| Understanding the ability of a liquid to transfer from a flat surface to fibers can provide basic information enabling the design and preparation of superoleophobic or oil self-cleaning materials. Based on the literature review, a Laplace pressure difference will change the shape of droplet and even move it when the force caused by this pressure difference overcomes the resistive forces such as gravitational and viscosity forces. The final shape and location of droplets on different materials or different geometrical structures are determined by the system free energy. Based on experimental observations and the predictions of the ability of a liquid to transfer, it is found that the theory can be used to predict and explain low surface tension liquid (oil) transfer and the final location of the liquid. It is also found that the height of a fiber which is vertically attached on a flat surface should be longer than the length of the drop on the fiber to prevent the drop wetting the flat surface; if a low surface tension liquid on a flat surface touches a cylindrical fiber resting on the flat surface and normal to it, the drop should move such that it lies on both the flat surface and the fiber. However, the liquid does not climb the cylindrical fiber or transfer to its tip. If subsequently the fiber is raised, then the droplet may remain with the flat surface, transfer to the fiber tip, or transfer to the tip and the body of fiber. The theoretical equations derived from Carroll's equation and our experimental observations prove that droplets do move along a conical fiber. However, the critical relationships between liquid motion and droplet size, surface tension, conical fiber geometry should be obtained to provide information on liquid transferring ability. |
