Remote Stimulation of Sciatic Nerve Using Cuff Electrodes and Implanted Diodes.

Area of Science:

• Biomedical Engineering
• Neuroscience
• Materials Science

Background:

• Chronic nerve stimulation often relies on wired implants, which can lead to instability and complications.
• Existing methods face challenges with long-term reliability and biocompatibility.
• Wireless alternatives are needed to improve the safety and efficacy of neurostimulation devices.

Purpose of the Study:

• To demonstrate a novel wireless neurostimulation technique using free-floating, inter-neural diodes.
• To optimize alternating current (AC) electrical parameters and diode characteristics for effective wireless nerve activation.
• To assess the feasibility of activating implanted microdiodes remotely using external AC fields.

Main Methods:

• Tested three packaged Schottky diodes (1.5 mm, 500 µm, 220 µm) in vivo (n=17 rats).
• Assessed sciatic nerve activation based on diode-dipole lengths and relative positioning.
• Implanted free-floating Schottky microdiodes in rat sciatic nerves (n=3) for wireless stimulation.
• Measured muscle twitch thresholds and recorded electromyograms (EMGs) to evaluate nerve response.

Main Results:

• Muscle twitch thresholds increased non-linearly with stimulation frequency.
• Significant current attenuation (~100-fold) was observed in implanted diodes, necessitating 1-2 mA drive currents for 17 µA thresholds.
• Muscle recruitment via EMG showed a steep response, particularly with deeper diode implantation relative to external electrodes.

Conclusions:

• Demonstrated the feasibility of wireless neurostimulation using untethered, implanted microdiodes.
• External AC fields can effectively activate remote, free-floating diodes for nerve stimulation.
• This technology offers a promising alternative to wired implants for chronic neurostimulation applications.