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exceptional point-based accelerometer device
July 27, 2022

Signal boost: Advance enables hyper-sensitive sensors

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A team of researchers from the University of Wisconsin-Madison and Wesleyan University has developed a new accelerometer that can take extraordinarily precise measurements. The advance opens the door to new sensors that are hyper-sensitive to tiny changes in conditions.

These hyper-sensitive sensors have potential applications in a variety of areas, including photonics, navigation systems, and biosensing. For example, a sensor based on this new technology could be sensitive enough to detect a single tiny molecule, helping to increase understanding of biological processes.

Such sensors could also be useful for monitoring the health of various structures, such as airplane wings and bridges.

Ramathasan Thevamaran
Ramathasan Thevamaran

“When a tiny crack occurs in an airplane wing, the mechanical properties of the structure will change and we should be able to detect that with a sensor that’s hypersensitive to the system’s parameters,” says Ramathasan Thevamaran, an assistant professor of engineering physics at UW-Madison who co-led the research. “So, this would allow us to detect much, much smaller cracks earlier—before they can grow into larger cracks that can lead to catastrophic failures. And we could embed these sensors in structures, allowing us to non-destructively evaluate their health.”

The researchers published details of their advance in the journal Nature on July 27, 2022.

To achieve its high sensitivity, the team’s electromechanical accelerometer exploits a complex spectral phenomenon, called an exceptional point, that occurs in certain systems where gain and loss in a system can be perfectly balanced by design. Scientists have been excited by the potential of using exceptional point-based sensors to take hyper-sensitive measurements, but a big barrier has hindered their development for practical applications.

“Other researchers have found that exceptional point-based sensors will not only amplify the signal that you want to measure, but also the noise,” Thevamaran says. “In fact, the noise is amplified so much that any hypersensitivity in the sensor is rendered useless because it’s drowned out by all the noise. This is a huge challenge.”

Now, with their new exceptional point-based accelerometer, the UW-Madison and Wesleyan team has found a solution. The researchers’ solution involves coupling a transmission line to their accelerometer device. This essentially creates an electronic circuit in which a signal is transmitted and creates another singularity, called transmission peak degeneracy.

The researchers then measure the signal that occurs in the transmission line, enabling them to achieve a threefold signal-to-noise-ratio improvement in the sensing performance of their device. In other words, they’ve circumvented much of the noise.

“So, the signal was enhanced at a significantly higher rate than the noise, which enables our device to take ultra-sensitive measurements,” Thevamaran says. “This advance paves the way for exceptional point-based sensors to be used for practical applications.”

The researchers are patenting their technology though the Wisconsin Alumni Research Foundation (WARF).

Co-authors on the Nature paper include Jizhe Cai from UW-Madison, and Rodion Kononchuk, Fred Ellis and Tsampikos Kottos from Wesleyan University.

The research was supported by grants from the National Science Foundation (NSF-CMMI-1925543, NSF-CMMI-1925530) and the U.S. Office of Naval Research (ONR N00014-19-1-2480) and received support from the University of Wisconsin-Madison Office of the Vice Chancellor for Research and Graduate Education with funding from the Wisconsin Alumni Research Foundation.

Top image: The researchers’ exceptional point-based accelerometer device. Photo credit: Rodion Kononchuk/Wesleyan University.