No thicker than a piece of paper - because it practically is a piece of paper - a solar panel created by an MIT researcher can be shoved into a pocket or made into a paper airplane, and it will still create energy when exposed to sunlight. The trick is in the way it is made. The panel is printed like ink onto a sheet of paper. Even folded up like a letter, it retains its ability to convert light to electricity. With her colleagues, Karen Gleason, a professor of chemical engineering at the Massachusetts Institute of Technology, published a paper last week in the journal Advanced Materials, demonstrating how they created a solar panel by printing tiny, lightweight layers of electrodes and semiconductors on a piece of paper.