The Tiny Lemon Battery, and other designs for zero cost electricity and led light without batteries

Step 5 How to make the cells

Cut about 1.5 cm of Iron wire.

Take one paper facial tissue and carefully extract one of the 3 or 4 layers that compose the tissue.
(The thinner, the better).

Cut a a rectangle 2 cm long and 1cm wide.

Roll the 2x1 cm rectangle cut out of the layer around it the iron wire.
Make sure to left space, about 5 mm, uncovered.

Cut a piece of copper wire about 10 cm long.
Extract the thin copper wire strands removing the insulating plastic around.

Finally, wrap around the copper wire strands around the paper, making sure it doesn't touch the iron directly.

Here, you just have made one cell.

Now just make 4 of them and solder them is series.
(That means, solder the copper tail of one cell to the exposed iron wire of the next one)

I put them alternately to minimize the overall size.