Ultra-Flexible Biocompatible Electrodes Designed to Monitor Neural Activity in a Three-Dimensional Space

Abstract

Biocompatible electrodes that span through different regions of the brain are still in its very early development stages. While many researchers are still focusing on creating the best two – dimensional implants, very few are exploring the possibilities of three – dimensional implants. The additional dimension will offer the electrodes the opportunity to seamlessly integrate with complex neural networks, to simultaneously monitor neural activity in various areas of the brain, and to multichannel interface with the central nervous system. The first half of the thesis provides a thorough overview of processing with HD-Microsystem’s PI-2611. Not only is PI-2611 biocompatible, its flexibility, thermal stability, and solvent resistance make it both an attractive substrate and a sturdy encapsulant. At the current moment, a batch of successful ultra-thin, flexible encapsulated samples have managed to survive the taxing back-side acid etch process. The current polyimide release process must be developed before attempting to fabricate another electrode sample. The second half of the thesis constructs an entire set-up surrounding the ultra-thin electrodes. The electrodes are arranged such that all three electrode clusters operate on different spatial planes. The electrodes can now send and collect signals on all three cellular levels. The set-up is designed to fit one 15 mm diameter cell culture dish in the middle that is capable of growing neurons. In order for the neurons to attach themselves onto the polyimide, an extracellular matrix must cover the electrode clusters in order to promote neural adhesion. Once a successful batch of neurons is growing on or through the electrode substrate, various steps can be taken to either optimize the system including developing new organic, ultra-soft substrates.