DIY Silver conductive ink
http://jordanbunker.com/archives/41
No formulas but a demo of inkjet conductive ink
http://makezine.com/2014/03/27/quickly-prototypes-circuits-with-new-inkjet-printable-conductive-ink/
https://www.kickstarter.com/projects/1597902824/agic-print-printing-circuit-boards-with-home-print