Natural sedimentation-assisted fabrication of Janus functional films for versatile applications in Joule heating, electromagnetic interference shielding and triboelectric nanogenerator

Various Janus structures-enabled physicochemical properties of biological materials inspire researchers to explore functional films with Janus characteristics in compositions and structures. It is highly desirable to explore such Janus functional films in simple, cost-effective and batch-production strategy. In this work, we present a natural sedimentation-assisted method for mass production of polymer-based films with Janus or gradient structures. The gravity driven settling and assemble of nanoparticles in dispersion medium gives rise to the delamination of the suspension, and Janus composite films are obtained following the solvent evaporation process. Typically, two kinds of polyvinylidene fluoride and waterborne polyurethane based Janus films with asymmetric electrical properties are fabricated, exhibiting outstanding performances when being developed for applications in Joule heating (145 °[email protected] V), electromagnetic interference shielding (749.8 dB·cm2·g−1@0.165 mm) and triboelectric nanogenerator (1.1 W m2). This strategy provides us new opportunities to develop more Janus functional films and further explore more novel properties.