| dc.description.abstract | The water-material interface is of fundamental importance in nature and in wide engineering applications. Behaviors such as wettability, adhesion and penetration are influenced by the surface morphology. There is growing need in textured surface leading to increased interests in understanding the surface properties of textured materials. To date, the existing wetting models are limited to well-defined surfaces. The adhesion mechanism between water and textured surfaces is not well-understood. Moreover, stability and kinetic behavior of a water drop on a porous surface has yet to be understood. The objectives of this research are:
1) Revealing the principles behind a water drop and a porous surface;
2) Obtaining understanding about wetting, adhesion and penetration of a water drop; and
3) Identifying key parameters related to wetting for materials design.
In this research, the investigation about water-solid interface of textured materials is divided to three parts: wettability and adhesion; stability of penetration; and kinetic behavior of penetration. To examine wettability and adhesion on textured surface, super-hydrophobic surfaces of micro-beads/nano-pores were studied. It is for the first time to consider the synergetic effect of wetting and adhesion in textured surfaces. Next, the stability of a drop was studied to understand the penetration mechanism on hydrophobic porous surfaces. An experimental method combined theoretical approach was used through force balance principles. Results show that a critical condition for spontaneous penetration on a porous surface, which is related to pore size, drop volume and surface wettability. During penetration, the kinetic behavior of a water drop has been investigated to reveal new principles such as the maximum penetrating rate, receding contact angle, slip-stick motion of contact circle. Results have revealed fundamental mechanisms of wettability, adhesion and penetration in water-textured material interfaces. Specific geometric design factors of textured materials, which are related to behaviors in water-solid interface, have been identified. The findings in this research lead to new approaches to optimize various applications of textured surfaces. | en |
