Researchers from C2N and the Instituto de Ciencia de Materiales de Madrid have developed a cost-effective approach to block sound waves oscillating at billions of vibrations per second. By allowing tiny polystyrene spheres to self-assemble, they created a network capable of trapping and controlling hypersound, paving the way for faster and more efficient nanoscale devices.
Controlling ultrahigh frequency sound waves, or hypersound, is a critical challenge for nanoscale technologies, including quantum devices, photonics, and ultrafast communication systems. In the gigahertz-to-terahertz range, hypersound can carry information, heat, or mechanical energy at microscopic scales. Developing accessible and scalable ways to manipulate these vibrations is essential for advancing the next generation of nanotechnologies.
A group of researchers in an international collaboration between the Centre de Nanosciences et de Nanotechnologies – C2N (CNRS, Université Paris-Saclay, France) and the Instituto de Ciencia de Materiales de Madrid – ICMM (CSIC, Spain), led by Dr. Norberto Daniel Lanzillotti-Kimura and Dr. Pedro D. García, has demonstrated that self-assembled polystyrene nanospheres are capable of controlling hypersound. Their work, recently published in Nanophotonics (2025), shows that depending on the arrangement of these spheres on a silicon substrate, they reshape how sound travels at the nanoscale.
Rather than relying on costly and complex nanofabrication techniques, the team used a bottom-up approach: polystyrene spheres about 200 nanometers wide self-assembled on a silicon wafer into a highly ordered 2D lattice. By adjusting how the spheres are arranged—from isolated to overlapping—they could control hypersound propagation, creating “phononic bandgaps” that block vibrations. “By letting the spheres organize naturally, we created a structure that can trap and control hypersound,” says Edson Cardozo, one of the authors. “It’s simple, scalable, and can be integrated into existing nanoscale devices.”
To characterize these vibrations, the researchers employed ultrafast pump–probe and Brillouin light scattering experiments. These techniques allowed them to observe how hypersound travels depending on the spheres’ arrangement. Isolated spheres suppress collective vibrations, acting as a mechanical insulator, while touching or overlapping configurations allow waves to propagate at speeds up to 8,000 meters per second. “This work allows us to visualize and manipulate hypersound at the nanoscale,” says Dr. Lanzillotti-Kimura. “It’s a major step toward devices where vibrations and heat can be controlled as precisely as electrical signals in a chip.”
Self-assembled phononic structures bring exciting perspectives for photonics and quantum technologies, enabling ultrafast information processing, quantum device stabilization, and nanoscale thermal management. The accessibility and scalability of self-assembly make this approach particularly promising for widespread applications. “Our findings demonstrate that natural self-organization can be harnessed to engineer and manipulate sound at the nanoscale,” adds Dr. García.
A self-assembled two-dimensional hypersonic phononic insulator
Pedro Moronta, Sandeep Sathyan , Edson R. Cardozo de Oliveira , Rafael J. Jiménez-Riobóo , Norberto Daniel Lanzillotti-Kimura, Pedro D. García and Cefe López
Nanophotonics 2025; 14(22): 3569–3577
https://doi.org/10.1515/nanoph-2025-0141
Figure : Schematic of a self-assembled array of nanospheres on a silicon substrate. A laser beam excites hypersound waves, which propagate through the substrate and interact with the nanospheres.
