Incidentally, you should always draw the full body of a character, even if you know part of the body will be obscured, or in this case, invisible. It really helps guide how to draw the body properly, otherwise, it'll come out all weird and stuff.
This was done with a Papermate Flair medium size marker for the majority of the lines and a Sharpie fat tip pen for the blacks. The machinery in the background was done with a .05 cm tip pen so the details don't overwhelm the Invisible Woman in the foreground. I kinda got a little too into drawing the machines on the left side of the picture because that side is really dark.