`”On the bacteria’s surface, there are these filaments that grab the nanoparticles,” said Saraf, who came to UNL last year from Virginia Tech. “When the humidity increases, the bacteria swells because it absorbs moisture, and it contracts when the humidity goes down. When it swells or contracts, it increases or decreases the distance between the nanoparticles.”
The distance between the particles, of course, affects their ability to exchange electrons and therefore their ability to pass on electrical current Saraf and Berry found that a decrease of less than 0.2 nanometers between the gold nanoparticles (reflecting a decrease in humidity from 20 percent to essentially 0 percent), resulted in more than a 40-fold increase in electrical current.
“So now we have a very, very sensitive device that can measure humidity,” Saraf said. “What is interesting is that the sensitivity of the device increases when the humidity goes down, which is completely opposite from other devices. [..]”‘