Fig. 4: Schematic representation of the underlying nanopore gating for macroscopic liquid movement.

The picture shows a side-view of the interacting KI and H₂O₂ droplets after placed on the nanoporous surface. The zoom schematics illustrate the locally active droplet resulting from the nanopore-mediated underlying communication with the neighboring droplet. The catalyzed decomposition of hydrogen peroxide takes place in the region where a fraction of the H₂O₂ droplet perimeter overlaps the annulus of the KI droplet. The droplet can locally escape from the steady-state shape if the energy associated with chemical reaction overcomes the pinning energy barrier. The temperature increases in the reaction zone, O₂ concentration follows the same trend and in turn the H₂O₂ concentration decreases. This chemical and thermal scenario leads to localized variations of the surface tension, which induce the Marangoni stress F_M (tangential force per unit area) that drag the liquid from the H₂O₂ droplet towards the KI droplet (red arrow), in the direction parallel to the substrate, over the KI annulus.