Although the number of total knee replacement (TKR) surgeries is growing rapidly, functionality and pain-reduction outcomes remain unsatisfactory for many patients. Continual monitoring of knee loads after surgery offers the potential to improve surgical procedures and implant designs. The goal of this study is to characterize a triboelectric energy harvester under body loads and to design compatible frontend electronics to digitize the load data. The harvester prototype would be placed between the tibial component and polyethylene bearing of a TKR implant. The harvester generates power from the compressive load. To examine the harvester output and the feasibility of powering a digitization circuitry, a triboelectric energy harvester prototype is fabricated and tested. An axial tibiofemoral load profile from normal walking (gait) is approximated as a 1 Hz sine wave signal and is applied to the harvester. Because the root mean square of voltages generated via this phenomenon is proportional to the applied load, the device can be simultaneously employed for energy harvesting and load sensing. With an approximated knee cyclic load of 2.3 kN at 1 Hz, the harvester generated output voltage of 18 V RMS, and an average power of 6 μW at the optimal resistance of 58MΩ. The harvested signal is rectified through a negative voltage converter rectifier and regulated through a linear-dropout regulator with a combined efficiency of 71%. The output of the regulator is used to charge a supercapacitor. The energy stored in the supercapacitor is used for low resolution sensing of the load through a peak detector and analog-to-digital converter. According to our analysis, sensing the load several times a day is feasible by relying only on harvested power. The results found from this work demonstrate that triboelectric energy harvesting is a promising technique for self-powering load sensors inside knee implants.

中文翻译：

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使用摩擦电能收集器的智能膝关节植入物

尽管全膝关节置换 (TKR) 手术的数量正在迅速增长，但许多患者的功能和减轻疼痛的结果仍然不令人满意。手术后持续监测膝关节负荷提供了改进手术程序和植入物设计的潜力。本研究的目标是表征身体负载下的摩擦电能收集器，并设计兼容的前端电子设备以数字化负载数据。采集器原型将放置在胫骨组件和 TKR 植入物的聚乙烯轴承之间。收割机通过压缩负载产生动力。为了检查采集器输出和为数字化电路供电的可行性，制造并测试了摩擦电能采集器原型。来自正常步行（步态）的轴向胫股负载曲线近似为 1 Hz 正弦波信号，并应用于采集器。由于通过这种现象产生的电压的均方根与施加的负载成正比，因此该器件可以同时用于能量收集和负载传感。在 1 Hz 时的近似膝关节循环负载为 2.3 kN 时，采集器在 58MΩ 的最佳电阻下产生 18 V RMS 的输出电压和 6 μW 的平均功率。采集的信号通过负电压转换器整流器进行整流，并通过线性压降稳压器进行调节，综合效率为 71%。稳压器的输出用于为超级电容器充电。存储在超级电容器中的能量通过峰值检测器和模数转换器用于负载的低分辨率感测。根据我们的分析，仅依靠收获的电力，一天数次感应负载是可行的。从这项工作中发现的结果表明，摩擦电能收集是一种用于膝关节植入物内自供电负载传感器的有前途的技术。