A Smart Knee Implant Using Triboelectric Energy Harvesters

Area of Science:

• Biomedical Engineering
• Materials Science
• Wearable Technology

Background:

• Total knee replacement (TKR) surgeries are increasing, yet patient outcomes regarding functionality and pain relief are often suboptimal.
• Continuous monitoring of knee joint loads post-surgery could significantly enhance surgical techniques and implant development.
• Existing methods for load monitoring in TKRs are limited, necessitating innovative self-powered solutions.

Purpose of the Study:

• To characterize a triboelectric energy harvester designed for integration into TKR implants.
• To develop compatible frontend electronics for digitizing load data using harvested energy.
• To assess the feasibility of self-powered load sensing within a TKR environment.

Main Methods:

• Fabrication and testing of a triboelectric energy harvester prototype for placement within a TKR.
• Application of a simulated 1 Hz sinusoidal axial tibiofemoral load profile (approximating normal walking gait).
• Design and implementation of a power management circuit including rectification, regulation, and supercapacitor charging for load sensing.

Main Results:

• The triboelectric harvester generated 18 V RMS and 6 μW average power under a 2.3 kN load at 1 Hz.
• A power management system achieved 71% efficiency, enabling supercapacitor charging for sensor operation.
• Analysis confirmed the feasibility of multiple daily load sensing events powered solely by harvested energy.

Conclusions:

• Triboelectric energy harvesting is a viable and promising technology for self-powering load sensors within knee implants.
• This approach can provide crucial data for monitoring knee loads, potentially leading to improved TKR performance and patient recovery.
• The developed system demonstrates the potential for long-term, in-situ monitoring of biomechanical forces in artificial joints.