The
World Health Organization and the United States Centers for
Disease Control have recommended universal face masking by the general
public to slow the spread of COVID-19. A number of recent studies
have evaluated the filtration efficiency and pressure differential
(an indicator of breathability) of various, widely available materials
that the general public can use to make face masks at home. In this
review, we summarize those studies to provide guidance for both the
public to select the best materials for face masks and for future
researchers to rigorously evaluate and report on mask material testing.
Of the tested fabric materials and material combinations with adequate
breathability, most single and multilayer combinations had a filtration
efficiency of <30%. Most studies evaluating commonly available
mask materials did not follow standard methods that would facilitate
comparison across studies, and materials were often described with
too few details to allow consumers to purchase equivalent materials
to make their own masks. To improve the usability of future study
results, researchers should use standard methods and report material
characteristics in detail.
Numerous living organisms possess biophotonic nanostructures that provide coloration and other diverse functions for survival. While such structures have been actively studied and replicated in the laboratory, it remains unclear whether they can be used for biomedical applications. Here we show a transparent photonic nanostructure inspired by the longtail glasswing (Chorinea faunus) butterfly and demonstrate its use in intraocular pressure (IOP) sensors in vivo. We exploit the phase separation between two immiscible polymers (poly(methyl methacrylate) and polystyrene) to form nanostructured features on top of a Si3N4 substrate. The membrane thus formed shows good angle-independent white light transmission, strong hydrophilicity and anti-biofouling properties that prevent adhesion of proteins, bacteria, and eukaryotic cells. We then developed a microscale implantable IOP sensor using our photonic membrane as an optomechanical sensing element. Finally, we performed in vivo testing on New Zealand white rabbits and show that our device reduces the mean IOP measurement variation compared to conventional rebound tonometry without signs of inflammation.
The biochemical processes of cell membranes are sensitive to the geometry of the lipid bilayer. We show how plasmonic "nanowells" provide label-free real-time analysis of molecules on membranes with detection of preferential binding at negative curvature. It is demonstrated that norovirus accumulate in invaginations due to multivalent interactions with glycosphingolipids.
We
present metallic nanohole arrays fabricated on suspended membranes
as an optofluidic substrate. Millimeter-sized suspended nanohole arrays
were fabricated using nanoimprint lithography. We demonstrate refractive-index-based
tuning of the optical spectra using a sucrose solution for the optimization
of SERS signal intensity, leading to a Raman enhancement factor of
107. Furthermore, compared to dead-ended nanohole arrays,
suspended nanohole arrays capable of flow-through detection increased
the measured SERS signal intensity by 50 times. For directed transport
of analytes, we present a novel methodology utilizing surface tension
to generate spontaneous flow through the nanoholes with flow rates
of 1 μL/min, obviating the need for external pumps or microfluidic
interconnects. Using this method for SERS, we obtained a 50 times
higher signal as compared to diffusion-limited transport and could
detect 100 pM 4-mercaptopyridine. The suspended nanohole substrates
presented herein possess a uniform and reproducible geometry and show
the potential for improved analyte transport and SERS detection.
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