Fully Passive Printed Wireless Wear Sensor

Wear of abradable materials presents a significant challenge across many industries, where the efficiency, efficacy, and safety of important systems rely on the detection and monitoring of component wear. Three design variations demonstrate real-time monitoring of wear by a novel, additively manufactured, embeddable, and fully passive wireless wear sensor. The three sensor designs incorporate closely spaced, narrow interconnects connected to a parallel resistor circuit, with a passive RFID chip for complete remote operation. The first design includes ten closely-spaced horizontal interconnects and tracks wear events orthogonal to the interconnects for a resolution of 200 μm. The second design divides horizontal interconnects into two inter-digitated sets of five lines each to achieve a resolution of 125 μm. The third design features ten interconnects printed vertically and connected to a sloped drain line to achieve a resolution of 50 μm. We fabricated all three designs with a singlelayer print on machinable glass-ceramics and commercial surfacemount resistors. Lab testing showed that the three sensor designs had an overall experimental resolution of 215.3 μm, 127.8 μm, and 57.34 μm, respectively. We attribute error to a combination of manufacturing challenges related to the printing of orthogonal and acute angled narrow interconnects, RFID sampling rates, and errors from testing. The maximum error in measured voltage steps for each of the three designs is 10%, 6.67%, and 6.78%. This study is limited in sample size due to testing constraints and is presented as proof of concept. Future work should assess the robustness of these designs and processes.