The Microsieve Electrode (μSE) As a Tool for Neuromodulation in Peripheral Nerves: A Design, Modeling and Fabrication study

Abstract

n BACKGROUND: An electrode array that operates within a cross-section of nerve is an attractive yet unfledged idea. Limitations in selectively recruiting individual fascicles restrict the promise and clinical viability of existing devices. Microsieve electrodes (mSE), a type of regenerative neural interface, have shown promise, providing a robust interface integrated into a transected nerve. We report a hybrid-field model demonstrating graded selective recruitment of fascicles, and a scalable microfabrication process based on current semiconductor technologies. n METHODS: A hybrid-field model was used to calculate the selectivity and recruitment of 16 electrode sites on 14 mSE designs varied by transparency (available regeneration area ranging from 20% to 80%) and hole size (30 mm and 100mm). A physical prototype was created using photolithography, physical vapor deposition and anodic metal dissolution. n RESULTS: All designs demonstrate graded recruitment by adjusting current. The 30 mm hole size favored lower stimulation currents and lessened variance in fascicle selection, however, inhibited the effects of transparency on recruitment. Contrary, the 100 mm version increased stimulation current requirements and increased variance, but enabled transparency effects on recruitment. Microfabrication was made feasible using polyimide thin-film, and platinum metal patterning of the electrodes on glass slides. The process avoided cytotoxic materials and processes, allowed multi-unit scalability, and arbitrary geometries. n CONCLUSIONS: These preliminary results provide a framework for neuromodulation using graded and selective recruitment of nerve fascicles using the mSE. Clinically, mSE could be used for rehabilitation of motor and sensory function, spinal cord injuries, chronic pain and as an enhancement to selective rhizotomies.