Cellulose as a Platform for Biodegradable Metasurfaces: THz Characterization and Fabrication

ABSTRACT

The growing need to reducing e‐waste has largely promoted the usage of biodegradable materials for the realization of flexible electronics and photonics. Terahertz (THz) technology is no exception to this trend, although very few flexible THz functional devices have been proposed so far. Still, the possibility to realize THz sensors with biodegradable and flexible materials can unlock the potential of THz sensing in agricultural and biomedical applications. This challenge is here addressed by combining the exceptional stability and processability properties of a specific biodegradable cellulose derivative, ethyl cellulose (EC), with a novel application of THz metasurfaces. Specifically, we realized resonant structures consisting of a back‐metallized cellulose film with a subresonant metasurface on top. By suitably engineering the electromagnetic properties of the metasurface we achieved nearly perfect absorption at predetermined THz frequencies through a completely analytical design workflow. These cellulose‐based THz devices are then experimentally validated with an extensive mechanical and electromagnetic characterization to respectively test their flexibility and their absorbing performance in the THz range. THz measurements through time‐domain spectroscopy in reflection mode reveal an effective critical absorption at 0.576 and 0.411 THz innovatively based on a capacitive‐ and inductive‐like metasurface on top of a grounded biodegradable substrate, respectively.