Transplanting assembly of individual carbon nanotubes

Abstract

Handling and assembling individual nanostructures to bigger scale systems such as MEMS have been the biggest challenge. A deterministic assembly of individual carbon nanotubes by transplanting them to MEMS structures is demonstrated with a new assembly method, "transplanting assembly." This thesis describes development of a novel assembly technique by transforming individual CNTs assemblable, which enables manual, parallel or automated assembly of individual CNTs in a deterministic way. The key idea of transplanting assembly is to grow individual CNT strands on a substrate at optimal growth conditions, to encapsulate individual CNTs into micro-scale carrier blocks and to transplant them to the target locations. This new assembly method enables products such as CNT-tipped AFM probes in a predictable and repeatable manner. The major research topics discussed in this thesis are: (1) the methods to grow vertically aligned single strand CNTs at predefined locations, (2) the encapsulation method to preserve/control the orientation/exposed length of an individual CNT during transplanting, and (3) the assembly scheme to locate/release an individual CNT at the target location. An array of CNTs was grown from the nickel nano-dots, which were defined on Si substrates using electron-beam lithography followed by metal deposition and lift-off processes. Each CNT strand was embedded into a MEMS scale polymer block which serves as a CNT carrier. A double polymeric layer encapsulation was designed and implemented: the top SU-8 forms the body of the carrier while the bottom PMGI layer holds the body until the release of the carrier from the substrate and then is going to be removed to expose the CNT tip with a predefined length. A model was developed to predict mechanical behavior of individual CNTs under the flow of liquid polymers. Manual assembly of a polymer block to the end of a tipless AFM cantilever forms a CNT-tipped AFM probe, which can be accomplished in minutes without laborious weeding, trimming and welding process. The AFM scanning results confirmed the CNTtipped AFM probe's much improved imaging performance and potential for scanning soft biological samples at nanometer resolutions.