Electrochemical micromachining of micro-dimple arrays using a polydimethylsiloxane (PDMS) mask

Graphical abstractSEM images of the micro-dimple arrays generated with PDMS mask. [Display omitted] ;Highlights•It is difficult to generate micro-dimple arrays with PDMS mask in hydrostatic mode.•Micro-dimple arrays with poor uniformity were obtained in lateral flow mode.•The forward flow mode was modified with multi-slits structure cathode.•With the modified mode, micro-dimple arrays could be generated uniformly.;AbstractMicro-dimple arrays on the surfaces of engineering parts play an important role in the behaviour of these parts. Through-mask electrochemical micromachining (TMEMM) is a popular method for generating micro-dimple arrays with controlled size, location and density. However, in conventional TMEMM, the electrochemical machining must be preceded by photolithography, which is time-consuming and expensive in mass production. In this paper, a polydimethylsiloxane (PDMS) mask is used in TMEMM for generating high-quality micro-dimple arrays. Compared with photolithography, this has the advantage that the PDMS mask can be re-used and has a micro-scale pattern. This technique could therefore replace photolithography in the application of TMEMM to generate micro-dimple arrays. With a PDMS mask being used for generating micro-dimple arrays, three electrolyte flow modes are investigated, and a modified forward mode with a multi-slit structured cathode is proposed for the generation of arrays that have uniform micro-dimple distributions and dimensions. Using this method, arrays are generated with average micro-dimple dimensions of 106μm diameter and 10μm depth, with a low standard deviation (STDEV). In addition, the results show that both direct current and pulsed current can be used to generate micro-dimple arrays with a high degree of localization, although pulsed current produces deeper micro-dimples.