These Quantum Bio-Robots Are Probably the Tiniest Cyborgs in Existence

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NERD is a bacterial spore. It's not just a mere spore, however, it's also a machine, a tiny reproductive biounit of bacteria coated in a layer of graphene-based quantum dots and sporting electrodes on either side. A nanoscale quantum bio-robot.

This is the creation of a team of chemical engineers based at the University of Illinois, Chicago. As described in a new ​paper in the journal Scientific Reports, NERD, or nano-electro-robotic device, functions as a humidity sensor, which is only a little bit disappointing. (But real-life utility always is, no?).

The general idea is that as the humidity around the bacterial spore declines, it responds by releasing water and shriveling up. This has the effect of bringing the quantum dots on its surface closer together, which increases the total conductivity across the spore's surface, registered by the electrodes. It's simple enough, but, in terms of speed, the spore-based method beats out prior techniques—based on synthetic water-absorbing polymers—10 times over.

"An endospore is robust, resilient, and highly responsive to water vapor due to their exceptionally hygroscopic biomolecular construct," Vikas Berry, the paper's lead author and head of Berry Re​search Labs, and his group write. "Further, it provides a rich surface chemistry available for nano-interfacing and a strong mechanical response to humidity."​

For NERD, the quantum dots offer highly-tunable degrees of conductivity. Just by squishing a dot—a nanoscale crystal small enough to experience quantum properties, like tunneling, which is basically where a particle disappears in one place and reappears in another—its conductivity changes. So, if we were to have a bunch of these dots lined up on some surface and that surface were to become smaller, the dots would shrink as well, boosting conductivity.

It's the tunneling that allows for the conductivity boost. As water moves in and out of the spore, the effect is of, "reversibly [modulating] the electron tunneling characteristics between the GQDs," the paper explains. The whole thing seems pretty clever and works even in extremely low pressure, near-vacuum environments with extremely low humidities.

"This is a fascinating device," Berry offered in a statement. "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."