Expanding on previous research intoelectronic devices that dissolve in water once they have reached the end oftheir useful life, researchers at the University of Illinois have developed anew type of "transient" electronic device that self-destructs inresponse to heat exposure. The work is aimed at making it easy for materialsfrom devices that usually end up in landfill to be recycled or dissolvedcompletely.
The research involved a group led by aerospaceengineering 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 apredetermined period of time, which was related to the thickness of outer protectivelayers encapsulating the actual electronics. But using heat as a trigger has now enabled the creation ofelectronic devices that can be prompted to self-destruct on demand.
The technology involves first printingmagnesium circuits on thin, flexible materials. Microscopic droplets of a weakacid are then trapped in wax, which is coated onto the devices. When exposed toheat, the wax melts and releases the acid, which completely dissolves thedevice. The researchers were also able to create devices that can be remotelytriggered to self-destruct by embedding a radio-frequency receiver andinductive heating coil. In response to a radio signal, the coil heats up andmelts the wax, leading to the destruction of the device.
"We have demonstrated electronics that are there whenyou 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 usedin modern-day electronics. This was our first attempt to use an environmentalstimulus to trigger destruction."
Similar to the devices that dissolve in water,the time it takes for the heat-triggered devices to dissolve can be controlledby 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 aslittle as 20 seconds or up to a couple of minutes after the heat is applied.
Additionally, by encasing different partsin waxes with different melting temperatures, it is possible to create devicesthat degrade in a series of predefined steps. This gives control over whichparts of the device are operative at what time, thereby providing the potentialfor devices that can sense and respond to conditions in their environment. The team is also exploring the potential for othertriggers, such as ultraviolet light and mechanical stress.
"If you can’t keep using something, whether it’sobsolete or just doesn’t work anymore, we’d like to be able to bring it back tothe 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 inlandfills," says White.
The team's work was supported by the National Science Foundation andDARPA, whose Vanishing Programmable Resources (VAPR) program has been investigating the potential for transient electronics designed toself-destruct on command to prevent classified technology finding its way into enemy hands.
The University of Illinois team's research isdetailed in a paper in the journal Advanced Materials.
The technology isdetailed in the video below.
Source: University ofIllinois
