Contact Angle Of Liquid Droplet Research Articles

Specific surface free energies of strontium chlorapatite single crystal determined by contact angles of liquid droplets

Contact angles of water and formamide droplets on a well-formed Sr 5Cl(PO 4) 3 crystal with an aspect ratio of 3.2 were observed. The specific surface free energies of the ( 1 0 1 ¯ 0 ) and ( 1 0 1 ¯ 1 ) faces, calculated using the approximation of Fowkes, are 35 ± 2 and 61 ± 1 mN/m, respectively. The stability of the ( 1 0 1 ¯ 0 ) face corresponds to the morphology of this crystal, which tends to elongate in the 〈0 0 0 1〉 direction. The wide distribution of the measured contact angles is ascribed to the variation in the steps on the surface. An ideal flat surface without step should have uniform specific surface free energy, estimated to be γ ter ⩽ 26 and ⩽50 mN/m for the ( 1 0 1 ¯ 0 ) and ( 1 0 1 ¯ 1 ) faces, respectively.

Mean-Field Theory of Liquid Droplets on Roughened Solid Surfaces: Application to Superhydrophobicity

We present calculations of the density distributions and contact angles of liquid droplets on roughened solid surfaces for a lattice gas model solved in a mean-field approximation. For the case of a smooth surface, this approach yields contact angles that are well described by Young's equation. We consider rough surfaces created by placing an ordered array of pillars on a surface, modeling so-called superhydrophobic surfaces, and we have made calculations for a range of pillar heights. The apparent contact angle follows two regimes as the pillar height increases. In the first regime, the liquid penetrates the interpillar volume, and the contact angle increases with pillar height before reaching a constant value. This behavior is similar to that described by the Wenzel equation for contact angles on rough surfaces, although the contact angles are underestimated. In the second regime, the liquid does not penetrate the interpillar volume substantially, and the contact angle is independent of the pillar height. This situation is similar to that envisaged in the Cassie-Baxter equation for contact angles on heterogeneous surfaces, but the contact angles are overestimated by this equation. For larger pillar heights, two states of the droplet can be observed, one Wenzel-like and the other Cassie-like.

B151 平板に衝突した液滴の見かけ接触角の速度依存性

B151 平板に衝突した液滴の見かけ接触角の速度依存性

Measuring the Contact Angles of Liquid Droplets on Wool Fibers and Determining Surface Energy Components

Contact angles of various liquids on wool fibers are measured using the liquid droplet method. A computational technique greatly simplifies contact angle calculations. Sur face energy components of differently treated wool fibers are determined from the contact angle data using current theories of surface energy. Values for the surface energy of wool fibers calculated using the equation of state and the geometric-mean equations show a dependence on the kind of liquid used. Calculations based on the acid-base approach give more consistent results, but for wool fibers with high polar components, reliable results are obtained only with particular liquids. Untreated wool fibers are weak γ- monopoles. Wool fibers set in steam have a higher γ LW and γ+, with the γ - remaining unchanged. Chlorination changes wool fibers to bipolar solids with substantial increases in γ LW,γ+, and γ-.