The process may make a suspended mass, or a slender bridge that connects to a wafer at one end. This turns out to be an extremely popular shape in microsystems because it allows measurements of such properties as acceleration and vibration. Manufacturing processes may require vacuums or special atmospheres, or may work only at very high temperatures. A significant cost saving to the method is that manufacture does not require a cleanroom. In an interview, Adam Cohen, project leader at USC, compared the instant mask to a printing plate.
Manufacturing requires a mask for each different horizontal cross section of a design.
The patterns can be derived from a CAD file. Last fall, during ASME's International Mechanical Engineering Congress in Nashville, Cohen, representing himself and five co-authors, presented a paper on the system, which they call EFAB, for electrochemical fabrication. The system can put down one layer every 40 minutes, or three dozen a day, and a mask can be large enough to contain multiple copies of a pattern and make products in batches. The layers can be stacked by the hundreds, or thousands, theoretically with no limit. However, a practical upper height is about a centimeter, mainly because there are faster ways to build devices larger than that, Cohen said.