Bubble-free electrophoretic shaping from aqueous suspension with micro point-electrode

The electrophoretic deposition (EPD) is a well-suited process for shaping compacts of nanosized powders. Aqueous suspensions are favorable for industrial application due to the high polarity of water enabling high solid loadings and for environmental reasons. Moreover, for many applications a local deposition is of interest. In this case the electric field has to be focused on a small point. This is a problematic issue when the aqueous suspension has a high electrical conductivity. The local resolution of the deposition was improved by moving both electrodes closer to each other. The limiting factor was the formation of bubbles by water electrolysis, which disturb the electric field at the electrodes. Therefore the electric field distribution of several electrode-configurations was calculated and the most suitable setup was selected. The formation of bubbles was suppressed by using unbalanced pulses of alternating voltage. Point deposits with diameter smaller than 740 mu m were obtained, which were only about 1.5 times larger than the point electrode diameter. Possible applications of this technique in the future are rapid prototyping or commercial manufacturing of individual structures like those required in the dental industry. (C) 2010 Elsevier Ltd. All rights reserved.