This study presents dual-responsive colloidal microgels to repair nonwoven fiber mats (NWFs) and recover their native morphological and functional properties. The formulation comprises poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAmco-AA) microgels loaded with iron oxide nanoparticles acting as magneto-responsive "bricks" and poly(N-isopropylacrylamide-co-N-4-benzoylphenyl acrylamide) (PNIPAm-co-BPAm) serving as photo-cross-linkable "mortar". The formulation is employed to repair small tears in meltblown polypropylene (PP) and polybutylene terephthalate (PBT) NWFs and recover the functional properties of the native membranes. Specifically, magnetically directed and UV-light-triggered repair recovers (i) the topological integrity, as shown by optical microscopy and image analysis of PP and PBT NWFs, (ii) the mechanical properties, as demonstrated by the values of tensile modulus of native, damaged, and repaired PP NWFs, and (iii) the permeability to sodium chloride of both PP and PBT NWFs. A comparative study of repair using magneto-responsive and photo-cross-linkable vs photocross-linkable-only formulations demonstrate that magnetic localization is vital to ensure rapid, spatially accurate, and effective recovery of the morphological and functional properties of damaged NWFs.

This study presents the development of the first composite nonwoven fiber mats (NWFs) with infrared light-controlled permeability. The membranes were prepared by coating polypropylene NWFs with a photothermal layer of poly­(N-isopropylacrylamide) (PNIPAm)-based microgels impregnated with graphene oxide nanoparticles (GONPs). This design enables “photothermal smart-gating” using light dosage as remote control of the membrane’s permeability to electrolytes. Upon exposure to infrared light, the GONPs trigger a rapid local increase in temperature, which contracts the PNIPAm-based microgels lodged in the pore space of the NWFs. The contraction of the microgels can be reverted by cooling from the surrounding aqueous environment. The efficient conversion of infrared light into localized heat by GONPs coupled with the phase transition of the microgels above the lower critical solution temperature (LCST) of PNIPAm provide effective control over the effective porosity, and thus the permeability, of the membrane. The material design parameters, namely the monomer composition of the microgels and the GONP-to-microgel ratio, enable tuning the permeability shift in response to IR light; control NWFs coated with GONP-free microgels displayed thermal responsiveness only, whereas native NWFs showed no smart-gating behavior at all. This technology shows potential toward processing temperature-sensitive bioactive ingredients or remote-controlled bioreactors.