When most people envision nanobots, they picture them as tiny, entirely mechanical creatures. The clanky gear and gizmo conception dates to some of the earliest experiments in nano-manufacturing, which turned out molecular-scale machinery that looked a lot like what you might find it any nineteenth-century industrial site… only much smaller.

Researchers have created a nanoscale biomicrorobot (or 'cytobot') that responds electrically to changes in its environment (Image: UIC)

But in more recent years, scientists have been making progress with an entirely different sort of nanomachine, one which taps into a different sort of sci-fi tradition: Cyborgs.

Researchers at the University of Illinois recently published a paper describing their success in adapting bacterial spores for nanotechnological purposes. Spores of bacillus subtilis, a common bacteria often found in ruminants and human beings, were coated with tiny specks of graphite (called "graphene quantum dots") to provide an electrically conductive surface. Using the bacteria’s natural inclination to swell to larger sizes by absorbing water in conditions of high humidity, or shrink in dryer conditions, they were then able to use the spores as conductors on chip-electrodes to detect conditions of high humidity by reading the resistance levels.

Creating a new type of humidity detector may not seem revolutionary in itself, but as a proof of concept, the experiment overcomes significant challenges in the field of nano robotics. The technique leverages millennia of natural progress in order to deal with some of the most basic problems in creating semi-autonomous nanotech devices.

Despite widespread advances since the late 1980s in scanning tunneling microscopy (which allows researchers to view structures at the atomic level) and micro-assembly, at this point, one of the biggest obstacles to nanobots is that there are no machines capable of making these tiny machines. Reliable, directed, and repeatable manipulation of components at the molecular level is still out of reach for human scientists.

For biological entities, this is an issue that was solved in distant antiquity. The chemical processes that drive life have (essentially) perfected the ability to churn out billions of perfect replicas of their own versions of gears and axles. Why, then, should nanoscientists reinvent the wheel in order to build nanobots?

The technique demonstrated in this instance allows researchers to avoid many of the difficult tasks of constructing a nano-scale device from the ground up and instead focus on adding capabilities to well-understood and easily-manipulated molecules. Constructing a purely mechanical nanodevice from scratch to detect moisture and signal humidity levels would be extremely complicated and take decades. Adding the ability to the bacillus subtilis spores to transmit their native humidity-detecting talents via varied electrical resistance was the work of just weeks.

As demonstrated by the rather rudimentary function of the nanobots created at the University of Illinois, this approach has along way to go before turning out anything resembling the science fiction version of the devices. But the work may give the best glimpse of the most likely way forward to a workable nanoscale assembly technology.

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