Design of Transcutaneous Stimulation Electrodes for Wearable Neuroprostheses

Ease of use and non-invasiveness has made transcutaneous stimulation a pervasive approach for restoration of hand function. Besides, limited targetability and induced discomfort pose a significant impediment for its clinical translation. By modifying the electrode geometry, we aim to improve the stimulation performance of small surface area electrodes that are suited for forearm muscles. Accordingly, the stimulation performance of twelve electrode geometries was assessed using a computational model and subsequent experimentation on healthy participants. Several metrics quantified their stimulation performance in terms of selectivity, comfort, and safety. Systematic analysis showed that electrode geometries and their underlying currents distribution influence selectivity and comfort, allowing for better stimulation performance. Ranking the electrode geometries identified the concentric serpentine, and the fractal-based Sierpiński and Hibert-types to outperform the circular electrodes. At a comfortable level, these electrodes provoked selective and substantial muscle contraction. Ideally, these geometries can be a reference for optimal electrode designs. The novelty of this study lies with both model-based and experimental assessments on a wide range of electrode geometries and the introduction of a computational model for electrode performance evaluation. Implications from this study can aid with easy to fabricate and personalized electrode designs. By integrating these optimized electrode designs with advanced material technologies, the applicability of wearable neuroprostheses can be improved.