The next generation of high-performance sensors for detecting force that can perform under extreme conditions may soon be a reality thanks to a new project underway at Penn State. The work, led by principal investigator and Assistant Professor of Electrical Engineering Mingyo "Leen" Park, is funded by a recently awarded two-year, $2 million Defense Advanced Research Projects Agency (DARPA) grant through the Higher-Order Composite Resonators for Extra Resilience (HORCREX) program.
The team is specifically focusing on inertial sensors, which sense force or gravity, and have broad applications in aerospace, defense and autonomous systems. Current commercial devices typically measure at a single frequency; measuring across multiple frequencies requires several discrete sensors, increasing size, weight and power consumption.
Park's team aims to replace that architecture with a single chip with a frequency comb - a spectrum of equally spaced vibration lines produced by a resonator operating in a nonlinear regime. The resonator itself is a micro-electro-mechanical systems (MEMS) resonator, a miniature mechanical structure - often smaller than the width of a human hair - fabricated in a cleanroom at Penn State Materials Research Institute.
"By driving the MEMS device hard enough, our team will coax it into generating the frequency comb, letting one sensor extract rich, multi-band data without added bulk," Park said. "Using a spectrum rather than a single tone allows us to obtain richer information while reducing the number of separate sensors."
According to the researchers, a key innovation of these sensors is the deliberate use of material nonlinearity - the way a material's properties change when it is bent or stretched - to boost sensitivity and functionality.
"The concept of nonlinear sensors is still in its infancy," said co-principal investigator and Assistant Professor of Electrical Engineering Morteza Kayyalha. "Leen's doctoral work was among the first to demonstrate its promise, and HORCREX gives us the opportunity to translate that idea into robust devices."
The researchers said they are designing the sensors to withstand wide temperature swings, high shock and other harsh conditions encountered by systems such as drones, spacecraft and defense platforms.
"Our performance target is simple," said Jon-Paul Maria, professor of materials science and engineering. "Even after severe mechanical or thermal stress, the sensor must keep working."
Park emphasized the project's collaborative foundation and her excitement to work with the other three team members: Kayyalha, Maria and Susan Trolier-McKinstry, Evan Pugh Professor and Steward S. Flashchen Professor of Materials Science and Engineering and professor of electrical engineering.
"This was the first proposal I submitted as a new faculty member, and it brought together an exceptional mix of expertise," she said. "Professor Maria provides materials design, Professor Trolier-McKinstry leads advanced film characterization, Professor Kayyalha contributes cryogenic and quantum-scale measurement capabilities, and my group focuses on MEMS device engineering. It's an ideal team for tackling this multifaceted challenge."
Kayyalha echoed this sentiment and added that Penn State is uniquely positioned to enable this collaboration.
"All the critical capabilities for developing and testing these micromechanical devices exist right here at Penn State," he said. "This collaboration is just the beginning of what we can accomplish."
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