Fabrication of micro-reentrant structures by liquid/gas interface shape-regulated electrochemical deposition

Micro-reentrant structures that are wide at the top and narrow at the bottom have important application values. However, the lack of an effective and universal method for fabricating micro-reentrant structures on various metallic materials is a bottleneck that restricts their development and application. In this work, the micro reentrant structures were proposed to be divided into two parts, viz., the upper roof structures and lower pillar structures. First, superhydrophobic micropillar arrays were fabricated by nanosecond laser ablation followed by a treatment for surface energy reduction. As the electrolyte droplet stands on the top of the micropillars, because of their superhydrophobicity, and the shape of the liquid/gas interface could be regulated, the microroof array could be fabricated on the top of the pillar array by electrochemical deposition, resulting in micro-reentrant structures. The influences of the processing parameters of the laser ablation and electrochemical deposition on the features of the micro-reentrant structures were studied comprehensively. Upon a further reduction in the surface energy with the use of fluoroalkylsilane, superamphiphobicity was achieved with a contact angle larger than 150 degrees for both water and peanut oil. The results of this study enrich the theory and technology of micro machining and promote the practical applications of micro-reentrant structures.