Flexible Humidity Sensitive Fiber with Swellable Metal-Organic Frameworks

Humidity sensors have become an essential need for improving daily life quality.Here,a novel humidity sensitive fiber was fabricated using the soft polydimethylsiloxane(PDMS)as the core layer and the non-swellable polyvinylidenedifluoride(PVDF)embedded with a swellable MIL-88A as the outer layer.Noticeably,the PDMS fiber was chosen as a carrier due to its smoothness,softness and good tensile properties.The isoreticular FeIII dicarboxylate MIL-88 family with swellable metal-organic frameworks(MOFs)can undergo reversible dynamic structural transformations with a response to external humidity change.The resulted fiber with swellable MOFs showed three kinds of deformation for a single solvent and also had good deformation performance for two-component miscible solution with different volume ratios.As a proof of concept,a shape-memory effect at relative humidity from 10 to 90%and the simulated salt solutions instead of relative humidity changes were used to evaluate humidity change.In addition,a deep insight into the self-shape-change mechanism among those phenomena was investigated,wherein expansion deformation of the PDMS fiber as well as the structural transforma-tion of the MIL-88A worked in different conditions.