The thermophoretic movement of DNA, stained with Sybr Gold, is monitored with a fluorescence micrsocope.
Using scanning mirrors we moved an IR-Laser along the letters "LMU". The aqueos solution absorbs the IR-Laser radiation and thus the temperature at these letters is locally heated up by 2K. The stained DNA moves from hot to cold, thus the concentration of molecules in the hot letters "LMU" decreases and so does the fluorescence.
As the IR-Laser is turned of the DNA "moves" back by ordinary diffusion.