Frontend Electronic System for Triboelectric Harvester in a Smart Knee Implant

Total knee replacement (TKR) is an increasingly common surgery, particularly among active young and elderly people who suffer from knee pain. Continuous monitoring of the load on the knee after the surgery is highly desirable for designing an efficient and more functional smart knee implant. This study involves designing a triboelectric harvester to produce a signal, which is used by the proposed frontend electronic system to monitor the load. At a knee cyclic load of 2.3 kN, the harvester produces 6 μW power and 18 V RMS signal at a frequency of 1 Hz. This paper proposes a novel self-powered frontend electronic system to process this harvested signal and monitor the load on the knee. First, an electrical model is generated for the fabricated harvester. In the next step, the output signal is processed using a filter, rectifier and regulator, and finally converted into digital bits using an analog-to-digital converter. The power consumption of the proposed design is 5.25 μW.