This looks like a really interesting way to make flexible circuits. It uses some specialty printers and materials, but the author does list alternative solutions. These circuits are ideal for applications where weight and/or size is critical. Check out the instructable for a nice step-by-step tutorial.
Produce your own single-sided flexible printed circuits using a solid ink printer, copper-coated polyimide film, and common circuit board etching chemicals. You will find flex PCBs inside most cellphones or similar miniaturized gadgets. Flex PCBs are useful for making tiny cables and extremely lightweight circuits. However, few shops yet make custom flex PCBs for reasonable prices in small volumes
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