Understanding the neural basis of brain function and dysfunction requires developing multimodal methods to record and stimulate neural activity in the brain with high spatiotemporal resolution. We have been designing high-density opto-electrical devices to enable bi-directional (read/write) interfacing with the brain for long-term chronic studies.
One of the challenges of optical techniques for structural and functional recording and imaging is the scattering and absorption of light, limiting light-based methods to superficial layers of tissue. To overcome this challenge, implantable photonic waveguides such as optical fibers or graded-index (GRIN) lenses have been used. The prohibitive size and rigidity of these optical implants cause damage to the brain tissue and vasculature. In this talk, I will discuss our research on developing next generation optical neural interfaces that are microfabricated on flexible materials to minimize damage to the tissue.
First, I will discuss a compact flexible photonic platform based on biocompatible polymers, Parylene C and PDMS, for high-resolution light delivery into the tissue in a minimally-invasive way. This photonic platform can be monolithically integrated with implantable electrical neural interfaces.
I will also discuss our recent work on developing a novel complementary method for confining and steering light in the tissue using ultrasound. I will show that ultrasound waves can sculpt virtual optical waveguides in the tissue to define and steer the trajectory of light, thus obviating the need for implanting invasive physical devices in the brain.
These novel neurophotonic techniques will enable a whole gamut of applications from fundamental science studies to designing next generation neural prostheses.