets distributed in a 3-dimensional pattern throughout the brain.

The agonist-antagonist myoneural interface enables bidirectional signaling for enhanced prosthetic control and sensation.

These results have the potential to enable future scientific optogenetic studies of pathologies implicated in the peripheral nervous system for awake, freely-moving animals, as well as a basis for future clinical studies.

No abstract