Closed-loop wearable neurostimulation system with triboelectric sensing to alleviate hemifacial spasms

Hemifacial spasm (HFS) is a neurological disorder characterized by involuntary contractions of the facial muscles, which can significantly influence patients' quality of life. Traditional diagnostic methods are often subjective, and electromyography (EMG) monitoring is constrained by equipment limitations and interference. Current treatments include short-term Botulinum toxin (BTX) injections and high-risk microvascular decompression (MVD), both of which suffer from low patient compliance. This study introduces a closed-loop facial nerve stimulation system integrated into eyewear, featuring triboelectric sensors doped with butylated melamine formaldehyde (BMF)-CaCu₃Ti₄O₁₂ (CCTO), and constructed with micrometer-scale hemispherical structures, which enhance performance by approximately 2.3 times. These sensors capture subtle dynamic signal changes in real-time, suitable for monitoring minute facial muscle activities, while consuming zero power. Additionally, a customized electrical stimulation module with adjustable parameters and a high-precision HFS detection model have been developed, enabling rapid activation of facial nerve stimulators for targeted neuromodulation upon detecting spasms. The system achieves a recognition accuracy of 98% for HFS. Preliminary clinical validation demonstrates effectiveness in reducing spasm severity with inter-patient variability in two involved patients. Overall, this integrated system offers enhanced convenience and patient compliance, presenting a promising solution for HFS treatment.