Transparent and flexible ECoG electrode arrays of metallic nanostructures for neural recordings

• Autor(a) principal: Bate, Ivânia Patrícia Rijo Trêpo
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/124847
• topic: Electrocorticography; Microelectrode Array; Patterned Metal Grids; Direct Laser Writing; Transparent and Flexible Electronics; Functional Calcium Imaging; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

Unraveling the functioning of the brain has been one of the greatest challenges of the scientific community. In order to obtain a full understanding of how neurons - the building blocks of the brain - coordinate their activity, tools capable of monitoring neural dynamics are necessary. It is possible to acquire neural data with high temporal and spatial resolution by placing flexible electrocorticography transparent electrodes over the brain surface, and measuring the electric potential variation while observing neurons activity with functional calcium imaging. In this project, transparent and flexible microelectrode arrays made of patterned metal grids were produced using microfabrication techniques, namely maskless photolithography through direct laser writing, reactive ion etching, and electron beam evaporation of gold. Afterwards, the device was characterized in saline solution and also tested in mice cerebellum. It is here demonstrated that the electrocorticography device is easily reproducible. Patterned metal grids with 1 μm of linewidth and 22 μm of spacing showed an individual sheet resistance of 6 Ω/sq, and a transmittance of 80% at 550 nm. As for the device itself, the microelectrode array has 16 electrodes with 500 μm of diameter distributed over 3 mm. Additionally, an improved mechanical stability, through Parylene-C flexible substrate pre-treatment, and an impedance of 13 kΩ at 1 kHz were attained. In vivo tests also showed the microelectrode array efficiency for its primary goal: recording brain activity. Hence, the presented microelectrode arrays are able to combine the superior temporal resolution of extracellular electrophysiology, offered by these low impedance electrocorticography electrodes, with the spatial resolution provided by functional calcium imaging in association with the transparent electrodes.