Development of super high slenderness ratio micro channels using precision filled wax electroforming

A novel approach to fabricate miniature structure having several layers of different forms of super high slenderness ratio micro channels by traditional micro manufacturing technologies is proposed and developed in this study. First of all, the micro straight slots array is fabricated by precision wire-EDM on the substrate. These micro slots are then filled with fine wax oil. After it is solidified the extra wax left on the top of the slots are shaved away. And then the precision electroforming process is carried out until a desired thickness of nickel is deposited on the top surface of micro slots. After this step the first layer is completed and ready for making the slots of any form on next layer if needed. The wax inside the work part is melted and cleaned by hot water. Finally, the super high slenderness ratio micro channels are obtained. Applying the proposed technology, micro channels with the slot width of 220 ?m and slenderness ratio of 300 have been fabricated successfully. The surface roughness of the micro channel can be achieved on the basis of the machining method used. Comparing with LIGA, LIGA-like and etching processes, the developed technology in meso-scale structure applied is more flexible, requires less time and it is cost effective in fabricating micro channels. The micro channels have been widely applied in industrial products such as miniature oil spray (Samuel, et al, 2003), miniature oil atomizer (Alessandro, et al., 2005), miniature mixer (Rife, et al, 2000), miniature heat pipe (Berre, et al., 2003), miniature refrigerator (Narayanan, et al., 1999), micro-droplet spray (Sohn, et al., 2005), etc. There is a trend of increasing demand of high slenderness ratio micro channel in recent years (Fofonoff, et al., 2002), but its fabrication becomes more difficult by comparison. Nowadays, the micro channel with high aspect ratio is made by means of LIGA process, LIGA-like process (Chien, et al, 2006), laser micromachining (Oh, et al., 2006), etc. followed by the diffused bonding or the anodic bonding (Xue, et al., 2005). These fabrication processes are quite costly. Besides, some of the approaches are limited to certain specific materials. Also, the form and the length of micro channel may be restricted. The purpose of this paper is to propose a new approach of fabricating micro channels, in particular super high slenderness ratio micro channels which it can probably take the place of the fabrication method of the high aspect ratio partially. In the study, the technology is verified by meso-scale examples. But the same idea can be extend to the fabrication of micro even nano scale channels.