We report an ultra-rapid prototyping technique for forming microchannel networks for
lab-on-a-chip applications, called masters on-demand. Channels are produced by replica molding
on masters formed by laser printing on flexible copper printed circuit board (PCB) substrates.
Masters of various designs and dimensions can be individually or mass produced in less than
10 minutes. Using this technique, we have fabricated channels as narrow as 100 lmwith heights
ranging between 9 lm and 70 lm. Multi-depth channel fabrication is also reported, using a
two-step printing process. The functionality of devices formed in this manner is verified by
performing in-channel electrophoretic separations and culture and analysis of primary
mammalian cells.