The machine used to spin up cotton candy, the sticky carnival treat, may also be the answer to a new generation of self-destructing electronics. Professor Leon Bellan of Vanderbilt University is developing a new form of electrical circuitry made of a spinable polymer that must be kept above a temperature of 32° C (89.6° F) or it dissolves in water.
Self-destructing circuitry is of increasing interest to scientists and engineers. Not only is it useful for the military, who want to avoid sensitive technology falling into the wrong hands, but also for doctors for creating implants that can be destroyed once they've done their job.
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However, the current generation of self-destructing circuits are designed to be stable under normal circumstances and only disable themselves when subjected to some outside influence, such as being exposed to light, acid, or water. Working with mechanical engineering graduate student Xin Zhang, Bellan is taking the opposite approach, by creating electronics that can only survive in special environments. In this case, silver nanowires set in a polymer that remains stable at body temperature, but dissolves if it cools to room temperature.
That may sound a bit like making a house out of ice cream, but there is a logic behind it. There are many instances where you might want a device that can be destroyed by neglect as well as intentionally.
"Let's say you use this technology to make an RFID wireless tag," says Bellan. "You could implant important information in a person, and body temperature would keep it intact. If the tag were removed or the bearer died, it would dissolve. You could use it for implanted medical devices as well – to cause them to disintegrate, it would only require applying ice to the skin."
The technology behind this was developed by Bellan using a special polymer that, when run through a regular cotton candy machine, forms networks of threads that are of similar size, complexity, and density to blood capillaries. These can be embedded in materials that mimic the extracellular matrix in the living body and then dissolve away by cooling to potentially create a vascular system for artificial organs. The triggering system to dissolve the polymer capillaries can also be used to produce transient, self-destructing electronics.
So far, Bellan has used silver nanowires embedded in the polymer to create a simple LED lighting circuit. Kept in a beaker of water on a hot plate, the polymer remains intact and the circuit functions. But turn off the heat and the water cools, the polymer dissolves, and the nanowire network falls apart in a matter of minutes to break the circuit.
Bellan says that he now plans to integrate semiconductors into the circuits to form transistors so the device can be operated wirelessly by users. In addition, other triggering systems could be developed to activate the self-destruct process.
"Transient electronics are cool, and once you start coupling that to a stimulus-responsive material, you start coming up with really sci-fi ideas," says Bellan. "You could have any cascade of events that results in a very unique stimulus that causes it to degrade or prevent it from falling apart. Temperature is just the beginning."
The research was published in ACS Applied Materials & Interfaces.
The video below discusses the self-destructing electronics.
Source: Vanderbilt University