Device Vanishes on Command after Military Missions

For many years, researchers have attempted to make these polymers, but were unsuccessful because of the materials’ instability at room temperature. Kohl’s research group at the Georgia Institute of Technology discovered that they could overcome this issue if they were careful to remove all impurities formed during the synthesis. In addition, they found a number of aldehydes, including phthalaldehyde, that readily form cyclic polymers. Once they had optimized this polymer’s synthesis, they focused on ways to make it disappear.

To do this, the researchers incorporated into the polymer a photosensitive additive, which absorbs light and catalyzes depolymerization. “Initially, we made it photosensitive to just ultraviolet light so we could make the parts in a well-lit room with fluorescent lighting, and it was just fine; it was stable,” Kohl says. But when the polymer was placed outside, exposure to sunlight vaporized it (or reverted it back to a liquid, in some cases). A vehicle deployed at night would, therefore, disappear with the sunrise.

Kohl’s group has since discovered new additives that can trigger depolymerization at different wavelengths of visible light, so the polymer can decompose indoors. “We have polymers designed for applications in which you come in the room, you turn the light on, and the thing disappears,” Kohl says.

The group has also determined how to stall depolymerization. “We have a way to delay the depolymerization for a specific amount of time – one hour, two hours, three hours,” he says. “You would keep it in the dark until you were going to use it, but then you would deploy it during the day, and you would have three hours before it decomposes.” The team has considered chemical methods to start the decomposition process, as well. In addition, they are testing various copolymers that can be added to phthalaldehyde to change the material’s properties without altering its ability to vanish.

Kohl says that this “James Bond”-like material is already being incorporated in military devices by other researchers. But he also sees the potential of the materials for non-military applications. For example, the researchers have made a disappearing epoxy for a temporary adhesive that could be used in building materials. They also imagine the material could be used as sensors for environmental monitoring. Once the sensors are finished collecting data, there is no risk of littering the environment since they can be triggered to vaporize. The material can also be used for delivery vehicles in remote areas where recovery is difficult.

The researchers acknowledge support and funding from the U.S. Department of Defense.