Biomechanical energy harvesting to improve post-stroke mobility

Abstract

Foot drop is a common post-stroke gait impairment that reduces toe clearance and compromises walking safety. Existing assistive interventions are often limited by passive compensation, external power requirements, and manual tuning. Here, we introduce a wearable, gait-timing-adaptive, self‑powered neuroprosthesis (SPN) that augments ankle dorsiflexion and corrects gait patterns, avoiding labor-intensive parameter tuning and eliminating the charging and reliability burdens of external batteries. The SPN leverages gait’s out‑of‑phase mechanics: it harvests mechanical energy during stance on the non‑paretic limb and immediately converts it into electrical stimulation of the tibialis anterior on the paretic limb during swing, increasing dorsiflexion when foot clearance is required. In ambulatory stroke survivors with preserved walking capacity, foot drop, and lower-limb impairment (Fugl-Meyer LE Score: 13-27/34, Modified Ashworth Scale-Ankle Plantarflexors: 0-2), the SPN assistance produced immediate, clinically meaningful gains during outdoor walking: dorsiflexion angle improved from −1.1° to 6.8°, walking distance increased by 67.3%, speed by 43.5%, and gait variability decreased by 71.9%. These findings demonstrate the SPN’s potential to restore dorsiflexion, enhance mobility, and improve overall quality of life for individuals recovering from stroke, particularly those at later stages of life. Foot drop after stroke reduces toe clearance and walking safety. Here, Pan et al. report a gait-timing-adaptive, self-powered neuroprosthesis that harvests gait energy to augment ankle dorsiflexion, improving outdoor walking distance and speed, and reducing gait variability in stroke survivors.