Flexible Thin‐Film Neural Electrodes with Improved Conformability for ECoG Measurements and Electrical Stimulation

Abstract

Neural electrodes for electrocorticography (ECoG) recording and electrical stimulation are used for diagnosis and treatment of epilepsy, which are temporarily attached to the surface of cerebral cortex within the subdural space. However, conventional electrodes have a mechanical mismatch with the surface curvature of the brain cortex. Thus, it is necessary to develop a thin and flexible ECoG electrode to overcome the mechanical mismatch with cortex tissue and achieve long‐term ECoG measurement. Herein, a flexible thin‐film electrode is reported with a thickness of ≈8 µm by exploiting printed electronics. A simple fabrication method of conductive wiring is proposed by inkjet printing Au nanoink on a flexible elastomeric thin film consisting of polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS). The conductive wiring printed on the SBS thin film is encapsulated by another SBS thin film as an insulation layer, with laser‐processed micropatterns. The flexible thin‐film electrode is implanted on the cortical surface of rats and used for in vivo ECoG recording and electrical stimulation without the occurrence of severe inflammatory reactions after 6 weeks of implantation. The flexible electrode with 35 ECoG channels visualized the epileptiform activity in a drug‐induced epilepsy rat model, which demonstrates the potential application for the management of intractable epilepsy.