Neuro-SWARM³: System-on-a-Nanoparticle for Wireless Recording of Brain Activity

A fundamental limitation of the implantable brain-machine interfaces (BMI) is the wiring requirements for power transfer and signal transmission. Existing microelectrode technologies can only record from localized sections of the brain and require implantation of invasive electrodes through cranial surgeries. Here, we introduce a system-on-a-nanoparticle probe, a Neurophotonic Solution-dispersible Wireless Activity Reporter for Massively Multiplexed Measurements (Neuro-SWARM
³
), enabling remote detection of in vivo bioelectric signals. Neuro-SWARM
³
offers five fundamental advancements simultaneously: (1) it enables use of infrared light within the biologically transparent near infrared (NIR-II, 1000-1700 nm) window for direct read-out through the skull, (2) it circumvents invasive surgical operations since no wiring or power supply is needed for the wireless (electro-plasmonic) excitation and remote detection, (3) due to its diminutive dimensions (<; 200 nm) that is comparable to viral particles, it can be delivered different regions of the brain without surgical operations, (4) as electro-plasmonic signal conversion removes front-end signal processing requirements, it opens the door to large scale in vivo measurements that are not restricted by electrode dimensions, physical wiring, and electronic bandwidth limitations, (5) by being much smaller than the critical dimensions that trigger glial cell response ( ~ 12 μm), it offers a long term operation capability. As we show below, NeuroSWARM
³
provides high signal to shot noise ratio (SSNR ~ 10
³
) wireless recording capability from single neurons due to its enhanced scattering cross-section ( ~ 10
⁴
nm
²
) and field-sensitivity (up to ~40%).