Humans and our machines have always been separated by a language barrier of sorts. Machines and gadgets use electrons (negatively charged particles) to send information and commands through their circuitry–turn on, turn off, increase volume, and so on. But living creatures use protons (positively charged particles) or ions (charged atoms) to send signals within our bodies and drive actions like flexing muscles or pumping molecules in and out of cells.
This basic difference in electrical languages keeps us from interfacing directly with computers, sensors, and other electronics. But this week, researchers from the University of Washington and the University of Waterloo published a new study the in journal Nature Communications that is a step toward getting around this language barrier.
A team led by Marco Rolandi, an assistant professor of materials science and engineering at the University of Washington, built a prototype of a simple, new transistor–a key component of nearly all electronic devices–that uses protons instead of electrons. Measuring about one twentieth the width of a human hair, the transistor could eventually lead to new types of biomedical sensors and tools that communicate directly with living cells.
Like other so-called “field-effect” transistors found in our gadgets, the new device acts sort of like a light switch, able to turn an electrical current (in this case a stream of protons, instead of the usual electrons) on or off. With a silicon base, two metal contacts, and a channel of a protein called chitosan to conduct the stream of protons, the device’s relatively simple construction is one of the things that makes it novel.
Research into nanoscale devices that speak nature’s electrical languages (protons and ions) is a growing field, but unlike many other prototypes, this transistor doesn’t rely on a reservoir of liquid–making it easier to build. “As far as we know, it’s the first solid-state field effect transistor that directly controls and measures the proton current,” Rolandi said in an email.
Using chitosan, a protein found in squid pens and crab shells, in the transistor was the brain child of Chao Zhong, a postdoctoral researcher in Rolandi’s lab. The team tried several materials before settling on chitosan, which is in not only a good proton conductor, but easy to work with, biodegradable, and nontoxic–important considerations for biomedical applications. It is also easy to come by: it can be harvested from waste left over by the seafood industry.
While he cautions that “applications are quite far off,” Rolandi imagines a range of practical uses on the horizon. “It would be nice if, in the far future, we could have implantable devices that, by monitoring proton-related biological processes, could help in
early disease detection and therapeutics,” he says, but adds: “It’s just daydreaming for now.”
Simpler applications in laboratory settings, like monitoring proton channels in cultured cells, are likely to come first. With the proof-of-concept prototype complete, the researchers will turn their efforts to fine-tuning the transistor, making it even smaller, and adapting it to be compatible with living tissue (the silicon base would need to be replaced or covered in order to be implanted in tissue).
If interest in these proton-based transistors takes off, manufacturing them on a large scale is feasible but will likely require outside resources. “The materials and processes are all readily available,” Rolandi says. “However, scaling up lab devices is rather difficult, and no one in my lab has the expertise to do so.”
