UC Berkeley

The increased use of microwave technology, encompassing electromagnetic waves in the gigahertz range for applications such as wireless communication, defense, and weather radar, has highlighted the importance of effectively controlling wave responses—transmission, absorption, and reflection— in engineering and science. Absorbing unwanted waves is crucial for applications like radar stealth, reducing electromagnetic interference, and protecting against electromagnetic pollution. While carbon-based and ferrite-based composites offer a simple solution for wave absorption, they are limited in bandwidth and absorption strength due to their fixed properties post-fabrication. Incorporating engineered structures alongside these materials presents a more effective solution, enhancing bandwidth, absorption strength, and additional functions such as lightweight and load- bearing capabilities. This thesis demonstrates the design of multifunctional electromagnetic wave- absorbing structures through various methods, including simulation-based, experimental-based, and data-driven approaches. Diverse structures such as octet-truss, octet-foam, and Kelvin foam— mechanical metamaterials known for their lightweight and load-bearing properties—are explored for their broadband absorption capabilities and multifunctionality. Additionally, a tunable crisscross structure inspired by a chameleon’s color-changing strategy is showcased, utilizing machine learning- based prediction and optimization.