Arthur Barnard

Synchronization of micromechanical oscillators using light

Synchronization on the nanoscale has a wide range of applications ranging from timing, navigation, signal processing, microwave communication and novel computing and memory concepts. Existing coupled micromechanical oscillators suffer from limited range, neighborhood restriction and non-configurable coupling which limit the control, physical size and possible topologies of complex oscillator networks [1]. Here, we demonstrate the synchronization of two micromechanical oscillators, which are actuated and coupled by optical radiation field. We show that the coupling between the two oscillators can be tuned continuously from uncoupled to maximally coupled. These results pave a path towards massive and long-range synchronized oscillator networks.

Fluctuation broadening in carbon nanotube resonators

We simulated the behavior of suspended carbon nanotube resonators over a broad range of temperatures to explore the physics of semiflexible polymers in underdamped environments. We find that thermal fluctuations induce strong coupling between resonance modes. This effect leads to spectral fluctuations that readily account for the experimentally observed quality factors Q ∼ 100 at 300 K. Using a mean-field approach to describe fluctuations, we analytically calculate Q and frequency shifts in tensioned and buckled carbon nanotubes and find excellent agreement with simulations.

Magnetically Actuated Single-Walled Carbon Nanotubes.

We couple magnetic tweezer techniques with standard lithography methods to make magnetically actuated single-walled carbon nanotube (SWNT) devices. Parallel arrays of 4-10 μm-long SWNT cantilevers are patterned with one end anchored to the substrate and the other end attached to a micron-scale iron magnetic tag that is free to move in solution. Thermal fluctuations of this tag provide a direct measurement of the spring constant of the SWNT cantilevers, yielding values of 10(-7)-10(-8) N/m. This tag is also a handle for applying forces and torques using externally applied magnetic field gradients. These techniques provide a platform on which interaction forces between SWNTs and other objects such as biomolecules and cells can be measured in situ.

Folded graphene nanochannels via pulsed patterning of graphene

We present a resist-free patterning technique to form electrically contacted graphene nanochannels via localized burning by a pulsed white light source. The technique uses end-point detection to stop the burning process at a fixed resistance to produce channels with resistances of 10 kΩ to 100 kΩ. Folding of the graphene sheet takes place during patterning, which provides very straight edges as identified by AFM and SEM. Electrical transport measurements for the nanochannels show a non-linear behavior of the current vs source-drain voltage as the resistance goes above 20 kΩ indicating conduction tunneling effects. Electrochemical gating was performed to further electrically characterize the constrictions produced. The method described can be interesting not only for fundamental studies correlating edge folded structures with electrical transport but also as a promising path for fabricating graphene devices in situ. Additionally, this method might also be extended to create nanochannels in other 2D materials.

Synchronization of coupled optomechanical oscillators

We demonstrate experimentally the synchronization of two micromechanical oscillators actuated by the optical radiation field. The mutual coupling is purely optical and fully tunable. Upon synchronization, the phase noise drops in agreement with the prediction.