Cracking a few eggs to make electronics that dissolve
Durability is often touted as the hallmark of good electronics, but sometimes you want components that don't last all that long. For example, it would be handy if microelectronic systems that delivered drugs to various parts of the body dissolved after their task was done. Or if sensors that monitor pollution simply dissolved after they were finished reporting, rather than contributing to even more environmentally-damaging material. A team of researchers from the UK and China has just figured out how to create one such chip out of eggs.
Specifically, the team used diluted egg albumen, the protein-rich clear part of an egg that turns white when it's cooked. They spun the albumen quickly on a silicon wafer to create a super-thin film. On one side of this film they laid electrodes made from magnesium, and on the other side, electrodes made from tungsten – both natural, dissolvable materials.
When the process was done, the researchers had created a completely natural, degradable transient memory resistor, also known as a memristor. Memristors are a type of circuit that had existed in theory only since 1971 until they were created by HP Labs in 2008. They can not only process electrical information, but also retain a memory of those charges. Such chips could, for example, allow a computer to retain information in its circuits so that boot time would be nearly instantaneous.
The team reports that testing proved that the memristor performed as well as similar components that weren't degradable. As long as the conditions in which they operated were kept dry, the chips worked for over three months. Once water was added, the albumen, tungsten and magnesium dissolved over the course of 10 hours with the rest of the chip (which was made from silicon and silicon dioxide) taking three days to disintegrate.
Research on transient electronics has been going on for a while. In 2012 a group of interdisciplinary researchers created electronics made from silicon, magnesium and silk that dissolved during a proscribed period of time in water. In 2014, researchers from Iowa State University came up with a tiny antenna that could broadcast information and then be completely dissolved. And just last year another group figured out how to use heat to melt acid-containing wax to dissolve magnesium circuits.
Applying the technology to memristors is another step in creating the now-you-see-it, now-you-don't tech that may some day be swimming through our blood steams, skies and rivers, lakes and oceans.
The research was conducted by scientists from Zhejiang University, Fujian University of Technology, the University of Cambridge and the University of Bolton. It was reported in the journal ACS Applied Materials & Interfaces earlier this month.
Source: American Chemical Society