ABSTRACT
Various complex self-assembled morphologies of lamellar- and cylinder-forming block copolymers comprising poly(dimethylsiloxane)-b-polylactide (PDMS-b-PLA) confined in cylindrical channels were generated. Combining top-down lithography with bottom-up block copolymer self-assembly grants access to morphologies that are otherwise inaccessible with the bulk materials. Channel diameter (D) was systematically varied with four diblock copolymers having different compositions and bulk domain spacing (L0), corresponding to a range of frustration ratios (D/L0 from 2 to 4). Excessive packing frustration imposed by the channels leads to contorted domains. The resulting morphologies depend strongly on both D/L0 and copolymer composition. Under several circumstances, mixtures of complex morphologies were observed, which hypothetically arise from the severe sensitivity to D/L0 combined with the inherent compositional/molar mass dispersities associated with the nonuniform synthetic materials and silicon templates. Stochastic calculations offer compelling support for the hypothesis, and tractable pathways toward solving this apparent conundrum are proposed. The materials hold great promise for next-generation nanofabrication to address several emerging technologies, offering significantly enhanced versatility to basic diblock copolymers as templates for fabricating complex nanoscale objects.
ABSTRACT
A fully controllable process for the fabrication of carbon nanotube assemblies is presented on the basis of a sequential electrochemical oxidation lithography process. This approach utilizes the local chemical conversion of a n-octadecyltrichlorosilane self-assembled monolayer into a template featuring polar acid groups. The capability to utilize such chemically active templates for the site-selective assembly of individual carbon nanotubes was demonstrated, and a hierarchical, sequential structuring routine to obtain crossed CNT configurations, formed by preselected carbon nanotubes, was implemented. The introduced process allows the reliable and well-controlled fabrication of tailor-made nanoscopic assemblies of nanomaterials toward their integration into complex device frameworks and could provide control over the electrical properties of the fabricated assemblies.
ABSTRACT
A new, fast, alternative approach for the fabrication of carbon nanotube (CNT) atomic force microscopy (AFM) tips is reported. Thereby, the tube material is grown on the apex of an AFM tip by utilizing microwave irradiation and selective heating of the catalyst. Reaction times as short as three minutes allowed the fabrication of CNT AFM tips in a highly efficient process. This method represents a promising approach toward a cheaper, faster, and straightforward synthesis of CNT AFM tips.
ABSTRACT
We describe a microfabricated Fabry-Pérot interferometer with nanochannels of various heights between 6 and 20 nm embedded in its cavity. By multiple beam interferometry, the device enables the study of liquid behavior in the nanochannels without using fluorescent substances. During filling studies of ethanol and water, an intriguing filling mode for partially wetting water was observed, tentatively attributed to the entrapment of a large amount of gas inside the channels.
