Scientists use sound to control material behavior, adjust device stiffness

Researchers at UC San Diego have developed a novel method to control the mechanical behavior of materials using sound waves, as detailed in a study published in Nature Communications. Their work focuses on manipulating tiny localized features called mechanical kinks—boundaries within a material where the internal structure changes orientation, resulting in different stiffness or softness on either side. Traditionally, moving these kinks has been difficult due to energy barriers that keep them fixed, and previous attempts using sound waves resulted in unpredictable motion. The UC San Diego team overcame this by creating a model material without such energy barriers, allowing precise, stepwise control of kink position through specific acoustic frequencies. By sending targeted sound pulses, the researchers effectively created an acoustic "tractor beam" that can pull the kink incrementally toward the sound source, thereby tuning the material’s stiffness gradient on demand. In their experimental setup, a life-sized model composed of stacked rotating disks connected by springs simulated atomic behavior, confirming that sound waves can reliably transfer momentum to move kinks despite partial reflection