Mn12-acetate thin film patterns and their interaction with superconductors

Mn12-acetate single-molecule magnets (SMMs) are nano-scale magnets showing a strong magnetic anisotropy, slow relaxation and stepwise magnetic hysteresis curves. Possible applications of Mn12-acetate, e.g. for ultra high density magnetic information storage device, quantum computation, and magnetic molecular electronics, have been suggested due to the unusual magnetic behavior. It is an important prerequisite for the applications to develop a reliable technique to organize the molecules on a surface and to detect the magnetic signals of the molecules. A solution evaporation technique combined with conventional lithography is a simple but reliable method to create Mn12-acetate thin film patterns on the micro/nano-scale. The method is demonstrated with a series of analysis. A superconducting quantum interference device (SQUID) shows a non-linear I-V (Current vs. Voltage) characteristic that is modulated by a magnetic flux inside the loop, allowing one to sense and analyze an extremely weak magnetic field. The miniaturized SQUID is appropriate for sensing the magnetic flux from the film structure of the molecular magnets. Theoretical ideas, fabrication, and a measurement technique of the device are presented. A new interesting system, the so-called superconductor/SMM hybrid, results from the experimental configuration. Understanding this new type of hybrid system is important not only because of the expectation of new phenomena affecting the functionality of superconducting devices, but also because the two coupled substances are fundamentally incompatible phases. The first experimental attempt to investigate the interaction between an aluminum superconducting film and Mn12-acetate SMMs will be discussed

Behavior of Kinesin Driven Quantum Dots Trapped in a Microtubule Loop

We report the observation of kinesin driven quantum dots (QDs) trapped in a microtubule loop, allowing the investigation of moving QDs for a long time and an unprecedented long distance. The QD conjugates did not depart from our observational field of view, enabling the tracking of specific conjugates for more than 5 min. The unusually long run length and the periodicity caused by the loop track allow comparing and studying the trajectory of the kinesin driven QDs for more than 2 full laps, <i>i.e.</i>, about 70 μm, enabling a statistical analysis of interactions of the same kinesin driven object with the same obstacle. The trajectories were extracted and analyzed from kymographs with a newly developed algorithm. Despite dispersion, several repetitive trajectory patterns can be identified. A method evaluating the similarity is introduced allowing a quantitative comparison between the trajectories. The velocity variations appear strongly correlated to the presence of obstacles. We discuss the reasons making this long continuous travel distances on the loop track possible

Molecular Motor-Powered Shuttles along Multi-walled Carbon Nanotube Tracks

As a complementary tool to nanofluidics, biomolecular-based transport is envisioned for nanotechnological devices. We report a new method for guiding microtubule shuttles on multi-walled carbon nanotube tracks, aligned by dielectrophoresis on a functionalized surface. In the absence of electric field and in fluid flow, alignment is maintained. The directed translocation of kinesin propelled microtubules has been investigated using fluorescence microscopy. To our knowledge, this is the first demonstration of microtubules gliding along carbon nanotubes