Compliant peripheral nerve interfaces

Abstract

Peripheral nerve interfaces (PNIs) record and/or modulate neural activity of nerves, which are responsible for conducting sensory-motor information to and from the central nervous system, and for regulating the activity of inner organs. PNIs are used both in neuroscience research and in therapeutical applications such as precise closed-loop control of neuroprosthetic limbs, treatment of neuropathic pain and restoration of vital functions (e.g. breathing and bladder management). Implantable interfaces represent an attractive solution to directly access peripheral nerves and provide enhanced selectivity both in recording and in stimulation, compared to their non-invasive counterparts. Nevertheless, the long-term functionality of implantable PNIs is limited by tissue damage, which occurs at the implant-tissue interface, and is thus highly dependent on material properties, biocompatibility and implant design. Current research focuses on the development of mechanically compliant PNIs, which adapt to the anatomy and dynamic movements of nerves in the body thereby limiting foreign body response. In this paper, we review recent progress in the development of flexible and implantable PNIs, highlighting promising solutions related to materials selection and their associated fabrication methods, and integrated functions. We report on the variety of available interface designs (intraneural, extraneural and regenerative) and different modulation techniques (electrical, optical, chemical) emphasizing the main challenges associated with integrating such systems on compliant substrates.

Modulus‐Tailorable, Stretchable, and Biocompatible Carbonene Fiber for Adaptive Neural Electrode

“…[ 1–5 ] According to their different implantation modes, the neural electrodes are divided into intraneural and extraneural electrodes. [ 6–9 ] As intraneural electrodes may damage the axons and blood vessels, noninvasive extraneural electrodes are preferred.…”

The Use of the Velocity Selective Recording Technique to Reveal the Excitation Properties of the Ulnar Nerve in Pigs

“…Individual fibres can be further characterised by their diameters (related to the conduction velocity and fibre excitability), direction of propagation (i.e., afferent or efferent), and degree of myelination [ 6 ]. Such characterisations are directly related to function, meaning that different groups of fibres are responsible for conveying specific information to the central nervous system and controlling, for instance, skeletal or cardiac muscles [ 7 ]. However, because of practical challenges (such as the low signal amplitude and interference from extraneural sources), decoding the peripheral neural information remains a significant challenge, considerably limiting the clinical usability of peripheral neural interfaces [ 8 , 9 ].…”

“…While intraneural and regenerative interfaces provide a better selectivity because of the smaller distance from the nerve fibres to the electrodes, their level of invasiveness increases the chance of inducing damage to the neural tissue, either directly or through inflammatory processes [ 10 ]. Still, recent studies have successfully used intraneural interfaces in chronic experiments (for a comprehensive review on implantable peripheral nerve interfaces, see [ 7 ], and for applications in sensory feedback for limb prosthesis, see, e.g., [ 11 ]). Extraneural interfaces are positioned outside the epineurium, being less invasive and, thus, preferable for chronic implantation [ 12 ]; however, due to the greater distance between the electrodes and the individual fibres, they have both a lower signal-to-noise ratio (SNR) and lower selectivity [ 10 ].…”

Three-dimensional multilayer concentric bipolar electrodes enhance the selectivity of optic nerve stimulation

“…Spatial selectivity in neuromodulation refers to interacting with neurons in a predefined and limited volume of tissue [35]. This ability is key in avoiding side effects and improving outcomes for neurological treatments.…”