Self-Powered Sensor for Medical Implant Fatigue Monitoring

The patent combines multiple functions into a single integrated circuit: the piezoelectric transducer generates electrical charge from mechanical stress, which is then rectified, stored in a floating gate transistor, and processed by a fatigue analysis algorithm all within one device. This merging allows the system to overcome the low energy conversion of PVDF by efficiently capturing and utilizing every bit of generated energy through integrated power management and data processing.

The sensor system is designed to be completely self-powered and self-managing. The piezoelectric transducer harvests energy from the mechanical environment, the floating gate transistor stores this energy without external power, and the integrated circuit autonomously performs fatigue analysis. The system serves itself by using the mechanical stress it detects to power its own operation and store its own data, eliminating the need for external batteries or power sources.

The patent replaces the chemical energy storage system (battery) with a mechanical energy harvesting system. Instead of using a battery that depletes over time, the system uses a piezoelectric transducer that continuously converts mechanical stress from the implant environment into electrical energy. This substitution eliminates the fundamental limitation of battery life while maintaining continuous power availability through the mechanical activity of the patient's body.

The system changes the power availability parameter from being time-limited (battery discharge curve) to being activity-dependent (mechanical stress magnitude and frequency). Power availability is no longer determined by remaining battery capacity but by the real-time mechanical environment, allowing the device to operate indefinitely as long as the patient's body generates mechanical stress.

The patent implements partial computation by performing only the essential fatigue analysis algorithms needed for clinical decision-making, rather than running comprehensive simulations. The floating gate transistor stores only the critical strain data required for fatigue calculation, and the integrated circuit executes simplified fatigue prediction algorithms that provide sufficient clinical information with minimal energy consumption, accepting partial functionality in exchange for operational autonomy.

The system uses periodic action by triggering computation and data storage only when specific mechanical events occur, such as when strain thresholds are exceeded or when characteristic fatigue patterns are detected. The floating gate transistor accumulates data during mechanical loading cycles and performs computation during designated periods, rather than continuously operating, thereby reducing overall power dissipation while maintaining operational autonomy for critical functions.