At the acclaimed IDTechEx Printed Electronics Europe event in April, Hewlett Packard described one of the most accomplished feats of engineering in reel to reel production of transistor circuits - producing aSi active matrix backplanes. Working with PowerFilm Solar, HP concludes that "R2R manufacturing of electronics on flexible substrates is feasible and will be cost effective. Its Self-Aligned Imprint Lithography (SAIL) solves the key challenge of high resolution, high throughput, patterning and alignment on dimensionally unstable flexible substrates in a R2R environment. Basic materials, processes, and architectures have been demonstrated. More work remains to be done to improve yield and scaling and it now has a complete toolset for R2R processing capable of pilot production."
Benefits and challenges of R2R electronics fabrication were seen as follows:

Source: Hewlett Packard~
Imprint Lithography is seen as the best choice for R2R patterning in this application.

Source: Hewlett Packard
The basic imprint lithography process is shown below, the bottom picture showing multi-level structures on flex at 5 m/min.

Source: Hewlett Packard
If you missed Printed Electronics Europe 2008 you can purchase the proceedings on line and you should attend Printed Electronics USA 2008.