# Nanophotonic neural probes for in vivo photostimulation, electrophysiology, and microfluidic delivery

## TL;DR

This paper introduces a new type of neural probe that combines light, electricity, and fluid delivery to study and control brain activity in live animals.

## Contribution

The novel contribution is a multifunctional neural probe with integrated nanophotonic, electrophysiological, and microfluidic capabilities.

## Key findings

- The probe successfully delivered light, recorded brain activity, and administered drugs in vivo.
- Local suppression of epileptic seizures was achieved using photostimulation after drug-induced seizures.
- The design is scalable and compatible with foundry fabrication for broader neuroscience applications.

## Abstract

Implantable silicon neural probes with integrated optical emitters and electrodes are emerging tools for simultaneous optogenetic stimulation and electrophysiological recording in deep brain regions. In parallel, neural probes with microfluidic channels have been developed for localized drug delivery and neurochemical sampling. However, thus far, such fluidic probes have lacked optical and electrical functionalities or been limited to a low number of optical emitters and/or electrodes, constraining their utility in multimodal investigations of neural circuits. Here, we introduce foundry-fabricated silicon nanophotonic neural probes with monolithically integrated microfluidics. Each probe has 16 silicon nitride grating coupler emitters, 18 titanium nitride microelectrodes, and one embedded microfluidic channel. We evaluate the photonic, electrophysiological, and microfluidic functionalities in vivo in optogenetic, blue-light-sensitive mice. With our multifunctional neural probes, we demonstrate local suppression of epileptic seizure activity (induced by microfluidic injection of 4-aminopyridine) using photostimulation. Through foundry-compatible microfluidics integration, this work advances the versatility of nanophotonic neural probes and presents new possibilities for multimodal neuroscience experiments leveraging this scalable neurotechnology.