Fabrication of hierarchical micro/nano structure surface on copper by EDM and its hydrophobicity

Abstract

The hierarchical micro-nano structure surface on copper was fabricated by electrical discharge machining (EDM). The hydrophobic property was increased due to the hierarchical micro/nano structure (HMNS), which consisted of the micro/nano scale holes, molten balls, recast regions and the micro thermal cracks. The effects of the pulse width on the hydrophobicity of HMNS were investigated. The results indicate that with the increase of the pulse width, the quantity of the micro-nano scale holes increases. The distribution of other hierarchical micro structures is more homogeneous. The effective area of "air cushion" increases, which can trap more air in the HMNS. And the hydrophobicity of HMNS also increases. The proportion of the solid-liquid interface area (fsl) reduces. The contact area between the water droplet and "air cushion" in the HMNS increases. Therefore, the effect of the physical adsorption for the HMNS on the water droplet is weakened. The contact angles of the HMNSs can be increased up to (144.7±2.1)°, and the range of contact angle hysteresis is (8.46±3.3)°-(14.10±1.2)°.

Keywords

• electrical discharge machining
• hierarchical micro/nano structure(hmns)
• hydrophobicity
• contact angle hysteresis