Functional Janus liquids

Abstract Janus structures have unique properties due to their distinct functionalities on opposing faces, but have yet to be realized with flowing liquids. We demonstrate such Janus liquids with a programmable distribution of nanoparticles (NPs) throughout their structures by joining two aqueous streams of NP dispersions in an apolar liquid. Using this anisotropic integration platform, different magnetic, conductive, or non-responsive NPs can be spatially confined to opposite sides of the original interface using magnetic graphene oxide (mGO)/GO, Ti 3 C 2 T x /GO, or GO suspensions. The resultant Janus liquids can be used as templates for programmable, responsive, and mechanically robust aerogels suitable for piezoresistive sensing, human motion monitoring, and electromagnetic interference (EMI) shielding with a tuned absorption mechanism. The EMI shields outperform their current counterparts in terms of wave absorption, i.e., SE T ≈51 dB, SE R ≈0.4 dB, A = 0.91, due to their multi-scale porosity along with non-interfering magnetic and conductive networks imparted by the Janus architecture.