This material, developed by AIST, is an organic substance where the adhesion strength can be varied repeatedly. This is achieved simply by shining light on the material, without heating or cooling it.
When the material has solidified, it’s yellow, but if it’s illuminated with UV light, it gradually liquefies and becomes orange. If you shine green light on the material, it hardens again, and reverts to yellow. This is the first example of a solid-liquid transition caused by light alone, deliberately and reversibly, in a single substance — via redwolf.newsvine.com