Designing Spoof Plasmonic Metasurfaces for Microwave Frequencies and Applications in Biological Processing

Plasmonic metasurfaces are a growing subclass of metamaterials which are materials whose properties are based on their structure rather than their composition and can be tuned and designed for different applications as a result. Metasurfaces are the two-dimensional analogs of three-dimensional metamaterials and plasmonic metasurfaces are those that use electron oscillations in metals, termed plasmons, to achieve their desired properties. Most applications of plasmonic materials have been limited to the visible and UV frequency ranges of light since lower frequency photons have insufficient energy to excite plasmons in metals, however “spoof plasmons” which mimic normal plasmons, have been created in the terahertz and microwave frequency ranges by utilizing subwavelength metal structures in periodic arrays. Spoof plasmonic metasurfaces (SPMs) are metasurfaces that can mimic plasmonic metasurfaces at lower frequencies by utilizing properties of spoof plasmons. In this work, we have designed several SPMs for use in the microwave frequency range using a combination of computational modeling and physical testing. SPMs were designed <i>in-silico</i> using finite-difference time-domain (FDTD) methods and then fabricated for physical testing with microwave irradiation. Once designed, these SPMs were assessed for their utility as a sample processing platform for biological samples such as microbes, nucleic acids, and proteins in a variety of laboratory assays such as genomic sequencing or diagnostic polymerase chain reaction (PCR). While many applications of metasurfaces to biological problems have been focused on sensing biological signals and imaging, this work is focused on using their properties to process biological samples via light-matter interactions and their products. Thus far this work has shown promise in applying SPMs to a new area of biological processing as well as exploring existing metasurface design principles for alternative applications.