Impact of the Imaginary Part of the Surface Dilatational Modulus on the Splashing Behavior of Drops

Abstract

The relation between the complex surface dilatational modulus E of aqueous surfactant solutions and the splashing behavior of their drops on liquid surfaces was investigated. The surface dilatational modulus E of selected surfactant systems has been determined in the frequency range of 3 to 500 Hz by means of the oscillating bubble technique. According to the functional dependence of the phase ϕ of the complex modulus E(ω, c)exp[iϕ(ω, c)] at higher frequencies, adsorption layers can be classified as surface elastic or surface viscoelastic. Each behavior shows pronounced differences in drop splashing experiments. The impact of a drop on the liquid was monitored with a high-speed camera. The splash of a drop is a rather complex phenomenon, so the focus of this article is to establish a relationship between the imaginary part of the surface dilatational modulus E and the height of the drop rebound. These findings may be of importance for formulations in crop protection, introducing a chemical way to influence the impact of drops on solid and liquid interfaces.

The Role of Surface Viscosity in the Escape Mechanism of theStenusBeetle

“…The system response is detected by a pressure sensor and evaluated by a lock-in scheme. A cross-sectional view of the apparatus is given in Figure . , …”

“…The surface area of an air bubble formed at the tip of a capillary is perturbed in a sinusoidal fashion in a frequency range from 2 to 500 Hz, and the change in pressure across the curved interface is measured by a sensitive transducer. Reprinted with permission from ref .…”

“…A cross-sectional view of the apparatus is given in Figure 2. 15,16 For each studied solution, three independent measurements were carried out; i.e., the sample chamber was opened and refilled with the solution to be studied. The frequencydependent results shown in Figures 4 and 5 represent the averaged values obtained from these measurements.…”

Automated system for measuring the surface dilational modulus of liquid–air interfaces

“…This voltage is digitized by the ADwin-system. Evaluating the pressure response and the corresponding changes in surface area by means of image processing allows one to investigate the amplitude of the surface dilational modulus E as well as its phase angle φ between the induced bubble deformation and pressure response [20].…”