The curling of a graphitic sheet to form carbon nanotubes produces a class of materials that seem to have extraordinary electrical and mechanical properties. In particular, the high elastic modulus of the graphite sheets means that the nanotubes might be stiffer and stronger than any other known material, with beneficial consequences for their application in composite bulk materials and as individual elements of nanometre-scale devices and sensors. The mechanical properties are predicted to be sensitive to details of their structure and to the presence of defects, which means that measurements on individual nanotubes are essential to establish these properties. Here we show that multiwalled carbon nanotubes can be bent repeatedly through large angles using the tip of an atomic force microscope, without undergoing catastrophic failure. We observe a range of responses to this high-strain deformation, which together suggest that nanotubes are remarkably flexible and resilient.

Magnetoresistanceoscillations periodic with respect to the flux h/e have been observed in submicron-diameter Au rings, along with weaker h/2e oscillations. The h/e oscillations persist to very large magnetic fields. The background structure in the magnetoresistance was not symmetric about zero field. The temperature dependence of both the amplitude of the oscillations and the background are consistent with the recent theory by Stone.

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We present a procedure for producing high-aspect-ratio cantilevered micro-and nanorod arrays of a PDMS−ferrofluid composite material. The rods have been produced with diameters ranging from 200 nm to 1 µm and aspect ratios as high as 125. We demonstrate actuation of these superparamagnetic rod arrays with an externally applied magnetic field from a permanent magnet and compare this actuation with a theoretical energy-minimization model. The structures produced by these methods may be useful in microfluidics, photonic, and sensing applications.High-aspect-ratio nanostructures have attracted increasing attention in the nanotechnology community due to their potential applications as sensors 1-3 and actuators 4-7 and the effect of their presence on the surface properties of a material such as adhesion 8-11 and wetting. 12-14 We are interested in producing high-aspect-ratio nanostructures to serve as biomimetic cilia for the purpose of studying the mechanics of nanoscale fluid flow in a ciliated system. To this end, we have produced soft polymeric, actuable nanostructures of the size of biological cilia (∼10 µm in length by ∼200 nm diameter.) High-aspect-ratio polymer rods have been produced with materials with elastic moduli on the order of 100 MPa, 12-13 but these are unsuitable as actuating mechanisms due to their stiffness. Softer materials, such as poly(dimethyl siloxane) (PDMS, E ∼ 2 MPa), have been reported to fail at large aspect ratios due to lateral or ground collapse. 15,16 In addition, in many cases, rodlike microstructures are fabricated via a photolithographic master 15,16 or anodized aluminum oxide (AAO) membrane. 17 However, conventional photolithographic molds involve lengthy or specialized processing to produce large arrays of upright high-aspectratio structures, and AAO membranes impose severe limits on the diameter and spacing of the pores. Furthermore, with soft materials, photolithographic lift-off procedures may lead to structure collapse. Particle track-etched membranes have successfully been used as a template for a variety of materials [18][19][20] and are able to produce high-aspect-ratio structures with variable spacing and diameter. We use polycarbonate track-etched (PCTE) membranes as templates, allowing us to freely select the length and diameter of the rods and the density of the rod array by choosing an appropriate membrane.The high-aspect-ratio and low elastic modulus of our PDMS rods lend them a flexibility that makes them ideally suited to serve as actuators. To this end, we have produced micro-and nanorod arrays using a composite material of PDMS and iron oxide nanoparticles, which results in flexible superparamagnetic rods that may be actuated by applied external magnetic fields. Other groups have devised highaspect-ratio magnetically actuated microstructures via linkedbead chains, 3,7 and Singh, et al. have succeeded in tethering these structures to a substrate. 6 Our templated structures do not necessarily require a liquid medium, have the advantage of being scalable b...