Topography characterization of sinusoidal surfaces obtained with electrochemical machining

The study and understanding of functionality and its link with surface topography requires surfaces that enable us to decouple the examined effect. The sinusoidal function offers an easy solution for the decoupling of amplitude and frequency. However, the corresponding surfaces would require very good characteristics: shape regularity, low waviness and low microroughness. This study thoroughly characterized sinusoidal surface (egg-box shapes) having periods ranging from 30 μm to 300 μm and peak-to-valley amplitudes comprised between 3 and 30 μm. The microroughness of the examined surfaces was quantified with the arithmetic mean deviation Sa and was found to be around 1 nm for most examined surfaces. The waviness of the surfaces, which was also quantified with Sa, was lower than 0.15 μm for all the surfaces. The relative error computed for the period of the sinusoidal surfaces was lower than 1.3%. Finally, the shape regularity was assessed by comparing the measurements to a mathematical function and the computed average residues were smaller than 0.8 μm. These characteristics highlighted the very good noise-to-signal ratio of the produced surfaces, which can be used in very different fields (biology, mechanics, optics...) to examine topography effect on functionality (cell adhesion, brightness...).