Engineers at MIT have developed a revolutionary laser-based technology, Laser-Induced Resonant Acoustic Spectroscopy (LIRAS), that proposes innovative real-world applications in the development of acoustic lenses and impact-resistant films. Metamaterials, engineered at the microscale using common materials like polymers, ceramics, and metals, are known for acquiring extraordinary properties.
While computer simulations are key in experimenting with assorted microstructures for creating these metamaterials, physical testing is crucial. Before LIRAS, there lacked a reliable, nondestructive method for metamaterial analysis at the microscale.
As per an article on MIT News, the LIRAS technique incorporates a two-laser system to safely and efficiently test metamaterials. One laser initiates the vibration of the structure while the other measures the response, akin to a bell reverberating when struck.
Using the resultant vibrations, the engineers can estimate various dynamic characteristics of the material, such as its response to impact or sound absorption. The LIRAS technique, with its ultrafast laser pulses, allows hundreds of small structures to be excited and measured within minutes. This provides a safe, reliable, and high-throughput approach to microscale metamaterial characterization.
Due to the delicate nature of metamaterials, a nondestructive method is required for validation. Earlier techniques like nanoindentation could cause structure damage and worked at a limited speed. The emergence of LIRAS provides a practical solution that enables the dynamic behavior assessment of metamaterials without inflicting any damage.
The LIRAS technology has been successfully used in scanning metamaterial towers for defects, possibly aiding in detecting imperfect structures during assembly production. The setup of LIRAS is simple enough to be recreated in any laboratory setup, potentially accelerating the metamaterial discovery process. Real-world applications of metamaterials, as suggested by researchers, include enhancing ultrasound probes' sensitivity and developing impact-resistant linings for bike helmets.
The promising research happened with the facilities of MIT.nano and the backing of the Department of Energy's Kansas City National Security Campus, the National Science Foundation, and the DEVCOM ARL Army Research Office through the MIT Institute of Soldier Nanotechnologies.