Controlling the shape, orientation, and linkage of carbon nanotube features with nano affinity templates

Abstract

Directed assembly of nanoscale building blocks such as singlewalled carbon nanotubes (SWNTs) into desired architectures is a major hurdle for a broad range of basic research and technological applications (e.g., electronic devices and sensors). Here we demonstrate a parallel assembly process that allows one to simultaneously position, shape, and link SWNTs with sub-100-nm resolution. Our method is based on the observation that SWNTs are strongly attracted to COOH-terminated self-assembled monolayers (COOH-SAMs) and that SWNTs with lengths greater than the dimensions of a COOH-SAM feature will align along the boundary between the COOH-SAM feature and a passivating CH3-terminated SAM. By using nanopatterned affinity templates of 16-mercaptohexadecanonic acid, passivated with 1-octadecanethiol, we have formed SWNT dot, ring, arc, letter, and even more sophisticated structured thin films and continuous ropes. Experiment and theory (Monte Carlo simulations) suggest that the COOH-SAMs localize the solvent carrying the nanotubes on the SAM features, and that van der Waals interactions between the tubes and the COOH-rich feature drive the assembly process. A mathematical relationship describing the geometrically weighted interactions between SWNTs and the two different SAMs required to overcome solvent-SWNT interactions and effect assembly is provided.self-assembly ͉ rings ͉ structured thin films ͉ Monte Carlo simulations S ingle-walled carbon nanotubes (SWNTs) show promise for applications ranging from ultra-small electronic and sensing devices to multifunctional materials (1). To date, a number of SWNT-based proof-of-concept devices (2-7) such as field effect transistors (2), field emission displays (7), and chemical sensors (3, 6) have been fabricated, and the integration of the nanotube materials in all cases relies on one's ability to control the placement, orientation, and shape of the nanotube components within the context of the device on the micrometer-to nanometer-length scale. Such positional control over large areas is extremely challenging and currently quite limited. Depending on the intended application, one wants to be able to pattern SWNTs as individual tubes (3, 4), small bundles (5), or thin films (6,8,9). Previous studies have shown that individual carbon nanotubes can be positioned (10), bent (11), and even welded (12) with nanometer accuracy by using scanning probe instruments. This level of manipulation is limited to serial and therefore slow processes that span relatively short distances (100 m). Other assembly methods such as Langmuir-Blodgett techniques (13), external field assisted routes (14-19), electrospinning (20), transfer printing (21), and DNA templates (22, 23) also have been explored for nanotube assembly. These parallel methods address the speed limitation posed by conventional scanning probe techniques, but thus far are quite limited with respect to registration control and have demonstrated only coarse placement capabilities. One promising approach to overcoming these limitations i...

Placement and orientation of individual DNA shapes on lithographically patterned surfaces

“…, carbon nanotubes 12,13 and nanowires 14 . Lithographic templates can also be used to create hierarchical order: the nanostructures they organize can themselves have internal features with dimensions significantly smaller than those of the original template 15 and can serve as scaffolds for the assembly of still smaller components.…”

Conductivity of carbon nanotube polymer composites

“…More specifically, block copolymer composition can be controlled to self-assemble a variety of phases: lamellar, bicontinuous, gyroid and discrete micelles [5]. Thus, with appropriate choice of polymers more structured arrangements with improved percolation of CNTs at low fractions might be possible.. Template-controlled assembly of CNTs is a problem relevant not only to nanocomposites, but to other diverse application areas [6]. Self-organization of inorganic nanoparticles in copolymers have been investigated both experimentally [7] and computationally [8,9] and dispersion of stiff rods, somewhat representative of CNTs, have been investigated in fluids and phase-separating fluid mixtures [10].…”

Patterning and Assembly of Single-Walled Carbon Nanotubes/Organic Semiconductor Composites

“…In the dip-pen nanolithography technique, AFM cantilever is inked with organic materials, which are then transferred to flat surfaces. Recently, Wang and co-workers have demonstrated that the microcontact printing and parallel dip-pen nanolithography technique allows one to pattern single-walled carbon nanotubes functionalized with COOH-terminated self-assembled monolayers (Wang et al, 2006). Another method, called fountain-pen nanolithography (FPN), has a potential to be effective large-area patterning technique, in which the modified AFM cantilever serves as a micro-pipet.…”