Ground-state cooling the vibrations of suspended carbon-nanotubes with constant electron current

We investigate the efficiency of cooling the vibrations of a nano-mechanical resonator, constituted by a partially suspended Carbon-nanotube and operating as double-quantum dot. The motion is brought to lower temperatures by tailoring the energy exchange via electromechanical coupling with single electrons, constantly flowing through the nanotube when a constant potential difference is applied at its extremes in the Coulomb-blockade regime. Ground-state cooling is possible at sufficiently high quality factors, provided that the dephasing rate of electron transport within the double dot does not exceed the resonator frequency. For large values of the dephasing rates cooling can still be achieved by appropriately setting the tunable parameters.Comment: 10 pages, 5 figure

Current-induced cleaning of graphene

A simple yet highly reproducible method to suppress contamination of graphene at low temperature inside the cryostat is presented. The method consists of applying a current of several mA through the graphene device, which is here typically a few $\mu$m wide. This ultra-high current density is shown to remove contamination adsorbed on the surface. This method is well suited for quantum electron transport studies of undoped graphene devices, and its utility is demonstrated here by measuring the anomalous quantum Hall effect.Comment: Accepted for publication in Applied Physics Letter

Carbon Nanotube Based Bearing for Rotational Motions

We report the fabrication of a nanoelectromechanical system consisting of a plate rotating around a multiwalled nanotube bearing. The motion is possible thanks to the low intershell friction. Indeed, the nanotube has been engineered so that the sliding happens between different shells. The plate rotation is activated electrostatically with stator electrodes. The static friction force is estimated at $\approx 2\cdot10^{-15}$ N/\AA$^2$.Comment: 4 pages, 3 figure

Sequential tasks performed by catalytic pumps for colloidal crystallization

Gold-platinum catalytic pumps immersed in a chemical fuel are used to manipulate silica colloids. The manipulation relies on the electric field and the fluid flow generated by the pump. Catalytic pumps perform various tasks, such as the repulsion of colloids, the attraction of colloids, and the guided crystallization of colloids. We demonstrate that catalytic pumps can execute these tasks sequentially over time. Switching from one task to the next is related to the local change of the proton concentration, which modifies the colloid zeta potential and consequently the electric force acting on the colloids

El comportament exòtic dels dispositius mecànics quan arriben a la nanoescala

Els ressonadors mecànics s'utilitzen àmpliament en la indústria d'alta tecnologia, per marcar el temps en els components electrònics i per estabilitzar les transmissions d'ones de radiofreqüència. Molts dels ressonadors mecànics s'amorteixen d'una manera lineal ben coneguda, però el treball innovador del professor Adrian Bachtold i el seu grup de recerca a l'Institut Català de Nanotecnologia demostra que els ressonadors de grafè i nanotubs de carboni nanomètrics s'amorteixen de forma no lineal, obrint pas a possibilitats excitants per detectors hipersensibles de força o massa.Los resonadores mecánicos se utilizan ampliamente en la industria de alta tecnología, para marcar el tiempo en los componentes electrónicos y para estabilizar las transmisiones de ondas de radiofrecuencia. Muchos de los resonadores mecánicos se amortiguan de una manera lineal bien conocida, pero el trabajo innovador del profesor Adrian Bachtold y su grupo de investigación en el Instituto Catalán de Nanotecnología demuestra que los resonadores de grafeno y nanotubos de carbono nanométricos se amortiguan de forma no lineal, abriendo paso a posibilidades excitantes para detectores hipersensibles de fuerza o masa.Mechanical resonators are extensively used in hightech industry, to mark time in electronic components, and to stabilise radio transmissions. Most mechanical resonators damp (slow down) in a wellunderstood linear manner, but groundbreaking work by professor Adrian Bachtold and his research group at the Catalan Institute of Nanotechnology has shown that resonators formed from nanoscale graphene and carbon nanotube sexhibit nonlinear damping, opening up exciting possibilities forsupersensitive detectors of for ce or mass

Aconsegueixen desplaçar objectes nanomètrics mitjançant canvis de temperatura

A través d'un nanotub multicapa de carboni s'ha demostrat que l'origen directe del moviment d'un objecte mòbil es troba en l'heterogeneïtat tèrmica d'aquest tub. Apareix quan flueix un corrent elèctric per l'interior del tub conductor -amb el seu corresponent escalfament- i els dos electrodes dels seus extrems estan a temperatura ambient

Imaging the proton concentration and mapping the spatial distribution of the electric field of catalytic micropumps

Catalytic engines can use hydrogen peroxide as a chemical fuel in order to drive motion at the microscale. The chemo-mechanical actuation is a complex mechanism based on the interrelation between catalytic reactions and electro-hydrodynamics phenomena. We studied catalytic micropumps using fluorescence confocal microscopy to image the concentration of protons in the liquid. In addition, we measured the motion of particles with different charges in order to map the spatial distributions of the electric field, the electrostatic potential and the fluid flow. The combination of these two techniques allows us to contrast the gradient of the concentration of protons against the spatial variation in the electric field. We present numerical simulations that reproduce the experimental results. Our work sheds light on the interrelation between the different processes at work in the chemomechanical actuation of catalytic pumps. Our experimental approach could be used to study other electrochemical systems with heterogeneous electrodes. © 2013 American Physical Society.We acknowledge support from the European Union (ERC-carbonNEMS project), the Spanish government (FIS2009-11284, FIS2011-22603, MAT2012-31338), and the Catalan government (AGAUR, SGR).Peer Reviewe