Thin-Film Grid
A thin-film grid is a flexible polyimide electrode array, 12 µm thick, that records from or stimulates the surface of the brain, the skull, a peripheral nerve or the heart rather than penetrating it.
It is the surface counterpart of the silicon probe: the same thin-film process lays platinum sites and traces on a polymer film instead of a silicon shank, and the finished array bends to the surface it rests on.
What the surface changes is the signal. Sites sit outside the tissue, separated from the neurons by the pia, the dura or the skull, so individual spikes are out of reach and the array records the field potential — the summed activity of the population beneath each site. That is why grid sites are large, 25 µm to 1 mm across, and why placement is the experiment: an epidural array on intact dura records less but survives chronically; a subdural array on the pia records more at the cost of opening it; a skull-surface array records rhythms and state with no craniotomy at all. Because nothing anchors a grid but its fit, conformity to a curved or moving surface is the design problem, and the catalog answers it differently per target — accordion and segmented layouts for the beating heart, pre-curved cuffs sized to a nerve's diameter, bregma-referenced layouts for the rodent skull.
Four families cover the four surfaces: ECoG grids for the cortex, EEG arrays for the skull, cardiac grids for the epicardium and nerve cuffs for peripheral nerves — 53 catalog designs, 3 to 256 sites. Each mounts on a package and mates to the same headstages as a silicon probe. Neural interfaces are not one size fits all; function follows fit. Research use only.
Typical values
| Catalog designs | 53, in 4 families |
|---|---|
| Substrate | polyimide, 12 µm |
| Sites per array | 3 to 256 |
| Site diameter | 25 µm to 1 mm |
| Site metal | platinum |
| Surfaces | cortex (epidural or subdural), skull, epicardium, peripheral nerve |