Through a pioneering system that doesn’t need power or an amplifier, University of Wisconsin-Madison engineers can enhance a signal without deteriorating its quality.
With collaborators at the Wave Transport in Complex Systems Lab of Wesleyan University, the researchers created an “elastodynamic” material system, coupled to an actuator, that amplified the force from the actuator by sixfold—which is two times higher than what is expected from common resonance effects—while maintaining a constant signal quality. (Elastodynamics is the study of waves and their propagation in materials that can stretch and return to their original shape.)
Ramathasan Thevamaran
The enhancement is due to a complex spectral phenomenon, called an exceptional point—a “convergence” that occurs in certain systems. The team’s research is the first experimental demonstration, in any area of physics, of the unusual signal enhancement beyond the expected boost from resonance effects, according to Ramathasan Thevamaran, an assistant professor of mechanical engineering at UW-Madison who led the research.
“So, if a system can produce a signal enhancement that’s 50 times greater due to standard resonance effects, we can enhance that signal 100 times by incorporating our new mechanism,” Thevamaran says. “It’s exciting that we’re achieving this signal enhancement without consuming any power or using an amplifier, which allows these systems to be less bulky since they don’t require a power source.”
He and his collaborators described their system in a paper on Feb. 14, 2023, in the journal Extreme Mechanics Letters.
The system has applications in areas that include optics, acoustics, microwaves and mechanics. It could, for example, lead to improved actuators in robotics, says Thevamaran. The technology could enable a robot to apply much more sensitive tactile forces as it grasps an object. Or, in assistive devices like exosuits, the system could help modulate the suits’ actuation forces (and thus improve wearers’ experience and capabilities). In the scientific characterization and analysis realm, the new system could increase the precision of indenters that measure metal hardness.
While the researchers focused on applications in mechanical systems, they also generalized their theory so that it’s relevant and useful in a variety of other application areas, including optics, acoustics and microwaves.
Scientists working in this area have mainly looked to exploit exceptional points for hyper-sensitive sensors. But Thevamaran says this discovery shows that exceptional points can be useful for more applications than previously thought.
“This advance opens up a new paradigm for the field, where we can now target signal enhancement by exceptional points,” Thevamaran says. “I expect these findings to ignite many new research directions.”
UW-Madison mechanical engineering PhD student Abhishek Gupta is the first author on the Extreme Mechanics Letters paper. Additional authors include Arkady Kurnosov and Tsampikos Kottos from Wesleyan University.
The research was supported by grants from the U.S. Army Research Office and the National Science Foundation.
Featured image caption: Mechanical engineering PhD student Abhishek Gupta experiments with non-Hermitian metamaterials in Assistant Professor Ramathasan Thevamaran’s lab. Submitted photo.