Rotaxanes were developed by Fraser Stoddart in 1991, who subsequently won the 2016 Nobel Prize in Chemistry with Jean-Pierre Sauvage and Bernard L. Feringa for their work on molecular machines.
“[Sir Fraser] threaded a molecular ring onto a thin molecular axle and demonstrated that the ring was able to move along the axle. Among his developments based on rotaxanes are a molecular lift, a molecular muscle and a molecule-based computer chip.” (nobelprize.org)
The light source alters the chemistry of the orange terminal to impart a negative charge, represented by colour change to blue. The positively charged rotaxane is magnetically attracted to the negative charge and migrates along the shaft. When the terminal returns to its base state and loses its charge the rotaxane returns to its original position.
This is happening at the molecular level!!
Paul G Stevenson 