Applying spoof-plasmonic metasurfaces to microwave sample preparation of biological samples

Abstract

Nucleic acid and protein extraction, digestion, and purification are common steps of sample preparation and assays such as DNA sequencing, cell-viability, and enzyme activity in the modern biomedical laboratory. To increase the throughput of assays, microplates are often used to process many samples in parallel by a single operator. In this work, we have fabricated microplates that have an array of metallic elements integrated with them to form a metasurface, a periodic array of subwavelength metal scattering elements on a dielectric substrate, that are designed for the radio frequency (RF)/microwave region of the electromagnetic spectrum. By integrating the metasurface with a microplate, high-throughput processing without transferring samples becomes possible since the entire microplate can be irradiated with a RF/microwave radiation source and the metasurface will distribute electric field intensity and dielectric heating to the desired regions of the microplate, analogous to how plasmonic materials can guide and confine field intensities of visible and infrared frequency radiation. This analogue of plasmonic excitations and localization at lower frequencies in the RF/microwave region of the spectrum is termed spoof plasmonics due to its similarity to the plasmonic phenomena observed at visible frequencies. Using finite-difference time-domain (FDTD) modeling software, metasurfaces were designed for the RF/microwave frequency range and then fabricated using standard 96-well microplates and metallic films. The properties of the finished microplate system were characterized using a variety of physical and chemical methods including forward-looking infrared (FLIR) imaging, fluorescence sensing, and microbial inactivation and the system was then applied to a common polymerase chain reaction (PCR) assay to assess its real-world applicability. Herein we report our findings for various physical properties of the metasurface under a range of conditions as well as its application to biomedical laboratory assays and processing techniques. Our results demonstrate both a novel application of metasurfaces in bioprocessing and comparisons of in silico results with actual results for microwave metasurfaces.