Low-loss hybrid polymer waveguide neural probes for visible-wavelength optical neuromodulation

Abstract

Optical neuromodulation techniques, including optogenetics and optopharmacology, offer promising clinical potential for epilepsy and neurodegenerative disorders. These methods require light delivery to deep brain regions via implantable probes, but chronic in vivo use faces challenges in biocompatibility, optical efficiency, and scalability. Conventional probes with integrated light sources or silica fibers ensure power delivery but are bulky and rigid, provoking foreign body responses. Flexible biocompatible probes improve tissue integration yet compromise optical performance. We introduce a waveguide-based probe using hybrid polymers fabricated with standard microfabrication methods. This probe achieves low propagation loss (<0.25 dB/cm across the visible spectrum) while balancing mechanical properties—soft yet stiff enough for direct implantation (Young’s modulus 1 GPa). In vivo tests in rats confirmed stable implantation and functionality for six weeks, demonstrating light-triggered seizure modulation.