Evaluation of the waterproof ability of a hydrophobic nickel micromesh with array-type microholes

Hydrophobic nickel micromeshes with array-type circular holes were designed and fabricated, and their waterproof abilities with respect to the hole diameter were theoretically and experimentally evaluated. The hole diameter increased from 20 mum to 100 mum in steps of 10 mum, while the hole pitch was fixed at 200 mum. Photolithography and nickel electroforming processes were used to fabricate 10 mum thick nickel micromeshes. In order to enhance the waterproof ability of nickel micromeshes, a plasma-polymerized fluorocarbon (PPFC) layer was coated on the nickel micromeshes. The contact angle of the micromesh increased from 63 deg for the non-coated nickel flat film to 106 deg for the PPFC-coated film. The maximum allowable hydraulic pressure decreased as the hole size increased and was inversely proportional to the hole diameter. The micromesh with a hole diameter of 20 mum showed the highest waterproof performance, with a water height of 111 cm in the experiment. The measured maximum allowable hydraulic pressures were about 31% lower than the calculated pressures on average.