Ultra-compliant peripheral nerve cuff electrode with hydrogel adhesion

This paper reports a method of fabricating peripheral nerve cuff electrodes attached to a sticky hydrogel. The nerve cuff electrode is much more compliant compared to typical cuff electrodes made of polyimide or PDMS and contains adhesion-promoting functional groups that allow for good electrical contact with the nerve without the need for continuous application of pressure on the nerve. A transfer process is used to fabricate the device using poly(acrylic acid) as the sacrificial material that has tunable solubility in aqueous media. This avoids the need for harsh release chemicals that may affect the properties of the hydrogel. The transfer process also allows for electrode contacts that are flush with the surface of the probe and allow intimate contact of with the nerve, as compared with typical recessed electrode contacts. Patterned SU-8 provides a gradual change in Young's modulus from the stiff pad region to the compliant electrode contact region. The measured impedance of the 75 μm radius Pt electrode contacts is ∼100 kΩ. In vivo recordings have been demonstrated using fabricated devices in the dorsal root ganglia of a cat.