Expanding on previous research into electronic devices that dissolve in water once they have reached the end of their useful life, researchers at the University of Illinois have developed a new type of "transient" electronic device that self-destructs in response to heat exposure. The work is aimed at making it easy for materials from devices that usually end up in landfill to be recycled or dissolved completely.

The research involved a group led by aerospace engineering professor Scott R. White teaming up with John A. Rogers, who previously led work in the development of transient electronics that biodegrade in water. These previous devices dissolved in water after a predetermined period of time, which was related to the thickness of outer protective layers encapsulating the actual electronics. But using heat as a trigger has now enabled the creation of electronic devices that can be prompted to self-destruct on demand.

The technology involves first printing magnesium circuits on thin, flexible materials. Microscopic droplets of a weak acid are then trapped in wax, which is coated onto the devices. When exposed to heat, the wax melts and releases the acid, which completely dissolves the device. The researchers were also able to create devices that can be remotely triggered to self-destruct by embedding a radio-frequency receiver and inductive heating coil. In response to a radio signal, the coil heats up and melts the wax, leading to the destruction of the device.

"We have demonstrated electronics that are there when you need them and gone when you don’t need them anymore," says White. "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."

Similar to the devices that dissolve in water, the time it takes for the heat-triggered devices to dissolve can be controlled by tuning the thickness of the wax, the concentration of the acid, and the temperature. The researchers say it is possible to create a device that dissolves in as little as 20 seconds or up to a couple of minutes after the heat is applied.

Additionally, by encasing different parts in waxes with different melting temperatures, it is possible to create devices that degrade in a series of predefined steps. This gives control over which parts of the device are operative at what time, thereby providing the potential for devices that can sense and respond to conditions in their environment. The team is also exploring the potential for other triggers, such as ultraviolet light and mechanical stress.

"If you can’t keep using something, whether it’s obsolete or just doesn’t work anymore, we’d like to be able to bring it back to the building blocks of the material so you can recycle them when you’re done, or if you can’t recycle it, have it dissolve away and not sit around in landfills," says White.

The team's work was supported by the National Science Foundation and DARPA, whose Vanishing Programmable Resources (VAPR) program has been investigating the potential for transient electronics designed to self-destruct on command to prevent classified technology finding its way into enemy hands.

The University of Illinois team's research is detailed in a paper in the journal Advanced Materials.

The technology is detailed in the video below.

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