Conductive ink is exactly what it sounds like: A colored liquid that transmits or conducts electricity. You're not likely to dip conductive ink out of an inkwell, though. The conductive particles must be transported within a non-conductive medium that dries or reduces once applied, which then stacks the conductive particles--usually carbon graphite powder or fine metallic flakes--in contact with each other, allowing electricity to be conducted throughout the expanse of conductive ink.
Things You'll Need
Black liquid tape
Carbon graphite powder, very fine
Tuluol or toluene solvent
Work in a very well-ventilated area--outdoors if possible--and wear gloves to protect your hands from the solvents you're using and safety goggles to protect your eyes.
Mix three parts carbon graphite powder to two parts liquid tape and six parts Tuloul solvent together in a glass container.
Use a paint brush or sponge brush to paint the conductive ink you've created onto your target surface.
Wait until the ink is completely dry to the touch--this should take half an hour or less.
Add clear cement adhesive to create a thicker conductive glue if you so desire. Most of the materials you need should be available at local hardware stores; carbon graphite powder is often sold as a lubricant. You can use fine silver or copper flakes in place of graphite powder if you wish.
Never work with these materials in an enclosed area; the fumes are dangerous.