Spreading Dynamics of a Precursor Film of Ionic Liquid or Water on a Micropatterned Polyelectrolyte Brush Surface

Abstract

Time evolution of the microscopic wetting velocity of 1-ethyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI) or water on a micrometer-scale line-patterned surface with a poly(3-sulfopropyl methacrylate) brush and a hydrophobic perfluoroalkyl monolayer was precisely measured by direct observation using optical microscopy and a selective dyeing method over a long period (178 days). When a liquid droplet was placed on the dyed linepatterned brush surface, the liquid penetrated and spread into the polymer brush layer, forming a precursor thin film that extended beyond the macroscopic contact line. The elongation proceeded in two stages by an adiabatic process followed by a diffusive process. The elongation distance X increased with time in proportion to t 2.6 for water and t 0.81 for EMI-TFSI during the adiabatic process. In a diffusive process, the advancing velocity of the precursor film was markedly reduced to be expressed as X ∝ t 0.66 for water and X ∝ t 0.21 for EMI-TFSI, indicating that the diffusive process was affected by the energy dissipation of the wetting system. The high viscosity and the strong molecular interaction of EMI-TFSI with the polymer brush gave a large entropy change during the wetting process to result in a slower spreading velocity.

Chemical Stability of Sputter Deposited Silver Thin Films

“…In this way, the liquid spreading is limited to the precursor layer. According to hydrodynamic theory, the diffusion coefficient D f equals H/3πηh liq with H the Hamaker constant, η the viscosity of the liquid, and h liq the thickness of the precursor layer [71,72]. The Hamaker constant for Ag/H 2 O has been reported in a range between 30 and 400 × 10 −21 J [73].…”

Elevating Outputs of Droplet Triboelectric Nanogenerator through Strategic Surface Molecular Engineering

“…Our surface functionalized D-TENG (FD-TENG) is constructed using a 1 H ,1 H ,2 H ,2 H -perfluorodecyltrimethoxysilane (PFDTMS) anchored PTFE film on an indium tin oxide (ITO) glass substrate, along with an aluminum top electrode , anchored PTFE film on an indium tin oxide (ITO) glass substrate and an aluminum top electrode (Figure a). The highly extensible characteristics of fluorosilane molecules are exploited to ensure adequate contact between water droplets and the surface of the molecularly functionalized triboelectric layer, thereby accelerating the contact electrification process (Figure b) .…”