March 25, 2015
Robotic germ equipped with graphene quantum dots
Researchers from the University of Illinois at Chicago have created a robotic germ by placing a humidity sensor on a bacterial spore. This is what they are calling the first-ever example of nanoscale bioengineering involving these minute, one-celled reproductive units.
The research is the latest entry in the first generation of bio-electromechanical devices designed to combine living organism with nonliving technology to conduct research and solve a variety of different problems by using miniature machines too small for the naked eye to see.
The UIC researchers, who described their work in a recent issue of the journal Scientific Reports, believe that their discovery could ultimately “lead to the evolution of next-generation bio-derived microarchitectures, probes for cellular/biochemical processes, biomicrorobotic-mechanisms, and membranes for micromechanical actuation.”
Their nanobot, the Nano-Electro-Robotic Device (NERD), and lead investigator/UIC associate professor of chemical engineering Vikas Berry explained that he and his colleagues created it by taking “a spore from a bacterium,” placing “graphene quantum dots on its surface” and attaching “two electrodes on either side of the spore. Then we changed the humidity around the spore.”
Once the humidity drops, the spore shrinks as water is forced out. While it shrinks, the quantum dots on the organism come closer together, increasing their conductivity as measured by the electrodes. Berry said that there is a drastic change once the humidity changes – a response that he describes as being 10 times faster than sensors made of advanced synthetic water-absorbing polymers. NERD was also more sensitive in extreme low-pressure, low-humidity situations.
“We get a very clean response--a very sharp change the moment we change humidity, [and] we can go all the way down to a vacuum and see a response,” the professor explained. This is vital to applications in which humidity must be kept low to prevent corrosion or food spoilage, as well as in space applications, when changes in humidity could indicate the presence of a leak.
More sensitive at low humidity
Furthermore, unlike current sensors that increase in sensitivity as humidity rises, NERD is actually more sensitive at low humidity, Berry and lead co-authors T. S. Sreeprasad and Phong Nguyen (who were also with UIC at the time of the research) discovered.
“The work provides an avenue for leveraging the unique biomolecular structure of the biological entities to achieve controlled nanoscale architecture and membrane transport for micromechanical actuation for a wide range of applications in microbotics, cellular actuation, single-cell biochemical analysis, cellular homeostasis, specific molecular or ionic detection, and implants for muscle, heart and cancer monitoring,” the study authors wrote.
“This is a fascinating device,” added Berry. “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.”