Nanotube Electronics Flex With Self-Styled Wrappers

Carbon nanotubes are now helping researchers bend flexible electronics to their whims. Engineers led by Zhenan Bao of Stanford University have combined nanotube films with shape-memory polymers to create self-wrapping three-dimensional devices, such as sensors and transistors (Adv. Sci. 2015, DOI: 10.1002/advs.201500103). The team constructed its devices on flexible bilayers of polyimide and shape-memory polystyrene, which bend into predetermined shapes upon heating. By building multiple miniature metallic heating circuits onto polymer bilayers, the team can controllably wrap their devices around objects with diameters as small as 750 µm. To add further functionality to this flexibility, the researchers have turned to thin films of semiconducting single-walled nanotubes. These nanotube films, which are deposited from solution, maintain their electronic properties as they bend and stretch with the polymers, allowing the team to wrap up previously planar nanotube devices, including hydrogen gas sensors and transistor circuits. Although nanotubes are a robust material choice for these devices, the researchers say the self-wrapping substrates could also support other flexible electronics, such as nanostructured metal or silicon.