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We study the bouncing dynamics of nanodroplets on superhydrophobic surfaces. We show that there are three velocity regimes with different scaling laws of the contact time, τ. Although τ remains constant over a wide velocity range, as seen for macroscale bouncing, we demonstrate that viscosity plays an essential role in nanodroplet bouncing even for low-viscosity fluids. We propose a new scaling τ ∼ (ρμR 0 4/γ2)1/3 = (R 0/v 0)We 2/3 Re –1/3 to characterize the viscosity effect, which agrees well with the simulated results for water and argon nanodroplets with various radii and hydrophobicities. We also find pancake bouncing of nanodroplets, which is responsible for an abruptly reduced τ in a high-velocity regime.

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The microstructure and electrochemical performance of electrical double layers (EDLs) have been extensively studied for many monocationic ionic liquids (MILs) and several dicationic ionic liquids; however, they have not been reported for linear tricationic ionic liquids (LTILs). Microstructures of three LTILs [C n (mim)3]­(Tf2N)3 (n = 3, 6, and 10) and a MIL [C6mim]­[Tf2N] at neutral and charged graphite electrodes have been investigated using molecular dynamics simulations. We show that the LTILs and MILs have different multilayer EDL structures, with more perpendicular orientations for imidazolium rings, especially the central ring, of trications on the negative electrode surface. We also demonstrate that capacitance–voltage curves of EDLs transform from a bell shape in the MIL to a camel shape in the LTILs, which is ascribed to the accumulation of ions on electrode surfaces and the ion–ion correlation. Moreover, the LTILs can enhance the energy storage density at high electrode potentials, regardless of positive or negative voltages.

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