Devices

A flexible, foldable surface array with a silicon transistor at each electrode so hundreds of sites share a few wires. 360 channels at 500 µm spacing, Penn, Illinois and collaborators, 2011.

Device — Cortical surface

Active-matrix flexible ECoG array (Viventi, 2011)

Official site →

ECoG · active matrix · silicon nanomembrane · multiplexed · flexible · UPenn · Rogers · Litt · academic · research

Active-matrix flexible ECoG array (Viventi, 2011)

One-line verdict: Put an amplifier and a multiplexing switch at every electrode so a dense surface array needs far fewer wires. Shown for large-area mapping, not yet a chronic human implant.

Quick tags: Recording · Cortical surface · Published: 2011 (Nature Neuroscience)

Overview

What it is: A flexible, non-penetrating electrode array whose circuit uses ultrathin silicon nanomembrane transistors. Each unit cell has two transistors: a buffer connected to the electrode and a multiplexing transistor that lets all sites share a small number of wires.

Why it matters: Passive arrays need one wire per electrode, which caps how much brain a high-resolution array can cover. The authors state that ECoG electrode spacing of 1.25 mm or closer is needed in humans to capture the spatial information, while clinical subdural electrodes are about 3 mm across on about 10 mm spacing.

What was shown: In vivo recordings of sleep spindles, single-trial visual evoked responses and electrographic seizures, with spatial detail the authors describe as new.

Spec Card Grid

Identity

  • Authors: Jonathan Viventi, Dae-Hyeong Kim and co-authors; senior authors include John A. Rogers and Brian Litt
  • Published: Nature Neuroscience, 13 November 2011

Geometry & Architecture

  • Transistors: 720 silicon nanomembrane transistors in the array described (two per unit cell)
  • Channels: 360-channel array pictured in Fig. 1
  • Electrode size and spacing: 300 × 300 µm electrodes on 500 µm spacing
  • Layers: silicon nanoribbons about 260 nm thick; polyimide insulation about 1.2 µm; encapsulation of polyimide about 1.2 µm and epoxy about 4 µm
  • Non-penetrating: yes

Evidence and limits

  • Shown: high-density mapping in vivo of spindles, evoked responses, seizures
  • Not covered here: chronic implantation and human use

Engineering Verdict

Strengths: wire count no longer scales with electrode count; flexible and foldable; very high spatial sampling.

Limitations: complex fabrication; the chronic reliability of thin transistor arrays in the body is not addressed in this paper.

References