Scientists have developed electronic devices that can self-destruct on demand when heated, a step towards greatly reducing electronic waste and boosting sustainability in device manufacturing.
They also developed a radio-controlled trigger that could remotely activate self-destruction on demand.
"We have demonstrated electronics that are there when you need them and gone when you don't need them anymore," said professor Scott R White from the University of Illinois.
"This is a way of creating sustainability in the materials that are used in modern-day electronics. This was our first attempt to use an environmental stimulus to trigger destruction," said White.
White's group teamed up with John A Rogers, director of the Frederick Seitz Materials Laboratory at Illinois.
Rogers' group has pioneered transient devices that dissolve in water, with applications for biomedical implants.
Together, the two research groups have tackled the problem of using other triggers to break down devices, including ultraviolet light, heat and mechanical stress.
The goal is to find ways to disintegrate the devices so that manufacturers can recycle costly materials from used or obsolete devices or so that the devices could break down in a landfill, researchers said.
The heat-triggered devices use magnesium circuits printed on very thin, flexible materials. The researchers trap microscopic droplets of a weak acid in wax, and coat the devices with the wax.
When the devices are heated, the wax melts, releasing the acid. The acid dissolves the device quickly and completely.
To remotely trigger the reaction, researchers embedded a radio-frequency receiver and an inductive heating coil in the device. The user can send a signal to cause the coil to heat up, which melts the wax and dissolves the device.
"This work demonstrates the extent to which clever chemistries can qualitatively expand the breadth of mechanisms in transience, and therefore the range of potential applications," Rogers said.
The researchers can control how fast the device degrades by tuning the thickness of the wax, the concentration of the acid, and the temperature.
They can design a device to self-destruct within 20 seconds to a couple of minutes after heat is applied.
The devices also can degrade in steps by encasing different parts in waxes with different melting temperatures.
This gives more precise control over which parts of a device are operative, creating possibilities for sophisticated devices that can sense something in the environment and respond to it, researchers said.
The research was published in the journal Advanced Materials.