Preparation of cell adhesive micropores by one-step potentiostatic polarization on 304 stainless steel

Non-conventional electrochemical machining in micro-manufacturing has atomic-scale machining accuracy only in theory. By taking full advantage of the material heterogeneity, the micropores which most easily initiate at the surface stoichiometric inhomogeneities for stainless steel can be prospectively obtained with the size kept under control by adjusting the machining parameters. Taking the economy and efficiency into account, a one-step potentiostatic polarization method was established. Optimization of the machining parameters for achievement of microporous structure required by cell adhesive surface on 304 stainless steel in natural 15 wt% NaNO3 solution was confirmed. Based on the potentiodynamic polarization curve, a DC voltage of 5 V in the region of secondary passivation was selected due to the porous secondary passivation film which results in the initiation of large amounts of pores. The effects of the machining time on the pore size, coverage ratio, density, unevenness degree and adhesive cell density on the porous surface were investigated through statistical analysis. The results show that there is a maximum value of machining time, tm, when the surface has a maximum pore density, and minimum pore unevenness degree. Meanwhile, adhesive cell density increases to significant level at tm then levels off over time. Therefore, this approach has been testified possible through the novel use of material microdefects and electrochemical machining to obtain cell adhesive micropores.