Injectable conductive hydrogel electrodes for minimally invasive neural interfaces.

Soft bioelectronic neural interfaces have great potential as mechanically favourable alternatives to implantable metal electrodes. In this pursuit, conductive hydrogels (CHs) are particularly viable, combining tissue compliance with the required electrochemical characteristics. Physically-aggregated CHs offer an additional advantage by their facile synthesis into injectable systems, enabling minimally invasive implantation, though they can be impeded by a lack of control over their particle size and packing.

Polymer Bioelectronics: A Solution for Both Stimulating and Recording Electrodes.

The advent of closed-loop bionics has created a demand for electrode materials that are ideal for both stimulating and recording applications. The growing complexity and diminishing size of implantable devices for neural interfaces have moved beyond what can be achieved with conventional metallic electrode materials. Polymeric electrode materials are a recent development based on polymer composites of organic conductors such as conductive polymers.

Controlled electroactive release from solid-state conductive elastomer electrodes.

This work highlights the development of a conductive elastomer (CE) based electrophoretic platform that enables the transfer of charged molecules from a solid-state CE electrode directly to targeted tissues. Using an elastomer-based electrode containing poly (3,4-ethylenedioxythiophene) nanowires, controlled electrophoretic delivery of methylene blue (MB) and fluorescein (FLSC) was achieved with applied voltage. Electroactive release of positively charged MB and negatively charged FLSC achieved 33.

A Pilot In Vivo Study of Flexible Fully Polymeric Nerve Cuff Electrodes.

Recent trends in the field of bioelectronics have been focused on the development of electrodes that facilitate safe and efficient stimulation of nervous tissues. Novel conducting polymer (CP) based materials, such as flexible and fully polymeric conductive elastomers (CEs), constitute a promising alternative to improve on the limitations of current metallic devices. This pilot study demonstrates the performance of tripolar CE-based peripheral nerve cuffs compared to current commercial tripolar platinum-iridium (PtIr) nerve cuffs in vivo.

Surface electromyography using dry polymeric electrodes.

Conventional wet Ag/AgCl electrodes are widely used in electrocardiography, electromyography (EMG), and electroencephalography (EEG) and are considered the gold standard for biopotential measurements. However, these electrodes require substantial skin preparation, are single use, and cannot be used for continuous monitoring (>24 h). For these reasons, dry electrodes are preferable during surface electromyography (sEMG) due to their convenience, durability, and longevity.

Preparation of Rat Sciatic Nerve for Ex Vivo Neurophysiology.

Ex vivo preparations enable the study of many neurophysiological processes in isolation from the rest of the body while preserving local tissue structure. This work describes the preparation of rat sciatic nerves for ex vivo neurophysiology, including buffer preparation, animal procedures, equipment setup and neurophysiological recording. This work provides an overview of the different types of experiments possible with this method.

Flexible Nanowire Conductive Elastomers for Applications in Fully Polymeric Bioelectronic Devices.

Soft, flexible polymer-based bioelectronics are a promising approach to minimize the chronic inflammatory reactions associated with metallic devices, impairing long-term device reliability and functionality. This work demonstrates the fabrication of conductive elastomers (CEs) consisting of chemically synthesized poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires embedded within a polyurethane (PU) elastomeric matrix, resulting in soft and flexible, fully polymeric electrode materials. Increasing PEDOT nanowire loadings resulted in an improvement in electrochemical properties and conductivity, an increased Young's modulus and reduced strain at failure.

Stretchable, Fully Polymeric Electrode Arrays for Peripheral Nerve Stimulation.

There is a critical need to transition research level flexible polymer bioelectronics toward the clinic by demonstrating both reliability in fabrication and stable device performance. Conductive elastomers (CEs) are composites of conductive polymers in elastomeric matrices that provide both flexibility and enhanced electrochemical properties compared to conventional metallic electrodes. This work focuses on the development of nerve cuff devices and the assessment of the device functionality at each development stage, from CE material to fully polymeric electrode arrays.

Multifocal stimulation of the cerebro-cerebellar loop during the acquisition of a novel motor skill.

Transcranial direct current stimulation (tDCS)-based interventions for augmenting motor learning are gaining interest in systems neuroscience and clinical research. Current approaches focus largely on monofocal motorcortical stimulation. Innovative stimulation protocols, accounting for motor learning related brain network interactions also, may further enhance effect sizes.

Conductive elastomer composites for fully polymeric, flexible bioelectronics.

Flexible polymeric bioelectronics have the potential to address the limitations of metallic electrode arrays by minimizing the mechanical mismatch at the device-tissue interface for neuroprosthetic applications. This work demonstrates the straightforward fabrication of fully organic electrode arrays based on conductive elastomers (CEs) as a soft, flexible and stretchable electroactive composite material. CEs were designed as hybrids of polyurethane elastomers (PU) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), with the aim of combining the electrical properties of PEDOT:PSS with the mechanical compliance of elastomers.

Development and Characterization of PEDOT:PSS/Alginate Soft Microelectrodes for Application in Neuroprosthetics.

Reducing the mechanical mismatch between the stiffness of a neural implant and the softness of the neural tissue is still an open challenge in neuroprosthetics. The emergence of conductive hydrogels in the last few years has considerably widened the spectrum of possibilities to tackle this issue. Nevertheless, despite the advancements in this field, further improvements in the fabrication of conductive hydrogel-based electrodes are still required.