Thomas D. Yuzvinsky

Rotational actuators based on carbon nanotubes.

Nanostructures are of great interest not only for their basic scientific richness, but also because they have the potential to revolutionize critical technologies. The miniaturization of electronic devices over the past century has profoundly affected human communication, computation, manufacturing and transportation systems. True molecular-scale electronic devices are now emerging that set the stage for future integrated nanoelectronics. Recently, there have been dramatic parallel advances in the miniaturization of mechanical and electromechanical devices. Commercial microelectromechanical systems now reach the submillimetre to micrometre size scale, and there is intense interest in the creation of next-generation synthetic nanometre-scale electromechanical systems. We report on the construction and successful operation of a fully synthetic nanoscale electromechanical actuator incorporating a rotatable metal plate, with a multi-walled carbon nanotube serving as the key motion-enabling element.

Precision cutting of nanotubes with a low-energy electron beam

We report on a method to locally remove material from carbon and boron nitride nanotubes using the low-energy focused electron beam of a scanning electron microscope. Using this method, clean precise cuts can be made into nanotubes, either part-way through (creating hingelike geometries) or fully through (creating size-selected nanotube segments). This cutting mechanism involves foreign molecular species and differs from electron-beam-induced knock-on damage in transmission electron microscopy.

Length control and sharpening of atomic force microscope carbon nanotube tips assisted by an electron beam

We report on the precise positioning of a carbon nanotube on an atomic force microscope (AFM) tip. By using a nanomanipulator inside a scanning electron microscope, an individual nanotube was retrieved from a metal foil by the AFM tip. The electron beam allows us to control the nanotube length and to sharpen its end. The performance of these tips for AFM imaging is demonstrated by improved lateral resolution of DNA molecules.

Nanoscale reversible mass transport for archival memory.

We report on a simple electromechanical memory device in which an iron nanoparticle shuttle is controllably positioned within a hollow nanotube channel. The shuttle can be moved reversibly via an electrical write signal and can be positioned with nanoscale precision. The position of the shuttle can be read out directly via a blind resistance read measurement, allowing application as a nonvolatile memory element with potentially hundreds of memory states per device. The shuttle memory has application for archival storage, with information density as high as 10(12) bits/in(2), and thermodynamic stability in excess of one billion years.

Imaging the life story of nanotube devices

Live imaging of operating multiwall carbon nanotube (MWCNT-) based electronic devices is performed by high resolution transmission electron microscopy. Our measurements allow us to correlate electronic transport with changes in device structure. Surface contamination, contact annealing, and sequential wall removal are observed. Temperature profiles confirm diffusive conduction in MWCNTs in the high bias limit. This technique provides a general platform for studying nanoscale systems, where geometric configuration and electronic transport are intimately connected.

Controlled placement of highly aligned carbon nanotubes for the manufacture of arrays of nanoscale torsional actuators

We have fabricated ordered arrays of nanoscale torsional actuators consisting of metal mirrors bonded to precisely oriented multiwall carbon nanotubes. The fabrication is facilitated by a new nanotube positioning method which employs localized electron beam activation of polymer residue on a silicon oxide surface.

Effect of fabrication-dependent shape and composition of solid-state nanopores on single nanoparticle detection.

Solid-state nanopores can be fabricated in a variety of ways and form the basis for label-free sensing of single nanoparticles: as individual nanoparticles traverse the nanopore, they alter the ionic current across it in a characteristic way. Typically, nanopores are described by the diameter of their limiting aperture, and less attention has been paid to other, fabrication-dependent parameters. Here, we report a comprehensive analysis of the properties and sensing performance of three types of nanopore with identical 50 nm aperture, but fabricated using three different techniques: direct ion beam milling, ion beam sculpting, and electron beam sculpting. The nanopores differ substantially in physical shape and chemical composition as identified by ion-beam assisted cross-sectioning and energy dispersive X-ray spectroscopy. Concomitant differences in electrical sensing of single 30 nm beads, such as variations in blockade depth, duration, and electric field dependence, are observed and modeled using hydrodynamic simulations. The excellent agreement between experiment and physical modeling shows that the physical properties (shape) and not the chemical surface composition determine the sensing performance of a solid-state nanopore in the absence of deliberate surface modification. Consequently, nanoparticle sensing performance can be accurately predicted once the full three-dimensional structure of the nanopore is known.

Electrically conductive bacterial nanowires in bisphosphonate- related osteonecrosis of the jaw biofilms

OBJECTIVE Bacterial biofilms play a role in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (BRONJ). The purpose of this preliminary study was to test the hypothesis that the extracellular filaments observed in biofilms associated with BRONJ contain electrically conductive nanowires. STUDY DESIGN Bone samples of patients affected by BRONJ were evaluated for conductive nanowires by scanning electron microscopy (SEM) and conductive probe atomic force microscopy (CP-AFM). We created nanofabricated electrodes to measure electrical transport along putative nanowires. RESULTS SEM revealed large-scale multispecies biofilms containing numerous filamentous structures throughout necrotic bone. CP-AFM analysis revealed that these structures were electrically conductive nanowires with resistivities on the order of 20 Ω·cm. Nanofabricated electrodes spaced along the nanowires confirmed their ability to transfer electrons over micron-scale lengths. CONCLUSIONS Electrically conductive bacterial nanowires to date have been described only in environmental isolates. This study shows for the first time that these nanowires can also be found in clinically relevant biofilm-mediated diseases, such as BRONJ, and may represent an important target for therapy.

Optical particle sorting on an optofluidic chip

We report size-based sorting of micro- and sub-micron particles using optical forces on a planar optofluidic chip. Two different combinations of fluid flow and optical beam directions in liquid-core waveguides are demonstrated. These methods allow for tunability of size selection and sorting with efficiencies as high as 100%. Very good agreement between experimental results and calculated particle trajectories in the presence of flow and optical forces is found.

Engineering Nanomotor Components from Multi‐Walled Carbon Nanotubes via Reactive Ion Etching

It has been shown that a multi‐walled carbon nanotube (MWCNT) can be used as the rotation enabling element for nanoelectromechanical systems. Modification of the MWCNT to create a rotational bearing in previous devices has concentrated on smaller diameter tubes and mechanical methods to create the bearing. We here investigate reactive ion etching of a MWCNT as a means to engineer nanomotor components, including the rotational bearing.