https://www.bc.edu/content/dam/files/schools/cas_sites/physics/pdf/Ren/p85.pdf

Advances in the science and technology of carbon nanotubes and their composites: a review

Small but strong: A review of the mechanical properties of carbon nanotube–polymer composites

Nanotubes from Carbon.

Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical-based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology.

/pdf/carbon-nanotube-actuators-1chbcyw6t7.pdf

Carbon Nanotube Actuators

The widespread use of controlled molecular-level motion in key natural processes suggests that great rewards could come from bridging the gap between the present generation of synthetic molecular systems, which by and large rely upon electronic and chemical effects to carry out their functions, and the machines of the macroscopic world, which utilize the synchronized movements of smaller parts to perform specific tasks. This is a scientific area of great contemporary interest and extraordinary recent growth, yet the notion of molecular-level machines dates back to a time when the ideas surrounding the statistical nature of matter and the laws of thermodynamics were first being formulated. Here we outline the exciting successes in taming molecular-level movement thus far, the underlying principles that all experimental designs must follow, and the early progress made towards utilizing synthetic molecular structures to perform tasks using mechanical motion. We also highlight some of the issues and challenges that still need to be overcome.

Synthetic molecular motors and mechanical machines.

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.

Bending and buckling of carbon nanotubes under large strain

The Virtual-Reality Peripheral Network (VRPN) system provides a device-independent and network-transparent interface to virtual-reality peripherals. VRPN's application of factoring by function and of layering in the context of devices produces an interface that is novel and powerful. VRPN also integrates a wide range of known advanced techniques into a publicly-available system. These techniques benefit both direct VRPN users and those who implement other applications that make use of VR peripherals.

VRPN: a device-independent, network-transparent VR peripheral system

is preferred over sliding, and it is expected to have an equally important role in the microscopic domain. Although progress has been made in our understanding of the dynamics of sliding at the atomic level 4 ,w e have no comparable insight into rolling owing to a lack of experimental data on microscopic length scales. Here we produce controlled rolling of carbon nanotubes on graphite surfaces using an atomic force microscope. We measure the accompanying energy loss and compare this with sliding. Moreover, by repro- ducibly rolling a nanotube to expose different faces to the substrate and to an external probe, we are able to study the object over its complete surface. The microscopic aspects of tribology have been explored by means of the surface force apparatus (SFA) 5 and atomic force microscopy (AFM) 6 , which have identified the intrinsic dependence of sliding friction on contact area 7,8 and crystallographic orientation 9,10 . Further, AFM has been used to perform friction mapping of surfaces with atomic resolution 4 and has identified stick-slip motion in the sliding of nanometre-scale objects 11 . Using AFM manipulation 12,13 of multiwall carbon nanotubes (CNTs), we have observed sliding and rolling. CNTs, with a range of available sizes down to the molecular scale, serve as interesting model systems for tribological studies. In addition, nanotubes are expected to play a part in future nanometre-scale electrical-mechanical devices, and rolling fullerenes have been proposed as ideal lubricants 14-16 . Our evidence for sliding and rolling comprises sequences of topogra- phical images of manipulated nanotubes and lateral force data acquired during the manipulation to measure energy loss. Samples were prepared by solvent evaporation on mica and graphite substrates from an ethanol solution of raw carbon soot produced by the carbon arc technique 17 . The multiwall CNTs were imaged and manipulated under ambient conditions. The nanomanipulator AFM system 18,19 , designed for manipulation, comprises an advanced visual interface, teleoperation capabilities for manual control of the AFM tip and haptic (touch) presentation of the AFM data (Topometrix Discoverer). Normal force, lateral force and AFM tip trajectory are recorded simultaneously for strict correlation. The AFM tip is used to apply lateral forces at locations along the tube to produce translations and rotations. These tubes are free of pinning material and move without deformation. The lateral force values have been calibrated from measured cantilever and tip geometry, literature values for the cantilever (Si) elastic moduli and the detector response from the z-translation of the cantilever. We estimate the absolute error in this calibration to be about 30%, with the largest contribution in the uncertainty coming

Nanometre-scale rolling and sliding of carbon nanotubes

In this article, we reiterate the characteristics that make the rainbow color map a poor choice, provide examples that clearly illustrate these deficiencies even on simple data sets, and recommend better color maps for several categories of display. The goal is to make the rainbow color map as rare in visualization as the goto statement is in programming - which complicates the task of analyzing and verifying program correctness

Rainbow Color Map (Still) Considered Harmful

Integrating force feedback with a complete real-time virtual environment system presents problems which are more difficult than those encountered in building simpler forcefeedback systems. In particular, lengthy computations for graphics or simulation require a decoupling of the haptic servo loop from the main application loop if high-quality forces are to be produced. We present some approaches to these problems and describe our force-feedback software library which implements these techniques and provides other benefits including haptic-textured surfaces, device independence, distributed operation and easy enhancement.

/pdf/adding-force-feedback-to-graphics-systems-issues-and-3kd0av8yho.pdf

Russell M. Taylor

Papers

Bending and buckling of carbon nanotubes under large strain

VRPN: a device-independent, network-transparent VR peripheral system

Nanometre-scale rolling and sliding of carbon nanotubes

Rainbow Color Map (Still) Considered Harmful

Adding force feedback to graphics systems: issues and solutions