Owners of the 1.6 million cellphones stolen in the US every year may not agree, but there's an argument to be made that cellphones (and other devices) should be able to just disappear.
Not as part of the global black market for smartphones, of course. A planned, gradual process of decomposition that allows even complex electronics to disappear into easily recyclable components and chemical compounds could keep smartphones, PCs, and other devices from becoming part of the 40 million to 50 million tons of electronics disposed of globally every year.
Gadgets that fade away when they're no longer useful is one goal of researchers working on transient materials. Knowing when such a material will dissolve is critical to making degradable composites practical for electronics implanted as part of surgical procedures, creating environmental sensors that dissolve into nontoxic materials when their useful lives have passed, or keeping tons of other gadgets from piling up in landfills, according to Reza Montazami, assistant professor of mechanical engineering at Iowa State University. His study on the stability and triggered dissolution of materials that would make an effective substrate for transient electronics was published by the journal Advanced Functional Materials on April 1.
For years, surgeons have used sutures, staples, and other supplies made of materials such as polyglactin and polyglycolic acid that disappear at predictable rates after being exposed to water or to enzymes and phagocytes in human tissue.
The idea of using transient material for electronics was popularized by the work of researchers at Tufts University and Northwestern University. A September 2012 paper in the journal Science described a technique that produced field-effect transistors, resistors, diodes, a heater, and a strain sensor made of material coated in magnesium oxide and layered in silk that worked properly and dissolved on schedule in both test tubes and mice. The goal was to produce devices that could be implanted in the body, received outside power through induction coils, and dissolved completely without poisoning the patient or having to be removed by surgery.
"These devices are the polar opposite of conventional electronics whose integrated circuits are designed for long-term physical and electronic stability," Fiorenzo Omenetto, professor of biomedical engineering at Tufts School of Engineering and one of the paper's authors, said in a Tufts press release. "Imagine the environmental benefits if cell phones, for example, could just dissolve instead of languishing in landfills for years."
Montazami's team built a series of degradable components for the study, including a data-transmitting antenna, resistors, capacitors, and LEDs. However, their real advance was the development of a polymer composite film that can act as a substrate for integrated circuits and can be programmed for different physical properties and dissolution speeds based on the materials used with or layered on the polymer.
In a video posted by Iowa State's Advanced Materials Lab, Montazami's team showing the electrical leads and the polymer base of a blue LED dissolving into liquid under the impact of two drops of water.
"The resistors, capacitors and electronics, you don't expect everything to dissolve in such a manner that there’s no trace of it," Montazami said in an Iowa State press release.
Dissolving electronics could reduce e-waste or for devices to be implanted in the human body. Implanting packets of solvent into smartcards or other devices made with transient electronics could protect them from being stolen. A "kill switch" would puncture the solvent container to destroy, not only any sensitive data, but also the guts of the device itself.
— Kevin Fogarty is a freelance writer for EE Times