Coupling Diffusion Welding Technique and Mesh Screen Creates Heterogeneous Metal Surface for Droplets Array

Abstract

Nonsilicon micromachining is a challenge, especially for large scale heterogeneous (hydrophilic/hydrophobic) surface fabrication. Here, mesh screen and diffusion welding technique are coupled to form a novel fabrication method. Mesh screen is used as mask. The diffusion welding technique sinters mesh screen on copper surface to form welding junction array. Chemical treatment of sintered package forms superhydrophobic nanostructures on surfaces except welding junction array. Separating mesh screen from copper substrate exposes hydrophilic dots array, corresponding to welding junction array. Thus, heterogeneous surface is created. By condensing wet air, main droplet and neighboring droplet occur on hydrophilic dot and superhydrophobic part, respectively. For horizontal surface, neighboring droplets initially generated on nanograsses behave consecutive events of coalescence, jump, and return, triggering contact/noncontact effect induced jumping. Thus, defect droplet area is formed and droplet size uniformity is broken. A nondimensional equation is proposed for the contact effect induced jumping analysis. Noncontact effect induced jumping is found for the first time. For vertical surface, droplet array behaves monodisperse size due to departure of merged neighboring droplets without returning, and equal opportunities of neighboring droplets captured by main droplets. The work opens a new way for large scale droplet array generation by controllable condensation.

Departure Velocity of Rolling Droplet Jumping

“…In the experiments, as shown in Figure , the squeezing process persists until t * = 1.05. The droplet squeeze phenomenon is a kind of interface behavior that probably relates to energy of the real interface; it may also due to the interaction between air and droplet (such as the air entrapment at the droplet contact point). , Actually, this droplet squeeze phenomenon is very interesting but have been less mentioned previously. We infer that targeted research on the droplet squeezing mechanism could change our previous perception on the droplet coalescence dynamics and help to reveal new coalescence mechanisms, and we will start researching this in our next work.…”

Dropwise Condensation on a Hierarchical Nanopillar Structured Surface

“…Since the condensation surface was set upward, the droplet that jumped fell on the surface again, which is similar to the phenomenon shown in the existing literature. 10,35,36 When the diameter of a jumping droplet was large, it jumped to a height of at least 1 mm. Additionally, this suggests that the effect of deceleration due to air resistance is relatively large for small droplets.…”

Porous surfaces with structural gradient: Enhancing boiling heat transfer and its application in phase-change devices

“…7 (Color online) Ultra-thin flat heat pipes using forest-like porous copper as the wick [81] . (a)-(d) The conception of forest-like array for flat heat pipes: (a) The common Ω-like groove for heat pipes; (b) the Ω-like groove can be formed between the trees; (c) the forest can form interconnected Ω-like grooves; (d) the SEM image of a typical forestlike wick; (e) the fabrication of the ultra-thin flat heat pipes; (f) the evaporation temperature of UTFHP and copper plates under different heating power; (g) surface temperature distribution (infrared image) of copper plates and the ultra-thin flat heat pipe at 6 W 结构多孔表面应用于冷凝传热的相关研究可以参考 Liao等人 [87] 、Xie等人 [88] 、Wen等人 [89] 、Ma等人 [90] 、 Niu和Tang [91] 、Chen等人 [92] 、Peng等人 [93] 的工作, 本 文不再赘述.…”