Implanted Neural Interfaces: Biochallenges and Engineered Solutions

Abstract

Neural interfaces are connections that enable two-way exchange of information with the nervous system. These connections can occur at multiple levels, including with peripheral nerves, with the spinal cord, or with the brain; in many instances, fundamental biophysical and biological challenges are shared across these levels. We review these challenges, including selectivity, stability, resolution versus invasiveness, implant-induced injury, and the host-interface response. Subsequently, we review the engineered solutions to these challenges, including electrode designs and geometry, stimulation waveforms, materials, and surface modifications. Finally, we consider emerging opportunities to improve neural interfaces, including cellular-level silicon to neuron connections, optical stimulation, and approaches to control inflammation. Overcoming the biophysical and biological challenges will enable effective high-density neural interfaces for stimulation and recording.

Stretchable silicon nanoribbon electronics for skin prosthesis

“…Ceria nanoparticles are adsorbed on PtNWs (Fig. 6b right) to suppress the ROS enrichment which is neurotoxic at high concentration 34 . The low material impedance of Pt and large surface area of NWs decreases impedance significantly lower than planar Au or Pt electrodes (Fig.…”

Materials for neural interfaces

“…2 Further research in this area led to one of the earliest successful neuroprosthetics-cochlear implants for hearing ( Figure 1 ), 3 , 4 followed by interfacing/stimulation efforts in the visual cortex 5 , 6 and retina. 7 Currently, a number of electrodes are available for applications in the central and peripheral nervous systems (for details, see References 1 ,8 ,and 9 ). From a materials perspective, current electrode interfaces are made of conductive materials such as gold, platinum, iridium oxide, and glassy carbon; however, they fail to conform to the biological tissue properties, resulting in an inability to produce complete integration.…”

Auditory-Nerve Responses to Varied Inter-Phase Gap and Phase Duration of the Electric Pulse Stimulus as Predictors for Neuronal Degeneration

“…Being consistently smaller after deafening, response amplitudes seem to reflect function better than threshold (Hall 1990;Shepherd and Javel 1997;Agterberg et al 2009). However, the amplitude largely depends on factors such as the distance between the stimulation electrode and the excitable tissue, the impedance between the two, and, likewise, on the distance and impedance between the excited neural tissue and the recording electrode (Grill et al 2009). …”