burden to various industries (e.g. energy, transportation, aviation, building). Employing repellent surface
chemistry on engineered surfaces (e.g. pillar, tubular, porous) delays icing and reduce ice adhesion. However, the
limiting parameters that fail the icephobic properties of "slippery" and "superhydrophobic (SH)" surfaces are not
well explored. Herein, we introduce anodized and chemically modified "slippery", and "SH" surfaces textured by
3D-printing to justify their ice-phobic properties considering the influencing factors, namely surface energy and
roughness, temperature and humidity gradient, and droplet-to-surface contact area. Although "slippery" and "SH"
surfaces can resist ice nucleation for a few hours at moderate subzero temperatures, they fail when the temperature
drops to -12◦C. Despite posing ~10 times lower adhesion strength (i.e. shear stress) than the control,
"SH" surface with moisture-induced micro ice-crystals exhibited twice the ice-adhesion measured without the
presence of micro ice-crystals on it. In contrast, the "slippery" sample, due to antifreeze properties, did not get
affected by the presence of moisture-induced micro ice-crystals, exhibiting ~17 times lower adhesion strength
than the control substrate. The comparative aspects and explored limiting factors of icing on "slippery" and "SH"
surfaces are significant for many industries that suffer from ice-fouling.

The gold standard for diagnostics of SARS-CoV-2 (COVID-19) virus is based on real-time
polymerase chain reaction (RT-PCR) using centralized PCR facilities and commercial viral RNA
extraction kits. One of the key components of these kits are magnetic beads composed of silica coated
magnetic iron oxide (Fe2O3 or Fe3O4) nanoparticles, needed for the selective extraction of RNA. At
the beginning of the pandemic in 2019, due to a high demand across the world there were severe
shortages of many reagents and consumables, including these magnetic beads required for testing for
SARS-CoV-2. Laboratories needed to source these products elsewhere, preferably at a comparable
or lower cost. Here, we describe the development of a simple, low-cost and scalable preparation of
magnetic nanoparticles (MNPs) from biowaste and demonstrate their successful application in viral
RNA extraction and the detection of COVID-19. These MNPs have a unique nanoplatelet shape with
a high surface area, which are beneficial features, expected to provide improved RNA adsorption,
better dispersion and processing ability compared with commercial spherical magnetic beads. Their
performance in COVID-19 RNA extraction was evaluated in comparison with commercial magnetic
beads and the results presented here showed comparable results for high throughput PCR analysis.
The presented magnetic nanoplatelets generated from biomass waste are safe, low-cost, simple to
produce in large scale and could provide a significantly reduced cost of nucleic acid extraction for
SARS-CoV-2 and other DNA and RNA viruses.