Ultra‐Broadband and Reconfigurable Liquid‐Based Microwave Metasurface Absorber

Liquids, with their advantages of fluidity, ease of shaping, and tunability, have exhibited promising potential in the creation of reconfigurable metamaterials (MMs). Water, being the ubiquitous liquid and cost‐effective resource on Earth, has been utilized for the construction of liquid‐based microwave metasurface absorber (MSA). However, due to the challenges associated with integrating microfluidics with MMs in both design and manufacturing, current MSs exhibit narrow frequency bands, particularly constrained at lower frequencies. Herein, a reconfigurable solid–liquid composite of liquid‐based MSs, utilizing the interbedded structure of cones, is proposed for ultra‐wideband microwave absorption. When water is used as the filling medium, the absorption rate exceeds 90% across a wide frequency range from 5.9 to 50 GHz. Upon substitution with ionic liquids, the frequency range demonstrating absorption efficiency exceeding 90% extends from 3.3 to 50 GHz. Furthermore, it is confirmed that the designed MSA demonstrates exceptional stability when subjected to oblique incidence and shows a high degree of insensitivity to polarization, highlighting its robust applicability. The low‐cost, easily manufacturable, and ultra‐wideband liquid‐based MSA holds promising potential for applications in radar countermeasures, energy harvesting, radiation protection, and other related fields.