On demand delivery and analysis of single molecules on a programmable nanopore-optofluidic device.

Nanopore-based single nanoparticle detection has recently emerged as a vibrant research field with numerous high-impact applications. Here, we introduce a programmable optofluidic chip for nanopore-based particle analysis: feedback-controlled selective delivery of a desired number of biomolecules and integration of optical detection techniques on nanopore-selected particles. We demonstrate the feedback-controlled introduction of individual biomolecules, including 70S ribosomes, DNAs and proteins into a fluidic channel where the voltage across the nanopore is turned off after a user-defined number of single molecular insertions. Delivery rates of hundreds/min with programmable off-times of the pore are demonstrated using individual 70S ribosomes. We then use real-time analysis of the translocation signal for selective voltage gating of specific particles from a mixture, enabling selection of DNAs from a DNA-ribosome mixture. Furthermore, we report optical detection of nanopore-selected DNA molecules. These capabilities point the way towards a powerful research tool for high-throughput single-molecule analysis on a chip.

Optical trapping assisted detection rate enhancement of single molecules on a nanopore optofluidic chip.

We use optical trapping to deliver molecular targets to the vicinity of a nanopore for high-throughput single molecule analysis on an optofluidic chip. DNA detection rates increase over 80× to enable detection at attomolar concentrations.

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.

Probing nanoscale solids at thermal extremes.

We report a novel nanoscale thermal platform compatible with extreme temperature operation and real-time high-resolution transmission electron microscopy. Applied to multiwall carbon nanotubes, we find atomic-scale stability to 3200 K, demonstrating that carbon nanotubes are more robust than graphite or diamond. Even at these thermal extremes, nanotubes maintain 10% of their peak thermal conductivity and support electrical current densities approximately 2 x 10{8} A/cm{2}. We also apply this platform to determine the diameter dependence of the melting temperature of gold nanocrystals down to three nanometers.

Shrinking a carbon nanotube.

We report a method to controllably alter the diameter of an individual carbon nanotube. The combination of defect formation via electron irradiation and simultaneous resistive heating and electromigration in vacuum causes the nanotube to continuously transform into a high-quality nanotube of successively smaller diameter, as observed by transmission electron microscopy. The process can be halted at any diameter. Electronic transport measurements performed in situ reveal a striking dependence of conductance on nanotube geometry. As the diameter of the nanotube is reduced to near zero into the carbon chain regime, we observe negative differential resistance.

Ultrahigh frequency nanotube resonators.

We report carbon-nanotube-based electromechanical resonators with the fundamental mode frequency over 1.3 GHz, operated in air at room temperature. A new combination of drive and detection methods allows for unprecedented measurement of both oscillation amplitude and phase and elucidates the relative mobility of static charges near the nanotube. The resonator serves as an exceptionally sensitive mass detector capable of approximately 10(-18) g resolution.

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.