This proposal leverages prior NSF funded work that resulted in the patent of a self-powered piezo-floating-gate (PFG) wireless sensor. The sensor is ultra low power and capable of storing strain data, making it highly suitable for embedding in safety-critical physical structures and infrastructure for structural health monitoring via wireless RFID readers over the lifetime of the structure. The proposed effort will address the technological gaps necessary to lead to a robust prototype and subsequent manufacture and commercialization, namely development of all supporting sensing circuitry and wireless interface circuitry and software, demonstrating remote configuration and interrogation of the PFG wireless sensor.

The PFG wireless sensor when incorporated into a prototype system via the proposed work, has the potential to have significant impact in the health monitoring and fault diagnosis of large classes of systems for which such monitoring systems must be autonomous, self-contained, generate their own power and be zero-maintenance. As a result such sectors as civil infrastructure, biomedical devices and systems, individual and civil transportation, and energy represent potential markets. Adoption of such embedded sensor elements in the safety critical systems used in these sectors can ultimately result in fewer injuries and fatalities arising from unexpected system failures.

Project Report

Physical structures such as bridges, roadways, rotor-blades, gear-boxes, aircraft parts and prosthetics like knee or hip-implants will degrade over time from repeated and long-term mechanical usage. Monitoring the details of this usage over the entire span of the structure could provide critical data that could then be used to prioritize structural maintenance and replacement of parts, and in the process significantly improve the safety and reduce life-cycle costs. Long-term and autonomous usage monitoring while the structure is in service, however, require sensors that can be embedded in or retrofitted to structures and continuously collect, process, save and communicate pertinent information. Currently, there exist significant challenges towards providing a sustainable solution for such long-term usage monitoring: (a) Long-term operational requirements preclude the use of batteries; and (b) Embedded sensors must be small (so as not to impact the structural integrity) precluding the integration of bulky energy scavenging and energy storage hardware (for e.g. super-capacitors). As a result, there exists a wide gap between the energy that can be scavenged from real-world structures and the energy density required for sensing, computing and communication. The Piezo-Floating-Gate-based (PFG) battery-less Health and Usage Monitoring (HUMS) technology developed in this project addresses these long-term monitoring concerns. It combines patented circuits (owned by Michigan State University) with piezoelectric transducers that act as both the sensor and the harvester of operational power for the sensor. A key feature of the PFG sensor are floating-gate sensing circuits that compute and store cumulative statistics of the strain-rates and stresses while achieving operational power limits not possible with any competing HUMS technology. The sensor requires only nanowatts of power that can be easily harvested from a miniature piezoelectric transducer operating in strain-mode (not vibration-mode). This enables PFG sensors to be embedded within civil structures (e.g., bridges, pavement, buildings, dams, and levees), vehicles, rotating machines (e.g., wind-turbines) and biomedical implants. Stored data, retrieved by commercial off-the-shelf (COTS) radio-frequency identification (RFID) technology, is used to monitor and predict the onset of structural fatigue and to remotely configure the sensor. Applications of the PFG sensing technology include early detection and prediction of structural or mechanical failure which can significantly reduce maintenance costs and, ultimately prevent loss of life. The project has resulted in the formation of Piezonix LLC, ( a startup company based in Michigan, responsible for translating the results of research and developmental activities of this project into commercial assets. Piezonix has signed an exclusive licensing options agreement with MSU and is currently working with potential customers in different application areas to develop a customer centric end-to-end system (hardware and software) according to the customer needs. This project has also offered mentoring opportunities for several undergraduate and graduate students in the area of technology commercialization and currently Piezonix’s commercialization efforts are being led by PI’s formal doctoral advisees.

National Science Foundation (NSF)
Division of Industrial Innovation and Partnerships (IIP)
Standard Grant (Standard)
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Barbara H. Kenny
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Michigan State University
East Lansing
United States
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