Ultrasound‐Powered, Battery‐Free Implants via Triboelectric Energy Harvesting

Abstract Implantable electronics enable physiological therapies that go beyond the capabilities of pharmacological approaches; however, these devices suffer from a persistent limitation: the absence of a sustainable energy source. Ultrasound‐driven triboelectric nanogenerators (US‐TENGs) offer a promising route to battery‐free implantable electronics by converting externally applied ultrasound into sustained electrical power within deep tissues. Since the first demonstration of ultrasound‐powered charging for rechargeable batteries, research has progressed toward the realization of battery‐free implants along two main tracks: long‐term, high‐performance systems targeting therapeutic applications such as neurostimulation and cancer therapy; and bioresorbable, short‐term devices designed for antibacterial activity, wound healing, and transient nerve modulation. Current device architectures, materials, and vibration‐mode control are critically assessed, and highlight challenges for future battery‐free implants. System‐level strategies are also proposed to integrate US‐TENGs with multifunctional electronics and advanced biodegradable triggers, paving the way toward clinically viable, miniaturized battery‐free implants.