Flexible Wireless Electrical Stimulator Based on Liquid Metal High‐Density Coils for Chronic Pain Therapy

Abstract Chronic pain imposes substantial burdens on both individuals and society. For patients who have not responded to conservative treatments, spinal cord electrical stimulation (SCS) may be used as a therapeutic option. However, existing SCSs rely on rigid power delivery systems that can cause inflammation, limiting their long‐term stability and usability. In this study, an implanted flexible wireless electrical stimulator (WES) based on liquid metal (LM) high‐density coils is proposed, which can be applied to chronic pain treatment. The LM coil is fabricated using soft lithography and reversible bonding techniques, providing a higher effective number of turns and greater flexibility than existing coils, while maintaining mechanical stability to withstand over 1000 bending cycles. Furthermore, the WES system provided precisely tunable output voltages (±0–2 V), enabling tailored stimulation protocols. In a rodent model of neuropathic pain, WES therapy elicited a remarkable 60% improvement in weight‐bearing capacity, and the expression of pain‐sensitive factors is significantly reduced after treatment. The inductive electromotive force remained stable after implantation, and the tissue at the implantation site is in favorable condition. This work demonstrates the efficacy of LM high‐density coils for chronic pain management through in vivo implantation experiments, thereby laying the foundation for future long‐term, implantable, and wirelessly powered medical devices.