Scavenging Thermal-noise Energy and Quantum Fluctuations for Self-powered Time-stamping and Sensing

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This research project is investigating self-powered sensing devices, circuits and algorithms for event time stamping and event reconstruction. As a proof-of-concept we are applying these techniques for designing passive, battery-less structural health monitoring (SHM) sensors that can continuously sense and time-stamp important and rare events that could have occurred during the operating life span of the structure. For instance in orthopedic implants like knee or hip implants, the use of these techniques would be able convey temporal information about any mechanical misalignment or any abnormal usage of the implant. This information could be useful to surgeons in diagnosing and planning of any revision surgery. For civil and aerospace structures, these techniques could be used to determine when the structure was subjected to large mechanical deformations or strains; or when a rare, unwanted mechanical impact with the structure could have occurred. In combination with computer models, the time-stamped event information could be used in prognosticating impending failures and can be used in determining condition-based maintenance schedules. Thus, the proposed self-powered sensing technology could be a key facilitator in achieving the grand vision for the internet-of-things, where millions of passive, inexpensive sensors could become an integral part of "smart" structures (civil, aerospace, mechanical and biomechanical) that can self-diagnose its own catastrophic failure. As a part of the outreach activities, the project is developing a cross-disciplinary forum between the electrical, structural and biomedical engineers; and includes design of educational modules and organization of tutorial and special sessions in the area of self-powered sensors. Also, in addition to the mentoring of graduate and undergraduate students, the project is also fostering student entrepreneurship activities in the area of sensors and structural health monitoring.The intellectual merit of the proposed research lies in the investigation of thermodynamically and quantum-mechanically driven electron transport phenomena that can be used to implement perpetual timers and clocks. Different device and layout topologies are being investigated that will lead to timers with different dynamical responses and to timers that can continuously operate over the entire monitoring period. The physics of the timer is being combined with the physics of the piezoelectricity driven impact-ionized hot-electron injection process to achieve self-powered monitoring of mechanical strain when the sensor is embedded or implanted inside a mechanically active structure. Using an array of these timer-modulated hot-electron injectors, the project is investigating sparse reconstruction algorithms that will be able to time stamp salient strain-related events. As a proof-of-concept, the circuits implementing the self-powered timers and the self-powered strain sensors are being prototyped in a standard CMOS process are also being integrated with previously developed radio-frequency identification (RFID) and wireless sensing system-on-chip architectures. This hybrid energy scavenging configuration will not only enable continuous, self-powered monitoring of salient and rare events but will also enable wireless retrieval of the sensor data along with remote initialization and configuration of the sensor under user command and control.