The future of electronics is photoswitches

But until now, it's not been easy to observe them in action. New research by assistant professor of chemistry Grace Han may change this.

Imagine a smartphone that's soft and flexible and shaped like a hand so you can wear it as a glove. Or a paper-thin computer screen that you can roll up like a window shade when you're done using it. Or a TV as thin as wallpaper that you can paste on a wall and hardly know it's there when you're not watching it.

If any of these devices come to fruition — and many experts predict they will — it may have a lot to due with a class of organic molecules known as photoswitches.

Photoswitches, which turn on and off in response to light, can be stitched together to replace the transistors used in electronic devices that control the flow of the electric current.

Commercial silicon transistors are brittle, nontransparent and typically several microns thick, about the same thickness as a red blood cell.

In contrast, photoswitches are one or two nanometers, about 1,000 times thinner. They can also be mounted on graphene, a transparent, flexible material.

The trouble with photoswitches is that even with powerful electron microscopes, their movements are very difficult to observe. This is because the photoswitches need to be placed on a background made of similar elements, making them hard to discern.

In a paper published in the journal ACS Nano in late January, assistant professor of chemistry Grace Han and her lab report that they've come up with a solution to this problem.

In their research, Han, first author Mihael Gerkman and colleagues worked with a popular type of photoswitch called azobenzene, an arrangement of carbon, hydrogen and nitrogen atoms. On either side of the azobenzene, they attached a platinum atom that is now
visible against the background under an electron microscope.

By analyzing the change in positions of the now visible ends of the azobenzene, researchers can begin to understand how photoswitches transform when exposed to light.

"Until now, we've really had no clear images of photoswitches," Han said. "Now we can see how exactly they switch on and off, so we can use them in the next generation of electronic materials."

The other authors on the paper were Sapna Sinha and Jamie H. Warner of the University of Oxford.