Opto-fluidic neural probes for optogenetic brain interrogation

The modulation and measurement of neuro-chemical and electrical signals with high sensitivity, spatial precision on the order of neurons, and temporal precision in milli seconds is the holy grail of neuroscience. To achieve this goal, novel tools to capture neurochemical dynamics with high spatiotemporal precision, and vast multiplexing ability are needed. On the other side, tools for neuromodulation at high speeds and high spatial precision are needed to interrogate brain networks at any arbitrary stimulation volume. Optogenetics is an ideal tool for this purpose providing fast dynamics coupled with spatial precision typically brought in by genetic specificity. Several optogenetic tools have been developed in recent years to achieve spatial resolution by beam shaping methods. However, these methods fundamentally lack the ability to focus light along the propagation axis of the beam, limiting the localization of excitation to only two dimensions. Further, the strength of excitation is highest closest to the implant, preventing selective excitation of distant neuronal volumes. In this dissertation, a novel metamaterial based beam shaper that can be integrated into thin neural probe shanks is presented along with its integrated photonics backbone. These beam shapers are experimentally demonstrated to focus light to a variable volume from 2 cubic micron to as small as 0.06 cubic micron, corresponding to NAs as high as 0.95. The focusing ability of these beam shapers in scattering media is demonstrated with the ability to localize light to a single neuron’s excitation volume along the axis of propagation. The preserving of focal volume despite tissue scattering due to the high numerical aperture of these lenses is also shown. Parallelly, the supporting building blocks of high yield fluidic packaging, a film stress tuning mechanism for straight microneedle fabrication, and an integration and co-packaging scheme with photonics are established to support the development of a state-of-the-art fluidics neural probe platform.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Iyer, Hrishikesh

Contributors dc:contributor

• Vlasov, Yurii
• Cunningham, Brian
• Goddard, Lynford
• Bahl, Gaurav

• neural probe
• metasurfaces
• optogenetics
• beam shaping
• integrated photonics

Statement dc:rights

• Copyright 2025 Hrishikesh Iyer

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132623

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132623