Electronic and Ionic Materials for Neurointerfaces

Abstract

Communication between living brain tissue and engineered devices is the key link to understand brain function and restore neurological deficits from disease, injury, and old age. Enabled by new materials and device designs, a new generation of brain interface technologies is replacing bulkier systems, offering lower tissue damage, reduced immunogenicity, and long‐term stability. New electrode materials with improved chronic performance and increasing emphasis on multimodal capabilities are being integrated onto ultraflexible and mechanically compliant architectures. As these scale to smaller dimensions and higher channel counts, the goal of bidirectional, single‐cell interfaces is nearly within reach. However, promising, long‐term reliability, toxicity, and performance of these systems are still largely unknown. Here, the basics of electrode materials and in vivo technologies are reviewed, and recent advances in electronic and ionic materials are highlighted.

Hydrogel bioelectronics

“…Unlike conventional electronics in which electrons serve as carriers of information, bioelectronic activities in the biological systems are essentially ionic through electrolytic media. 10,[31][32][33] Ever-evolving microenvironments due to diffusive and convective exchange of mobile ionic and biochemical species in water-rich tissues further highlight the distinctive nature of the biological systems over electronic systems. Together with mechanical and compositional dissimilarities, these inherent mismatches between biology and electronics signify the high hurdles to bring the two realms closer.…”

Direct Electrical Neurostimulation with Organic Pigment Photocapacitors

“…Stimulation of neurons in a localized and safe manner is important both as an investigative tool and as a therapeutic means. Great progress in nano‐ and microengineered electrode platforms and ion delivery techniques for electrically communicating with neurons has enabled bioelectronic therapeutic devices in recent decades. Eliminating the need for wiring, optical stimulation is an alternative approach, which is inherently less invasive than electrodes .…”

Nanoneedle Platforms: The Many Ways to Pierce the Cell Membrane

“…Especially for current neuroscience, direct measurement of intracellular electrophysiological states is of great interest for gaining in‐depth knowledge of the network forming activity and complicated communications among a neuronal population. [ 178–181 ] Although conventional patch clamp techniques provide intracellular recording with high signal to noise ratio, this invasive insertion into cells lacks the capability of long‐term recording, and cannot monitor more than several cells or locations at once. Multielectrode arrays can record extracellular signals at many locations at a time, yet the extracellular electrical signal quality is limited compared to intracellular signals, resulting in signal distortion and crosstalk.…”