Researchers create tiny bio-robot on bacterial spore

The spore reacts to humidity; the reaction is translated to an electronic response from the graphene quantum dots. Illustration: Berry Research Laboratory at UIC. Click on image to download.

It’s a far cry from Robocop. But UIC researchers have engineered a new nanobot — basically a robotic germ — that could be used as a humidity sensor to prevent food spoilage or keep space travelers safe.

Called NERD, for Nano-Electro-Robotic Device, it’s an electromechanical device on a bacterial spore.

“We’ve taken a spore from a bacteria, and put graphene quantum dots on its surface — and then attached two electrodes on either side of the spore,” said Vikas Berry, associate professor of chemical engineering and principal investigator on the study.

“Then we change the humidity around the spore,” he said.

When the humidity drops, the spore shrinks as water is pushed out. As it shrinks, the quantum dots come closer together, increasing their conductivity, as measured by the electrodes.

“We get a very clean response — a very sharp change the moment we change humidity,” Berry said. The response was 10 times faster, he said, than a sensor made with the most advanced man-made water-absorbing polymers.

There was also better sensitivity in extreme low-pressure, low-humidity situations. “We can go all the way down to a vacuum and see a response,” Berry said.

The device could be useful in applications where humidity must be kept low, for example, to prevent corrosion or food spoilage. “It’s also important in space applications, where any change in humidity could signal a leak,” he said.

Currently available sensors increase in sensitivity as humidity rises, Berry said. NERD’s sensitivity is actually higher at low humidity.

“This is a fascinating device,” Berry said. “Here we have a biological entity. We’ve made the sensor on the surface of these spores, with the spore a very active complement to this device. The biological complement is actually working towards responding to stimuli and providing information.”

The report is online at Scientific Reports, a Nature open access journal.

T. S. Sreeprasad and Phong Nguyen of UIC were lead co-authors on the study. Sreeprasad, a postdoctoral fellow, is now at Rice University in Houston. Ahmed Alshogeathri, Luke Hibbeler, Fabian Martinez and Nolan McNeiland, undergraduate students from Kansas State University, were also co-authors on the paper.