‘Robotic germ’ speeds up humidity detection

Scientists have created a ‘robotic germ’ that could be used as a tiny, rapidly responding environmental sensor.

UIC robotic germ
Graphene quantum dots deposited on a sporating bacteria produces a graphene-coated spore.

Researchers at the University of Illinois at Chicago (UIC) equipped a bacterial spore with a nano-scale electromechanical device made from graphene that produces a signal as humidity drops.

The response from this cyborg sensor was reported to be 10 times faster than one made with the most advanced man-made water-absorbing polymers.

“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, UIC associate professor of chemical engineering and principal investigator on the study.

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.

The researchers said the device, known as Nano-Electro-Robotic Device (NERD), was more effective than existing technology in extreme low-pressure, low-humidity situations.

“We get a very clean response — a very sharp change the moment we change humidity,” Berry said in a statement. “We can go all the way down to a vacuum and see a response.”

This means the device could be particularly useful in monitoring environments where humidity must be kept to a minimum for example, to prevent corrosion or food spoilage. “It’s also important in space applications, where any change in humidity could signal a leak,” said Berry.

Currently available sensors increase in sensitivity as humidity rises, but NERD’s sensitivity is actually higher at low humidity, he added.