Nanotube surface arrays: Weaving, bending, and assembling on patterned silicon

The fabrication of ordered arrays of oriented and bent carbon nanotube on a patterned silicon surface with a micron scale spacing extending over millimeter size surface areas, was presented. A combination of multistep purification and oxidation procedures were used to generate bundles containing 3-20 nanotubes of high purity. The patterned surface was composed of alternating hydrophilic and hydrophobic stripes. The results suggest that the patterning is controlled by the hydrodynamic behavior of a fluid front and orientation and bending mechanisms are facilitated by the pinned carbon nanotubes trapped by the liquid-solid-vapor contact line.open849

Combing and bending of carbon nanotube arrays with confined microfluidic flow on patterned surfaces

Ordered arrays of carbon nanotubes in bent and straight states were prepared using "wet" deposition of nanotube solutions on a patterned surface. This approach provided a means for the formation of highly oriented and textured nanotube arrays of different types. Moreover, under certain conditions, nanotube loops of different shapes were formed on amine-terminated silicon surface stripes. Atomic force microscopy observations indicated that the majority of the deposited nanotubes (up to 90%) are uniformly oriented and up to 40% of aligned nanotubes are folded into different nanoscale shapes (open and closed loops with 200-300 nm radius of curvature). We suggested that the dewetting of the SAM-confined liquid film was responsible for the alignment of carbon nanotubes and for the formation of the looped nanotubes. The instability of a receding contact line caused water microdroplets behind the dewetting film, which could serve as nuclei for nanotube trapping. The nanotubes pinned to the functionalized surface can be trapped by these drying microdroplets and bent along their shrinking circumference. In addition, highly packed ordered arrays of carbon nanotubes were formed by casting from solution on tilted patterned substrates. The preparation of the ordered arrays of uniform nanotube loops or woven nanotube stripes may be useful in microelectronic and microelectromechanical devices, where tunable electronic and surface properties result from different nanotube shapes, locations, and orientations.close727

Synthesis and Properties of Asymmetric Heteroarm PEO n -b-PS m Star Polymers with End Functionalities

ABSTRACT: We report on the "core-first" synthesis of asymmetric three-and four-arm poly(ethylene oxide) (PEO)-polystyrene (PS) star polymers with functional terminal groups of a general formula PEO nb-PSm with n ) 0, 1, and 2 and n + m e 4. The synthesis was conducted by anionic polymerization of ethylene oxide and followed by atom transfer radical polymerization (ATRP) of styrene. The properties of asymmetric star-shaped macromolecules with different numbers of arms (n ) 1; m ) 2 and 3) and similar lengths of the PEO arm were compared with homoarm star polymers (PEO4 and PS4) and corresponding linear polymers. All star polymers obtained here possessed well-defined architecture with a relatively narrow molecular weight distribution as confirmed by NMR, FTIR, and arm-disassembling techniques. Star polymers showed suppression of melting temperature and lower crystallinity PEO phase due to the presence of a junction point. Preliminary studies demonstrated surface activities of these block copolymers with a rich polymorphism of micellar surface structures expected for amphiphilic block copolymers despite the presence of the bulky terminal functionalized groups

Hydrogel-Encapsulated Microfabricated Haircells Mimicking Fish Cupula Neuromast

A hydrogel-capped hair-cell flow microsensor, which closely mimics a superficial neuromast of a fish, is introduced. By encapsulating the hair sensor into the artificial hydrogel cupula a dramatic increase in hair-sensor sensitivity to the oscillating and the steady flow is achieved. It opens the way toward the remote monitoring of the underwater environment by autonomous, unmanned microvehicles with self-navigating capability