By Matthew Benbenek
Chiara Daraio, Professor of Mechanical Engineering and Applied Physics at the California Institute of Technology, gave a Midwest Mechanics Series lecture on Sept. 22 to University of Wisconsin-Madison students and faculty regarding her research into plant nanobionics. Her group has spent years trying to artificially grow wood through the combination of wood cells and carbon in the form of nanotubes and graphene. After much trial and error, Daraio’s lab was not only able to create an artificial “cyberwood”, but also made it flexibly manufacturable, through 3D printing and other processes.
Daraio made another fascinating discovery: their “cyberwood,” in addition to having the strength properties of wood, was also conductive due to the incorporation of the graphene and carbon nanotubes. When they measured its’ resistance, however, they found that they were getting very inconsistent readings. Further study showed that the resistance was varying heavily with respect to both humidity and temperature. In fact, upon further inspection, her group showed that they were able to measure the temperature to a sensitivity of two orders more accurate than any other temperature sensor. Dariao discovered that the addition of graphene enabled them to utilize the incredibly accurate temperature response of plants, making it usable for scientific measurements. The plant substance responsible for this heat sensitivity was pectin, a product you can find in every grocery store.
Looking into other sensitive heat sensors in nature, Daraio’s group noted the pit organ that snakes use to detect the heat of their prey when hunting in the dark. Expanding on this idea, her lab constructed a synthetic sheet of their own to detect heat. Although limited in some mechanical aspects, namely flexibility, Daraio was able to construct an extremely accurate, thin thermal measurement sheet. Their next step is to try to decrease the production cost, thermal inertia and improve the mechanical properties so that it can be commercialized for consumer electronics.