Droplet shapes on fiber networks

Droplet shapes on fiber networks

Chair: Physics of Complex Fluids

The shape of droplets that are attached to fiber networks, and their detachment, are important in the cleaning of textiles, materials science of carbon nanotube based polymer composites, and optical fiber processing. Here, the wettability of the fiber is an important parameter in determining the droplet shape. The wettability can be expressed as the angle that the droplet makes with the wire.

By using electrowetting, we apply an electric field to the droplet to change this contact angle, and thereby the shape of the droplets! We have already seen that we can tune the droplet shape on a single fiber reversibly from an (axisymmetric) barrel state to an (a-symmetric) clamshell state (see Figure 1) by changing the contact angle or droplet volume [1].

On a fiber crossing we have observed similar transitions (see Figure 2), which we would like to study in more detail.

The goal of the project is to investigate the various morphologies of a (microliter volume) droplet on a fiber network. As a model, we use two parallel fibers or the junction of two crossed fibers. The control parameters are the droplet volume, the contact angle (varied using electrowetting), the fiber spacing and the junction angle. Analysis of the obtained images will be performed using Matlab. Further, you will learn about general wetting theory, capillarity, electrowetting, and the energy considerations that dictate morpho-logical transitions.

Figure 1. (A) Barrel and Figure 2. Different morphologies of a drop on a crossed
(B) clamshell droplet. fiber [2].

[1] Eral et al., DOI: 10.1039/c0sm01403f





Tutor: Burak Eral

Riëlle de Ruiter, Jolet de Ruiter




Teacher: Frieder Mugele