  The per- and polyfluoroalkyl substances (PFAS) constitute a group of
organofluorine chemicals treated as the emerging pollutants and currently are
of particularly acute concern. These compounds have been employed intensively
as surfactants over multiple decades and are already to be found in surface and
ground waters at amounts sufficient to have an effect on the human health and
ecosystems. Because of the carbon-fluorine bonds the PFAS have an extreme
environmental persistence and their negative impact accumulates with further
production and penetration into the environment. In Germany alone, more than
thousands sites have been identified to be contaminated with PFAS and thus
timely detection of PFAS residues is becoming a high-priority task. In this
paper we report on the high performance optical detection method based on
whispering gallery modes microcavities applied for the first time for detection
of the PFAS contaminants in aqueous solutions. A self-sensing boosted 4D
microcavity fabricated with two-photon polymerization is employed as an
individual sensing unit. On example of the multiplexed imaging sensor with
multiple hundreds of simultaneously interrogated microcavities we demonstrate
the possibility to detect the PFAS chemicals representatives at the level of
down to 1 ppb.
