Though the function of the molecular switches is similar to that of memory metal, like the kind used to control the tiny mirrors that comprise the surface of a DLP (digital light processing) chip, they function without electrical stimulus. Rather than using an on-off state powered by charge, they react to ultraviolet and visible spectrum light.

These types of molecules, molecules that react and switch states of configurations to light, are not uncommon. The process is called photoisomerization. The molecules can either be in a trans or cis state. For their results, the trans state, which represented the “on” state of the switch, was the default state under normal visible light. The molecules, composed of two benzene rings joined by double bonded nitrogen atoms, “flipped” to a cis or “off” state when exposed to ultraviolet light instead.

While these types of molecules function flawlessly in solutions, flipping back and forth between states easily, when attached to a surface, they do not react in the same manner. To overcome this, the group created a self-assembled metallic monolayer and used a special molecular tether to isolate the reactive azobenzene molecules from its surface.

To confirm their work, the scientists used a specially built scanning tunneling microscope which measured the height of the azobenzene molecule while exposing it to alternating visible and ultraviolet light.

The results of the multi-university group can be found in the June issues of the journal Nano Letters.