Tetherless subnanolitre optoelectronic microsystem for chronic neural recording in awake mice

• A subnanolitre tetherless optoelectronic microsystem enables chronic neural recording in awake mice. ¹
• The device advances neural recording hardware and preclinical BCI/neuroprosthetics tooling. ¹
• The work was published in Nature (November 2025). ^{1 1}

Weekly enrichment (2026-07-20)

• The study appeared in Nature Electronics (vol. 8, issue 12, pp. 1259–1271; published online 3 November 2025); the device is called a microscale optoelectronic tetherless electrode (MOTE), integrating silicon CMOS circuitry with compound semiconductors.^{2 3}
• MOTE uses a single AlGaAs diode that serves simultaneously as a photovoltaic cell for power and as a light-emitting diode for the data uplink, eliminating any need for wires or tethers.^{2 3}
• The implant contains 186 CMOS transistors providing low-noise amplification, pulse-position-modulation (PPM) encoding, and electro-optical transduction; PPM is more power-efficient for communication than amplitude modulation.²
• Operationally, an external 623-nm LED source powers the device while the MOTE emits 825-nm PPM light pulses encoding the electrophysiological signal, detected by a silicon avalanche photodiode and digitized by an oscilloscope.²
• The device demonstrated chronic (365-day) in vivo recordings in awake mice, addressing challenges of electrode–tissue motion and the excess tissue volume displaced by bulkier implants.^{2 3}
• In the reported cohort of six implanted mice, two had MOTEs placed on the brain surface to capture electrocorticographic (ECoG) signals, while four had MOTEs inserted into the barrel cortex (around layers 2/3).²
• Compact encapsulation against corrosive biological media was achieved with two-dimensional materials processing, vacuum annealing, and atomic layer deposition combined with a standard CMOS fabrication flow.^{2 3}
• The work was co-led by Cornell’s Alyosha Molnar with Sunwoo Lee (now at Nanyang Technological University); coverage notes the implant is small enough to rest on a grain of salt and is the smallest known implant to wirelessly report brain electrical activity.⁴
• An earlier generation MOTE measured roughly 60 × 30 × 330 µm, functioned in saline for more than six months and in a mouse brain for about two months, could be handled with micropipettes, and was mass-fabricated with high yield via photolithography.⁵
• Investigators suggest the material composition could allow neural recording during MRI scans (largely infeasible with current implants) and could be adapted to other tissues such as the spinal cord or paired with optoelectronics in artificial skull plates.⁴

Footnotes

1. https://news.google.com/rss/articles/CBMiX0FVX3lxTFBoVUk0R2dOc0tPQ1FlVWFCaHBjYTRfN3BjcnRnRm9mX3VoUmp2Nno0LVN4Q25sN3FIUV9ITGpIeFpoeUh5WmluVl9XS0lXVktqUzhTaHhsbXVYUWE4dGc0?oc=5 ↩ ↩² ↩³ ↩⁴

2. https://www.nature.com/articles/s41928-025-01484-1 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

3. https://pmc.ncbi.nlm.nih.gov/articles/PMC12727521/ ↩ ↩² ↩³ ↩⁴

4. https://www.eurekalert.org/news-releases/1104425 ↩ ↩²

5. https://doi.org/10.1109/jmems.2020.2999496 ↩