Integrating multi-responsive polymers such as microgels onto optical
fiber tips, in a controlled fashion, enables unprecedented
functionalities to Lab-on-fiber optrodes. The creation of a uniform
microgel monolayer with a specific coverage factor is crucial for
enhancing the probes responsivity to a pre-defined target parameter.
Here we report a reliable fabrication strategy, based on the dip coating
technique, for the controlled realization of microgel monolayer onto
unconventional substrates, such as the optical fiber tip. The latter was
previously covered by a plasmonic nanostructure to make it sensitive to
superficial environment changes. Microgels have been prepared using
specific Poly(N-isopropylacrylamide)-based monomers that enable
bulky size changes in response to both temperature and pH variations.
The formation of the microgel monolayer is efficiently controlled
through the selection of suitable operating pH, temperature and
concentration of particle dispersions used during the dipping procedure.
The effect of each parameter has been evaluated, and the validity of
our procedure is confirmed by means of both morphological and optical
characterizations. We demonstrate that when the coverage factor exceeds
90%, the probe responsivity to microgels swelling/collapsing is
significantly improved. Our study opens new paradigms for the
development of engineered microgels assisted Lab-on-Fiber probes for
biochemical applications.

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