New developments in through-mask electrochemical micromachining of titanium

Abstract

Aiming at topographical surface micromachining of metallic and in particular Ti surfaces, we have investigated the possibility of using robust SU-8 and more recent electrophoretic photoresist technology in combination with flexible, non-contact maskless UV and electron beam lithography for mask generation in a through-mask electrochemical micromachining process. The shape evolution during diffusion controlled isotropic metal dissolution under circular mask openings of different sizes is in good agreement with numerical simulations, the cavities approaching hemispherical shape before their diameter reaches three times the initial mask opening diameter. Taking advantage of an important size effect in current density in combination with the developed methods, it was for the first time possible to create topographical gradient structures in a single micromachining step, difficult or impossible to achieve with competing techniques. Via through-mask anodization a locally confined nano-topography could be created within Ti surfaces. We further present an original method capable of electrochemical micromachining of highly curved conductive surfaces through electrophoretically deposited photoresist patterned by maskless 3D-UV lithography, going beyond the limitations of existing approaches.