Tunable honeycomb-hierarchical multiscale structures of 2D/3D porous PLA/CCN composite films fabricated by the breath figure method

Highly ordered porous structures of PLA composite films can be designed with the addition of calcium carbonate nanoparticles (CCN) in polymeric film formation using the breath figure (BF) technique at controlled humidity. Both 2D and 3D monodispersed honeycomb-like porous structures of the PLA composite films are achieved by the adding CCN at the concentration of up to 1.00 phr, whereas hierarchically multiscale porous structures of the PLA/CCN films are obtained when the CCN concentration in the composites increases to more than 1.00 phr. These structures can be fabricated due to three mechanisms: water absorption and condensation, nano-Pickering emulsion, and capillary flow by self-assembly of the nanoparticles. Moreover, the nano effects of CCN on polymeric film fabrication are maximized by increasing the relative humidity to 90%, resulting in the formation of porous multilayers up to 95-120 μm in thickness. The application of the prepared porous composite films of PLA/CCN in the food and medical industries was illustrated. A model colorimetric sensor is made from PLA/CCN composite films enriched with bromothymol blue. The color of the films quickly changes from yellow to blue within 10 minutes after coming into contact with histamine, a representative gas generated from spoiled food.