DIY PCBs are quite simple to make these days but DIY Flexible Circuit Boards are still something that is not easy and also not common in most PCB production houses. With this technique you can now dabble with flexible boards in your next project.
Via: 3ders
Thanks to Wheedal for the tip
“A fairly new elastomeric rubber filament is now available that sticks quite well to copper. It is called Ninjaflex. In fact, it sticks quite well to almost anything including acrylic, blue painters tape, and glass.
A circuit board pattern can be drawn in a free program like 123D Design and then extruded to a thin thickness and saved as an STL file. It can then be printed on top of a thin copper clad board or plated conductive fabric: step 1 pic. It can then be etched in the standard way with a Ferric Chloride solution.”