Removal of islands from micro-dimple arrays prepared by through-mask electrochemical micromachining

•The island can be removed from the dimple by using presented method.•The diameter of the micro-dimple is mainly determined by the applied voltage.•The dimple with a flat bottom can be prepared at low voltage.•The dimple with a round bottom can be obtained at high voltage.

Surface texture plays a fundamental role in tribology, allowing for the improvement of the friction and lubrication performances of various mechanical components. Through-mask electrochemical micromachining (TMEMM) is a feasible alternative for generating surface texture. However, in TMEMM the “island” phenomenon often occurs, which weakens the effect of micro-dimples on tribological properties. This study is the first to focus on removing islands by using a thick mask. Simulations were performed to analyze the distribution of current density on an anode surface and predict the anodic dissolution process under a thick mask. For reuse, the mask was fabricated from a PDMS layer measuring 200 μm in thickness. The simulations and experimental results verified that the island phenomenon can be avoided by use of a thick (200 μm) mask. In addition, the effects of the applied voltage and machining time on micro-dimple formation were experimentally investigated. The results indicate that the dimensions of micro-dimples are mainly determined by the applied voltage: the micro-dimple diameter increases with increasing voltage, and machining localization increases sharply. With prolonged machining time at constant voltage, only a slight increase in dimple diameter is observed. Moreover, because of a current valve in the electrolyte, micro-dimples with a flat bottom can be obtained at low voltage, whereas micro-dimples with a round bottom can be generated at high voltage.

Graphical abstractMicro-dimple array prepared by TMEMM with different mask thicknesses. (a) Micro-dimple array prepared with a mask thickness of 5 μm. (b) Micro-dimple array prepared with a mask thickness of 200 μm.Figure optionsDownload full-size imageDownload as PowerPoint slide