High-density transparent graphene array (UC San Diego)
High-density transparent graphene array
A transparent cortical-surface array with cell-scale contacts. The 2024 paper reports arrays up to 256 channels and 20 µm electrode diameters. Platinum nanoparticles improve the small graphene contacts’ electrical interface; interlayer-doped double-layer graphene reduces open-circuit failures in the long, thin traces.
Hardware distinction
Unlike the 2014 CLEAR device, this design has a transparent recording field without gold trace extensions in the field of view. The 256-channel maximum is a design capability reported by the paper, not a statement that every experiment used 256 channels.
| Field | Published detail |
|---|---|
| Array scale | Up to 256 channels |
| Contact diameter | 20 µm |
| Contact treatment | Platinum nanoparticles |
| Trace conductor | Interlayer-doped double-layer graphene |
| Substrate | Thin, transparent flexible polymer strip, described by UC San Diego |
| Complete geometry | Not reconstructed here; film thickness, contact map and full outline are not grounded in the sources used for this entry |
What was measured and predicted
The team combined cortical electrical recordings with two-photon calcium imaging in mouse visual cortex. UC San Diego reports imaging neurons as deep as 250 µm below the surface. The paper found a relationship between surface multiunit-band power and cellular calcium activity.
Neural networks and dimensionality reduction were used to predict single-cell and population-average calcium activity from surface potentials. This is an inference trained against optical measurements, not direct electrical recording from a deep implanted electrode. It is not evidence of reading arbitrary thoughts or of an uncalibrated human decoder.
Evidence limits
The reported experiments are in mice. No human implantation or clinical BCI result is asserted. The institutional article discusses future longer-duration experiments and BCI possibilities; those aims are separate from the paper’s demonstrations. A full 3D device model is deliberately omitted until the remaining geometry is checked.
Source and organization
The University of California San Diego announcement identifies Duygu Kuzum’s group and describes the device, fabrication changes and mouse experiments. The paper was published January 11, 2024.
- Ramezani M, Kim JH, Liu X, et al. High-density transparent graphene arrays for predicting cellular calcium activity at depth from surface potential recordings. Nature Nanotechnology (2024). DOI: 10.1038/s41565-023-01576-z. Primary paper abstract.
- UC San Diego. Transparent Brain Implant Can Read Deep Neural Activity From the Surface, January 11, 2024.