A research team led by professor Wang Yapei from the Department of Chemistry at Renmin University of China (RUC) achieved major breakthroughs in wireless power supply for implantable medical devices. Their research findings were published in the internationally renowned journal Advanced Materials under the title “Skin Thermal Management for Subcutaneous Photoelectric Conversion Reaching 500 mW”.
Implantable medical devices such as pacemakers and neurostimulators are of great importance for they can significantly improve patients’ symptoms and enhance their quality of life. However, these devices often struggle to achieve long-term power supply. Once the battery is exhausted, they may end up as useless “electronic waste”, forcing patients to face the substantial risks and financial burdens of a second operation to replace the batteries. In answer to this problem, Professor Wang Yapei and his team developed a range of long-term power supply technologies based on second near-infrared (NIR-II) light, which may permanently resolve the long-term power supply issue of implantable medical devices.
Wireless Power Supply Technology for Implantable Medical Device Based on Second Near-Infrared Light-Thermal-Electric Energy Conversion Strategy
The existing transdermal wired power supply technology can continuously offer electric supply in a high-power density. However, prolonged use of transdermal power supply can easily lead to infections and even endanger patients’ lives. In comparison, wireless charging technology that can convert electromagnetic waves that penetrate the skin barrier into electricity has better biosafety and can provide long-term power supply for implantable medical devices. NIR-II light, whose wavelength ranges from 1000 to 1350 nm, has higher tissue transmittance and maximum permissible exposure power density. For the same subcutaneous implanted device, the theoretical maximum charging power of NIR-II light is tens of times that of other electromagnetic waves.
Based on the aforementioned research background, the research team proposes the implementation of wireless power supply technology for implantable medical devices based on second near-infrared light-thermal-electric energy conversion strategy. During illumination, the device can first convert light energy into thermal energy through a selective absorbing coating with high photothermal conversion efficiency and low thermal emissivity, and then convert thermal energy into electrical energy through thermoelectric conversion. At the same time, the presence of a thermal protection layer ensures that this process does not cause thermal damage to biological tissues. Based on this, the research team uses a simulation software to further improve the overall energy conversion efficiency of the device by designing thermal management structures, regulating internal convective and radiative heat exchange in the device, and introducing modified phase-change heat storage materials. Compared with the unshielded photothermal-thermoelectric devices, this method reduces heat loss by 70% and increases energy conversion efficiency by more than 20 times. Further biological experiments show that external light can cause the device implanted in the abdominal cavity of rabbits to produce extremely high output power (10 milliwatts), which is sufficient to drive the regular operation of implantable medical devices such as pacemakers or endoscope, demonstrating significant advantages compared to existing technical solutions.
Enhancing Energy Efficiency of Implantable Medical Devices through Skin Thermal Management-based Photothermoelectric-Photoelectric Synergistic Energy Conversion Strategy
Building upon earlier research, the research team further proposes a skin thermal management-based photothermoelectric-photoelectric synergistic conversion strategy. By integrating photothermoelectric conversion devices with photoelectric conversion devices and designing multi-level thermal management structures, the team aims to reduce the heat exchange between photovoltaic cells and biological tissues. The energy is then exported, converted, and stored in thermal-electric conversion devices. Under the premise of biological safety, this approach decreases heat loss from photovoltaic cells while increasing photoelectric conversion efficiency. Additionally, excess heat is converted into electricity through thermal-electric conversion devices, resulting in efficient energy utilization. These processes synergistically enhance the energy conversion efficiency of the device for NIR-II light.
Through animal experiments and clinical trials, the device has demonstrated a maximum energy output of 500 milliwatts and a peak energy conversion efficiency of 9.4%, which is sufficient to directly power devices such as cameras or cardiac pacemakers. Further cell staining analysis and animal experiments have indicated that the device does not cause damage to biological tissues. This achievement provides robust support for the future development of implantable medical devices.
(power supply test in rabbits)
The above work received funding from the National Natural Science Foundation of China (NSFC) and the department of Science and Technology Construction of RUC. The results have been published respectively in Nature Communications and Advanced Materials. The first author of both papers is Lyu Shanzhi, a graduate from the Master’s program in the Department of Chemistry of RUC. The corresponding author is Professor Wang Yapei, with RUC as the primary corresponding institution. (For more details, please refer to Adv. Mater. 2023, 2306903; Nat. Commun. 2022, 13, 6596.)
Professor Wang Yapei’s research team has long been engaged in research areas such as photothermal conversion, complex emulsions, green electronics, and medical materials. They focus particularly on the innovative uses of these expertise in skin tissue engineering and smart agricultural and forestry. The team is dedicated to addressing major national strategic needs and actively promotes interdisciplinary integration between chemistry and other fields. Through close collaboration between disciplines, they aim to solve critical challenges in areas such as national energy and environment, clinical medicine, and agricultural technology.