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Project

Flexible Electrode Arrays Based on Thin-Film Transistors for High-resolution Cortical Mapping

Neurotechnologies are rapidly evolving, providing ever more sophisticated tools for interfacing with the brain at unprecedented resolution. Electrocorticography (ECoG), an electrophysiological technique used in neuroscience research and clinical practice, records brain electrical activity through electrode grids placed directly on the cortical surface. Current ECoG technologies face a significant challenge in achieving both high spatial resolution and wide cortical coverage, while maintaining low noise levels and a compact acquisition system. The electrode count and density are restricted by the fact that each electrode must be individually wired and sampled by the recording electronics, ultimately hindering the development of implantable systems with high-channel counts.

This work presents an active micro electrocorticography (µECoG) array that tackles this limitation by integrating amorphous indium‑gallium‑zinc oxide (a‑IGZO) thin‑film transistors (TFTs) into a flexible electrode grid. The use of transistors enables the multiplexing of the recording signals, allowing multiple electrodes to be addressed through a shared readout line, thereby drastically reducing the required number of connecting lines and channels in the recording electronics. The array can operate in two acquisition modes: 1) addressing mode, which allows the selection and recording of subsets of electrodes using standard electrophysiology acquisition systems, and 2) time‑division multiplexing mode, which enables the simultaneous recording of all the electrodes in the array by employing a dedicated readout integrated circuit. Leveraging a well‑established flexible electronics technology based on metal‑oxide TFTs allows for the development of a scalable fabrication process compatible with existing thin‑film semiconductor foundries, a critical step for the potential translation of the µECoG arrays from a laboratory setting into clinical practice.

By combining the a‑IGZO based µECoG array with a dedicated silicon readout integrated circuit, our proof‑of‑concept system is capable of recording from up to 256 electrodes simultaneously, thanks to the implemented 16:1 time-division multiplexing scheme. Compared to state-of-the-art active µECoG‑ arrays, our system offers lower noise over a broader frequency band. In vivo validation is demonstrated acutely in mice by recording spontaneous activity and somatosensory evoked potentials over a cortical surface of 8×8 mm2. The developed system overcomes the wiring bottleneck limiting high‑channel count ECoG arrays, offering high spatial resolution and large‑area neural recordings from the surface of the brain, while preserving excellent electrical recording characteristics. The proposed neural interface holds promise as a powerful tool for improved mapping of the cerebral cortex and as an enabling technology for future brain-machine interfaces.

Date:4 Nov 2016 →  20 Feb 2024
Keywords:neurotechnologies
Disciplines:Biological system engineering, Biomaterials engineering, Biomechanical engineering, Medical biotechnology, Other (bio)medical engineering, Neurosciences, Biological and physiological psychology, Cognitive science and intelligent systems, Developmental psychology and ageing
Project type:PhD project